Patent Application
20220155416
The present disclosure relates to laser emission control in Light Detection and Ranging (LiDAR) systems, and more particularly to, systems and methods for determining a multi-pulse laser emission scheme for the LiDAR systems.
Optical sensing systems such as LiDAR systems have been widely used in autonomous driving and producing high-definition maps. For example, a typical LiDAR system measures the distance to a target by illuminating the target with pulsed laser light beams and measuring the reflected pulses with a sensor such as a photodetector. Differences in laser light return times, wavelengths, and/or phases can then be used to construct digital three-dimensional (3D) representations of the target. Because using a narrow laser beam as the incident light can map physical features with very high resolution, a LiDAR system is particularly suitable for applications such as sensing in autonomous driving and/or high-definition map surveys.
A LiDAR system can use a transmitter to transmits a signal (e.g., pulsed laser light) into the surroundings, and use a receiver to collect the returned signal (e.g., laser light reflected by an object in the surroundings). The LiDAR system can then calculate parameters such as the distance between the object and the LiDAR system based on, e.g., the speed of light and the time the signal travels (e.g., the duration of time between the time the signal is transmitted and the time the returned signal is received) and use the parameters to construct 3D maps and/or models of the surroundings. To improve the detection range and the signal-to-noise-ratio (SNR), higher energy of the laser light is often needed. On the other hand, however, the energy of the signal also needs to be limited to avoid potential harm to human eye. Therefore, it is challenging to balance the performance demands and regulatory safety mandate in LiDAR system development.
Embodiments of the disclosure address the above challenges by systems and methods for determining a multi-pulse laser emission scheme used in LiDAR systems to improve the detection range and SNR while complying with the safety requirements.
Embodiments of the disclosure provide a system for determining a laser emitting scheme of an optical sensing device. The system includes a controller communicatively coupled to a laser emitter of the optical sensing device. The controller is configured to perform operations that includes determining a safety distance range in a field of view of the optical sensing device based on a predetermined tolerance value, causing the laser emitter to emit a first laser pulse having a first power-associated value lower than the predetermined tolerance value in the safety distance range, and detecting whether an object is detected in the safety distance range based on the first laser pulse. In response to no object being detected in the safety distance range, the controller causes the laser emitter to emit a second laser pulse having a second power-associated value higher than the first power-associated value.
Embodiments of the disclosure also provide a method for determining a laser scanning scheme of an optical sensing device. The method includes determining a safety distance range in a field of view of the optical sensing device based on a predetermined tolerance value, causing a laser emitter of the optical sensing device to emit a first laser pulse having a first power-associated value lower than the predetermined tolerance value in the safety distance range, and detecting whether an object is detected in the safety distance range based on the first laser pulse. The method also includes, in response to no object being detected in the safety distance range, causing the laser emitter to emit a second laser pulse having a second power-associated value higher than the first power-associated value.
Embodiments of the disclosure also provide an optical sensing device that includes a laser emitter, a receiver, and a controller. The laser emitter is configured to emit laser pulses in a field of view of the optical sensing device. The receiver is configured to detect laser pulses returned from the field of view. The controller is communicatively coupled to the laser emitter and the receiver. The controller is configured to perform operations include determining a safety distance range in the field of view of the optical sensing device based on a predetermined tolerance value, causing the laser emitter to emit a first laser pulse having a first power-associated value lower than the predetermined tolerance value in the safety distance range, and detecting whether an object is detected in the safety distance range based on the first laser pulse detected by the receiver. The controller is also configured to perform an operation, in response to no object being detected in the safety distance range, causing the laser emitter to emit a second laser pulse having a second power-associated value higher than the first power-associated value.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
Consistent with some embodiments, LiDAR system 102 may be configured to capture data as vehicle 100 moves along a trajectory. For example, a transmitter of LiDAR system 102 is configured to scan the surrounding and acquire point clouds. LiDAR system 102 measures distance to a target by illuminating the target with pulsed laser light and measuring the reflected pulses with a receiver. The laser light used by LiDAR system 102 may be ultraviolet. visible. or near infrared. In some embodiments of the present disclosure, LiDAR system 102 may capture point clouds. As vehicle 100 moves along the trajectory, LiDAR system 102 may continuously emit/scan laser beams and receive returned laser beams.
Consistent with the present disclosure, a controller may be included for controlling the operation of LiDAR system 102. In some embodiments, the controller may determine laser emission scheme(s) for controlling the laser emission power in an aperture. In some embodiments, the controller may be further used for processing and/or analyzing collected data for various operations. For example, the controller may process received signals and adjust the laser emission schemes based on the processed signals. In some embodiments, the received signal is processed and the laser emission scheme(s) may be generated in real-time. A distance between the object and LiDAR system 102 may be updated in real-time for the determination of the laser emission scheme(s).
The controller may also communicate with a remote computing device, such as a server (or any suitable cloud computing system) for operations of LiDAR system 102. In some embodiments, the controller is connected to a server for processing the received signal. For example, the controller may stream the received signal to the server for data processing and receive the processed data from the server. Components of the controller may be in an integrated device or distributed at different locations but communicate with one another through a network. In some embodiments, the controller may be located entirely within LiDAR system 102. In some embodiments, one or more components of the controller may be located in LiDAR system 102, inside vehicle 100, or may be alternatively in a mobile device, in the cloud, or another remote location.
Transmitter 202 may include any suitable components for generating laser beam 209 of a desired wavelength and/or intensity. For example, transmitter 202 may include a laser source 206 that generates a native laser beam 207 in the ultraviolet, visible. or near infrared wavelength range. Transmitter 202 may also include a light modulator 208 that collimates native laser beam 207 to generate laser beam 209. Scanner 210 can scan laser beam 209 at a desired scanning angle and a desired scanning rate. Each laser beam 209 can form a scanning point on a surface facing transmitter 202 and at a distance from LiDAR system 102. Laser beam 209 may be incident on object 212, reflected back as laser beam 211, and collected by a lens 214. Object 212 may be made of a wide range of materials including, for example, live objects, non-metallic objects, rocks, rain, chemical compounds, aerosols, clouds and even single molecules. In some embodiments of the present disclosure, scanner 210 may include optical components (e.g., lenses, mirrors) that can focus pulsed laser light into a narrower laser beam to increase the scan resolution.
Receiver 204 may be configured to detect returned laser beam 211 (e.g., returned signals) reflected from object 212. Upon contact, laser light can be reflected by object 212 via backscattering. Receiver 204 can collect returned laser beam 211 and output electrical signal indicative of the intensity of returned laser beam 211. As illustrated in
Photodetector 216 may be configured to detect returned laser beam 211 reflected by object 212. Photodetector 216 may convert the laser light (e.g., returned laser beam 211) collected by lens 214 into a receiver signal 218 (e.g., a current or a voltage signal). Receiver signal 218 may be generated when photons are absorbed in photodiode 216. Receiver signal 218 may be transmitted to a data processing unit, e.g., controller 252 of LiDAR system 102, to be processed and analyzed. Controller 252 may be configured to control transmitter 202 and/or receiver 204 to perform detection/sensing operations.
Receiver signal 218 may include an electrical signal of returned laser beam 211, e.g., converted from the light signal of returned laser beam 211. Returned laser beam 211 may be caused by the reflection of laser beam 209 from object 212 in the FOV of LiDAR system 102. Receiver signal 218 may be indicative of the power of returned laser beam 211. Controller 252 may further determine the distance of object 212 from LiDAR system 102 based on the received signal. In some embodiments, controller 252 may determine subsequent laser emission scheme(s) of laser beam 209 based on the distance of object 212.
For example, to obtain a desired coverage of the surroundings and/or the resolution of the scanning/sensing result, the power of laser beam 209 can be controlled/adjusted. For example, the power of laser beam 209 needs to be sufficiently high for LiDAR system 102 to detect object 212 from a desired distance. The span of the scanning angles of laser beam 209, e.g., in the three-dimensional (3D) space, also needs to be sufficiently large to cover a desired range of the surroundings laterally and vertically. Scanner 210 may scan laser beam 209 in the 3D space along a lateral scanning direction and a vertical scanning direction, e.g., from left to the right and from top to bottom, at a desired scanning rate.
Controller 252 may be further configured to control the operations of transmitter 202 to execute the laser emission scheme(s). In some embodiments, controller 252 may adjust laser emission schemes of LiDAR system 102, e.g., in real-time, based on the ranging and detection of a desired safety distance range, and the distance of any object 212 from LiDAR system 102 determined based on receiver signal 218 and data of laser beam 209. When object 212 is close to LiDAR system 102 relatively to the detection range, using a high-power laser emission—would cause potential harm and pose safety concerns when object 212 is a human being. Accordingly, in some embodiments, controller 252 may determine no object 212 is detected in the safety distance range before emitting a laser pulse of a relatively high power for long-distance ranging and detection (e.g., of an area beyond the safety distance range). Because its beam size increases as propagation distance, the power density of the emitted laser beam may decrease when propagating at a longer distance. The laser beam can thus be safe to object 212 farther away from LiDAR system 102. In some embodiments, controller 252 may determine the safety distance range based on a power-associate value and a safety limit required by regulation. The power-associated value may reflect the total power of laser beam 209. The safety limit is a standard value defined by regulation, exceeding which the power of laser beam 209 may cause harm to the human eyes.
For example, to reduce or avoid the potential harm to human eye, controller 252 may first employ a first laser emission scheme to detect whether any object 212 is in the safety distance range. The first laser emission scheme may include a first laser pulse with power desirably low to ensure the power incident on an area representative of the size of a human eye would not exceed the safety limit. On the other hand, the power of the first laser pulse may also be sufficiently high to cover the safety distance range. Controller 252 may determine whether object 212 is present in the safety distance range by detecting the returning laser pulse within an expected time window. If object 212 is detected in the safety distance range, controller 252 may not emit any further laser pulses after the first laser pulse. Controller 252 may determine a distance between object 212 and LiDAR system 102 based on the detection of the first laser pulse returned from object 212. For example, the distance between object 212 and LiDAR system 102 may be calculated based on the speed of light, the scanning angle of laser beam 209 (e.g., the first laser pulse), the round-trip travel time of laser beam 209/211 (e.g., from transmitter 202 to object 212 and back to receiver 204), and/or the power of returned laser beam 211 (e.g., the intensity of the light signal converted by photodetector 216 to receiver signal 218).
If no object 212 is detected in the safety distance range, controller 252 may determine to execute a second laser emission scheme to range the area beyond the safety distance range. The second laser emission scheme includes a second laser pulse after the first laser pulse, and the second laser pulse has a power value higher than the power value of the first laser pulse. Controller 252 may determine the power values of the first and second laser pulses such that at any given time, the total power incident on the area representative of the size of a human eye is lower than the safety limit. With the second laser pulse, a longer-distance ranging and detection can be performed by LiDAR system 102. In some embodiments, the adjustment of laser emission scheme is performed in real-time or near real-time. Functions of controller 252 for the determination of the distance, and the adjustment of laser emission scheme of laser beam 209, are described in greater detail in connection with
In some embodiments, as shown in
Communication interface 228 may send data to and receive data from components of transmitter 202 and receiver 204 such as laser source 206 and photodetector 216 via wired communication methods, such as Serializer/Deserializer (SerDes), Low-voltage differential signaling (LVDS), Serial Peripheral Interface (SPI), etc. In some embodiments, communication interface 402 may optionally use wireless communication methods, such as a Wireless Local Area Network (WLAN), a Wide Area Network (WAN), wireless communication links such as radio waves, a cellular network, and/or a local or short-range wireless network (e.g., Bluetooth™), or other communication methods. Communication interface 228 can send and receive electrical, electromagnetic or optical signals that carry digital data streams representing various types of information.
Consistent with some embodiments, communication interface 228 may receive receiver signal 218 (e.g., containing data of returned laser beam 211). In some embodiments, communication interface 228 may sequentially receive receiver signals 218 as scanner 210 continues to scan laser beams 209 at the scanning rate. Communication interface 228 may transmit the received receiver signal 218 to processor 230 for processing.
Processor 230 may include any appropriate type of general-purpose or special-purpose microprocessor, digital signal processor, or microcontroller. Processor 230 may be configured as a stand-alone processor module dedicated to analyzing signals (e.g., receiver signal 218) and/or controlling the scan schemes. Alternatively, processor 230 may be configured as a shared processor module for performing other functions unrelated to signal analysis/scan scheme control.
In many LiDAR systems with laser wavelengths shorter than 1400 nm such as between 800 nm and 900 nm, laser energy is strictly regulated due to its potential damage to human eyes. Traditionally, the power of each laser pulse is set to be within the regulation/safety limit, based on the assumption of worst case scenario that all pulses emitted towards an eye-sized aperture is absorbed by the aperture. For high resolution and long-range LiDAR systems, this becomes a fundamental challenge. For example, long distance LiDAR requires high energy pulses, which is difficult or even impossible to achieve with the power limit set by the regulation.
The present disclosure provides systems and methods for safe ranging and detection fora long-safety distance range. A novel strategy is implemented to achieve a long detection range without violating the laser safety regulation. The LiDAR system (e.g., via the controller) may determine certain scanning parameters based on a relationship between the safety limit and the power-associated value of the laser beam to ensure power of one or more laser pulses of the laser beam satisfies the safety standards. The LiDAR system (e.g., via the controller) may also adjust the laser emission schemes based on whether an object is detected in a safety distance range (e.g., a short-safety distance range). The adjustment of laser emission schemes can ensure, if an object is detected to be in the safety distance range, a total power of a laser beam along a respective scanning direction does not exceed the safety limit. Meanwhile, if no object is detected to be in the safety distance range, the adjustment of laser emission schemes can allow the detection range beyond the safety distance range (e.g., a long-safety distance range) to be detected without violating the safety standards. The human-eye, assuming the object is a human being, is thus less susceptible to harm caused by the LiDAR system, and long-distance detection and ranging can be safely implemented. Details of the embodiments are described in greater detail as follows.
As shown in
Processor 230 may also adjust the laser emission scheme based on whether object 212 is detected in the safety distance range. When object 212 is not detected in the safety distance range, processor 230 may determine to emit a high-power laser pulse to detect any object 212 in the detection range beyond the safety distance range. Processor 230 may determine the power value of the high-power laser pulse so that no harm can be caused to human eyes by laser beam 209 beyond the safety distance range. When object 212 is detected in the detection range, processor 230 may determine a distance between object 212 and LiDAR 102 based on receiver signal 218 derived from the returned low-power laser pulse, and may not emit any further laser pulse after the low-power laser pulse. That is, at each scanning direction, processor 230 may avoid, in real-time, scanning potentially harmful high-power laser pulse towards object 212 based on the ranging result of the low-power laser pulse. Thus, when object 212 is a human being, the human eyes are less susceptible to harm caused by laser beam 209. In some embodiments, transmitter adjusting module 250, object detecting unit 238, and units 232-236 are configured to perform the above operations. The respective functions of transmitter adjusting module 250 and units 232-238 therein are described as follows.
Transmitter adjusting module 250 may determine the safety distance range, a first laser emission scheme, and a second laser emission scheme. Transmitter adjusting module 250 may also determine the actual distance between object 212 and LiDAR system 102.
Transmitter adjusting module 250 may determine the safety distance range, E1, and E2 based on the safety limit and certain power-associated values of first and second laser pulses 302 and 304. In some embodiments, the safety limit is a predetermined tolerance value such as a maximum permissible exposure (or MPE) value, which represents the highest power or energy density of a light source that is considered safe to a human eye and can be a known value. In some embodiments, the power-associated values of first and second laser pulses 302 and 304 include respective and combined power densities of first and second laser pulses 302 and 304. That is, for laser beam 209 to be safe in the detection range of LiDAR system 102, the power density on object 212, caused by laser beam 209 along a respective scanning direction, must not exceed the MPE value.
Transmitter adjusting module 250 may determine the safety distance range based on the total power density of first and second laser pulses 302 and 304 and the MPE value. By definition, the power density of laser beam 209 at a respective distance (e.g., from LiDAR system 102) may be calculated as the power of laser beam 209 divided by its beam size at the distance. Because laser beam 209 diverges in transmission, for detection range beyond the safety distance range, the beam size of laser beam 209 has its minimum value at an upper bound of the safety distance range, and continues to increase beyond the safety distance range. The upper bound may be the maximum distance of the safety distance range or the radius of the safety distance range. Accordingly, for detection range beyond the safety distance range, the total power density of first and second laser pulses 302 and 304 has its maximum value at the upper bound of the safety distance range, and decreases beyond the safety distance range.
In some embodiments, transmitter 202 repeatedly scans laser beam 209 vertically and laterally to cover the FOV of LiDAR system 102. Laser beam 209 may be emitted along its respective scanning direction within the FOV at the time it is being scanned. At any location in the FOV, on a vertical plane facing laser beam 209, the scanning pattern of laser beams 209 may form a plurality of scanning points, each scanning point corresponding to laser beam 209 scanned or to be scanned at a given time. In other words, the laser beams 209 emitted or to be emitted along a plurality of angles may project to the vertical plane to form the plurality of projections, forming the plurality of scanning points. The beam size at the location may be determined based on the diameter or width of laser beam 209 at a respective scanning point. In some embodiments, the lateral scanning angle, the vertical scanning angle, the lateral delta angles, the vertical delta angles, the scanning rate, and/or divergence characteristics of laser beam 209 may be used to determine the spatial/geometric distribution of laser beam 209 in the 3D space and the distribution of scanning points at any suitable surface/location.
As shown in
The total power density of first and second laser pulses 302 and 304 may then be equal to ETOT/Sbeam(L), where Sbeam(L) represents the beam size of laser beam 209 at distance L and ETOT represents the total power value of first and second laser pulses 302 and 304 at distance L. In various embodiments, ETOT is equal to the total power value of laser beam 209 at a respective scanning direction. To determine the safety distance range, transmitter adjusting module 250 may solve the inequality of MPE≥ETOT/Sbeam(L). Often, the total power is a known value defined by the specification of LiDAR system 102. Because Sbeam(L) is a function of L, for detection range beyond the safety distance range, Sbeam(L) may increase as L increases. The value of ETOT/Sbeam(L) may decrease as L increases, and has its maximum value (i.e., MPE) when L is equal to its minimum value LMIN. The upper bound of the safety distance range may thus be determined to be equal to or greater than LMIN from LiDAR system 102.
Transmitter adjusting module 250 may determine the power value of first laser pulse 302 based on the power density of first laser pulse 302 at a threshold distance, which is a shortest viewing distance from transmitter 202 that a human eye can accommodate to. The threshold distance can be desirably close to the exit of transmitter 202 (or scanner 210) such that the power density of first laser pulse 302 at the threshold distance can be reasonably close to the power density of first laser pulse 302 at the exit of transmitter 202. Based on the safety standards, the power density value of first laser pulse 302 may not exceed the MPE value at the threshold distance. In some embodiments, according to a safety standard, transmitter adjusting module 250 determines the threshold distance to be 100 mm, and the power density of first laser pulse 302 at the threshold distance to be E1/Sbeam(100 mm), where Sbeam(100 mm) represents the beam size of laser beam 209 at the threshold distance of 100 mm. E1 may be equal to the product of the MPE value and Sbeam(100 mm). As described earlier, laser beam 209 diverges in transmission, E1 is thus equal to its maximum value E1MAX at the threshold distance, e.g., E1MAX being equal to the product of MPE value and Sbeam(100 mm). In some embodiments, transmitter power control unit 232 determines E1 to be a value equal to or less than E1MAX . In some embodiments, E1 is sufficiently low to ensure the safety of any human eye in the safety distance range. Meanwhile, E1 may be sufficiently high to cover the safety distance range and capture data for calculating results of detection. It should be noted that, the value of the threshold distance can vary based on different safety standards. For example, according to a more restrictive safety standard, the value of the threshold distance may be longer than 100 mm, such as 150 mm. The specific value of the threshold distance should not be limited by the embodiments of the present disclosure.
Transmitter adjusting module 250 may further determine the power of second laser pulse 304 based on ETOT and E1. In some embodiments, the power value of the second laser pulse, represented by E2, is calculated to be equal to (ETOT−E1), in which ETOT is determined by LiDAR system 102 and E1 is the power value of first laser pulse 302. In some embodiments, the power density value of the second laser pulse may or may not exceed the MPE value in the safety distance range. However, because, at a respective scanning direction, LiDAR system 102 may only emit the second laser pulse when no object 212 is detected in the safety distance range, no potential harm can be caused by the emission of the second laser pulse within the safety distance range. In the meantime, because the total power density of laser beam 209 does not exceed the MPE value in the detection range beyond the safety distance range, no potential harm can be caused by the emissions of the first and second laser pulses in the safety distance range.
Transmitter pulsing control unit 234 may execute first emission scheme by controlling transmitter 202 to emit first laser pulse 302, having power of E1. Object detecting unit 238 may determine whether any object 212 is in the safety distance range and send an alert signal to transmitter adjusting module 250 after determining that object 212 is detected in the safety distance range. For example, based on receiver signal 218, object 212 detecting unit 238 may determine, e.g., in real-time, if object 212 is detected in the detection range, object detecting unit 238 may calculate a distance between object 212 and LiDAR system 102, and compare the distance with the upper bound of the safety distance range. Object detecting unit 238 may then determine whether object 212 is in the safety distance range. When no object 212 is detected in the safety distance range, object detecting unit 238 may send an alert signal to transmitter adjusting module 250 so that transmitter pulsing control unit 234 may switch from the first laser emission scheme to the second laser scheme. In some embodiments, transmitter pulsing control unit 234 controls transmitter 202 to emit second laser pulse 304, having a power of E2. Transmitter power control unit 232 may adjust the power of scanner 210 for the emission of first and second laser pulses 302 and 304.
In some embodiments, when object detecting unit 238 determines that the distance between LiDAR system 102 and object 212 is equal to or less than the upper bound of the safety distance range, object detecting unit 238 determines object 212 is in the safety distance range. Object detecting unit 238 may send another alert signal to transmitter adjusting module 250. Transmitter pulsing control unit 234 may determine to maintain the first emission scheme such that no laser pulse is emitted after first laser pulse 302. Thus, object 212, in the safety distance range, is less susceptible to (or free of) potential harm caused by laser beam 209. Meanwhile, object detecting unit 238 may determine the distance between object 212 and LiDAR system 102 based on, e.g., the round-trip travel time of laser beams 209 and 211 and the scanning angle of scanner 210. In some embodiments, after the emission of second laser pulse 304, object detecting unit 238 determines the distance between object 212 and LiDAR system 102 based on the second laser pulse if object 212 is detected beyond safety distance range.
In some embodiments, transmitter scan control unit 236 controls the scanning of various scanning points along a vertical direction and a horizontal direction. Transmitter scan control unit 236 may control scanner 210 to move to the next scanning direction after the scanning of a respective scanning direction is completed. Transmitter scan control unit 235 may provide data of the scanning, such as scanning angle and divergence angle of laser beam 209, for the calculation of, e.g., the beam size at any distance from LiDAR system 102 and the distance between object 212 and LiDAR system 102.
Units 232-238 (and any corresponding sub-modules or sub-units) and module 250 can be hardware units (e.g., portions of an integrated circuit) of processor 230 designed for operation independently or with other components or software units implemented by processor 230 through executing at least part of a program. The program may be stored on a computer-readable medium. When the program is executed by processor 230, the executed program may cause processor 230 to perform one or more functions or operations. Although
Memory 240 and storage 242 may include any appropriate type of mass storage provided to store any type of information that processor 230 may need to operate. Memory 240 and/or storage 242 may be volatile or non-volatile, magnetic, semiconductor-based, tape-based, optical, removable, non-removable, or other type of storage device or tangible (i.e., non-transitory) computer-readable medium including, but not limited to, a ROM, a flash memory, a dynamic RAM, a static RAM, a hard disk, an SSD, an optical disk, etc. Memory 240 and/or storage 242 may be configured to store one or more computer programs that may be executed by processor 230 to perform functions disclosed herein. For example, memory 240 and/or storage 242 may be configured to store program(s) that may be executed by processor 230 to analyze LiDAR signals and control the emission schemes of laser beams.
Memory 240 and/or storage 242 may be further configured to store/cache information and data received and/or used by processor 230. For instance, memory 240 and/or storage 242 may be configured to store/cache receiver signal 218, data of laser beam 209, predetermined tolerance value(s), look-up tables storing mapping relationship between values indicating the total power incident to a unit area/size at various distances and the corresponding tolerance values indicating the safety limits, and calculation results obtained by different units of processor 230. The various types of data may be stored permanently, removed periodically, or disregarded immediately after each frame of data is processed.
As shown in
Referring back to
Controller 252 may also determine the first and second laser emission schemes, e.g., as shown in
Referring back to
Referring back to
At step 510, if no object is detected in the safety distance range, method 500 proceeds to step 512, in which second laser pulse 304 is emitted along the respective scanning direction according to the second laser emission scheme. In some embodiments, controller 252 may execute the second laser emission scheme when no object 212 is detected in the safety distance range. Second laser pulse may have a power value of E2 that is higher than E1, and can be used for detection and ranging in the area beyond the safety distance range and in the detection range of LiDAR system 102, e.g., between the bounds of D0 and Dd.
Referring back
At step 510, if an object is detected in the safety distance range, method 500 proceeds to step 516, in which a distance between the object and the LIDAR system is determined and no other laser pulses are emitted in the scanning direction. As shown in
Referring back to
In various embodiments, controller 252 may perform at least part of method 500 for each scanning direction during the scanning of the FOV. In some embodiments, controller 252 perform method 500, repeatedly, for each scanning direction. In some embodiments, steps 502 and 504 may be performed once to determine the same safety distance range, and the same first and second laser pulses for each respective scanning direction. In some embodiments, at least steps 506-516 are performed for the respective scanning direction. In some other embodiments, steps 502-516 are performed at least for a plurality of scanning directions. For example, controller 252 may determine different values of ETOT for different safety distance ranges, as long as the value of ETOT does not exceed the total power that can be emitted by LiDAR system 102.
It is also noted that, the predetermined tolerance value used in the calculation of various scanning parameters in this disclosure may also be in forms other than MPE. For example, instead of the MPE value, the predetermine tolerance value may be an accessible emission limit (AEL) value for Class 1, which represents the maximum accessible emission level permitted under normal use and is determined as a product of the MPE value times an area factor called the limiting aperture. In the present disclosure, the AEL value may reflect the total power of laser beam 209 received by a calibration detector (e.g., a photodetector, a meter, or the like) along a respective scanning direction during a measurement setup of a laser safety setup, and may be greater than or equal to ETOT×Sdetector/Sbeam(L), where Sdetector represents the area of the calibration detector and Sbeam(L) represents the beam size at distance L. The power-associated values, in this case, may include power values of the first and second laser pulses, respectively, instead of the respective power density values. The equality of AEL may also be used, e.g., as an alternative, to calculate the upper bound (e.g., radius) of the safety distance range.
Although the disclosure is made using a LiDAR system as an example, the disclosed embodiments may be adapted and implemented to other types of optical sensing systems that use receivers to receive optical signals not limited to laser beams. For example, the embodiments may be readily adapted for optical imaging systems or radar detection systems that use electromagnetic waves to scan objects.
Another aspect of the disclosure is directed to a non-transitory computer-readable medium storing instructions which, when executed, cause one or more processors to perform the methods, as discussed above. The computer-readable medium may include volatile or non-volatile, magnetic, semiconductor, tape, optical, removable, non-removable, or other types of computer-readable medium or computer-readable storage devices. For example, the computer-readable medium may be the storage device or the memory module having the computer instructions stored thereon, as disclosed. In some embodiments, the computer-readable medium may be a disc or a flash drive having the computer instructions stored thereon.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed system and related methods. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed system and related methods.
It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.
