Patent Application
20240201341
Various aspects of the present disclosure are related to a LIDAR (“Light Detection and Ranging”) system and methods thereof (e.g., a method of emitting light in a LIDAR system).
Light detection and ranging is a sensing technique that is used, for example, in the field of autonomous driving for providing detailed information about the surrounding of an automated or partially automated vehicle. Light is used to scan a scene and determine the properties (e.g., the location, the speed, the direction of motion, and the like) of the objects present therein. A LIDAR system typically uses the time-of-flight (ToF) of the emitted light to measure the distance to an object. A LIDAR system may be configured as a pulsed LIDAR system, in which light pulses with adjustable amplitude and/or adjustable pulse shape are emitted to enable more sophisticated functionalities, as described for example in WO 2020 182 591 A1.
Various aspects of the present description are related to an approach for modulating light (e.g., a light signal) emitted from a LIDAR module. The modulation strategy described herein may provide a high degree of freedom and a high degree of control over the properties of the emitted light, to enable a simple and cost-efficient implementation of advanced functionalities (e.g., data transmission, etc.) in a LIDAR module. According to various aspects, the modulation may be carried out as a controlled combination of a plurality of partial signals (e.g., of partial electrical signals and/or of partial light signals) that together contribute to providing the emitted light signal. Controlling how the partial signals combine with one another may enable controlling the properties of the emitted light signal. In various aspects, the combination of the partial signal may be carried out as a function of a sequence of symbols to be encoded in the emitted light signal. The combination of the partial signals as a function of a sequence of symbols may enable transmitting information with the emitted light signal, thus providing an optical communication channel for the LIDAR module.
The term “LIDAR module” may be used herein to describe a device configured for LIDAR applications. A “LIDAR module” as used herein may be configured to carry out monitoring of a scene based on a LIDAR approach (e.g., based on the emission and detection of light, for example laser light). A “module” may be understood as an entity including a plurality of parts (e.g., a plurality of components) that together define the function of the module. Illustratively, a module may be understood as an entity configured to carry out a complex function that requires the contribution of a plurality of parts interacting together. A “LIDAR module” may also be referred to herein as “LIDAR system”, “LIDAR sensor”, “LIDAR product”, or simply “system” or “product”.
A “component” of a LIDAR module (also referred to herein as “element” of a LIDAR module) may be understood as a single part that individually contributes to the operation of a larger entity (e.g., of a module). A component may be understood as a single part configured to carry out a simple (e.g., general purpose) function, e.g. with a limited scope. A component may itself include a plurality of components (sub-elements, or sub-components) that provide the simple function of the component. A component including a plurality of sub-components may be understood as a sub-module (also referred to herein as sub-system), e.g. configured to implement a more complex functionality compared to an individual component (via the interaction of the sub-components). As an example, a component may be an array of laser diodes, and the individual laser diodes may be the sub-components of the array. As another example, a laser diode itself may be understood as a component, and the individual parts forming the laser diode (e.g., a semiconductor substrate, the electrical connections, etc.) may be understood as sub-components of the laser diode. In the following, references to a sub-system or sub-module may be understood to apply to a component including a plurality of sub-components.
The term “LIDAR light” may be used herein to describe light emitted by a LIDAR module (e.g., by a light emitting device of the LIDAR module). “LIDAR light” may be understood as the light used for illuminating a field of view of the LIDAR module (and, in some aspects, for implementing additional functionalities, such as data communication). “LIDAR light” may include, as an example, non-coherent light, e.g. emitted by a light emitting diode (e.g., by an array of light emitting diodes). In various aspects, “LIDAR light” may include laser light, e.g. emitted by a laser diode (e.g., by an array of laser diodes). “LIDAR light” may also be referred to herein as “LIDAR signal”. The term “LIDAR pulse” may be used herein to describe a light pulse (e.g., a laser pulse) in the emitted LIDAR light.
The term “modulation” may be used herein to describe an intentional modification of a physical quantity over time (e.g., of a charging voltage, a discharging current, an emitted light intensity, and the like) to provide a modulated signal. A modulated signal may differ with respect to a non-modulated signal in that at least one property of the modulated signal varies over time, e.g. a signal level, a time between pulses, a phase, etc. Illustratively, the term “modulation” may be used herein to describe a controlled variation of at least one property of a signal (e.g., an emitted light signal) over time.
The expression “signal level” may be used herein to describe a parameter associated with a signal (e.g., with a light signal, a current signal, a voltage signal, etc.) or with a portion of a signal (e.g., with a peak). A “signal level” as used herein may include at least one of a power level (PL), a current level, a voltage level, or an amplitude level (also referred to herein as amplitude).
According to various aspects, different approaches are provided to achieve a modulation. Various aspects are related to an “electrical modulation”, which may describe a modulation carried out at the electrical level, e.g. controlling (modulating) the electrical signals (e.g., a current, a voltage, a power) used to drive a light source. Various aspects are related to an “optical modulation”, which may describe a modulation carried out at the optical level, e.g. controlling one or more properties of a light signal by using one or more optical components.
The term “binary-coded modulation” may be used herein to describe a modulation including the encoding of binary symbols (e.g., a logic “0” and a logic “1”) onto a light signal, e.g. onto a light pulse. A “binary-coded modulation” may be carried out as an optical modulation, by modulating the light itself, and/or as an electrical modulation, by modulating an electrical quantity (e.g., a voltage, or a current) that then is used to generate the light (e.g., by means of a laser diode), as described in further detail below.
According to various aspects, the modulation of an emitted light signal (e.g., an adjustment of the amplitude, for example a modulation of laser power) may also properly illuminate the scene to be analyzed (illustratively, the field of view of the LIDAR module). The modulation of the emitted light may ensure that the scene is sufficiently lit, without over-illuminating the scene, an aspect that may be critical, for example, in the context of high-reflectivity objects and the resulting crosstalk between measurements. Avoiding over-illumination may allow preventing a saturation of the receiver of the LIDAR module (e.g., of some of the receiver elements, for example of one or more detector pixels). The saturation could otherwise deteriorate amplitude resolution and, in some cases, receiver dynamics, as it may take some time for a saturated receiver element to return to a normal operating mode. In various aspects, an angle-dependent modulation of the emitted light (e.g., an angle-dependent intensity modulation) may be provided, for example in the case that the LIDAR module includes multiple light sources illuminating different parts of the scene and/or in the case that the LIDAR module includes a scanning system for sequentially illuminating different parts of the scene. The angle-dependent modulation may provide a fine adjustment in the illumination of the scene. An improved illumination of the field of view may thus be provided in the case that the LIDAR module is configured as a FLASH LIDAR module and in the case that the LIDAR module is configured as a scanning LIDAR module.
According to various aspects, the modulation of an emitted light signal may enable communication capabilities in a LIDAR module, e.g. the LIDAR system may be configured to communicate via amplitude modulation. A modulated signal may be used, for example, to convey information. In communication technology such signal may be referred to as a baseband signal. As an example, a modulated signal may include a sequence of symbols over time. Information may be conveyed by choosing a symbol (e.g., from a predefined set of symbols) corresponding to some quantity of data, e.g. a certain number of bits. Generating (or transmitting) a certain number of symbols (each corresponding to a certain number of bits) in a certain amount of time, may be understood as generating (or transmitting) a certain amount of data per time, also referred to as data rate. In various aspects, in the communication scheme provided in the LIDAR module described herein, a symbol (e.g., from a predefined set of symbols) may correspond to a LIDAR pulse (e.g., from a set of possible pulse shapes). An alternative approach for data communication in a vehicle may include a separate system, e.g. a dedicated LiFi or radio communication system, for transmitting data instead of utilizing the LIDAR module. The approach described herein may provide a more compact or a less expensive solution for providing data communication functionalities in a vehicle (e.g., in an autonomous or partially autonomous car).
According to various aspects, the possibility of adjusting the amplitude of the LIDAR signal over time may also include creating pulse sequences (e.g., a sequence comprising one or more light pulses, for example with a time period of inactivity in between the pulses). A pulse sequence may be configured to create a unique pattern that allows LIDAR signals to be distinguished from one another. Illustratively, a pulse sequence may be understood, in some aspects, as a unique signature associated with a LIDAR signal, so that different LIDAR signals including different pulse sequences may be distinguished from one another. For example, a LIDAR signal may be distinguished from the LIDAR signals emitted by other LIDAR systems in close vicinity. As another example, LIDAR signals originating from several LIDAR sensors mounted on a same vehicle (e.g., on the same car) may be distinguished from one another for concurrent operation. As a further example, a signal emitted by a vehicle's own LIDAR sensor may be distinguished from the signal emitted by another LIDAR sensor (e.g., of another vehicle), thus providing alien crosstalk detection and mitigation. A unique pattern may be applied, additionally or alternatively, to individual components, individual sub-components, or even individual pixels of the same LIDAR sensor. The unique patterns of individual components, sub-components, or pixels may allow concurrent operation in case the field of view (and/or field of emission) of the components, sub-components, or pixels have a partial or full overlap. The unique patterns may also allow refining of the detection result of the individual components, sub-components, or pixels.
In the context of LIDAR applications, in particular for use in the automotive field, the aspects of linearity, dynamics, and energy efficiency may play an important role in ensuring a reliable and cost-effective operation of a LIDAR module.
According to various aspects, high linearity between the control signal (illustratively, the set value for the amplitude) and the generated amplitude of the emitted light signal (e.g., of a laser pulse) may be provided. The high linearity may ensure low bit error-rates, in the case of amplitude modulation for communication purposes, and/or control-loop stability. Illustratively, a control loop with non-linear elements may be more difficult to stabilize, for example due to the tendency of such control loops to oscillate and/or to become unstable more easily. High linearity may be typically achieved with sophisticated circuitry and/or calibration, both associated with high cost, thus making such systems expensive (the higher the linearity requirements the more expensive the system). The modulation strategy described herein may provide a cost-effective solution for providing high linearity between a control signal and an emitted light signal of a LIDAR system. High linearity may be understood as the control signal and the emitted light signal having a substantially (e.g., exactly) linear relationship with one another.
According to various aspects, high dynamics of the power stage may be provided, which may enable communication with high data rates, and may provide little amplitude error (e.g., between the set value for the amplitude, e.g. from the amplitude control, and the amplitude of the emitted light). High dynamics of the power stage may allow for short settling times when going from a high amplitude to a low amplitude and vice versa. High dynamics may be understood as the circuit being configured to provide a pulse with a very high amplitude followed by a pulse with a very low amplitude, and vice versa.
According to various aspects, the LIDAR module described herein may provide high energy efficiency (while providing high linearity and high dynamic performance), which may be an important aspect in the context of automotive, in which heating induced by (excessive) power losses may be problematic for the overall performance of a vehicle. In conventional RF circuitry (e.g., RF power amplifier circuitry), as an example, high linearity and high dynamic performance may be achieved by operating transistors in linear mode, using high bias currents/voltages and low amplitudes compared to the quiescent current. This configuration may include arranging multiple power stages, all contributing to poor energy efficiency, expensive circuitry coming with efforts and cost for cooling concepts for heat sinking, and large size unsuited for miniaturization of the overall power stage (and hence of the overall LIDAR system). The modulation strategy described herein may enable emission of a modulated light signal in an energy-efficient manner. The LIDAR system described herein may include, in some aspects, an energy-efficient transmitter with high linearity and high dynamic range. The configuration of the LIDAR system described herein may provide, in some aspects, emitting very fast light pulses, e.g. with a pulse width in the nanosecond range or in the picosecond range.
Robust communication may be an important aspect in applications where a system transmitting light (e.g., laser light) is used for data communication (regardless of whether the light in addition to the data communication is used for ranging). Robust communication may be understood, for example, as low bit-error-rates (BER). Assuming a given communication channel, e.g. the foggy air between two vehicles that want to communicate with each other using the respective LIDAR modules, low bit-error-rates may be achieved by using appropriate transmitters, receivers and coding schemes. The strategy described herein may help addressing some or all of these aspects, while particularly taking into account the aspect of energy efficiency.
According to various aspects, a LIDAR system may include: a light emitting device configured to emit a light signal in accordance with (e.g., as a function of) a combination of a plurality of partial signals; and one or more processors configured to: encode a sequence of symbols, wherein each symbol is associated with a respective combination of the plurality of partial signals, and control the light emitting device to combine the plurality of partial signals in accordance with the encoded sequence of symbols to emit the light signal. The LIDAR module may illustratively be adapted for emitting a sequence of modulated light pulses. The LIDAR module may be configured as a pulsed LIDAR module with dynamically adjustable amplitude, in which the dynamic adjustment of an emitted light signal may be implemented optically and/or electrically. In various aspects, a binary-coded communication scheme may be provided (e.g., a binary power modulation system and a corresponding operating scheme may be implemented in the LIDAR module), e.g. a value-discrete communication scheme utilizing amplitude shift keying. The LIDAR module may be configured to implement coding with built-in redundancy.
According to various aspects, a LIDAR system may include: a light emitting device configured to emit a light signal in accordance with a combination of a plurality of partial light signals; and one or more processors configured to: encode a sequence of symbols, each symbol associated with a respective combination of the plurality of partial light signals, and control the light emitting device to optically combine the plurality of partial light signals in accordance with the encoded sequence of symbols to emit the light signal (illustratively, to optically combine the plurality of partial light signals in accordance with the encoded sequence of symbols to be encoded in the emitted light signal).
According to various aspects, a method of emitting light in a LIDAR system may be provided, the method including: encoding a sequence of symbols, each symbol associated with a respective combination of a plurality of partial signals; and controlling the combination of the plurality of partial signals in accordance with the encoded sequence of symbols to emit the light signal (illustratively, controlling the combination of the plurality of partial light signals in accordance with the encoded sequence of symbols to be encoded in the emitted light signal).
In the context of the present description, reference may be made to implementations for automotive applications (e.g., in case the LIDAR module is installed or to be installed in a vehicle). The approach described herein may provide implementing advanced functionalities of a LIDAR module for use in an at least partially autonomous vehicle. It is however understood that the applications of a LIDAR module are not limited to the automotive context, and a LIDAR module may be applied in other applications and markets such as professional, industrial, consumer, etc.
The term “processor” as used herein may be understood as any kind of technological entity that allows handling of data. The data may be handled according to one or more specific functions executed by the processor. Further, a processor as used herein may be understood as any kind of circuit, e.g., any kind of analog or digital circuit. A processor may thus be or include an analog circuit, digital circuit, mixed-signal circuit, logic circuit, processor, microprocessor, Central Processing Unit (CPU), Graphics Processing Unit (GPU), Digital Signal Processor (DSP), Field Programmable Gate Array (FPGA), integrated circuit, Application Specific Integrated Circuit (ASIC), etc., or any combination thereof. Any other kind of implementation of the respective functions, which will be described below in further detail, may also be understood as a processor or logic circuit. It is understood that any two (or more) of the processors or logic circuits detailed herein may be realized as a single entity with equivalent functionality or the like, and conversely that any single processor or logic circuit detailed herein may be realized as two (or more) separate entities with equivalent functionality or the like.
Unless explicitly specified, the term “transmit” encompasses both direct and indirect transmission (e.g., via one or more intermediary points). Similarly, the term “receive” encompasses both direct and indirect reception. Furthermore, the terms “transmit,” “receive,” “communicate,” and other similar terms encompass both physical transmission (e.g., the transmission of radio signals) and logical transmission (e.g., the transmission of digital data over a logical software-level connection). The term “calculate” as used herein encompasses both ‘direct’ calculation via a mathematical expression/formula/relationship and ‘indirect’ calculation via lookup or hash tables and other array indexing or searching operations.
As used herein, “memory” or “memory device” is understood as a computer-readable medium (e.g., a non-transitory computer-readable medium) in which data or information can be stored for retrieval. References to “memory” or “memory device” included herein may thus be understood as referring to volatile or non-volatile memory, including random access memory (RAM), read-only memory (ROM), flash memory, solid-state storage, magnetic tape, hard disk drive, optical drive, 3D XPoint™, among others, or any combination thereof. Registers, shift registers, processor registers, data buffers, among others, may also be embraced herein by the term “memory” or “memory device”. The term “software” refers to any type of executable instruction, including firmware.
In the figures, a notation to indicate various components of a light emitting device is provided, in which components associated with different partial signals (different branches of the light emitting device) are denoted by a corresponding letter associated with the component and a corresponding number associated with the respective branch. Illustratively, the notation X1 may be used to denote the component “X” of the first branch (BR1), the notation X2 may be used to denote the component “X” of the second branch (BR2), etc. As an example, the notation C1 may be used to denote a capacitor of the first branch, the notation D1 may be used to denote a diode of the first branch, the notation B1 may be used to denote a control signal provided at the first branch, etc. Other components with the corresponding notation will be described in further detail below. In the case that a branch includes more than one component of the same type (e.g., more than one capacitor, more than one diode, etc.), the notation may be expanded with a further number denoting the component, e.g. the notation X11 may used to denote the first component “X” of the first branch (BR1), the notation X12 may used to denote the second component “X” of the first branch (BR1), etc.
In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles disclosed herein. In the following description, various aspects disclosed herein are described with reference to the following drawings, in which:
The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and implementations in which the aspects disclosed herein may be practiced. These aspects are described in sufficient detail to enable those skilled in the art to practice the disclosed implementations. Other aspects may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the disclosed implementations. The various aspects are not necessarily mutually exclusive, as some aspects may be combined with one or more other aspects to form new aspects. Various aspects are described in connection with methods and various aspects are described in connection with devices (e.g., a LIDAR module, one or more processors, a light emitting device, etc.). However, it is understood that aspects described in connection with methods may similarly apply to the devices, and vice versa.
The emission of laser pulses in the light emitting devices 100a, 100b, 100c may be based on repeatedly discharging one or more capacitors 108 into one or more laser diodes 106. The amplitude of an emitted laser pulse may be varied by modifying the set-value of the voltage up to which the pulse capacitor(s) 108 is/are charged (illustratively, the voltage up to which the capacitor(s) may be charged after the discharge for generating the previous laser pulse). In addition, during the discharge phase, the current flowing from the capacitor 108 through the laser diode 106 may be limited to a certain amplitude or modulated according to a set value.
The light emitting devices 100a, 100b, 100c in
In the configuration
The light emitting device 100a, 100b may include a charging circuit 112 configured to control the charging of the capacitor 108. In the configuration in
In the configuration in
As an additional or alternative approach with respect to varying and/or modulating the charging voltage and a resistance in series with a laser diode, the capacity of the discharge capacitor 108 may be varied and/or modulated to modulate the pulse shape. A possibility, shown in the light emitting device 100c in
The transistors 118-1, 118-2, 118-3 and the capacitors 108-1, 108-2, 108-3 may form a plurality of transistor-capacitor pairs connected in parallel with one another, and controllable to individually provide electric power to the laser diode 106. Each capacitor 108-1, 108-2, 108-3 may have an associated charging circuit (e.g., first to third charging circuits 112-1, 112-2, 112-3 in the configuration in
The control of a transistor 118-1, 118-2, 118-3 by the control circuit 110 may include a modulation of the respective gate-source voltage to create a current to the laser diode current 106 to provide the desired laser pulse shape, e.g. to create a current provided by the controlled sum of the drain currents of the transistors 118-1, 118-2, 118-3. As an example, each of the transistors 118-1, 118-2, 118-3 may carry a same fraction of the current to be provided to the laser diode 106 (e.g., a transistor may be used as a controllable resistor). As another example, each of the transistors 118-1, 118-2, 118-3 may be used as a switch to turn fully ON or fully OFF the contribution of respective capacitor to the current provided at the laser diode 106.
Various aspects may be related to a more advanced strategy with respect to the approach described in relation to
The LIDAR module 200 may include a light emitting device 202 configured to emit light 204, e.g. a light signal 204. The light emitting device 202 may be configured to emit the light signal 204 in accordance with (e.g., as a function of) a combination of a plurality of partial signals (e.g., partial electrical signals and/or partial light signals, as described in further detail below). Illustratively, the light emitting device 202 may include one or more electrical components configured to provide respective electrical signals and/or one or more optical components configured to provide respective light signals (in other words, respective optical signals) that may be combined with one another to provide the emitted light signal 204.
The light signal 204 may have a predefined wavelength, for example in the visible range (e.g., in the range from about 380 nm to about 700 nm), infra-red and/or near infra-red range (e.g., in the range from about 700 nm to about 5000 nm, for example in the range from about 860 nm to about 1600 nm, or for example at 905 nm or 1550 nm), or ultraviolet range (e.g., in the range from about 100 nm to about 400 nm).
In various aspects, the light emitting device 202 may include a light source 210 configured to emit light. In some aspects, an adaptation of the signal level of the emitted light signal 204 may include an adaptation of the light source 210, as described in further detail below. The light source 210 may include any suitable type of light source to provide light at a desired signal level and in a desired wavelength range. As an example, the light source 210 may include one or more light emitting diodes. As another example, the light source 210 may include one or more laser diodes (e.g., one or more edge emitting laser diodes, or one or more vertical cavity surface emitting laser diodes). The light source 210 may be configured as an array, or a stack, of light sources (e.g., a one- or two-dimensional array of light emitting diodes or laser diodes, or a stack of laser diodes).
In various aspects, the light emitting device 202 may include a driving circuit 212 configured to drive the light source 210. In some aspects, an adaptation of the signal level of the emitted light signal 204 may include an adaptation of the driving circuit 212, as described in further detail below. The driving circuit 212 may be configured to provide an electrical signal (e.g., a current, a voltage, or a power) to the light source 210 to drive the emission of light (e.g., the light source 210 may be configured to emit light in response to an electrical signal received from the driving circuit 212). In various aspects, the driving circuit 212 may include a plurality of driving circuits, each being configured to provide a respective electrical signal to the light source 210. In this configuration, different driving circuits may be assigned to different functions. As an example, at least one driving circuit may be assigned to provide the respective electrical signal for a ranging operation associated with the emitted light signal 204 (illustratively, for inducing the emission of light used for investigating the scene, e.g. the field of view of the LIDAR module 200). A ranging operation may include determining (e.g., measuring or calculating) the time-of-flight of the emitted light signal 204 (e.g., of at least one light pulse of the emitted light signal 204). As another example, at least one driving circuit may be assigned to provide the respective electrical signal for data transmission associated with the emitted light signal 204 (e.g., for encoding the sequence of symbols 208 in the emitted light signal 204).
The LIDAR module 200 may include one or more processors 206 (e.g., as part of a control circuit) configured to provide an instruction to the light emitting device 202 for controlling the emission of the light signal 204 (illustratively, to control the combination of the partial signals). The one or more processors 206 may be configured to encode a sequence of symbols 208, e.g. the one or more processors 206 may be configured to determine (e.g., generate, calculate) an instruction for controlling the light emitting device 202 as a function of the sequence of symbols 208. In various aspects, encoding the sequence of symbols may include generating a digital signal representing the sequence of symbols 208 in a way that may be provided as an instruction to the light emitting device 202. For example, the one or more processors 206 may include a microprocessor, a microcontroller, a discrete logic gate, a programmable logic, a field-programmable gate array (FPGA), and/or an application-specific integrated circuit (ASIC). In various aspects, the one or more processors 206 may be part of the light emitting device 202.
In various aspects, a symbol of the sequence of symbols may be representative of data or of a portion of data that may be transmitted via the emitted light signal 204. A symbol may be understood as an input to the communication channel, e.g. as a certain (modulated) light intensity input to the optical communication channel defined by the LIDAR module 200.
The sequence of symbols 208 may be configured to carry data to be transmitted. Illustratively, the sequence of symbols 208 may encode data to be transmitted optically via the emitted light signal 204. The data may include, for example, information to identify the LIDAR module 200 (e.g., information uniquely associated with the LIDAR module 200). As another example, additionally or alternatively, the data may include information to characterize the emitted light signal 204 (e.g., to distinguish a received light signal that was caused by the system's own emitted light signal 204, from other light signals, so-called alien signals, that were caused by other LIDAR modules). In various aspects, at least a portion of the sequence of symbols 208 may be uniquely associated with the LIDAR module 200, e.g. at least a portion of the sequence of symbols 208 may represent data uniquely identifying the LIDAR module 200 (e.g., a serial number of the LIDAR module 200). Additionally or alternatively, at least a portion of the sequence of symbols 208 may be uniquely associated with the light emitting device 202, e.g. at least a portion of the sequence of symbols 208 may represent data uniquely identifying the light emitting device 202 (e.g., an identifier of the light emitting device 202, for example the combination of an identifier and a serial number). It is understood that a portion of the sequence of symbols 208 may be also uniquely associated with other components of the LIDAR module 200 (e.g., a detector, a control circuit, etc.).
At least one symbol (e.g., each symbol) of the sequence of symbols 208 may be associated with a respective combination of the plurality of partial signals. Illustratively, at least one (e.g., each) symbol may be represented by a respective combination of the plurality of partial signals (e.g., by a respective light signal emitted according to that combination). A light signal 204 (or a portion of the light signal 204, e.g. a light pulse) emitted in accordance with the combination of the plurality of partial signals associated with a symbol may represent that symbol (e.g., may be decoded, at a receiver side, to extract the transmitted symbol from the light signal 204).
The one or more processors 206 may be configured to control the light emitting device 202 to combine the plurality of partial signals in accordance with (e.g., as a function of) the encoded sequence of symbols 208 to emit the light signal 204. The one or more processors 202 may be configured to generate an instruction to control the light emitting device 202, and the instruction may represent how to combine the partial signals (e.g., which partial signals, at which time point, for how long, etc.) to emit the light signal 204 in a way that the emitted light signal 204 represents the sequence of symbols 208.
In the following, different approaches for emitting the light signal 204 are described, which may be characterized as “electrical approach” and “optical approach”. The LIDAR module 200 (e.g., the light emitting device 202) may be configured according to the “electrical approach”, or according to the “optical approach”, or according to a combination of the “electrical approach”, and the “optical approach”. Illustratively, in some aspects, the plurality of partial signals may include a plurality of partial light signals, and the combination of the plurality of partial signals may include an optical combination of the plurality of partial light signals (see
Within the context of the electrical approach and the optical approach, two implementations will be described, which may be characterized as “additive combination” and as “subtractive combination”. Illustratively, the combination of the plurality of partial signals may include an additive combination of the plurality of partial signals and/or a subtractive combination of the plurality of partial signals. As described above, the various implementations may be combined with one another, e.g. the light emitting device 202 may be configured to provide an additive combination of partial electrical signals, and/or a subtractive combination of partial electrical signals, and/or an additive combination of partial light signal, and/or a subtractive combination of partial light signals, as described in further detail below.
Controlling the combination of partial signals to emit the light signal 204 may provide modulating the light signal 204, e.g. for encoding therein the sequence of symbols 208. According to various aspects, the emitted light signal 204 may include one or more light pulses (e.g., one or more laser pulses). The one or more light pulses may represent the encoded sequence 208, e.g. each light pulse may be associated with (e.g., may be representative of) respective one or more symbols of the sequence of symbols 208.
Various possibilities may be provided for encoding the sequence of symbols 208 into one or more light pulses of the emitted light signal 204. As an example, at least one (e.g., each) light pulse may be associated with a respective one symbol of the sequence of symbols 208, e.g. there may be a one-to-one correspondence between the light pulses and the symbols. As another example, at least one (e.g., each) light pulse may be associated with a respective plurality of symbols of the sequence of symbols 208, e.g. there may be a one-to-many correspondence between the light pulses and the symbols. As a further example, a subset of the plurality of light pulses may be associated with a respective one symbol of the sequence of symbols 208, e.g. there may be a many-to-one correspondence between the light pulses and the symbols. A symbol may thus be represented by a single light pulse, by a portion of a light pulse, or by a (sub-)plurality of light pulses of the emitted light signal 204.
The control over the combination of partial signals may provide generating light pulses with adjustable properties, e.g. adjustable amplitude and/or adjustable pulse shape and/or adjustable timing between the pulses.
The light signal 302a, 302b may include one or more light pulses 308a, 308b, e.g. n light pulses 308a, 308b (for example, a sequence of light pulses). In the exemplary configuration in
A light pulse 308a, 308b may have an amplitude (also referred to as pulse height). The amplitude may be or may represent a maximum value of a signal level associated with the light pulse. In other words, the amplitude may be or may represent the magnitude of a signal level associated with the light pulse. Illustratively, the amplitude may be or may represent a signal level associated with the light pulse evaluated with respect to a reference signal level, e.g. a base signal level, for example 0. The amplitude may also be referred to as peak amplitude. Each light pulse 302a, 302b, may have one or more signal levels (e.g., one or more amplitude levels) associated therewith, as a function of the pulse shape, as described in further detail below.
The shape of a light pulse 308a, 308b may be adjusted by controlling the combination of partial signals to emit the light signal 300a, 300b. In various aspects, as shown in
In the case that a light pulse 300b includes a plurality of pulse portions, each pulse portion may have a respective signal level, e.g. a respective amplitude. In the exemplary configuration in
The signal level of a light pulse 308a, 308b may be selected as a function of the one or more symbols associated with that light pulse 308a, 308b, e.g. the amplitude itself may be used to convey information. Illustratively, the signal level of a light pulse 308a, 308b may be defined by the one or more symbols associated with the light pulse 308b. In the case that a light pulse 308b includes a plurality of pulse portions, the individual signal levels of the plurality of pulse portions may be selected as a function of the symbols that the light pulse 308 represents, e.g. the signal levels of the plurality of pulse portions may be defined by the one or more symbols associated with the light pulse 308b. As an example, a first light pulse (e.g., the light pulse 308a-1) associated with one or more first symbols may have a first signal level, and a second light pulse (e.g., the light pulse 308a-2) associated with one or more second symbols may have a second signal level, and the first signal level may be different from the second signal level.
Additionally or alternatively, the shape of a light pulse 308a, 308b may be selected as a function of the one or more symbols associated with that light pulse 308a, 308b, e.g. the shape may be used to convey information (e.g., the shape of a light pulse 308a, 308b may be associated with the one or more symbols associated with the light pulse 308a, 308b). Illustratively, the shape of a light pulse 308a, 308b may be defined by the one or more symbols associated with the light pulse 308a, 308b. In the case that a light pulse 308b includes a plurality of pulse portions, the plurality of pulse portions may define the shape of the light pulse. As an example, a light pulse 308a, 308b (or a pulse portion) may have as pulse shape one of a rectangular pulse shape, a quasi-rectangular pulse shape, or a Gaussian pulse shape. In the following, for sake of simplicity, reference may be made to quasi-rectangular pulse sections. It is however understood that the aspects described herein, e.g. the electrical approach and optical approach described below, may apply to any suitable pulse shape (see also
A light pulse 308a, 308b may have a pulse width Tp (also referred to as pulse length or duration). The pulse width Tp may be, in some aspects, determined as so called full width at half maximum (FWHM) of a pulse. In the case that a light pulse 300b includes a plurality of pulse portions, the total pulse duration Tp may be calculated from the durations of the sub-pulses. A sub-pulse i may have a duration Tp,i, and a “gap” between sub-pulses may be considered itself as a sub-pulse (as long as the “gap” logically belongs to the same pulse, e.g. as the pulse portion 310-2 in
As a numerical example, at least one (e.g., each) light pulse 308a, 308b of a light signal 302a, 302b may have a (total) duration in the range from 1 ps to 1 ms, for example in the range from 10 ps to 10 μs, for example in the range from 100 ps to 100 ns, for example in the range from 200 ps to 25 ns. In the exemplary configuration in
A distance between consecutive light pulses 308a, 308b in a light signal 302a, 302b may be adjusted depending on a desired data rate and/or depending on the capabilities of a light emitting device (e.g., of the light emitting device 202). As a numerical example, a repetition time TR (a centre-to-centre distance between consecutive light pulses 308a, 308b) may be in the range from 100 ns to 2 μs (microseconds), for example in the range from 500 ns to 1.5 μs (e.g., 1.1 μs in the exemplary configuration in
A light signal 302a, 302b may have a total duration TT defined by the individual durations of the light pulses 302a, 302b, and the durations of the repetition time(s). As a numerical example, a light signal 302a, 302b may have a total duration in the range from 1 ps to 100 ms, for example in the range from 10 ps to 1 ms, for example in the range from 100 ps to 10 ps, for example in the range from 200 ps to 2.5 μs. In the exemplary configuration in
The time durations relevant in LIDAR applications may be on different orders of magnitude. Various aspects may be based on the realization that such differences may be relevant for circuits and the used technology in general. The optimal pulse duration Tp for a certain use case or application may depend on several factors, e.g. including the available technologies, the required precision, the allowed cost, energy consumption, and system complexity. For applications and technologies relevant for a LIDAR module (e.g., for the LIDAR module 200), even considering technological improvements over the next two decades, a pulse duration of 3 ps (picoseconds) to 800 μs (microseconds) may be in a relevant range, for example in the range from 300 ps to 8 μs, for example in the range from 10 ns to 500 ns.
In this regard,
The second light pulse 308e-2 may have a first portion and a second portion having different shape characteristics, e.g. may have a sinusoidal first portion and an exponential second portion. The third light pulse 308e-3 may have a linear first portion and a sinusoidal second portion. The fourth light pulse 308e-4 may be an exponential pulse, e.g. may have an exponential first portion and an exponential second portion. It is understood that the combination of shape characteristics in
According to various aspects, the encoding of a sequence of symbols and the emission of a light signal (e.g., the encoding of the sequence of symbols 208 and the emission of the light signal 204) may be based on a so-called “binary light amplitude modulation” (or, more in general, binary modulation of a signal level of the emitted light signal). The combination of the plurality of partial signals may be controlled to provide a desired signal level (e.g., a desired amplitude) of the emitted light signal over time (e.g., in different light pulses, see
Which partial signals are combined and in what manner may define the modulation of the emitted light signal and may represent the encoded sequence of symbols. As an example, the combination of the plurality of partial signals associated with a symbol may include a combination of a subset of the plurality of partial signals (e.g., only some of the available partial signals may be combined to emit a light signal, or a portion of light signal, representing that symbol). As another example, the combination of the plurality of partial signals associated with a symbol may include a combination of all the partial signals of the plurality of partial signals (e.g., all the available partial signals may be combined to emit a light signal, or a portion of light signal, representing that symbol).
Only as an example, Table 1 describes a variation of the amplitude of a LIDAR pulse between zero light (minimum amplitude) and full light (maximal amplitude) in 8 equidistant power steps. As a numerical example the peak laser power may be varied between 0 W and 10.5 W. Table 1 describes the different light levels (illustratively, the different optical power levels). Table 1 may describe the generation of light pulses (e.g., laser pulses) with 8 intensity levels (from the 0-th level to the 7-th level) controlling the combination of three partial signals B1, B2, B3.
As described above, different approaches may be provided to emit a light signal (e.g., the light signal 204) as a combination of a plurality of partial signals, e.g. an “optical approach” and an “electrical approach”, which will be described in the following.
The light emitting device 400 may include a plurality of partial light sources 402, e.g. first to third partial light sources 402-1, 402-2, 402-3 in the exemplary configuration in
The plurality of partial light sources 402 may include any suitable light source to provide a light signal having optical power in the desired power range. As an example, the plurality of partial light sources 402 may include at least one light emitting diode. As another example, the plurality of partial light sources 402 may include at least one laser diode. The plurality of partial light sources 402 may each include a same type of light source (e.g., each may be a light emitting diode, or a laser diode), or may include different types of light sources (e.g., one partial light source may include a light emitting diode, and another partial light source may include a laser diode, as an example). In the exemplary configuration in
In various aspects, each partial light source 402 may include a respective driving circuit 410 (e.g., first to third driving circuits 410-1, 410-2, 410-3, DE1, DE2, DE3, in
The configuration in
In various aspects, each partial light source 402 of the plurality of partial light sources 402 may be configured to emit the respective partial light signal 404 at a signal level (e.g., a respective amplitude, or optical power) different from the signal level of the other partial light signals 404 emitted by the other partial light sources 402. Illustratively, each partial light source 402 may be associated with a respective (e.g., unique) signal level, such that the combination of the partial light signals 404 (of some, or all the partial light signals 404) may provide the desired signal level over time of the emitted light signal 406. In the exemplary arrangement in
The respective signal levels associated with the different partial light sources 402 may be selected as a function of a desired range for the signal level of the emitted light signal 406 (e.g., taking into account eye safety regulations for example).
In various aspects, a factor of two may be provided for the luminous flux of the different partial light sources 404. Illustratively, at least one partial light source 402 of the plurality of partial light sources 402 (e.g., the second partial light source 402-2) may be configured to emit twice the luminous flux of at least one other partial light source 402 of the plurality of partial light sources 402 (e.g., the first partial light source 402-1). In relation to the configuration of
In various aspects, the control of the light emitting device 400 to combine the plurality of partial signals may include controlling which partial light sources 402 emit the respective partial light signal 404. The light emitting device 400 may include (or may be connected to) one or more processors 414 (e.g., configured as the one or more processors 206) configured to control a combination of the partial light signals 404 by controlling which partial light sources 402 emit the respective partial light signal 404. Illustratively, the desired signal level of the emitted light signal 406 may be controlled by selecting the partial light sources 402 whose outputs combined provide that signal level. In various aspects, the one or more processors 414 may be part of a control circuit (CTL).
The light emitting device 400 may include an emitter optics arrangement 408 configured to receive the partial light signals 404, and to combine together the partial light signals 404 to emit the light signal 406. The emitter optics arrangement 408 may include suitable optical components (e.g., one or more mirrors, one or more lenses, one or more beam combiners, etc.) configured to direct the received partial light signals 404 along a same direction (such that the received partial light signals 404 overlap to provide the light signal 406).
In an exemplary scenario, in case the combining optics (the emitter optics arrangement 408) forms a single beam (the light signal 406) out of the up to three laser sources (the diodes 412-1 to 412-3) with an electrical-to-optical efficiency of 75%, then the first laser diode may be configured to generate 2 W, the second laser diode may be configured to generate 4 W, and the third laser diode may be configured to generate 8 W of laser power (optical power). It may be assumed that the optical efficiency for the different “branches” is identical, e.g. it may be assumed that the optical efficiency may be 75% irrespective of the “branch” in which the light was generated. The optical efficiency may be determined by considering all the light losses after the light leaves the semiconductor through the primary and secondary optics up to point where the “final light pulse” is generated (e.g., directly in front of the LIDAR module including the light emitting device 400, e.g. the LIDAR module 200).
The additive optical approach considering the scenario above may be illustrated with exemplary values in Table 2.
The desired light level “Level” in Table 2 may be determined by the one or more processors 414 (e.g., by the control circuit (CTL)), for example depending on the scene, etc. The binary representation of the desired light level may be identical to the signals B1-B3 (which may be understood as respective control signals provided by the one or more processors 414 to the light sources 402) in case of a 3-bit representation of the light level. In accordance with the configuration shown in
According to various aspects, the one or more processors 414 may be configured to control the combination of the partial light signals 404 by providing a respective signal at the partial light sources 402 (e.g., at the respective driving circuit 410). The one or more processors 414 may be configured to generate a gating signal 416 (shown in
The light signals 422c, 422d shown in
It is understood that the light signals 422c, 422d are shown for illustrative purposes, and also light signals with different configurations (e.g., a different number of pulses, a different signal level, etc.) may be provided. The light signal 422c, 422d may include one or more light pulses 428c, 428d (e.g., first to sixth light pulses 428c-1, 428c-2, 428c-3, 428c-4, 428c-5, 428c-6 for the light signal 422c in
In addition to the generated light level shown in the graphs 420c, 420d,
As shown in
The waveforms of the gating signals 432c-1 to 432c-3, 432d-1 to 432d-3, Q1-Q3 may define whether the respecting branch is contributing to the overall light generation at any point in time. As in LIDAR applications the timing may be critical, the generation of these signals may play an important role.
With relation to Table 2, the individual gating signals 432c-1 to 432c-3, 432d-1 to 432d-3, Q1-Q3 may be generated from the signals B1-B3 by gating or masking with the gating signal Q. The gating signal Q may be generated by the one or more processors 414, e.g. by using a clock running at a frequency of 1/TR where TR is the repetition time as described above. Illustratively, the one or more processors 414 may be configured to generate the gating signal 416 by using a same clock signal as the clock signal determining the repetition rate of the light emitting device 400.
The clock may trigger a timer (mono-flop) with pulse train duration TT. The gating may be carried out inside the driver electronics as shown in
According to various aspects, as shown in
With the configuration in
In various aspects, the switches 434 may be configured to be fast-switching. As an example, as shown in
In the configuration of the light emitting device 400 described in relation to
A different approach, referred to as “subtractive optical approach” will be described with relation to
The subtractive optical approach may be illustrated with exemplary values in Table 3 (e.g., assuming the same power levels and efficiencies as described in relation to Table 2), e.g. for the exemplary scenario of the generation of 8 intensity levels using three branches and 75% efficiency.
The light emitting device 500 may include a light source 502 configured to emit light (e.g., a light signal, also referred to herein as “light beam”, or simply “beam”). The light source 502 may be configured as the light source 202 and/or as one of the (partial) light sources 402 described in in relation to
The light emitting device 500 may include a beam-splitting device 508 configured to split the light emitted by the light source 502 into a plurality of partial light signals 510. The beam-splitting device 508 may be configured to receive the light emitted by the light source 502 (e.g., by the laser diode 504), and to distribute the received light into a plurality of branches, each associated with a respective partial light signal 510.
In the configuration in
The light emitting device 500 may further include an optical arrangement 520 (also referred to herein as optics arrangement, OX1) configured to absorb or redirect one or more of the plurality of partial light signals 510. Illustratively, the optical arrangement 520 may be configured to provide the desired combination of partial light signals 510, by optically controlling which (and how many) partial light signals 510 contribute to the generation of a light signal 516 emitted by the light emitting device 500. The optical arrangement 520 may be configured to absorb or redirect one or more of the plurality of partial light signals 510 as a function of a sequence of symbols to be encoded in the emitted light signal 516 (e.g., as a function of the encoded sequence of symbols 208). In various aspects, the one or more processors 512 may be configured to control the optical arrangement 520 to control the combination of partial light signals 510, as described in further detail below.
The optical arrangement 520 may include one or more optical components to provide the optically “subtractive” function. In the exemplary configuration in
The primary optics 522 may be arranged optically upstream of the light absorbing device 524, and may be configured to collect the light emitted by the light source 502 (e.g., may be configured to collect the plurality of partial light signals 510 split by the beam splitting device 508). The primary optics 510 may be the first element of the optical arrangement 520 (the most optically upstream element with respect to the incoming light).
The secondary optics 526 may be arranged optically downstream of the light absorbing device 524 and may be configured to combine the partial light signals (not absorbed or redirected by the light absorbing device 524) to provide the emitted light signal 516.
The light absorbing device 524 may be a controllable light absorbing device configured to receive the plurality of partial light signals 510 (e.g., collected by the primary optics 522). The light absorbing device 524 may be configured to controllably absorb or redirect one or more of the partial light signals 510. Illustratively, in relation to the description of
By way of illustration, the operation of the optical arrangement 520 may be described as follows. The primary optics 522 may collect the light emitted by the light source 502. Thereafter, the light may be partially or completely absorbed or redirected by the light absorbing device 524 (also referred to herein as light absorbing element, LAE). The light absorbing device 524 may be realized, for example, by a liquid crystal device/element/matrix similar to a LCD (liquid crystal display), DMD (digital mirror device, also referred to as digital light processing device (DLP) device, or LCPG (liquid crystal polarized grating). A DMD and a LCPG may be configured (e.g., controlled) to redirect the received light (e.g., towards a light absorbing area). The light absorbing device 524 may be controlled by the one or more processors 512, e.g. via signal lines 518 (Q1, . . . , Qn). The remaining light then gets collected by the secondary optics 526 (SO) and finally directed and formed creating the beam 516 leaving the light emitting device 500 (e.g., leaving the LIDAR module).
In the following, reference may be made in general to a light-absorbing area or light-absorbing segment of the light absorbing device 524. A light-absorbing area or light-absorbing segment may describe both a portion configured to directly absorb light (e.g., in the case that the light absorbing device 524 includes a liquid crystal device/element/matrix) and a portion configured to redirect light onto a light-absorbing area (e.g., in the case that the light absorbing device 524 includes a DLP or LCPG).
The light absorbing device 530b, 530c, 530d, 530e may include (e.g., may be divided into) a plurality of segments 532b, 532c, 532d, 532e. Each segment 532b, 532c, 532d, 532e may be configured, in a first state, to absorb or redirect light (e.g., a partial light signal 510) impinging onto that segment, and configured, in a second state, to transmit the light (e.g., the partial light signal 510) impinging onto that segment. Illustratively, a segment 532b, 532c, 532d, 532e may be understood as a switchable light-absorbing area, which may be controlled between an “absorbing state” and a “transparent state” to determine whether a partial light signal 510 contributes to the emission of the overall light signal 516. The light-absorbing areas may be associated with the plurality of branches along which the plurality of partial light signals 510 propagate.
The one or more processors 512 may be configured to control the plurality of segments 532b, 532c, 532d, 532e to be in the respective first state or second state as a function of the sequence of symbols to be encoded in the emitted light signal 516 (e.g., as a function of the encoded sequence 208). The one or more processors 512 may be configured to control the plurality of segments 532b, 532c, 532d, 532e to absorb, redirect, or let through the respective partial light signal 510 in accordance with the desired combination of partial light signal 510.
In various aspects, the one or more processors 512 may be configured to provide a gating signal (e.g., a plurality of gating signals Q1, . . . , Qn) to the light absorbing device 530b, 530c, 530d, 530e (e.g., one gating signal for each segment, or for each light-absorbing area), to control the switching of the plurality of segments 532b, 532c, 532d, 532e. Illustratively, the one or more processors may be configured to generate a gating signal representative of which segments 532b, 532c, 532d, 532e to switch in the first state and which segments 532b, 532c, 532d, 532e to switch in the second state, and may be configured to control the light absorbing device 530b, 530c, 530d, 530e by using the gating signal (e.g., provided via the signal lines 518).
The number and the configuration (e.g., the size) of the segments 532b, 532c, 532d, 532e may be adjusted depending on the light emitted by the light source 502. It is understood that the number and configuration of segments 532b, 532c, 532d, 532e shown in
In various aspects, the number of segments may be a function of the selected implementation for the light absorbing device 532b, 532c, 532d, 532e (e.g., a liquid crystal device/element/matrix, DMD, LCPG, etc.). Only as a numerical example, the plurality of segments 532b, 532c, 532d, 532e may include a number of segments in the range from 2 to 20, for example in the range from 4 to 16. It is understood that the plurality of segments 532b, 532c, 532d, 532e may include any suitable number of segments, e.g. also more than 50, or more than 100, or more than 1000 segments depending on the implementation.
In the case that the rectangular shaped light beam has a homogeneous intensity distribution (illustratively, constant intensity over the entire rectangular beam), a light absorbing device 530b with a regular distribution of segments may be provided. For example, as shown in
The “binary concept” may be provided by selecting a length of the rectangular segments 532b (e.g., a first length L1 of the first segment 532b-1 A1, a second segment L2 of the second segment 532b-2 A2, a third length L3 of the third segment 532b-3 A3, and a fourth length L4 of the fourth segment 532b-4 A4, assuming a same width W (a same height) for each segment) as follows,
The length L2 of a second segment 532b-2 may be twice the length Li of a first segment 532b-1. The length L3 of a third segment 532b-3 may be twice the length L2 of the second segment 532b-2. The length L4 of a fourth segment 532b-4 may be twice the length L3 of the third segment 532b-3, etc. Stated in a different fashion, in some aspects, different segments 532b may have a different surface area (e.g., varying by a factor of 2). A first segment 532b-1 may have a first surface area, a second segment 532b-2 may have a second surface area, a third segment 532b-3 may have a third surface area, etc. The second surface area may be greater than the first surface area, the third surface area may be greater than the second surface area, etc. As an example, the second surface area may be at least two times greater (e.g., exactly two times greater) than the first surface area, the third surface area may be at least two times greater (e.g., exactly two times greater) than the second surface area, etc.
As an exemplary scenario, the subtractive approach may be described for the case that the light absorbing device 530b includes an LCD. The one or more processors 508 (e.g., the control circuit) may control the 4 intensity bits (to provide 16 levels). The intensity bits B1-B4 may be assigned to the respective areas 532b-1, 532b-2, 532b-3, 532b-4 (A1-A4). Turning a bit B1-B4 “on” (e.g., having a logic value of “1” for the bit) may include turning “on” the corresponding control line Q1-Q4 (e.g., a corresponding line of the control lines 518) and thereby have the respective area A1-A4 “turned on” for the respective pulse duration Tp. During this pulse time, respective areas (the “turned on” areas) of the LCD may be transparent to light. At other time points (when “turned off”) the areas may absorb the incoming light.
In the case that the rectangular shaped light beam is not homogeneous (e.g., in case it has an inhomogeneous intensity distribution), the distribution of the rectangular segments 532c may be adapted accordingly, as shown in
In the configurations in
In case of a circular shaped light beam with homogeneous intensity distribution (constant intensity over the entire beam) the light absorbing device 500d may be shaped as shown in
For a light absorbing device 530d with an outer radius R covering a dynamic range of n bits (illustratively, having n branches), the n radii Rk for each of the concentric segments may be chosen according to the following formula,
With the selection of the radii according to equation (2), the respectively defined areas A1, . . . , An, may provide the binary order A2=2× A1, A3=2× A2, . . . , An=2×A (n−1). Illustratively, as described in relation to
As described in relation to the rectangular arrangement in
For a light absorbing device 530e with an outer radius R covering a dynamic range of n bits (illustratively, having n branches), the 2n−1 radii Rk of the concentric segments may be chosen according to the following formula,
With the selection according to equation (3) a configuration as shown in
In various aspects, a light absorbing device may include a segment configured to be light-absorbing independently of its state, e.g. may include a light-absorbing area configured only to absorb light impinging thereon. This configuration is shown for example in
Other possible configurations of a light emitting device and light absorbing device (e.g., of the light emitting device 500 and light absorbing device 524) will be described in relation to
Often, cost-effective light absorbing elements may have poor temporal reactiveness, e.g. regarding the achievable switching speeds. This poor temporal reactiveness may be also referred to as poor dynamic performance. In various aspects, the gating may be carried out electrically via the gating signal 534 (Q) as shown in
In the case that the gating is realized electrically, the “no light” level, e.g. the state B1=B2=B3=0, may be dispensed with in controlling the light absorbing element 520, as it may be provided by the light source 502 directly, e.g. creating no light output may be achieved by keeping the gating signal 534 constantly at a level defining that state (e.g., constantly at zero).
The otherwise redundant state B1=B2=B3=0 may then be used to expand the dynamic range by one level at almost no cost. This approach is illustrated in Table 4 and
In various aspects, a light absorbing device 530g, 530h, 530i may include a segment 532g-0, 532h-0, 532i-0 configured to be light-transparent independent of its state, e.g. a light absorbing device may include as part of the arrangement a light-transparent area A0. Illustratively, the light absorbing devices 530g, 530h, 530i may be configured as the light absorbing devices 530c, 530d, 530e described in relation to
As an example, the area A0 may be realized by an area of a liquid crystal device being always turned on and having the same size as the area A1. Realizing A0 by the liquid crystal device and not by a “whole”, the inherent and small absorption of the liquid crystal device in areas where it is turned on also applies to the area A0. This may provide the advantage that manufacturing tolerances will not harm the binary nature of the proposed scheme.
The presence of the additional area A0 may increase the available resolution by one state. This may provide an improvement with respect the previously outlined approach (e.g., shown in
As shown in
For the light absorbing device 530h, the radii may be selected according to the following formula,
The transparent segment 532h-0 may have a radius R0, the first segment 532d-1 may have a first radius R1, the second segment 532d-2 may have a second radius R2, etc.
For the light absorbing device 530i, the radii may be selected according to the following formula,
The transparent segment 532i-0 may have a radius R0, the first segment 532i-1 may have a first radius R1, the second segment 532i-2 may have a second radius R2, etc.
Table 5 and Table 6 illustrate exemplary numerical values for the ratios Rk/R for n=3 and n=4, respectively, for option 1 (the light absorbing device 530d (no electrical gating), 530h (with electrical gating) shown in
In various aspects, the transparent segment 532g-0, 532h-0, 532i-0 (A0) may be addressable by the one or more processors 512 (e.g., by the control circuit), e.g. the one or more processors 512 may be configured to control the transparent segment 532g-0, 532h-0, 532i-0 to absorb light. This may provide improving the heat spreading inside the light absorbing device 530g, 530h, 530i. The energy of the absorbed light within the light absorbing device 530g, 530h, 530i may lead to heating of the light absorbing device.
As increased temperatures may shorten a component life proper thermal management is important, and may be even more critical for a light absorbing device with circular-shaped areas than for a light absorbing device with rectangular shaped areas.
In the configuration of the light emitting device 500 in
Whenever an uneven power level is set (illustratively, a power level that would turn off the area A1), the one or more processors 512 may be configured to flip A0 and A1 on a regular basis (e.g., system clock-based, or with the repetition frequency of a line of the entire image). Illustratively, the one or more processors 512 may be configured to alternatively turn on and off A0 and A1, so that one of the two areas is transparent whereas the other is absorbing.
An additional or alternative option, in some aspects, A0 may be only half of the size of A1. In combination with the addressing via B0, this may provide a setup having double the resolution. The improved resolution may be “traded” for a slightly worse thermal behavior.
Additionally or alternatively to the “optical approach” described in relation to
The light emitting device 600a, 600b, 600c may include a light source 602a, 602b, 602c configured to emit light (e.g., a light signal). The light source 602a, 602b, 602c may be configured as the light source 210 described in
The electrical approach may include an adaptation of a driving circuit used to drive the light source 602a, 602b, 602c.
The light emitting device 600a, 600b, 600c may include a (adapted) driving circuit 604a, 604b, 604c configured to drive the light source 602a, 602b, 602c, e.g. configured to provide an electrical signal to the light source 602a, 602b, 602c. A signal level of the emitted light signal may be dependent on a signal level of the electrical signal provided to the light source 602a, 602b, 602c. Illustratively, a modulation of the electrical signal used to drive the light source 602a, 602b, 602c may provide the desired modulation of the emitted light signal. The driving circuit 604a, 604b, 604c may be an example of driving circuit of a LIDAR module, e.g. of the driving circuit 212 of the LIDAR module 200.
The electrical signal may include a current signal (e.g., a current pulse), a voltage signal (e.g., a voltage pulse), or a power signal (e.g., a power pulse), depending on the configuration of the driving circuit 604a, 604b, 604c, as described in further detail below. A power signal or power pulse may be understood as an energy per unit time that is transferred to the light source 602a, 602b, 602c.
The light emitting device 600a, 600b, 600c may include one or more processors 606a, 606b, 606c configured to control the driving circuit 604a, 604b, 604c, e.g. to control the modulation of the electrical signal. The one or more processors 606a, 606b, 606c may be configured as the one or more processors 206 (and/or as the one or more processors 414, 512), e.g. may be an exemplary configuration of the one or more processors 206.
In various aspects, the driving circuit 604a, 604b, 604c may be configured such that the electrical signal is split into a plurality of partial electrical signals. The control of the light emitting device 600a, 600b, 600c to combine the plurality of partial signals may include the one or more processors 606a, 606b, 606c being configured to control the driving circuit 604a, 604b, 604c to combine the plurality of partial electrical signals. Illustratively, the one or more processors 606a, 606b, 606c may be configured to control which partial electrical signals contribute to the driving of the light source 602a, 602b, 602c to emit the light signal.
In various aspects, the driving circuit 604a, 604b, 604c may include an electrical energy source 608a, 608b, 608c configured to generate an electrical signal. As an example, the electrical energy source 608a, 608b, 608c may be or include a current source (
By way of illustration, in analogy to the optical approach of “subtractive optical binary power modulation”, a “subtractive electrical binary power modulation” may be provided, in which an electrical pulse source is generating a pulse which is attenuated electrically/electronically in a binary fashion before being applied to the light source (e.g., the laser diode).
There may be various possibilities for circuits and systems configured to consecutively split a pulse (e.g., current, voltage, power) into two pulses of identical magnitude. In the following, in relation to
Depending on the selected output level, the first pulse either contributes to the output signal or is ignored (e.g., short or open circuit or dissipated in a resistor). The second pulse may be split further into two pulses. The nested/consecutive splitting may be performed as many times as the number of bits (and the resolution) of the application require.
Illustratively, the splitting circuit 610a, 610b, 610c may be configured such that a first partial electrical signal and a second partial electrical signal are in a first relationship with one another, and such that the second partial electrical signal and a third partial electrical signal are in the first relationship with one another (and a fourth partial electrical signal and the third partial electrical signal are in the first relationship, etc.). As an example, the first relationship may include the first partial electrical signal having a first signal level (e.g., a first amplitude) two times smaller than a second signal level of the second partial electrical signal (and the second signal level being two times less than the third signal level, etc.). It is understood that other “splitting” (other relationships) may be provided, e.g. a one-third or a one-fourth relationship, as other examples.
There may be two ways of handling the “last” “second pulse” of this consecutive splitting action.
As a first option, the last second pulse may be handled identically to the “last” “first pulse” and therefore selectively (e.g., depending on signal status “B0”) contributing to the output or not. This configuration may enable turning off all contributions from all branches. With this configuration a pulse with zero magnitude at the output may be provided, e.g. by controlling the signal lines B0, . . . , Bn (in other words, the output may be turned off by commanding the signal lines B0, . . . , Bn).
As a second option, the last second pulse may be contributing to the output signal in any case. In this configuration, the “switching circuitry” in the path of the last second pulse may be dispensed with, thus reducing cost and complexity. This arrangement may include gating the pulse source to turn the pulse fully off (illustratively, to generate a pulse with zero amplitude), for example via “blanking” of the signal Q commanding the pulse generator to deliver a pulse.
For both the first option and the second option, the output pulse can be varied between zero and the full pulse in steps of 1/((2n)−1) of the full pulse. The magnitude of the full pulse may be assumed to be substantially equal to the magnitude of the initially generated pulse minus the unintentional losses of the circuitry.
As an exemplary implementation, in some aspects, the splitting circuit 610a, 610b may include one or more transformers 612a, 612b, as shown in
As another exemplary implementation, in some aspects, the splitting circuit 610c may include one or more power splitters 614c, as shown in
In various aspects, the splitting circuit 610a, 610b, 610c may include a plurality of switches 616a, 616b, 616c (S1, . . . , S4). The plurality of switches 616a, 616b, 616c may be configured to connect or disconnect a respective electrical path associated with one of the partial electrical signals. Illustratively, the plurality of switches 616a, 616b, 616c may be configured to allow or prevent a respective electrical signal from contributing to the generation of the electrical signal provided at the light source 602a, 602b, 602c.
The one or more processors 606a, 606b, 606c may be configured to control the combination of the plurality of partial electrical signals by controlling the plurality of switches 616a, 616b, 616c. The one or more processors 606a, 606b, 606c may be configured to control the plurality of switches 616a, 616b, 616c via a plurality of signal lines 628a, 628b, 628c (e.g., one signal line for each switch, illustratively one signal line for each “bit”).
In various aspects, the one or more processors 606a, 606b, 606c may be configured to generate a gating signal (Q) representative of which switches 606a, 606b, 606c are to be activated to connect the respective electrical path, and may be configured to control the plurality of switches 606a, 606b, 606c by using the gating signal. Illustratively, the splitting circuit 610a, 610b, 610c may provide along each electrical path a respective partial electrical signal having a respective signal level (e.g., with a factor of two between different partial electrical signals), and the controlling of the switches 616a, 616b, 616c may provide controlling which partial electrical signals contribute to driving the light source 602a, 602b, 602c to provide the desired modulation of an emitted light signal. The one or more processors 606a, 606b, 606c may be configured to provide the gating signal (Q) via a gating signal line 630a, 630b, 630c. In various aspects, the gating signal line 630a, 630b, 630c may also be used by the one or more processors 606a, 606b, 606c to provide a trigger signal (to the electrical energy source 608a, 608b, 608c), and may be understood also as a trigger signal line.
The exemplary configuration in
Triggered by the signal Q from the one or more processors 606a (the control CTL) the current source 608a (I1) may generate a pulse. An exemplary pulse waveform of such a pulse is shown in the graph 618a in
A first transformer 612a (TR2) with a winding ratio of 1:1 may split the incoming current into two currents of equal amplitude. In various aspects, the wires of the two windings may be wound around the body of the core together (a so-called bifilar-wound). This may provide a good coupling between the two windings of the first transformer 612a (TR1). The current in the upper winding may flow through a first diode 620a (D31) and then through the light source 602a (the laser diode D1 or a stack of laser diodes) and then back to the source 608a, unless the respective switch 616a (S3) is closed. In the case that the respective switch 616a (S3) is closed, then the current may flow through the switch 616a (S3) directly back to the source 608a. The first diode 620a (D31) may be reverse biased and may block any current potentially coming from the light source 602a, allowing other branches of the circuit to feed the light source 602a.
The current in the lower winding of the first transformer 612a (TR2) get split by a second transformer 612a (TR1) into two currents of equal amplitude flowing out of the upper and lower winding of the second transformer 612a (TR1). As the current out of the lower winding of the second transformer 612a (TR1), in this configuration, may be the “last second pulse” according to the above description the respective switch 616a (S1) may be dispensed with, as the “complete darkness” (no current through the light source 602a) may be realized by “blanking” of the signal Q (as described for the second option above).
In the case the switch 616a (S1) is present, it may swap its function with another switch 616a (S2) from time to time, e.g. as described in relation to the addressable A0 and the toggling of A0 and A1. This may provide a better thermal homogeneity of the circuitry.
The exemplary configuration in
The circuit 604b may be configured to generate pulses with 7 amplitude levels, and an additional (eighth) level may be zero (illustratively, no light output at all). The pulse magnitude may be selected with a step size of n=3 bits, leading to a total of 8 possible levels.
Triggered by the signal Q from the one or more processors 606b (the control CTL) the voltage source 608b (V1) may generate a pulse. A first transformer 612b (TR3), e.g. with a winding ratio of 2:1:1, may split the incoming voltage into two voltages of equal amplitude on its two secondary windings. In various aspects, four wires may be wound around the body of the core together, and then two of them may be serially connected forming the primary winding, and the two other windings may form the two secondary windings. This configuration may provide good coupling between the windings. The voltage of the upper secondary winding may be selected to be part of the voltage applied to the light source 602b (the laser diode D1) by the respective switch 616b (S4) connected to this winding. The voltage generated on the lower secondary winding may be feeding the primary winding of a second transformer 612b (TR2) for further splitting. The voltages of the selected secondary windings of all the transformers may add up to the voltage applied to the light source 602b.
A (e.g., reverse biased) diode 620b (D2) may be dispensed with (e.g., assuming ideal components). If present, the diode 620b (D2) may be configured to protect the light source 602b against reverse voltages that may be potentially generated by ringing effects.
As described in relation to the current splitting setup in
The exemplary configuration in
The circuit 604c may be configured to generate pulses with 7 amplitude levels, and an additional (eighth) level may be zero (illustratively, no light output at all). The pulse magnitude may be selected with a step size of n=3 bits, leading to a total of 8 possible levels.
Triggered by the signal Q from the one or more processors 606c (the control CTL) the power source 608c (P0) may generate a pulse. The power source 608c may also be referred to herein as pulse power source, or pulse power generator. The power source 608c (P0) may be configured to provide a pulse with a defined amount of energy, irrespective of the connected load. The pulse may be split by a first power splitter 614c (PS3). A power splitter may also be referred to as power divider.
The two pulses of equal magnitude may be fed to either the switch 616c (S3) associated with the first power splitter 614c (PS3), or to a second power splitter 614c (PS2). Based on the signal B3 provided to the switch 616c (S3) associated with the first power splitter 614c (PS3), the switch 616c (S3) either dumps the pulse into a first dummy load 622c (DL3) or feeds it into a respective (first) adjustable phase and adjustable attenuation circuit 624c (AA3).
An adjustable phase and adjustable attenuation circuit 624c may be configured to delay the pulse as well as to attenuate the pulse. As an exemplary implementation, an adjustable phase and adjustable attenuation circuit may include delay lines, power resistors, and impedance matching networks.
Both functionalities, e.g. manipulating amplitude and phase of the RF signal, may allow tuning of the circuit in such a way that each branch truly contributes the respective fraction of power to the overall pulse after the final output pulse has been created by the power combiners 626c (PC1 to PC3). The output pulse may be then fed to the light source 602c (the laser diode D1). In various aspects, an impedance matching network may be provided so that that ideally the entire power of the pulse may be absorbed by the light source 602c (and no power is reflected back towards the power source 608c).
An additional or alternative “electrical approach” based on an “additive” combination of a plurality of partial electrical signals will be described in relation to
The light emitting device 700a-700h may include a light source 702a, 702b, 702c, 702d, 702e, 702f, 702g, 702h (in the following, 702a-702h) configured to emit light (e.g., a light signal). The light source 702a-702h may be configured as the light source 210 described in
The additive electrical approach may include an adaptation of a driving circuit used to drive the light source 702a-702h.
The light emitting device 700a-700h may include a (adapted) driving circuit 704a, 704b, 704c, 704d, 704e, 704f, 704g, 704h (in the following, 704a-704h) configured to drive the light source 702a-702h, e.g. configured to provide an electrical signal to the light source 702a-702h. The driving circuit 704a-704h may be an example of driving circuit of a LIDAR module, e.g. of the driving circuit 212 of the LIDAR module 200.
In the configuration according to the additive electrical approach, the driving circuit 704a-704h may include a plurality of electrical energy sources 706a, 706b, 706c, 706d, 706e, 706f, 706g, 706h (e.g., a plurality of current sources, and/or a plurality of voltage sources, and/or a plurality of power sources, and/or a plurality of energy storage elements), in the following 706a-706h. Each electrical energy source 706a-706h may be configured to generate a respective partial electrical signal. Illustratively, the additive electrical approach may be based on controlling which (and how many) electrical energy source 706a-706h provides the respective electrical signal for driving the light source 702a-702h. In various aspects, the plurality of electrical energy sources 706a-706h may be connected in series with one another. In other aspects, the plurality of electrical energy sources 706a-706h may be connected in parallel with one another. In general, two basic approaches or circuitry types may be distinguished for additive electrical binary power modulation: series connection or parallel connection of sources contributing to the final electrical pulse. It is understood that also a combination of serially and parallel connected sources may be provided.
In various aspects, each electrical energy source 706a-706h may be configured to provide the respective partial electrical signal having a signal level different from the other partial electrical signals provided by the other electrical energy sources 706a-706h. Illustratively, the plurality of electrical energy sources 706a-706h may be configured in such a way that each electrical energy source generates an electrical signal having a specific signal level (e.g., a current value, a voltage value, an amplitude value). This configuration may allow providing a (combined) electrical signal having a desired signal level at the light source 702a-702h by selecting which electrical energy sources 706a-706h are active, thus enabling binary modulation (in a similar manner as described above for the optical approach in Table 2).
As described above for the optical approach and the subtractive electrical approach, a defined relationship between the signal levels associated with different electrical energy sources 706a-706h may be provided, so that a defined modulation may be imposed to the electrical signal provided at the light source 702a-702h. A first electrical energy source may be associated with a first signal level, a second electrical energy source may be associated with a second signal level, a third electrical energy source may be associated with a third signal level, etc. The first signal level may be in a first relationship with the second signal level, the second signal level may be in the first relationship with the third signal level, etc.
As an example, the first relationship may include the first signal level being two times less than the second signal level, the second signal level being two times less than the third signal level, etc. It is understood that other relationships may be provided, e.g. a one-third or a one-fourth relationship, as other examples.
The light emitting device 700a-700h may include (or may be connected to) one or more processors 708a, 708b, 708c, 708d, 708e, 708f, 708g, 708h, (e.g., configured as the one or more processors 206, e.g. part of a control circuit CTL), in the following 708a-708h. According to the additive electrical approach, the control of the light emitting device 700a-700h to combine the plurality of partial signals may include the one or more processors 708a-708h being configured to control the plurality of electrical energy sources 706a-706h to generate the respective partial electrical signal.
In various aspects, the one or more processors 708a-708h may be configured to generate a gating signal representative of which electrical energy sources 706a-706h to activate to emit the respective partial electrical signal, and may be configured to control the plurality of electrical energy sources by using the gating signal (e.g., provided to the driving circuit 704a-704h via one or more gating signal lines 710a, 710b, 710c, 710d, 710e, 710f, 710g, 710h). In the configuration in
In various aspects, each electrical energy source 706a-706h may be associated with (e.g., connected to) a respective switch configured to connect or disconnect the associated electrical energy source 706a-706h to a respective electrical path. Illustratively, the light emitting device 700a-700h may include a plurality of switches 712a, 712b, 712c, 712d, 712e, 712f, 712g, 712h, each configured to open or close a respective electrical path connecting an electrical energy source 706a-706h with the light source 702a-702h.
The gating signal generated by the one or more processors 708a-708h may be representative of which switches 712a-712h to activate (illustratively, to close) to connect the associated electrical energy source 706a-706h to the respective electrical path. The control of the switches 712a-712h may provide controlling which electrical energy sources 706a-706h may deliver the respective electrical signal to the light source 702a-702h, providing the desired modulation of the emitted light signal. The one or more processors 708a-708h may control the switches 712a-712h via a plurality of signal lines 714a, 714b, 714c, 714d, 714e, 714f, 714g, 714h (e.g., one signal line for each switch, e.g. one signal line for each “bit”). In various aspects, the gating signal lines 710a-710h may be used as signal lines 714a-714h.
In various aspects, as shown in
Depending on the impedance of the used electrical energy sources 706a-706h (or in case of a combination of series and parallel connection of sources the impedance of the resulting “stitched” sources may be considered), ether a serial connection or a parallel connection may be more suited in terms of energy efficiency (e.g., to have as least energy as possible provided by one source dissipated in another source of the circuit). In the case that the sources 706a-706h have a relatively low impedance, e.g. in case of sources that may be well modelled by voltage sources, a series connection of sources may be provided (see
The light emitting device 700a in
In the case that the light source 702a has an approximately linear characteristic between applied voltage and flux of the emitted light, the voltage of a branch may be selected to be approximately twice the voltage of the preceding branch (the voltage V2 of the second branch may be twice the voltage V1 of the first branch, the voltage V3 of the third branch may be twice the voltage V2 of the second branch, etc.):
In a real case scenario, a laser diode may not behave as a voltage source. To take into account this deviation from the ideal behavior, the final selected values for the voltage signals provided by the voltage sources 706a may be tuned based on the laser diode or laser diodes used as light source 702a (e.g., a series connection, a parallel connection, or a combination of series and parallel connection of laser diodes).
The light emitting device 700b in
As laser diodes (and alternatively used light emitting diodes) exhibit an approximately linear characteristic between applied current and flux of the emitted light, the current of a branch may be selected to be approximately twice the current of the preceding branch (the current I2 of the second branch may be twice the current I1 of the first branch, the current I3 of the third branch may be twice the current I2 of the second branch, etc.):
The final selected values may be tuned based on the laser diode or laser diodes used as light source 702b (e.g., a series connection, a parallel connection or a combination of series and parallel connection of laser diodes).
There is another consideration to be made when looking at additive electrical power modulation, namely the time-characteristics of the sources 706a-706h.
In the case that the characteristics of the sources are 706a-706h are substantially time-independent, switches 712a-712h may be utilized to connect and disconnect the sources 706a-706h to the light sources 702a-702h (e.g., to the laser diode(s)).
Substantially time-independent may be understood as the voltage or current not changing significantly over time after “loading” the source, e.g. in case of “ideal” voltage sources or “ideal” current sources. In this case, the resulting light pulse may be mainly shaped by the switches of the circuitry.
In the case of sources 706a-706h that may be “drained” and only provide a limited amount of energy, thus having a time-dependent contribution, the shape of the light pulse is not only shaped by switching actions of the circuitry, but may also be significantly impacted by the time-behavior of the sources contributing to the “final” electrical pulse.
In various aspects, as shown in the light emitting device 700c, 700d in
According to the desired output level the respective sources 706c, 706d may be utilized to form the aggregated pulse. This approach may be referred to herein as additive electrical binary power modulation by energy aggregation. A pulse source 706c, 706d may be configured to create the electrical pulse by releasing previously stored capacitive or inductively stored electrical energy.
In the case that the laser diode 702c, 702d exhibits an approximately linear characteristic between applied electrical pulse energy and the energy emitted by the optical pulse, each pulse source 706c, 706d may be selected to provide a contribution to the aggregated pulse of approximately twice the energy of the preceding pulse source 706c, 706d.
In some aspects, the disconnection (or short-circuiting) of the laser diode(s) 702c, 702d to end the light generation may be carried out without switches or switching action as the sources 706c inherently stop providing power to the laser diode(s) 702c, 702d (when the discharge is complete).
As mentioned above, the three branches BR1-BR3 may be basically identical except for the component values of the pulse sources 706c. The energy provided by each branch may be chosen to be approximately twice the energy provided by the preceding branch (the energy E2 of the second branch may be twice the energy E1 of the first branch, the energy E3 of the third branch may be twice the energy E2 of the second branch, etc.):
Vk(t) is the voltage and Ik(t) is the current of a respective pulse source 706c, 706d, and TP is the pulse duration of an electrical pulse provided by the pulse source 706c, 706d.
The final selected values may be tuned based on the laser diode or laser diodes used as light source 702c, 702d (e.g., a series connection, a parallel connection or a combination of series and parallel connection of laser diodes).
The switches 712c, 712d (S1, S2 and S3) may be used to short-circuit pulse sources 706c, 706d not contributing to the overall pulse. In various aspects, the switches 712c, 712d (S1, S2 and S3) may be dispensed with, thus reducing complexity and cost, in case the utilized pulse sources 706c, 706d not being active have low impedance.
As stated above, a pulse source may use capacitive or inductively stored electrical energy to create the electrical pulse. In the following, configurations including inductively stored energy (
The light emitting device 700e, 700f in
The currents through the respective inductors 706e, 706f may continue to flow turning on the respective diodes 716e, 716f Di and the light source 702e, 702f (the laser diode DO). All previously charged inductors 706e, 706f may freewheel and dump their energy into the light source 702e, 702f (and considering non-ideal components some small amount of this energy may be dissipated in diodes the 716e, 716f D1-D3).
The selection of the inductance values of the inductors 706e, 706f L1-L2 may depend on the characteristic of the light source 702e, 702f (the laser diode DO).
In case the laser diode behaves resistively (illustratively, the forward voltage increases linearly with the diode forward current), then each branch may be configured to provide twice the energy compared to the energy provided by the preceding branch (L may denote the respective inductance of the inductor, L1 may be the inductance of the first inductor, L2 may be the inductance of the second inductor, etc.),
In the case that the laser diode behaves as an ideal voltage source (illustratively, in case it may be well modeled by a constant forward voltage irrespective of the diode current), the branches B1-B3 may be configured such that the current provided by each branch may be twice the current provided by the preceding branch (L may denote the respective inductance of the inductor, L1 may be the inductance of the first inductor, L2 may be the inductance of the second inductor, etc.),
As soon as the pulse duration TP has lapsed, the light source 702f may be short-circuited by an additional switch 718f S0, as shown in
In this configuration, the remaining energy stored in the inductors 706f may be dissipated in the inductors 706f L1-L3, the diodes 716f D1-D3 and the switch 718f S0. Other options (not shown) for dissipating the remaining energy may include, for example, a snubber circuit dissipating most of the energy, or energy regeneration by feeding the stored energy back to the voltage source 720e, 720f V0 used to charge the inductors 716e, 716f by an additional switch arrangement which may allow the diode current flow into the negative pole of the voltage source 720e, 720f V0 (V0 may be applied in reverse direction onto the inductors to demagnetize them until their currents have turned to zero).
In a real case scenario, a laser diode 702e, 702f may have a characteristic in-between an ideal voltage source and an ideal resistor. Based on this consideration, the inductor values used in the circuits represented in
The light emitting device 700g, 700h in
The energy of one or multiple of the capacitors 706g, 706h C1-C3 may be dumped into the light source 702g, 702h (the laser diode D0). The pulse may be ended without any switching action, as the pulse provided at the light source 702g, 702h naturally ends with the discharge of the contributing capacitors 706g, 706h, neglecting the currents flowing through the resistors 722g, 722h Ri, which may be assumed to be small compared to the “current pulse” provided by the capacitors 706g, 706h.
The shape of the generated pulse may deviate from the above mentioned quasi-rectangular shape, depending on the characteristics of light source 702g, 702h as well as the parasitic elements being part of the circuit arrangement.
In the case that the sources 706g, 706h exhibit high impedance for those sources 706g, 706h that do not contribute to the overall pulse, the switches 712g, 712h may be dispensed with.
As mentioned above, the three branches BR1-BR3 may be basically identical except for the component values. As one branch (e.g., B2) may be configured to generate twice the pulse power compared to another branch (e.g., B1), its capacitor 706g C2 may have about twice the capacity compared to the capacitor 706g C1 of the other branch (assuming a same charging voltage for all branches BR1-BR3). The diode D2 of the second branch may have about twice the semiconductor area (assuming same design) compared to the diode D1 of the first branch. And finally, the switch S2 of the second branch may be configured to carry about twice the peak current compared the switch Si of the first branch (e.g., may have twice the semiconductor area (assuming same design) of S1). The pulse provided by the third branch BR3 may be about “double” that of the second branch BR2, and thus roughly “four times bigger” compared to the pulse provided by the first branch BR1.
In the configuration in
The time diagram 730i is provided for illustrating the data transmission capabilities of the light emitting devices 700g, 700h. As an exemplary sequence of symbols to be encoded, the symbol stream 2,3,1,7,0,0,7,7,4,4 may be provided. The light signal 732i may include the light output pulses 734i generated by the light emitting devices 700g, 700h considering this example symbol stream. The resulting waveform may be similar to the waveform shown in
As shown in the time diagram 730i, using the symbol 0 results in no pulse. In this case, due to data communication functionality the ranging functionality of a LIDAR module (e.g., of the LIDAR module 200) may be impacted, especially if measures are not taken (e.g., by suitable coding) to avoid that a sequence of 0s is transmitted. An alternative (more rigorous) approach may include the exclusion of the symbol 0 (and potentially also of the symbol 1) from the used symbols in order to provide sufficiently high light amplitude and ensure at least a minimal ranging performance of the LIDAR system for every pulse transmitted.
A configuration of a light emitting device according to the additive electrical approach may provide the possibility of a herein so-called “residual gating”, described in further detail below in relation to
In the configuration in
The residual gating may be understood as the one or more processors 708h being configured to control a discharge of a first part (e.g., a first subset) of the electrical energy storage elements (e.g., the capacitors 706h, or the inductors in a different configuration) during a first portion of the emitted light signal, and to control a discharge of a second part (e.g., a second subset) of the electrical energy storage elements during a second portion of the emitted light signal. The discharge of the first part of the electrical energy storage elements may provide a (first) electrical signal (e.g., a current or a voltage) to the light source to emit a first light pulse or a first portion of a light pulse, and the discharge of the second part of the electrical energy storage elements may provide a (second) electrical signal to the light source to emit a second light pulse or a second portion of the light pulse.
In various aspects, according to the residual gating approach, a light pulse may include a first pulse portion having a first energy and a second pulse portion having a second energy, and the first energy may be complementary to the second energy with respect to a total energy of the light pulse. In various aspects, the first energy being complementary to the second energy may be understood as a result of a summation of the first energy with the second energy to be substantially 100% of the total energy of the light pulse.
The residual gating may be achieved via a residual gating signal 736j (R), as shown in
The shape of the residual sub-pulse may be given by the shape of the first sub-pulse, as the amount of energy available in the circuit may be constant for two corresponding sub-pulses (the pair of sub-pulses). Having a second sub-pulse may increase the robustness of the communication, not only thanks to having twice the chance to receive a sub-pulse that carries the encoded information, but also in view of the relationship between the two sub-pulses. The second sub-pulse may be the “inverse” of the first sub-pulse, as shown in the time diagram 740k in
Residual gating may provide the additional advantage of data-independent thermal loading of all components including the light source 702h (e.g., the laser diode). This may provide higher reproducibility with respect to communication and ranging performance as well as device aging. It may also simplify the power supply design, as a branch always consumes the same amount of current/power, helping to ease the control and electromagnetic compatibility (EMC) design.
The residual gating may alleviate the above-described issue with minimal signal amplitude for symbols 0 and 1, as the second sub-pulse is even stronger if the first pulse is very small or even non-existent (as shown in
The circuitries 700g, 700h described in relation to
In various aspects, multiple options may be provided to generate such pulse trains (e.g., pulse trains configured as shown in
As a first option, more complex circuitry compared to the circuitries 700g, 700h described in relation to
As a second option, light pulses generated by multiple circuits may be aggregated using optical methods (e.g., as described in relation to the additive optical binary power modulation).
As a third option, electrical pulses of multiple circuits configured as the circuitries 700g, 700h described in relation to
The light emitting device 800a may illustratively include a plurality (e.g., two in this example, a first driving circuit 802a-1, and a second driving circuit 802a-2, but not limited to this number) of driving circuits 802a with associated one or more processors 804a-1, 804a-2. The driving circuits 802a shown in
Each driving circuit 802a contributing to the overall electrical pulse may be made up of so-called sub-pixel (SP). The first sub-pixel SP1 is also referred to as first driving circuit 802a-1, the second sub-pixel SP2 is also referred to as second driving circuit 802a-2, etc. Each sub-pixel may include multiple branches, e.g. the sub-pixel SP1 may include three branches BR1 through BR3. Illustratively, the individual driving circuits 802a-1, 802a-2 may be understood as sub-pixels not in the strict optical sense (e.g., as described in relation to the optical approach), but in the sense of a circuit contributing in part to the driving of the light source 806a. The entire power circuit arrangement including all sub-pixels and the light source 806a (e.g., the laser diode) may be understood as a pixel.
In various aspects, the circuit and components of a sub-pixel may be identical to the neighboring sub-pixels (e.g., the first driving circuit 802a-1 may be configured as the second driving circuit 802a-2, etc.), the individual components may be shown with the same reference designators. The components of different sub-pixels may be distinguished by a leading number identical to the number of the respective sub-pixel, e.g. the resistor R3 in the first sub-pixel SP1 may be shown as 1R3, and the resistor with the same function in sub-pixel SP2 may be referenced as 2R3, etc.
Each sub-pixel 802a may contribute to two sub-pulses. The two sub-pixels 802a in the exemplary configuration in
For LIDAR applications the pulse duration TP and the repetition time TR may be an order of magnitude or even more different from each other, as described above.
The light signal 812c shown in the diagram 810c may be provided by using a joint residual gating, illustratively a residual gating for both sub-pixels 802a at the same time and before the “very first sub-pulse” (illustratively, before emitting the initial pulse 814c of the signal 812c). This approach may provide a leading sub-pulse of typically significant amplitude which may be used as the “primary (sub-)pulse” for the ranging functionality of the LIDAR system (e.g., of the LIDAR module 200).
The symbol rate (two symbols per pulse) remains unchanged compared to the approach of a residual gating per sub-pixel provided for the light signal 812b in
This approach provides advantages from a ranging precision point of view (as the very strong residual sub-pulse may provide a better signal-to-noise ratio compared to a regular “first sub-pulse” as in the case of residual gating per sub-pixel). The approach according to
In various aspects, the initial sub-pulse for ranging and/or calibration may be generated by a separate sub-pixel. This approach may provide the freedom to freely select the amplitude of the initial sub-pulse, making waveforms as shown in the light signal 812d in
In various aspects, for saving complexity and cost, a sub-pixel, e.g. the third sub-pixel 802e, may include a single branch (differently from the two other sub-pixels 802a). This configuration may be provided in case no variation of the generated pulse amplitude is required (in this case, the switch 3501 may be dispensed with, as the signal 3B1 may be always high).
In various aspects, the sub-pixel controls 804a, 804e may be coordinated by a common pixel control 808e PiCTL. The communication between the individual sub-pixel controls 804a, 804e and the pixel control 808e may be realized by bi-directional communication (illustrated by dashed lines with arrows on both ends). In various aspects, the pixel control 808e may be configured to communicate with an overall emitter control ECTL (not shown) via bi-directional communication. The overall emitter control ECTL may be configured to control (illustratively, orchestrate) multiple pixels, all part of the same LIDAR module (e.g., of the LIDAR module 200).
As an example, the overall emitter control may be part of a main LIDAR module control circuit, controlling not only the emitters via the pixel controls, but also the optics (such as a DMD, digital mirror device, or oscillating MEMS mirror) as well as the individual parts of the light receivers. An overview of used terms and abbreviations is provided in Table 7 (each object may include one or more of the objects listed in the lines below). Table 8 provides a summary of the objects relevant in the scope of this description (each object may include one or more of the objects listed in the lines below).
As mentioned above, an arrangement with an additional sub-pixel (e.g., the third sub-pixel 802e SP3 in
Illustratively, a light signal may include a (first) light pulse (or a first plurality of light pulses) associated with ranging, and a (second) plurality of light pulses associated with data transmission, and the first light pulse may be separated from the second plurality of light pulses by the additional gap. An example combining both, the strong leading ranging sub-pulse, and separation of ranging sub-pulse and following data-based sub-pulses, is shown in
This concept allows providing basic and advanced LIDAR functionality. The basic functionality may provide good ranging functionality but no data communication. This functionality may be realized by simple receivers (low cost) only utilizing the first sub-pulse and the following “gap”. The “gap” may provide a “nicely shaped pulse” suited for primitive ranging concepts.
With the same modulation/pulse scheme also higher-grade systems may be provided (with the same transmitters). More complex receivers may be used, utilizing the first sub-pulse for initial (fast) ranging and for channel estimation. Considering the derived channel information, the subsequently coded symbols may be decoded. In addition to the initial ranging, a precision ranging (high accuracy distance measurement) may be implemented by using the entire pulse waveform (including the first “ranging sub-pulse” and all consecutive “data sub-pulses”) for ranging. The precision ranging and the data decoding may be carried out in a single step, e.g. by correlation analysis in a correlation receiver, providing distance and the most likely transmitted symbols.
In various aspects, for making the communication more robust (in addition to the built-in redundancy by the residual sub-pulses), the residual sub-pulses may be moved to the end of the train of sub-pulses while all (non-residual) data sub-pulses may come first (right after the initial “ranging sub-pulse”) thereby reducing the probability that a single interference event or noise pulse would disturb both the data sub-pulse and its residual counterpart. An example of this configuration is shown in the timing diagram 810h in
In various aspects, the robustness may be further increased by adding error check information to the sequence of symbols to be encoded (e.g., to the sequence of symbols 208). Illustratively, the sequence of symbols to be encoded (e.g., to the sequence of symbols 208) may include at least one error check symbol (e.g., a parity symbol) representative of error check information associated with the sequence. In various aspects, at least one driving circuit (illustratively, a parity sub-pixel) may be assigned provide the respective electrical signal for emitting the light signal (or the individual light pulse) including (e.g., encoding) the error check symbol.
Robustness may be increased by adding parity information. Multiple options may be provided to add parity information to the above data stream.
As a first option (a), the parity information is added by adding additional sub-pulses. As a second option (b), the parity information may be added as “additional data” into the data stream.
In relation to the first option (a) an additional sub-pixel (similar to the one assigned to the initial ranging sub-pulse) may be provided in a driving circuit (e.g., as described in relation to
The intensity of light level generated by the “parity sub-pixel” may be chosen freely. In other words, the two amplitude levels of the parity sub-pulse and the residual parity sub-pulse may be chosen freely. Table 10 and Table 11 show exemplary values for emitted light pulses, in which amplitudes of 6 and 0 were chosen for the parity information, allowing a “parity sub-pixel” with only a single branch. In Table 11 the residual even parity pulse may be directly following the even parity pulse. In Table 10 and Table 11, as well as in Table 12 below, the values in the rows R, G, Q, R, and P provide the total stream in row T (the sequence of values in row T). The row P provides both the parity and the residual parity (which is the inverted of the parity). In Table 11, the reverse sequence for the residual data is provided compared with the data.
Depending on where the one or multiple parity sub-pulses are added, the shape of the pulse varies (and in any case the pulse may become longer). This approach does not reduce the data rate, but it may be provided with additional energy and hardware. The additional hardware, which is additional sub-pixels (additional driving circuits) to create the parity sub-pulse(s) may be provided as long as the circuit does not allow recharging capacitors within the duration of the pulse in which the capacitor has been discharged (even with a longer pulse due to the presence of the parity information).
As mentioned, for the above examples shown in Table 10 and Table 11, amplitudes of 6 and 0 were chosen, allowing a “parity sub-pixel” with only a single branch.
As an alternative, two “regular” sub-pixels with 3 branches each may be provided to generate the ranging sub-pulse as well as the parity and the residual parity sub-pulses. In this configuration, the driving circuit may include 4 identical sub-pixels each having three branches (e.g., four sub-pixels 802a). With this configuration, the stream of sub-pulses shown in Table 12 may be provided. As in the previous example, the ranging pulse has an amplitude of 8, but the levels used for parity are 2 and 4.
As an exemplary configuration, the two data sub-pixels may be denoted as sub-pixels SP1 and SP2 (and sub-pixels SP3 and SP4 are provided for ranging). The ranging pulse may be created by “firing” all branches of SP3 and branch BR1 of SP4 at the same time creating the ranging pulse. This leaves BR2 and BR3 of SP4 for the parity and the residual parity. In this configuration, the parity and residual parity sub-pulses may have the amplitudes of 2 (created by firing BR2) or 4 (generated by firing BR3). Aside from the advantage that identical sub-pixels are used, thereby reducing complexity and easing integration, the generated pulse waveforms may be always of the same length. Every pulse may begin with amplitude 8 and may end with an amplitude of 2 or 4. This pulse property may be advantageous when it comes to building highly sensitive and robust receiver topologies.
In the example above, a parity bit per pulse was added. It is however understood that more parity bits may be added, e.g. two parity bits per pulse. The first parity bit may be calculated from the bits transmitted in the lower branches (e.g., BR1 of all sub-pixels), and the second parity bit may be calculated from the upper branches (e.g., BR2 and BR3 of all sub-pixels). In various aspects, the upper branches may include more branches, and the respective parity bits may be calculated from a larger number of bits, compared to the parity bit calculated from the lower branches, as the upper branches may correspond to the more resilient bits. In addition a (e.g., third) parity bit calculated from all the parity bits may be added.
The number of parity bits per a certain amount of data bits may be selected depending on the implementation addressing a specific application and use case. The more parity bits are added, the more robust the communication becomes, but at the same time the higher the hardware effort for additional sub-pixels (in case of option (a)) and error correction (e.g., computational power and memory). The additional hardware may lead to increased associated cost. Another possible drawback may be a reduced data rate, as described in further detail below.
For a given use case an optimum may be found (e.g., based on channel characteristics, e.g. optical channel characteristics between transmitter and receiver, and a required minimum data throughput, e.g. 100k bps hundred kilobits per second).
One or multiple parity sub-pulses within a pulse may provide an overall more robust communication. The parity bit may be calculated from one multiple symbols within the same pulse. This may provide not only the possibility of identifying if a bit has flipped but also to correct the flipped bit, as the parity sub-pulses would indicate whether the data sub-pulse or the respective residual sub-pulse should be trusted.
In various aspects, either an even or an odd parity sub-pulse may be added. In both cases the residual pulse of the parity sub-pulse may also be added. This may be achieved by utilizing a separate sub-pixel for the parity sub-pulse, and firing this sub-pulse and its residual sub-pulse in every pulse.
In various aspects, the parity information may be added only from time to time, e.g. only every 10th pulse (as an example) based on the information of the previous 10 pulses. However, having parity information in every pulse may provide a more robust approach, and the information integrity of multiple pulses may be secured with a CRC (cyclic redundancy check).
In relation to the option (b) above, parity information may be added as “additional data” in the data stream. This approach may reduce the effective data rate, but may be implemented without any additional hardware. With this approach, care should be taken as to where to add the parity bit into the data stream, as there may be bits (those being created by higher order branches, using a lot of light) that are more robust than others. In various aspects, one of the “more resilient” bits may be used as parity bit. This approach may be implemented with a setup similar to the one above, e.g. the light emitting device 800a described with relation to
The light signal emitted with this configuration may include a pulse having three data sub-pulses, each data sub-pulse carrying 3 bits (and the light signal may also include the residual data sub-pulses). These 9 bits may be used to represent one byte of data, and the parity bit of that data byte. In the case that the parity bit would be transmitted with one of the “more resilient” bits, then the parity bit may be assigned to one of the third branch out of the 3 data sub-pixels. This may ensure that the parity bit is transmitted using an energy amount equaling 4 LP, light power, (either an intensity of four light levels would be in the data sub-pulse or the residual data sub-pulse).
Aside from the parity bit (depending on the approach) being encoded in a “more resilient” bit, the more resilient bits may be used, in some aspects, for the data flow control. The data flow control (as part of the lower layer communication stack) may be used for communication between two LIDAR communication nodes to negotiate the data communication protocol.
In the following, a summary of methods for power modulation described above is provided.
The above described methods realizing intensity modulation are quite different in their nature, and have different properties, including strength and weaknesses. As an example, the concept of “subtractive optical power modulation” may be less energy efficient, as light falling on “turned off” areas is being dissipated (illustratively wasted), but it may provide a better linearity. Depending on the use case and application the best-suited method may be chosen. Table 13 provides an overview and may be used to select the best-suited approach. As described above, multiple approaches may be combined. The combination of optical modulation (either subtractive or additive) and electrical modulation (either subtractive or additive) may be utilized to generate systems with very large dynamic ranges.
The system efficiency for additive electrical power modulation may be highest for small number of branches/modulation levels. The linearity of “subtractive electrical power modulation” may be poor for voltage splitting, mediocre for power splitting, and good for current splitting. The linearity of “additive electrical power modulation” may be poor for voltage aggregation, mediocre for power aggregation, and good for current aggregation.
In various aspects, an additional functionality may be provided in a LIDAR module (e.g., in the LIDAR module 200) by detecting the emitted light signal, and adjusting the emission/reception as a function of the detected signal, as described in further detail below in relation to
A LIDAR module (e.g., the LIDAR module 200) may include a photo detector configured to detect the emitted light signal (e.g., a photo detector including one or more photo diodes, such as avalanche photo diodes, or pin photo diodes, as examples). In various aspects, the photo detector may be part of the light emitting device of the LIDAR module (e.g., part of the light emitting device 202).
The photo detector may be configured to provide the detected signal (e.g., a signal representative of the detected light signal 204) to the one or more processors of the LIDAR module (e.g., to the one or more processors 206). The one or more processors may be configured to adjust the control of the light emitting device as a function of the detected signal. For communicating with the one or more processors, the photo detector may include a wired or wireless communication channel with the one or more processors, e.g. a unidirectional or a bidirectional communication channel.
In some aspects, adjusting the control of the light emitting device may include adjusting the set value determining a capacitor charge voltage (illustratively, of one or more of the capacitors used to provide an electrical signal to the light source). The adjustment may be implemented in a feed-forward or in a closed-loop. Illustratively, based on the signal level of the previously detected signal, the one or more processors may control the charging of one or more of the capacitors to increase or reduce the stored charge (and thus the signal level of the next emitted light signal or light pulse).
As another example, additionally or alternatively, adjusting the control of the light emitting device may include the photo detector being configured to adjust a sensitivity level based on an expected signal level of the emitted light signal. Illustratively, based on the signal level of the previously detected signal, the one or more processors may instruct the photo detector to increase or reduce its sensitivity for better capturing the next emitted light signal.
In various aspects, the photo detector may be configured to receive a trigger signal from the one or more processors, and may be configured to be sensitive to incoming light for a predefined period of time after reception of the trigger signal. Illustratively, the photo detector may be activated only for the time necessary for detecting the emitted light signal, e.g. may be activated in accordance (e.g., in synchronization) with the emitted light signal. As an example, the trigger signal may include a gating signal (e.g., may be provided via a gating line to the photo detector).
The possibility of adjusting light emission and/or detection provided by the photo detector may enable automatic calibration and charge voltage control. This may provide dealing with component and manufacturing tolerances, temperature drifts, component aging, and their impact on the generated light output levels.
In the following, in relation to
The driving circuits 902a, 902b, 902c shown in
In the configuration in
The control 904a may “fire” each branch separately and calculate the ratio of consecutive branches, e.g. to assess the linearity of the arrangement.
In various aspects, as shown in
As an example, the charge circuit may include an adjustable linear regulator with adjustable output voltage or a DC/DC converter with adjustable output voltage. In the case that the charge circuit is commanded off, then the circuit behaves as a high impedance (illustratively, between its two “power terminals”, one of them being connected to the capacitor and the other connected to ground; the supply terminal of the charge circuit, which would be the “third power terminal” is not shown).
In particular, during “firing” of a branch and the charge/discharge of the respective capacitor C1-C3 through the laser diode DO, the charge circuit is turned “off” by the control 904b thereby avoiding a current flow from the charge circuit 910b over the closed respective switch S1-S3 into the laser diode DO.
In various aspects, the reduction of the photodetector's sensitivity may be carried out in a binary fashion thereby taking advantage of the output level being provided in a binary fashion (illustratively, without data conversion) and keeping the output signal of the photo detector 906b always close to 1. Deviations from 1.000 may be seen as imperfections which may be addressed, for example, by adjusting the charge voltages 910b VC1-VC3 or by considering the deviations in the later processing of the received LIDAR data.
In various aspects, the photo detector 906b shown in
In addition to the amplitude, also the branch delay times tBR1-tBR3 between “firing” a branch may be assessed, e.g. by toggling the gating signal Q and the peak seen in the detector signal. Typically, “larger branches” may take longer to fire compared to “smaller branches”, as the switches (e.g., the transistors) may require more time to turn on compared to smaller switches S1-S3 due to parasitic effects, e.g. in the semiconductor of the switch. The same may be true for the other components like the capacitors C1-C3 (the larger the capacitor the larger the parasitic inductance). The individual delay elements 914b DE1-DE3 may be provided to synchronize all switches. The delay time may be adjusted by the control 904b using the delay signals 916b DL1-DL3. The delay signals 916b may be set (in case of an analog signal) or calculated (in case of a digital signal) in such a way that the delay times tDE1-tDEn for each of the n branches (in the example shown in
This adjustment of the delay times may be achieved by an iterative approach, in which the branches are fired individually. The delay times tBR1-tBR3 may be measured, and the delay signals 916b may be (e.g., incrementally) adjusted.
In various aspects, the adjustment of charge voltages and delay times may be carried out on a regular basis. As an example, the adjustment may be carried out whenever an “update event” occurs. An update event may be triggered with every power-up, after a certain time (e.g., every 5 minutes after turn-on, and every 30 minutes after more than one hour of operation), or after a certain number of “shots” (e.g., every 5000 “shots”, illustratively 5000 toggling of signal line Q) of the respective sub-pixel, as examples.
A combination of multiple “update events” in a fashion of “whatever comes first” may be provided. After each update event, all counters and timers responsible to create update events may be reset.
In various aspects, as shown in
For example, the external detector 918c EDET may be connected temporarily for the calibration purposes. In such configuration, an overall external control circuit 920c ECU (external to the sub-pixel, or to the LIDAR module) may be provided. The external control circuit 920c ECU may be configured to control the external photo detector 918c EDET and to read out the (analog) signal or (digital) measurement value ELM provided by the external photo detector 918c EDET. In addition, the external control circuit 920c ECU may be configured to control the LIDAR module, in particular the respective pixel PI1. As an example, the (remote) control of pixel PI1 may be carried out via bi-directional data communication ECOM with the pixel control 904c CTL (e.g., ECOM sending commands and calibration data to CTL and CTL responding accordingly). The data communication between the two circuits may be established through an internal communication interface INT1 and an external communication interface EINT.
In
The control circuits 904c, 918c on both sides, CTL and ECTL respectively, may communicate with the respective communication interface INT1 and EINT, via bi-directional digital data busses, ICOM and ECM respectively.
The calibration according to the configuration shown in
The calibration may be conducted at least once, e.g. during production, for example as part of the end of line testing and programming of the LIDAR module. Numerous ways may be provided to calibrate the sub-pixel(s), photo detector(s), pixel(s), or the entire LIDAR module, such as laser trimming, or writing to a non-volatile memory, e.g. a FLASH memory of components of the LIDAR module.
The above approach with the external photo detector 918c may be provided also for LIDAR modules not having built-in photo detectors. In this configuration, the calibration of the photodetectors may be dispensed with, and the rest of the above procedure may be applied.
In the following, exemplary circuitries and components that may be used to implement the approaches described above will be illustrated. The circuitries and components described in the following are provided to show exemplary ways to put into practice the principles described herein. It is understood that the circuitries and components are only exemplary, and other circuitries and components may be provided to implement the same functionalities.
The laser diode drive circuits described below may be used to generate laser pulses, and may be applied to the different approaches described herein. For the sake of representation, the laser diode drive circuits will be illustrated for the case of “additive electrical power modulation”, but it is understood that may be applied also the other approaches described above.
According to various aspects, the switching action of the switches may be very fast. The switches used may be electronic switches, e.g. transistors made of doped semiconductor material. In various aspects, the switches may be transistors of MOSFET (metal oxide field effect transistor) or jFET (junction field effect transistor) construction, e.g. including or being made of silicon (Si), silicon carbide (SiC), or gallium nitride (GaN).
As laser diodes or laser diode arrays may include a “common cathode”, a “common cathode circuit architecture” may be provided, in some aspects. In case of “common cathode” components, the cathode of the laser diode die may be electrically connected with a metal part of the component housing. The metal part of the component housing may be typically mounted to a grounded heatsink.
In the following figures
In the configuration in
In the configuration in
The light emitting device 1000b, 1000c may include three branches, each including a capacitor 1014b, 1014c C1/C2/C3, corresponding charging circuit 1016b, 1016c VC1/VC2/VC3, transistor 1004b, 1004c T1/T2/T3, and corresponding high-side driver 1002b, 1002c Dr1/Dr2/Dr3, and laser diode 1018b, 1018c D1/D2/D3. The light emitting device 1000b, 1000c may provide a LIDAR emitter featuring laser pulses with 8 intensity levels.
In various aspects, the branches may be sized in such a way that the light pulse generated by the second branch has twice the magnitude of that of first branch, the third branch generates a pulse of twice the magnitude of the second branch and so on. More energy may be stored and converted from branch to branch. This increased storing and conversion may be achieved by having double the number of capacitors (all of the same capacity and same charging voltage) connected in series, or in parallel, or connected in a combination of both serial and parallel connections. The same may be true for the laser diodes per branch. This implementation is shown in the light emitting device 1000c in
The light emitting device 1000c may include three branches BR1-BR3 utilizing identical components for capacitors 1016c and laser diodes 1018c (e.g., the laser diodes may be part of a laser diode array) arranged in series and parallel connections forming effectively “larger” capacitors and laser diodes.
In various aspects, “effective transistors” 1004c may be provided, including identical “smaller transistors”, connected in series and/or parallel. In this configuration, care should be taken when selecting components, designing circuit and actual circuit layout, as transistors connected in series should equally share the voltage across them, and in case of paralleling transistors, current should be equally shared amongst the transistors. There may be two options for the implementation of the “smaller transistors”: either just multiple identical transistors where gate, drain and source terminals are connected together, or multiple identical transistors each with its own high-side drivers where the drain and source as well as the input to the high-side drivers are connected together. In both cases, connecting switches (illustratively, “smaller transistors”) in series may be cumbersome and error prone due to component tolerances in components that are not monolithically integrated. In addition, the parallel connection of the “smaller transistors” may cause issues, as precise timing/synchronization of the switches and their high-side drivers may be hard to achieve as long as the “smaller transistors” are not monolithically integrated or at least integrated in the same package (e.g., multi-die approach in a single component package).
In the configuration in
By way of illustration, the light emitting device 1000d may be analogous to a “gear shift converter” (GSC), which includes series-connected light emitting diodes arranged in a binary fashion, thereby creating branches. The LEDs of a branch may be short-circuited for periods of times by parallel-connected transistors. A more advanced “gear shift converter” may implement automatically switching between serial and parallel connection of LED strings, in order to increase LED utilization. A GSC circuitry may be not only suited for AC but also for DC input voltage, thereby enabling emergency lighting with automatic switching from AC mains to battery operation. However, the circuitry “around” the branches, its control as well as the purpose of the arrangement in a GSC is completely different from the circuits proposed, e.g. unrelated to LIDAR applications and to data communication in a LIDAR module. For a GSC, the goal may be to generate a low-cost lighting device operated from AC mains voltage for illumination purposes, for example, with a constant light output. In order to achieve low-cost, a linear regulator in series to the LED string, which is sub-divided in branches, may be used instead of a switch-mode power supply providing the LED current. The linear regulator comes with the drawback of dissipating power proportional to the LED current and to the difference of instantaneous line voltage and the LED string voltage. In order to minimize the power dissipation in the linear regulator, the string voltage is dynamically adjusted with the instantaneous line voltage by short-circuiting more or less branches of the LED string. The switching of the LED strings may lead to serious flickering of the light source. The LED string voltage may be smoothed by a parallel-connected capacitor for each branch and decoupling of the shorting action of the parallel-connected transistor by additional diodes.
In various aspects, the purpose of the arrangements described herein may be to create modulated light output for ranging and communication. The input supply (e.g., an input voltage, for example nominal 12 V in case of an automotive LIDAR system) may be in very good approximation constant for a “full switching cycle” of all power switches involved, thereby generating a single light pulse. The input supply may be assumed to be constant over many pulses. Differently than in a GSC, the light sources used in a LIDAR module described herein are not used to emit light for long periods of time. Thus, capacitors, especially large capacitors or any other sources of power (e.g., the current source described below) may be disconnected from the light emitting devices as soon as the pulse duration is reached, and the light emitting devices are off most of the time. On the contrary, in a GSC, it is the aim of the circuitry to have the light emitting devices emit light as long as possible, in order to reduce flickering, leading to visual irritation of living beings in the lit space.
The light emitting device 1000e, 1000f, 1000g may include a common current source 1022e, 1022f utilized by all branches (e.g., via a fast-switching power transistor 1020e, 1020f). The advantage of a circuit arrangement configured as shown in
Extending the concept to a very large number of pixels, which would be fired sequentially, and being supplied by a single current source may be limited by parasitic stray inductances of the electrical connections between the different pixels, leading to more and more non-rectangular sub-pulses and ringing within the circuit.
The light emitting device 1000f in
The light emitting device 1000g in
The light emitting device 1000h in
The light emitting device 1000i in
As noted above, when paralleling transistors, care should be taken to ensure proper current sharing among the devices, which for most FETs is not an issue due to their internal structure and temperature behavior. In addition, in the configuration in
The current source 1100 may include an inductor 1102 L100 of significant size which gets energized to a defined current level set by a (analog or digital) current set signal IS provided by the control CTL or the pixel control PiCTL.
A significant inductor size may be understood as the inductor having an inductance value large enough so that the inductor current during the pulse gets reduced only by a fraction, not reaching zero. Ideally the inductor current only decreases by 10% during the pulse.
Illustratively, the circuit formed by capacitor 1104 C100, transistor 1106 T100 and associated gate driver 1108 Dr100, inductor 1102 L100 and diode 1110 D100 is a buck converter as known in the art. The control circuitry 1112 ICTL of the current source 1100 may be configured to establish a control loop, with the aim that the output current I+ measured by the current measuring circuit 1114 IME providing the current measurement signal IM equals the set current provided by the current set signal IS.
The control circuit 1112 ICTL may be configured to generate a pulse width modulated signal at its output DRV. The control may be implemented using various known control approaches, like a PID control or a hysteretic control, as known in the art.
The switching frequency of the drive signal DRV may be on the order of about 10 kHz to a few 10 MHz, leading to the control loop being typically not able (due to its mediocre dynamic performance) to regulate the current in time spans of sub-pulses. Therefore the above-mentioned significant size of the inductor may be provided to keep the current approximately constant during a sub-pulse and also during an entire pulse.
In the following, in relation to
The modular approach mentioned in relation to
Such a unit may be referred to herein as the fundamental (light) pulse (emitting) cell FPC.
The FPC 1200 may include, at a minimum an electronic switch/transistor 1202 T, a capacitor 1204 C, and a laser diode 1206 D. More components may optionally be present in the FPC 1200, such as a photo detector 1208 DET, delay element 1210 DE, gate driver 1212 Dr, and capacitor charge circuit 1214 VC.
The light emitting device 1220 may include a plurality of (e.g., seven) fundamental pulse cells 1200 FPC11, . . . , FPC34, configured as described in relation to
As described above, a sub-pixel may include multiple branches depending on how granular the light levels should be provided. Each branch may include one or multiple fundamental pulse cells 1200, and all cells of a branch may be “fired” simultaneously (except for small timing differences due to parasitic effects caused by the layout, or manufacturing tolerances, which effects may be offset by adjusting the respective delay elements 1210). In this configuration, a single control line from the sub-pixel control 1222 CTL to each branch for “firing” the respective branch may suffice. In the case that an addressability of individual parts of a branch (e.g., for calibration) is to be provided, more signal lines Q may be implemented.
The light emitting device 1230 in
Using multiples of the minimal set of fundamental pulse cells 1200 may allow the use of fundamental pulse cells 1200 of a given technologically or economically optimal size. It may also allow highly-integrated arrangements, e.g. the integration of multiple sub-pixels, pixels or even the entire emitter into a single component package. Also, monolithic integration may be provided with this approach.
The light emitting device 1230 in
Examples of optoelectronic integration in a single package and/or monolithic integration may include a die pixelated but not diced II-V in the middle of Si (in case of III-V-semiconductors), the die may be mounted on a Cu leadframe, or a Si-die with a plurality (illustratively, lots) of small III-V-single-laser diodes on top. A combination of both methods may also be provided, e.g. many III-V dies on a large Si-die where each III-V holds a number of individually addressable laser diodes. Laser diodes may be realized as VCSEL arrays. These VCSEL arrays may be diced on a plurality of small VCSEL arrays part of the arrangement or the VCSEL arrays may be a non-diced array or arrays being part of the described arrangement.
In the following, system implementations, including mechanical arrangements and thermal considerations will be described.
As described above, a light emitting device (e.g., the light emitting device 202) may include pixels, each pixel may include one or multiple sub-pixels, each sub-pixel may include one or multiple branches, and each branch may include of one or multiple fundamental pulse cells. The above configurations, for example as shown in
Two main aspects may be considered with regard to how to arrange these parts: thermal and optical considerations, assuming that the electrical wiring of the parts is a hard boundary.
From an optical point of view, deterioration of optical properties of the primary and secondary optics may be more likely be found on the periphery than in the inner section of the optics. This may be provided by the design of the optics itself, and/or by the production process (e.g., molds may be typically made in such a way that imperfections like spots and the like are on the outside of the optical part rather than in the center) and quality control.
Considering this optical aspect, the “lower order” branches may be provided more to the inside in order to reduce the relative error. Let's consider, for explanation purposes, a non-transparent spot with the size of a laser diode, absorbing half of the light of the respective laser diode. In case the deterioration would impact branch 1, e.g. including a single laser diode, then in case the commanded light output would only come from branch 1, only 50% of the commanded light output would be available, whereas if branch 3, having 4 laser diodes, would be impacted by the spot and even considering light from branch 3 only, still 3.5/4=87.5% of the commanded light output would be available.
From a thermal point of view, the parts that are further to the inside of a structure typically get hotter (assuming that the parts are generating heat) than parts further to the outside. In case of an adaptive light level adaptation, the light level is rarely changing a lot in most applications, therefore the branches of higher order may be either “fired” every pulse or not “fired” for a long time, whereas the status of “lower order” branches may be fluctuating more often.
Considering that thermal issues (e.g., the risk of overheating) will more likely occur at high light output levels, the parts belonging to higher order branches may be arranged more to the outside (also in case of 2D arrangements there is more space toward the outside than towards the middle), whereas lower order branches may be arranged more the inside.
Considering these aspects from the other way round, then the “lowest bit” (illustratively, the branch 1 of each sub-pixel) may be on average “on” for only half of the pulses. Therefore this branch may be arranged in the center (where cooling is worst), as it may not be guaranteed that the higher order branches will not be “on” for very long periods of time and then potentially overheat if arranged in the center.
Thus, the derived rule makes sense from a thermal and an optical point of view.
In various aspects, a “spiral rule” may be provided for arranging branches in a light emitting device. The “spiral rule” may include arranging the branches with increasing order from the inside to the outside (see
The rotational symmetry (the pattern may be rotational symmetric around the center) may also be advantageous from an optical point of view (all the branches, even if the individual laser diode are not exactly providing the same amount of light, may be in this case on average generating a beam by with least irregularities).
There may be another consideration. Either all parts of a single branch (of a specific sub-pixel) generate heat (all the electronics as well as all the laser diodes) or none of the parts. Therefore, the distances between the individual parts of a specific branch may be made as large as possible for best heat spreading. In various aspects, a “chess board rule” may be provided, based on these considerations (see
In case thermal considerations are to be weighted higher than optical consideration—which may be true for most applications and use cases—then the chess board rule takes precedence over the spiral rule. For those applications and use cases some examples are presented below in
The LIDAR emitter 1300 may include a single pixel with a single sub-pixel having two branches (B1 and B2). The LIDAR emitter 1300 may thus include three laser diodes (D00, D10, D11) in total. Discrete electronics and a single optoelectronic laser component may be used, holding all three laser diodes on a single-die. Then according to the above rules the laser diodes may be connected in such a way that the diode D00 is the middle one, as shown in
The optoelectronic component 1302 may be integrated on a silicon die 1304 (having all the electronic circuitry except for the laser diodes embedded in it), and another smaller die 1036 made of III-V-semiconductor material carrying the three laser diodes may be bonded on top.
In
The substrate 1304 may be soldered to a leadframe (not shown), for example made from copper or a copper alloy. This arrangement may be encapsulated, for example using injection molding by a light-absorbing plastic housing (not shown) except for the top part (where the laser diodes are) which may be filled with transparent silicone in a last step (not shown).
As the arrangement is used as laser transmitter line (1D-Array) forming a single pixel with two 2 branches, the arrangement may be similar to the one shown in
In case the three individual laser diodes (each as on own die, e.g. as the case with edge emitting laser diodes) are used in the design of the optoelectronic component 1308, then the layout may be changed in order to separate the dies from each other for better thermal spreading.
As the selection about which laser diode is assigned to which function (e.g., to which branch) may be made irrespective of the exact making of the optoelectronic component or module, an even more simplified configuration of the arrangement may be provided.
In the following this kind of representation may be used. “D” may refer to the laser diode only. Each figure showing a “mechanical arrangement” may be understood as representing the mechanical arrangement of a laser diode, e.g. in a package or a module. The laser diodes may be arranged in a line (1D-Array) or rectangle (2D-Array). In case of 2D arrays the shape of a square may be provided for some application, for other applications a pronounced rectangular shape may be provided, considering the resolutions of the LIDAR module in both dimensions. “D” may also refer to a “sandwich” of laser diode and electronics as illustrated above.
By expanding the pixel of the LIDAR module described in
The arrangement 1400 may form a single pixel with three sub-pixels (with 3 branches each). The sub-pixel may be indicated by the leading digit, similar to the nomenclature above. Each sub-pixel may be arranged in a separate line. However, this arrangement does not obey the “chess board rule” (e.g., may be optimal from an optics but not from a thermal point of view). Therefore, the arrangement may be adapted as shown in the
In the case of a single branch, the chess board rule may also apply, two examples for LIDAR modules having a single pixel with a single sub-pixel and only two branches are shown in
In various aspects, an “artificial branch” called MO holding all not-used spots (N0, N1, N2, . . . ) of the arrangement may be provided in order to make up a quadratic (or in general a rectangular) shaped array.
As for
In various aspects, coding schemes which take into consideration the above-mentioned rules may be provided. Such coding schemes may take into account that there are bits (those being created by higher order branches, using a lot of light) that are more robust than other bits.
In the present description, according to various aspects, methods realizing binary intensity modulation may be provided. The control setting the required amplitude for the next laser pulse may be implemented in a digital control, hence providing the set value in a binary way is just natural/the most trivial implementation, e.g. no coding into another digital format or even a digital to analog conversion of the set value may be needed. Using a binary-coded digital signal as the set value and for the command of the power stage can be implemented in a simple manner (low effort/low complexity/low cost). The set value may be combined with the trigger signal via AND gates (e.g., the set value may define which power switches/transistors get turned on by the trigger signal).
Compared with a modulation of the charging voltage of the pulse capacitor(s) the described method may provide a very high linearity, due to a simple summation of optical or electrical power, thus being not or effectively not dependent on non-linearities in the Phi-I-curve of the laser diode(s).
Due to its modular approach the integration of the circuit or a part of the circuit in a “component plus” (Laser diode (s) plus some additional components) may be provided (e.g., providing advantages in terms of cost, scalability to many “bits” of resolution, improved reliability, etc.).
Applying the “additive approach” may be energy-efficient, as for stronger pulses (higher amplitude) energy is summed up, rather than always consuming the same amount of energy (as it would be the case in a “subtractive approach” or in case of modulation of an in-series resistance). The approach may also ensure high dynamic performance. Regardless of whether pulses with high or low energy are generated the circuit always uses the same amount of time to “charge” and then deliver the pulse.
In the following, various aspects of this disclosure will be illustrated. The aspects may refer to the LIDAR module 100 described above.
Example 1 is a LIDAR module including: a light emitting device configured to emit a light signal in accordance with a combination of a plurality of partial signals; and one or more processors configured to: encode a sequence of symbols, wherein each symbol is associated with a respective combination of the plurality of partial signals, and control the light emitting device to combine the plurality of partial signals as a function of the encoded sequence of symbols to emit the light signal.
In Example 2, the LIDAR module of example 1 may optionally further include that the combination of the plurality of partial signals associated with a symbol includes a combination of a subset of the plurality of partial signals; and/or that the combination of the plurality of partial signals associated with a symbol includes a combination of all the partial signals of the plurality of partial signals.
In Example 3, the LIDAR module of example 1 or 2 may optionally further include that the sequence of symbols is configured to carry data to be transmitted. As an example, the data may include information to identify the LIDAR module. As another example, additionally or alternatively, the data may include information to characterize (e.g., distinguish) the emitted light signal.
In Example 4, the LIDAR module of any one of examples 1 to 3 may optionally further include that the plurality of partial signals include a plurality of partial light signals, and that the combination of the plurality of partial signals includes an optical combination of the plurality of partial light signals.
In Example 5, the LIDAR module of any one of examples 1 to 4 may optionally further include that the plurality of partial signals include a plurality of partial electrical signals, and that the combination of the plurality of partial signals includes an electrical combination of the plurality of partial electrical signals.
In Example 6, the LIDAR module of any one of examples 1 to 5 may optionally further include that the combination of the plurality of partial signals includes an additive combination of the plurality of partial signals and/or a subtractive combination of the plurality of partial signals.
In Example 7, the LIDAR module of any one of examples 1 to 6 may optionally further include that the emitted light signal includes one or more light pulses (e.g., one or more laser pulses), and that each light pulse of the one or more light pulses is associated with respective one or more symbols of the sequence of symbols.
In Example 8, the LIDAR module of example 7 may optionally further include that at least one light pulse of the one or more light pulses is associated with a respective one symbol of the sequence of symbols, and/or that at least one light pulse of the one or more light pulses is associated with a respective plurality of symbols of the sequence of symbols, and/or that the one or more light pulses include a plurality of light pulses, and a subset of the plurality of light pulses is associated with a respective one symbol of the sequence of symbols.
In Example 9, the LIDAR module of example 7 or 8 may optionally further include that a first light pulse of the one or more light pulses is associated with one or more first symbols of the sequence of symbols, a second light pulse of the one or more light pulses is associated with one or more second symbols of the sequence of symbols, and that the first light pulse has a first signal level different from a second signal level of the second light pulse.
In Example 10, the LIDAR module of any one of examples 7 to 9 may optionally further include that at least one light pulse of the one or more pulses includes a plurality of pulse portions, each pulse portion having a respective signal level, and that the signal levels of the plurality of pulse portions are defined by the one or more symbols associated with the at least one light pulse.
In Example 11, the LIDAR module of example 10 may optionally further include that the plurality of pulse portions define a shape of the at least one light pulse, and that the shape is associated with the one or more symbols associated with the at least one light pulse.
In Example 12, the LIDAR module of any one of examples 7 to 11 may optionally further include that at least one light pulse of the one or more pulses includes a first pulse portion having a first energy and a second pulse portion having a second energy, and that the first energy is complementary to the second energy with respect to a total energy of the at least one light pulse.
In Example 13, the LIDAR module of example 12 may optionally further include that the first energy being complementary to the second energy includes a result of a summation of the first energy with the second energy being substantially 100% of the total energy of the at least one light pulse.
In Example 14, the LIDAR module of any one of examples 7 to 13 may optionally further include that at least one light pulse of the one or more light pulses has a pulse shape selected from the list of shapes including: rectangular, quasi-rectangular, or Gaussian.
In Example 15, the LIDAR module of any one of examples 7 to 14 may optionally further include that at least one light pulse of the one or more pulses has a duration in the range from 1 ps to 1 ms, for example in the range from 10 ps to 10 μs, for example in the range from 100 ps to 100 ns, for example in the range from 200 ps to 25 ns.
In Example 16, the LIDAR module of any one of examples 7 to 15 may optionally further include that the one or more light pulses include a number of light pulses in the range from 1 to 100, for example in the range from 2 to 10.
In Example 17, the LIDAR module of any one of examples 1 to 16 may optionally further include that the emitted light signal has a total duration in the range from 1 ps to 100 ms, for example in the range from 10 ps to 1 ms, for example in the range from 100 ps to 10 μs, for example in the range from 200 ps to 2.5 μs.
In Example 18, the LIDAR module of any one of examples 1 to 17 may optionally further include that at least a portion of the sequence of symbols is uniquely associated with the LIDAR module and/or with the light emitting device.
In Example 19, the LIDAR module of example 18 may optionally further include that the at least one portion of the sequence of symbols includes a serial number of the LIDAR module and/or a serial number of the light emitting device.
In Example 20, the LIDAR module of any one of examples 1 to 19 may optionally further include that a signal level of the emitted light signal includes at least one of an amplitude or a power of the emitted light signal.
In Example 21, the LIDAR module of any one of examples 1 to 20 may optionally further include that the light emitting device includes a plurality of partial light sources, each partial light source being configured to emit a respective partial light signal.
In Example 22, the LIDAR module of example 21 may optionally further include that each partial light source of the plurality of partial light sources is configured to emit the respective partial light signal at a signal level different from the signal level of the other partial light signals emitted by the other partial light sources.
In Example 23, the LIDAR module of example 22 may optionally further include that at least one partial light source of the plurality of partial light sources is configured to emit twice the luminous flux of at least one other partial light source of the plurality of partial light sources.
In Example 24, the LIDAR module of example 22 or 23 may optionally further include that the plurality of partial light sources include a first partial light source, a second partial light source, and a third partial light source, that the second partial light source is configured to emit twice the luminous flux of the first partial light source, and that the third partial light source is configured to emit twice the luminous flux of the second partial light source.
In Example 25, the LIDAR module of any one of examples 22 to 24 may optionally further include that the control of the light emitting device to combine the plurality of partial signals includes the one or more processors being configured to control a combination of the partial light signals by controlling which partial light sources emit the respective partial light signal.
In Example 26, the LIDAR module of any one of examples 22 to 25 may optionally further include that the plurality of partial light sources include at least one light emitting diode.
In Example 27, the LIDAR module of any one of examples 22 to 26 may optionally further include that the plurality of partial light sources include at least one laser diode (e.g., a plurality of laser diodes, for example an array or a stack of laser diodes).
In Example 28, the LIDAR module of any one of examples 22 to 27 may optionally further include that the light emitting device further includes an emitter optics arrangement configured to receive the partial light signals, and to combine together the partial light signals to emit the light signal.
In Example 29, the LIDAR module of any one of examples 22 to 28 may optionally further include that the one or more processors are configured to generate a gating signal, the gating signal being representative of which partial light sources to activate as a function of the encoded sequence of symbols, and that the one or more processors are configured to control the plurality of partial light sources by using the gating signal.
In Example 30, the LIDAR module of example 29 may optionally further include that the one or more processors are configured to generate the gating signal by using a same clock signal as the clock signal determining a repetition rate of the light emitting device.
In Example 31, the LIDAR module of example 29 or 30 may optionally further include that each partial light source is associated with (e.g., connected to) a respective switch, and that the gating signal includes a respective instruction for each switch to connect or disconnect the associated partial light source from a power supply.
In Example 32, the LIDAR module of example 31 may optionally further include that at least one switch is realized as a logic gate. As an example, the logic gate may include an AND gate.
In Example 33, the LIDAR module of any one of examples 1 to 32 may optionally further include that the light emitting device includes a light source configured to emit light, and that light emitting device includes a beam-splitting device configured to split the light emitted by the light source into a plurality of partial light signals.
In Example 34, the LIDAR module of example 33 may optionally further include that the light emitting device further includes an optical arrangement configured to absorb or redirect one or more of the plurality of partial light signals as a function of the encoded sequence.
In Example 35, the LIDAR module of example 34 may optionally further include that the optical arrangement includes a controllable light absorbing device configured to receive the plurality of partial light signals, and that the control of the light emitting device to combine the plurality of partial signals includes the one or more processors being configured to control the light absorbing device as a function of the encoded sequence to control the combination of the partial light signals.
In Example 36, the LIDAR module of example 35 may optionally further include that the light absorbing device includes a plurality of segments, each segment being configured, in a first state, to absorb or redirect a partial light signal impinging onto that segment, and configured, in a second state, to transmit the partial light signal impinging onto that segment.
In Example 37, the LIDAR module of example 36 may optionally further include that the one or more processors are configured to control each segment of the plurality of segments to be in the respective first state or second state as a function of the encoded sequence of symbols.
In Example 38, the LIDAR module of example 36 or 37 may optionally further include that at least one segment is configured to be light-absorbing independently of its state.
In Example 39, the LIDAR module of any one of examples 36 to 38 may optionally further include that the one or more processors are configured to generate a gating signal representative of which segments to switch in the first state and which segments to switch in the second state, and that the one or more processors are configured to control the light absorbing device by using the gating signal.
In Example 40, the LIDAR module of any one of examples 36 to 39 may optionally further include that each segment of the plurality of segments has a same surface area as the other segments of the plurality of segments.
In Example 41, the LIDAR module of any one of examples 36 to 39 may optionally further include that at least a second segment of the plurality of segment has a second surface area greater than a first surface area of a first segment of the plurality of segments.
In Example 42, the LIDAR module of example 41 may optionally further include that the second surface area is at least two times greater than the first surface area.
In Example 43, the LIDAR module of any one of examples 36 to 42 may optionally further include that at least one segment has a rectangular shape, and/or that at least one segment has a circular shape, and/or that at least one segment has a ring shape.
In Example 44, the LIDAR module of any one of examples 36 to 43 may optionally further include that the plurality of segments include a number of segments in the range from 2 to 20, for example in the range from 4 to 16.
In Example 45, the LIDAR module of any one of examples 36 to 44 may optionally further include that the light absorbing device includes at least one of a liquid crystal device or a digital mirror device.
In Example 46, the LIDAR module of example 45 may optionally further include that the liquid crystal device includes one of a liquid crystal display or a liquid crystal polarization grating.
In Example 47, the LIDAR module of any one of examples 36 to 46 may optionally further include that the optical arrangement includes primary optics arranged optically upstream of the light absorbing device and configured to collect the light emitted by the light source.
In Example 48, the LIDAR module of any one of examples 36 to 47 may optionally further include that the optical arrangement includes secondary optics arranged optically downstream of the light absorbing device and configured to combine the partial light signals to provide the emitted light signal.
In Example 49, the LIDAR module of any one of examples 1 to 48 may optionally further include that the light emitting device includes a light source configured to emit the light signal, and a driving circuit configured to provide an electrical signal to the light source, and that a signal level of the emitted light signal is dependent on a signal level of the electrical signal provided to the light source.
In Example 50, the LIDAR module of example 49 may optionally further include that the electrical signal includes one of a current signal, a voltage signal, or a power signal.
In Example 51, the LIDAR module of example 50 may optionally further include that wherein the electrical signal is or includes one of a current pulse, a voltage pulse, or a power pulse.
In Example 52, the LIDAR module of any one of examples 49 to 51 may optionally further include that the driving circuit is configured such that the electrical signal is split into a plurality of partial electrical signals.
In Example 53, the LIDAR module of example 52 may optionally further include that the control of the light emitting device to combine the plurality of partial signals includes the one or more processors being configured to control the driving circuit to combine the plurality of partial electrical signals.
In Example 54, the LIDAR module of example 52 or 53 may optionally further include that the driving circuit includes an electrical energy source configured to generate an electrical signal, and a splitting circuit configured to split the electrical signal into the plurality of partial electrical signals. As examples, the electrical energy source may include at least one of a current source, a voltage source, or a power source.
In Example 55, the LIDAR module of example 54 may optionally further include that the splitting circuit is configured such that a first partial electrical signal and a second partial electrical signal of the plurality of partial electrical signals are in a first relationship with one another, and such that the second partial electrical signal and a third partial electrical signal of the plurality of partial electrical signals are in the first relationship with one another. As an example, the first relationship includes the first partial electrical signal having a first signal level two times less than a second signal level of the second partial electrical signal.
In Example 56, the LIDAR module of example 54 or 55 may optionally further include that the splitting circuit includes one or more transformers.
In Example 57, the LIDAR module of example 56 may optionally further include that at least one transformer of the one or more transformers has a winding ratio of 1:1, and/or at least one transformer of the one or more transformers has a winding ratio of 2:1:1.
In Example 58, the LIDAR module of any one of examples 54 to 57 may optionally further include that the splitting circuit includes one or more power splitters, each power splitter being associated with a respective partial electrical signal.
In Example 59, the LIDAR module of example 58 may optionally further include that each power splitter is associated with a respective adjustable phase and adjustable attenuation circuit configured to delay and/or attenuate the respective partial electrical signal.
In Example 60, the LIDAR module of any one of examples 54 to 59 may optionally further include that the splitting circuit includes a plurality of switches, each switch being configured to connect or disconnect an electrical path associated with one of the partial electrical signals, and that the one or more processors are configured to control the combination of the plurality of electrical signals by controlling the plurality of switches.
In Example 61, the LIDAR module of example 60 may optionally further include that the one or more processors are configured to generate a gating signal representative of which switches are to be activated to connect the respective electrical path, and that the one or more processors are configured to control the plurality of switches by using the gating signal.
In Example 62, the LIDAR module of any one of examples 49 to 61 may optionally further include that the driving circuit includes a plurality of electrical energy sources, each configured to generate a respective partial electrical signal.
In Example 63, the LIDAR module of example 62 may optionally further include that each electrical energy source is configured to provide the respective partial electrical signal having a signal level different from the other partial electrical signals provided by the other electrical energy sources.
In Example 64, the LIDAR module of example 63 may optionally further include that a first signal level associated with a first electrical energy source of the plurality of electrical energy sources and a second signal level associated with a second electrical energy source of the plurality of electrical energy sources are in a first relationship with one another, and that the second signal level associated with the second electrical energy source and a third signal level associated with a third electrical energy source of the plurality of electrical energy sources are in the first relationship with one another. As an example, the first relationship may include the first signal level being two times less than the second signal level.
In Example 65, the LIDAR module of any one of examples 62 to 64 may optionally further include that the plurality of electrical energy sources include at least one electrical energy storage element, and that the generation of the respective partial electrical signal includes a discharge of the electrical energy storage element.
In Example 66, the LIDAR module of example 65 may optionally further include that the at least one electrical energy storage element includes one of an inductor or a capacitor.
In Example 67, the LIDAR module of any one of examples 62 to 66 may optionally further include that the control of the light emitting device to combine the plurality of partial signals includes the one or more processors being configured to control the plurality of electrical energy sources to generate the respective partial electrical signal.
In Example 68, the LIDAR module of example 67 may optionally further include that the one or more processors are configured to generate a gating signal representative of which electrical energy sources to activate to emit the respective partial electrical signal, and that the one or more processors are configured to control the plurality of electrical energy sources by using the gating signal.
In Example 69, the LIDAR module of any one of examples 62 to 68 may optionally further include that each electrical energy source is associated with (e.g., connected with) a respective switch configured to connect or disconnect the associated electrical energy source to a respective electrical path.
In Example 70, the LIDAR module of example 69 may optionally further include that the one or more processors are configured to generate a gating signal representative of which switches to activate to connect the associated electrical energy source to the respective electrical path.
In Example 71, the LIDAR module of any one of examples 62 to 70 may optionally further include that the plurality of electrical energy sources are connected in series and/or in parallel with one another.
In Example 72, the LIDAR module of any one of examples 62 to 71 may optionally further include that the plurality of electrical energy sources include at least one of a current source, a voltage source, or a power source.
In Example 73, the LIDAR module of any one of examples 62 to 72 may optionally further include that the plurality of electrical energy sources include a plurality of electrical energy storage elements, and that the one or more processors are configured to control a discharge of a first part of the electrical energy storage elements during a first portion of the emitted light signal, and to control a discharge of a second part of the electrical energy storage elements during a second portion of the emitted light signal.
In Example 74, the LIDAR module of example 73 may optionally further include that the discharge of the first part of the electrical energy storage elements provides an electrical signal to the light source to emit a first light pulse or a first portion of a light pulse, and that the discharge of the second part of the electrical energy storage elements provides an electrical signal to the light source to emit a second light pulse or a second portion of the light pulse.
In Example 75, the LIDAR module of any one of examples 1 to 74 may optionally further include that the light emitting device includes a light source and a plurality of driving circuits, each driving circuit being configured to provide a respective electrical signal to the light source.
In Example 76, the LIDAR module of example 75 may optionally further include that at least one driving circuit is assigned to provide the respective electrical signal for a ranging operation associated with the emitted light signal.
In Example 77, the LIDAR module of any one of examples 1 to 76 may optionally further include that the sequence of symbols includes at least one error check symbol representative of error check information associated with the sequence. As an example, the error check symbol may include a parity symbol.
In Example 78, the LIDAR module of examples 75 and 77 may optionally further include that at least one driving circuit is assigned to provide the respective electrical signal for emitting the light signal including the error check symbol.
In Example 79, the LIDAR module of any one of examples 1 to 78 may optionally further include a photo detector configured to detect the emitted light signal.
In Example 80, the LIDAR module of example 79 may optionally further include that the photo detector is configured to provide the detected signal to the one or more processors, and that the one or more processors are configured to adjust the control of the light emitting device in accordance with the detected signal.
In Example 81, the LIDAR module of example 79 or 80 may optionally further include that the photo detector is configured to adjust a sensitivity level based on an expected signal level of the emitted light signal.
In Example 82, the LIDAR module of any one of examples 79 to 81 may optionally further include that the photo detector is configured to receive a trigger signal from the one or more processors, and is configured to be sensitive to incoming light for a predefined period of time after reception of the trigger signal. For example, the trigger signal may include a gating signal.
In Example 83, the LIDAR module of any one of examples 79 to 82 may optionally further include that the photo detector includes a wired or wireless communication channel with the one or more processors. In some aspects, the communication channel may be a unidirectional or a bidirectional communication channel.
In Example 84, the LIDAR module of any one of examples 1 to 83 may optionally further include that the one or more processors include at least one of: a microprocessor, a microcontroller, a discrete logic gate, a programmable logic, a field-programmable gate array (FPGA), and/or an application-specific integrated circuit (ASIC).
Example 85 is a method of emitting light in a LIDAR module, the method including: encoding a sequence of symbols, each symbol associated with a respective combination of a plurality of partial signals; and controlling the combination of the plurality of partial signals as a function of the encoded sequence of symbols to emit the light signal.
In Example 86, the method of example 85 may include one, or some, or all of the features of any one of example 1 to 84, where appropriate.
Example 87 is a LIDAR module including: a light emitting device configured to emit a light signal in accordance with a combination of a plurality of partial light signals; and one or more processors configured to: encode a sequence of symbols, each symbol associated with a respective combination of the plurality of partial light signals, and control the light emitting device to optically combine the plurality of partial light signals as a function of the encoded sequence of symbols to emit the light signal.
In Example 88, the LIDAR module of example 87 may include one, or some, or all of the features of any one of example 1 to 84, where appropriate.
While various implementations have been particularly shown and described with reference to specific aspects, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope as defined by the appended claims. The scope is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 110 495.5 | Apr 2021 | DE | national |
This application is a US National Stage Application of International Application PCT/EP2022/058127, filed on 28 Mar. 2022, and claims priority under 35 U.S.C. § 119(a) and 35 U.S.C. § 365(b) from German Application 10 2021 110 495.5, filed on 23 Apr. 2021, the contents of which are incorporated herein by reference in their entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/058127 | 3/28/2022 | WO |
