FIELD OF THE TECHNOLOGY
This disclosure relates generally to a detector device and, more particularly, to a device for transceiver alignment in a light ranging and detection (LiDAR) system.
BACKGROUND
Light detection and ranging (LiDAR) systems use light pulses to create an image or point cloud of the external environment. A LiDAR system may be a scanning or non-scanning system. Some typical scanning LiDAR systems include a light source, a light transmitter, a light steering system, and a light detector. The light source generates a light beam that is directed by the light steering system in particular directions when being transmitted from the LiDAR system. When a transmitted light beam is scattered or reflected by an object, a portion of the scattered or reflected light returns to the LiDAR system to form a return light pulse. The light detector detects the return light pulse. Using the difference between the time that the return light pulse is detected and the time that a corresponding light pulse in the light beam is transmitted, the LiDAR system can determine the distance to the object based on the speed of light. This technique of determining the distance is referred to as the time-of-flight (ToF) technique. The light steering system can direct light beams along different paths to allow the LiDAR system to scan the surrounding environment and produce images or point clouds. A typical non-scanning LiDAR system illuminate an entire field-of-view (FOV) rather than scanning through the FOV. An example of the non-scanning LiDAR system is a flash LiDAR, which can also use the ToF technique to measure the distance to an object. LiDAR systems can also use techniques other than time-of-flight and scanning to measure the surrounding environment.
SUMMARY
Embodiments provided in this disclosure are devices and methods for transceiver alignment in a LiDAR system. In one embodiment, a device for transceiver alignment in the LiDAR system is provided. The device is friendly to high-volume production. The device comprises a detector package and a plurality of detector elements mounted to the detector package. The device further comprises one or more light forming markers mounted to the detector package at predetermined positions with respect to the plurality of detector elements. The predetermined positions of the one or more light forming markers are configured to facilitate alignment of each of the plurality of detector elements to a corresponding transmitter channel of a plurality of transmitter channels.
In one embodiment, a method for transceiver alignment in a LiDAR system is provided. The method comprises controlling a plurality of transmitter channels to transmit a plurality of transmission beams toward an imaging device, and causing one or more light forming markers to emit light toward the imaging device. The one or more light forming markers are positioned with respect to a plurality of detector elements at locations predetermined based on an alignment requirement of the plurality of detector elements. The method further comprises forming images of the plurality of transmission beams and images of the one or more light forming markers, and aligning the plurality of transmitter channels with respect to the plurality of detector elements based on the images of transmission beams and the images of the one or more light forming markers.
In one embodiment, a LiDAR system comprising a device for transceiver alignment in the LiDAR system is provided. The device comprises a detector package and a plurality of detector elements mounted to the detector package. The device further comprises one or more light forming markers mounted to the detector package at predetermined positions with respect to the plurality of detector elements. The predetermined positions of the one or more light forming markers are configured to facilitate alignment of each of the plurality of detector elements to a corresponding transmitter channel of a plurality of transmitter channels.
In one embodiment, a LiDAR system comprising a device that performs a method for transceiver alignment in the LiDAR system is provided. The method comprises controlling a plurality of transmitter channels to transmit a plurality of transmission beams toward an imaging device, and causing one or more light forming markers to emit light toward the imaging device. The one or more light forming markers are positioned with respect to a plurality of detector elements at locations predetermined based on an alignment requirement of the plurality of detector elements. The method further comprises forming images of the plurality of transmission beams and images of the one or more light forming markers, and aligning the plurality of transmitter channels with respect to the plurality of detector elements based on the images of transmission beams and the images of the one or more light forming markers.
In one embodiment, a vehicle comprising a LiDAR system is provided. The LiDAR system comprises a device for transceiver alignment in the LiDAR system. The device comprises a detector package and a plurality of detector elements mounted to the detector package. The device further comprises one or more light forming markers mounted to the detector package at predetermined positions with respect to the plurality of detector elements. The predetermined positions of the one or more light forming markers are configured to facilitate alignment of each of the plurality of detector elements to a corresponding transmitter channel of a plurality of transmitter channels.
In one embodiment, a vehicle comprising a LiDAR system is provided. The LiDAR system comprises a device that performs a method for transceiver alignment in the LiDAR system is provided. The method comprises controlling a plurality of transmitter channels to transmit a plurality of transmission beams toward an imaging device, and causing one or more light forming markers to emit light toward the imaging device. The one or more light forming markers are positioned with respect to a plurality of detector elements at locations predetermined based on an alignment requirement of the plurality of detector elements. The method further comprises forming images of the plurality of transmission beams and images of the one or more light forming markers, and aligning the plurality of transmitter channels with respect to the plurality of detector elements based on the images of transmission beams and the images of the one or more light forming markers.
BRIEF DESCRIPTION OF THE DRAWINGS
The present application can be best understood by reference to the embodiments described below taken in conjunction with the accompanying drawing figures, in which like parts may be referred to by like numerals.
FIG. 1 illustrates one or more example LiDAR systems disposed or included in a motor vehicle.
FIG. 2 is a block diagram illustrating interactions between an example LiDAR system and multiple other systems including a vehicle perception and planning system.
FIG. 3 is a block diagram illustrating an example LiDAR system.
FIG. 4 is a block diagram illustrating an example fiber-based laser source.
FIGS. 5A-5C illustrate an example LiDAR system using pulse signals to measure distances to objects disposed in a field-of-view (FOV).
FIG. 6 is a block diagram illustrating an example apparatus used to implement systems, apparatus, and methods in various embodiments.
FIGS. 7A and 7B are diagrams illustrating examples of devices for transceiver alignment in a LiDAR system according to some embodiments.
FIGS. 8A-8C are diagrams illustrating examples of transceiver alignments using light forming markers according to some embodiments.
FIGS. 9A-9G are diagrams illustrating examples of light forming markers according to some embodiments.
FIGS. 10A-10I are diagrams illustrating examples of positions of light forming markers with respect to detector elements according to some embodiments.
FIG. 11 shows an illustrative method for transceiver alignment in a LiDAR system according to some embodiments.
FIG. 12 shows an illustrative method for causing light forming marks to emit light according to some embodiments.
FIG. 13 shows an illustrative method for aligning a plurality of transmitter channels according to some embodiments.
DETAILED DESCRIPTION
To provide a more thorough understanding of various embodiments of the present invention, the following description sets forth numerous specific details, such as specific configurations, parameters, examples, and the like. It should be recognized, however, that such description is not intended as a limitation on the scope of the present invention but is intended to provide a better description of the exemplary embodiments.
Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise:
The phrase “in one embodiment” as used herein does not necessarily refer to the same embodiment, though it may. Thus, as described below, various embodiments of the disclosure may be readily combined, without departing from the scope or spirit of the invention.
As used herein, the term “or” is an inclusive “or” operator and is equivalent to the term “and/or,” unless the context clearly dictates otherwise.
The term “based on” is not exclusive and allows for being based on additional factors not described unless the context clearly dictates otherwise.
As used herein, and unless the context dictates otherwise, the term “coupled to” is intended to include both direct coupling (in which two elements that are coupled to each other contact each other) and indirect coupling (in which at least one additional element is located between the two elements). Therefore, the terms “coupled to” and “coupled with” are used synonymously. Within the context of a networked environment where two or more components or devices are able to exchange data, the terms “coupled to” and “coupled with” are also used to mean “communicatively coupled with”, possibly via one or more intermediary devices. The components or devices can be optical, mechanical, and/or electrical devices.
Although the following description uses terms “first,” “second,” etc. to describe various elements, these elements should not be limited by the terms. These terms are only used to distinguish one element from another. For example, a first sensor could be termed a second sensor and, similarly, a second sensor could be termed a first sensor, without departing from the scope of the various described examples. The first sensor and the second sensor can both be sensors and, in some cases, can be separate and different sensors.
In addition, throughout the specification, the meaning of “a”, “an”, and “the” includes plural references, and the meaning of “in” includes “in” and “on”.
Although some of the various embodiments presented herein constitute a single combination of inventive elements, it should be appreciated that the inventive subject matter is considered to include all possible combinations of the disclosed elements. As such, if one embodiment comprises elements A, B, and C, and another embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if no explicitly discussed herein. Further, the transitional term “comprising” means to have as parts or members, or to be those parts or members. As used herein, the transitional term “comprising” is inclusive or open-ended and does not exclude additional, unrecited elements or method steps.
As used in the description herein and throughout the claims that follow, when a system, engine, server, device, module, or other computing element is described as being configured to perform or execute functions on data in a memory, the meaning of “configured to” or “programmed to” is defined as one or more processors or cores of the computing element to execute the set of functions on target data objects stored in the memory.
It should be noted that any language directed to a computer should be read to include any suitable combination of computing devices or network platforms, including servers, interfaces, systems, databases, agents, peers, engines, controllers, modules, or other types of computing devices operating individually or collectively. One should appreciate the computing devices comprise a processor configured to execute software instruction stored on a tangible, non-transitory computer readable storage medium (e.g., hard drive, FPGA, PLA, solid state drive, RAM, flash, ROM, or any other volatile or non-volatile storage devices). The software instructions configure or program the computing device to provide the roles, responsibilities, or other functionality a discussed below with respect to the disclosed apparatus. Further, the disclosed technologies can be embodied as a computer program product that includes anon-transitory computer readable medium storing the software instructions that causes a processor to execute the disclosed steps associated with implementations of computer-based algorithms, processes, methods, or other instructions. In some embodiments, the various servers, systems, databases, or interfaces exchange data using standardized protocols or algorithms, possibly based on HTTP, HTTPS, AES, public-private key exchanges, web service APIs, known financial transaction protocols, or other electronic information exchanging methods. Data exchanges among devices can be conducted over a packet-switched network, the Internet, LAN, WAN, VPN, or other type of packet switched network; a circuit switched network; cell switched network; or other type of network.
A LiDAR system comprises a plurality of transmitter channels configured to transmit a plurality of transmission beams. When the transmission beams travel to illuminate one or more objects in a FOV, at least a portion of the transmission beams is reflected or scattered to form return light. The LiDAR system further comprises a plurality of detector elements on the receiver side configured to detect the return light. In one example, the plurality of the detector elements can be an avalanche photodiode (APD) array. The plurality of transmitter channels and the plurality of the detector elements are parts of a transceiver and may sometimes be collectively referred to as transceiver. It is desired to have a transceiver alignment in the LiDAR system, so that the plurality of detector elements can collect as much as possible the return light formed based on the transmission beams, thereby achieving a high sensitivity for the LiDAR system.
The LiDAR system is sensitive to the efficiency of light collection. The alignment of the plurality of detector elements may have side effects to the LiDAR's performance. A method for alignment of the plurality of detector elements is using a target with a known reflectivity at a long distance (e.g., >200 m) to optimize return light from the target. However, this may not be feasible for production. Another method for the transceiver alignment comprises two steps. The first step is measuring properties of the transmission beams, e.g., beam angles, beam heights, beam divergences, etc. The second step is applying a device to simulate or replace return light from an illuminated target at a far distance (e.g., >200 m). However, this method is time consuming, which limits the production capacity. Therefore, there is a need for an alignment method that is friendly to high-volume production and improves the production capacity.
Embodiments of present invention are described below. In various embodiments of the present invention, an alignment method that is friendly to high-volume production is provided. The method also provides measurable metrics for optimization to achieve good alignment. The method comprises controlling a plurality of transmitter channels to transmit a plurality of transmission beams toward an imaging device, and causing one or more light forming markers to emit light toward the imaging device. The one or more light forming markers are positioned with respect to a plurality of detector elements at locations predetermined based on an alignment requirement of the plurality of detector elements. The method further comprises forming images of the plurality of transmission beams and images of the one or more light forming markers, and aligning the plurality of transmitter channels with respect to the plurality of detector elements based on the images of transmission beams and the images of the one or more light forming markers.
FIG. 1 illustrates one or more example LiDAR systems 110 and 120A-120I disposed or included in a motor vehicle 100. Vehicle 100 can be a car, a sport utility vehicle (SUV), a truck, a train, a wagon, a bicycle, a motorcycle, a tricycle, a bus, a mobility scooter, a tram, a ship, a boat, an underwater vehicle, an airplane, a helicopter, an unmanned aviation vehicle (UAV), a spacecraft, etc. Motor vehicle 100 can be a vehicle having any automated level. For example, motor vehicle 100 can be a partially automated vehicle, a highly automated vehicle, a fully automated vehicle, or a driverless vehicle. A partially automated vehicle can perform some driving functions without a human driver's intervention. For example, a partially automated vehicle can perform blind-spot monitoring, lane keeping and/or lane changing operations, automated emergency braking, smart cruising and/or traffic following, or the like. Certain operations of a partially automated vehicle may be limited to specific applications or driving scenarios (e.g., limited to only freeway driving). A highly automated vehicle can generally perform all operations of a partially automated vehicle but with less limitations. A highly automated vehicle can also detect its own limits in operating the vehicle and ask the driver to take over the control of the vehicle when necessary. A fully automated vehicle can perform all vehicle operations without a driver's intervention but can also detect its own limits and ask the driver to take over when necessary. A driverless vehicle can operate on its own without any driver intervention.
In typical configurations, motor vehicle 100 comprises one or more LiDAR systems 110 and 120A-120I. Each of LiDAR systems 110 and 120A-120I can be a scanning-based LiDAR system and/or a non-scanning LiDAR system (e.g., a flash LiDAR). A scanning-based LiDAR system scans one or more light beams in one or more directions (e.g., horizontal and vertical directions) to detect objects in a field-of-view (FOV). A non-scanning based LiDAR system transmits laser light to illuminate an FOV without scanning. For example, a flash LiDAR is a type of non-scanning based LiDAR system. A flash LiDAR can transmit laser light to simultaneously illuminate an FOV using a single light pulse or light shot.
A LiDAR system is a frequently-used sensor of a vehicle that is at least partially automated. In one embodiment, as shown in FIG. 1, motor vehicle 100 may include a single LiDAR system 110 (e.g., without LiDAR systems 120A-120I) disposed at the highest position of the vehicle (e.g., at the vehicle roof). Disposing LiDAR system 110 at the vehicle roof facilitates a 360-degree scanning around vehicle 100. In some other embodiments, motor vehicle 100 can include multiple LiDAR systems, including two or more of systems 110 and/or 120A-120I. As shown in FIG. 1, in one embodiment, multiple LiDAR systems 110 and/or 120A-120I are attached to vehicle 100 at different locations of the vehicle. For example, LiDAR system 120A is attached to vehicle 100 at the front right corner; LiDAR system 120B is attached to vehicle 100 at the front center position; LiDAR system 120C is attached to vehicle 100 at the front left corner; LiDAR system 120D is attached to vehicle 100 at the right-side rear view mirror; LiDAR system 120E is attached to vehicle 100 at the left-side rear view mirror; LiDAR system 120F is attached to vehicle 100 at the back center position; LiDAR system 120G is attached to vehicle 100 at the back right corner; LiDAR system 120H is attached to vehicle 100 at the back left corner; and/or LiDAR system 120I is attached to vehicle 100 at the center towards the backend (e.g., back end of the vehicle roof). It is understood that one or more LiDAR systems can be distributed and attached to a vehicle in any desired manner and FIG. 1 only illustrates one embodiment. As another example, LiDAR systems 120D and 120E may be attached to the B-pillars of vehicle 100 instead of the rear-view mirrors. As another example, LiDAR system 120B may be attached to the windshield of vehicle 100 instead of the front bumper.
In some embodiments, LiDAR systems 110 and 120A-120I are independent LiDAR systems having their own respective laser sources, control electronics, transmitters, receivers, and/or steering mechanisms. In other embodiments, some of LiDAR systems 110 and 120A-120I can share one or more components, thereby forming a distributed sensor system. In one example, optical fibers are used to deliver laser light from a centralized laser source to all LiDAR systems. For instance, system 110 (or another system that is centrally positioned or positioned anywhere inside the vehicle 100) includes a light source, a transmitter, and a light detector, but has no steering mechanisms. System 110 may distribute transmission light to each of systems 120A-120I. The transmission light may be distributed via optical fibers. Optical connectors can be used to couple the optical fibers to each of system 110 and 120A-120I. In some examples, one or more of systems 120A-120I include steering mechanisms but no light sources, transmitters, or light detectors. A steering mechanism may include one or more moveable mirrors such as one or more polygon mirrors, one or more single plane mirrors, one or more multi-plane mirrors, or the like. Embodiments of the light source, transmitter, steering mechanism, and light detector are described in more detail below. Via the steering mechanisms, one or more of systems 120A-120I scan light into one or more respective FOVs and receive corresponding return light. The return light is formed by scattering or reflecting the transmission light by one or more objects in the FOVs. Systems 120A-120I may also include collection lens and/or other optics to focus and/or direct the return light into optical fibers, which deliver the received return light to system 110. System 110 includes one or more light detectors for detecting the received return light. In some examples, system 110 is disposed inside a vehicle such that it is in a temperature-controlled environment, while one or more systems 120A-120I may be at least partially exposed to the external environment.
FIG. 2 is a block diagram 200 illustrating interactions between vehicle onboard LiDAR system(s) 210 and multiple other systems including a vehicle perception and planning system 220. LiDAR system(s) 210 can be mounted on or integrated to a vehicle. LiDAR system(s) 210 include sensor(s) that scan laser light to the surrounding environment to measure the distance, angle, and/or velocity of objects. Based on the scattered light that returned to LiDAR system(s) 210, it can generate sensor data (e.g., image data or 3D point cloud data) representing the perceived external environment.
LiDAR system(s) 210 can include one or more of short-range LiDAR sensors, medium-range LiDAR sensors, and long-range LiDAR sensors. A short-range LiDAR sensor measures objects located up to about 20-50 meters from the LiDAR sensor. Short-range LiDAR sensors can be used for, e.g., monitoring nearby moving objects (e.g., pedestrians crossing street in a school zone), parking assistance applications, or the like. A medium-range LiDAR sensor measures objects located up to about 70-200 meters from the LiDAR sensor. Medium-range LiDAR sensors can be used for, e.g., monitoring road intersections, assistance for merging onto or leaving a freeway, or the like. A long-range LiDAR sensor measures objects located up to about 200 meters and beyond. Long-range LiDAR sensors are typically used when a vehicle is travelling at a high speed (e.g., on a freeway), such that the vehicle's control systems may only have a few seconds (e.g., 6-8 seconds) to respond to any situations detected by the LiDAR sensor. As shown in FIG. 2, in one embodiment, the LiDAR sensor data can be provided to vehicle perception and planning system 220 via a communication path 213 for further processing and controlling the vehicle operations. Communication path 213 can be any wired or wireless communication links that can transfer data.
With reference still to FIG. 2, in some embodiments, other vehicle onboard sensor(s) 230 are configured to provide additional sensor data separately or together with LiDAR system(s) 210. Other vehicle onboard sensors 230 may include, for example, one or more camera(s) 232, one or more radar(s) 234, one or more ultrasonic sensor(s) 236, and/or other sensor(s) 238. Camera(s) 232 can take images and/or videos of the external environment of a vehicle. Camera(s) 232 can take, for example, high-definition (HD) videos having millions of pixels in each frame. A camera includes image sensors that facilitate producing monochrome or color images and videos. Color information may be important in interpreting data for some situations (e.g., interpreting images of traffic lights). Color information may not be available from other sensors such as LiDAR or radar sensors. Camera(s) 232 can include one or more of narrow-focus cameras, wider-focus cameras, side-facing cameras, infrared cameras, fisheye cameras, or the like. The image and/or video data generated by camera(s) 232 can also be provided to vehicle perception and planning system 220 via communication path 233 for further processing and controlling the vehicle operations. Communication path 233 can be any wired or wireless communication links that can transfer data. Camera(s) 232 can be mounted on, or integrated to, a vehicle at any location (e.g., rear-view mirrors, pillars, front grille, and/or back bumpers, etc.).
Other vehicle onboard sensor(s) 230 can also include radar sensor(s) 234. Radar sensor(s) 234 use radio waves to determine the range, angle, and velocity of objects. Radar sensor(s) 234 produce electromagnetic waves in the radio or microwave spectrum. The electromagnetic waves reflect off an object and some of the reflected waves return to the radar sensor, thereby providing information about the object's position and velocity. Radar sensor(s) 234 can include one or more of short-range radar(s), medium-range radar(s), and long-range radar(s). A short-range radar measures objects located at about 0.1-30 meters from the radar. A short-range radar is useful in detecting objects located near the vehicle, such as other vehicles, buildings, walls, pedestrians, bicyclists, etc. A short-range radar can be used to detect a blind spot, assist in lane changing, provide rear-end collision warning, assist in parking, provide emergency braking, or the like. A medium-range radar measures objects located at about 30-80 meters from the radar. A long-range radar measures objects located at about 80-200 meters. Medium- and/or long-range radars can be useful in, for example, traffic following, adaptive cruise control, and/or highway automatic braking. Sensor data generated by radar sensor(s) 234 can also be provided to vehicle perception and planning system 220 via communication path 233 for further processing and controlling the vehicle operations. Radar sensor(s) 234 can be mounted on, or integrated to, a vehicle at any location (e.g., rear-view mirrors, pillars, front grille, and/or back bumpers, etc.).
Other vehicle onboard sensor(s) 230 can also include ultrasonic sensor(s) 236. Ultrasonic sensor(s) 236 use acoustic waves or pulses to measure objects located external to a vehicle. The acoustic waves generated by ultrasonic sensor(s) 236 are transmitted to the surrounding environment. At least some of the transmitted waves are reflected off an object and return to the ultrasonic sensor(s) 236. Based on the return signals, a distance of the object can be calculated. Ultrasonic sensor(s) 236 can be useful in, for example, checking blind spots, identifying parking spaces, providing lane changing assistance into traffic, or the like. Sensor data generated by ultrasonic sensor(s) 236 can also be provided to vehicle perception and planning system 220 via communication path 233 for further processing and controlling the vehicle operations. Ultrasonic sensor(s) 236 can be mount on, or integrated to, a vehicle at any location (e.g., rear-view mirrors, pillars, front grille, and/or back bumpers, etc.).
In some embodiments, one or more other sensor(s) 238 may be attached in a vehicle and may also generate sensor data. Other sensor(s) 238 may include, for example, global positioning systems (GPS), inertial measurement units (IMU), or the like. Sensor data generated by other sensor(s) 238 can also be provided to vehicle perception and planning system 220 via communication path 233 for further processing and controlling the vehicle operations. It is understood that communication path 233 may include one or more communication links to transfer data between the various sensor(s) 230 and vehicle perception and planning system 220.
In some embodiments, as shown in FIG. 2, sensor data from other vehicle onboard sensor(s) 230 can be provided to vehicle onboard LiDAR system(s) 210 via communication path 231. LiDAR system(s) 210 may process the sensor data from other vehicle onboard sensor(s) 230. For example, sensor data from camera(s) 232, radar sensor(s) 234, ultrasonic sensor(s) 236, and/or other sensor(s) 238 may be correlated or fused with sensor data LiDAR system(s) 210, thereby at least partially offloading the sensor fusion process performed by vehicle perception and planning system 220. It is understood that other configurations may also be implemented for transmitting and processing sensor data from the various sensors (e.g., data can be transmitted to a cloud or edge computing service provider for processing and then the processing results can be transmitted back to the vehicle perception and planning system 220 and/or LiDAR system 210).
With reference still to FIG. 2, in some embodiments, sensors onboard other vehicle(s) 250 are used to provide additional sensor data separately or together with LiDAR system(s) 210. For example, two or more nearby vehicles may have their own respective LiDAR sensor(s), camera(s), radar sensor(s), ultrasonic sensor(s), etc. Nearby vehicles can communicate and share sensor data with one another. Communications between vehicles are also referred to as V2V (vehicle to vehicle) communications. For example, as shown in FIG. 2, sensor data generated by other vehicle(s) 250 can be communicated to vehicle perception and planning system 220 and/or vehicle onboard LiDAR system(s) 210, via communication path 253 and/or communication path 251, respectively. Communication paths 253 and 251 can be any wired or wireless communication links that can transfer data.
Sharing sensor data facilitates a better perception of the environment external to the vehicles. For instance, a first vehicle may not sense a pedestrian that is behind a second vehicle but is approaching the first vehicle. The second vehicle may share the sensor data related to this pedestrian with the first vehicle such that the first vehicle can have additional reaction time to avoid collision with the pedestrian. In some embodiments, similar to data generated by sensor(s) 230, data generated by sensors onboard other vehicle(s) 250 may be correlated or fused with sensor data generated by LiDAR system(s) 210 (or with other LiDAR systems located in other vehicles), thereby at least partially offloading the sensor fusion process performed by vehicle perception and planning system 220.
In some embodiments, intelligent infrastructure system(s) 240 are used to provide sensor data separately or together with LiDAR system(s) 210. Certain infrastructures may be configured to communicate with a vehicle to convey information and vice versa. Communications between a vehicle and infrastructures are generally referred to as V2I (vehicle to infrastructure) communications. For example, intelligent infrastructure system(s) 240 may include an intelligent traffic light that can convey its status to an approaching vehicle in a message such as “changing to yellow in 5 seconds.” Intelligent infrastructure system(s) 240 may also include its own LiDAR system mounted near an intersection such that it can convey traffic monitoring information to a vehicle. For example, a left-turning vehicle at an intersection may not have sufficient sensing capabilities because some of its own sensors may be blocked by traffic in the opposite direction. In such a situation, sensors of intelligent infrastructure system(s) 240 can provide useful data to the left-turning vehicle. Such data may include, for example, traffic conditions, information of objects in the direction the vehicle is turning to, traffic light status and predictions, or the like. These sensor data generated by intelligent infrastructure system(s) 240 can be provided to vehicle perception and planning system 220 and/or vehicle onboard LiDAR system(s) 210, via communication paths 243 and/or 241, respectively. Communication paths 243 and/or 241 can include any wired or wireless communication links that can transfer data. For example, sensor data from intelligent infrastructure system(s) 240 may be transmitted to LiDAR system(s) 210 and correlated or fused with sensor data generated by LiDAR system(s) 210, thereby at least partially offloading the sensor fusion process performed by vehicle perception and planning system 220. V2V and V2I communications described above are examples of vehicle-to-X (V2X) communications, where the “X” represents any other devices, systems, sensors, infrastructure, or the like that can share data with a vehicle.
With reference still to FIG. 2, via various communication paths, vehicle perception and planning system 220 receives sensor data from one or more of LiDAR system(s) 210, other vehicle onboard sensor(s) 230, other vehicle(s) 250, and/or intelligent infrastructure system(s) 240. In some embodiments, different types of sensor data are correlated and/or integrated by a sensor fusion sub-system 222. For example, sensor fusion sub-system 222 can generate a 360-degree model using multiple images or videos captured by multiple cameras disposed at different positions of the vehicle. Sensor fusion sub-system 222 obtains sensor data from different types of sensors and uses the combined data to perceive the environment more accurately. For example, a vehicle onboard camera 232 may not capture a clear image because it is facing the sun or a light source (e.g., another vehicle's headlight during nighttime) directly. A LiDAR system 210 may not be affected as much and therefore sensor fusion sub-system 222 can combine sensor data provided by both camera 232 and LiDAR system 210, and use the sensor data provided by LiDAR system 210 to compensate the unclear image captured by camera 232. As another example, in a rainy or foggy weather, a radar sensor 234 may work better than a camera 232 or a LiDAR system 210. Accordingly, sensor fusion sub-system 222 may use sensor data provided by the radar sensor 234 to compensate the sensor data provided by camera 232 or LiDAR system 210.
In other examples, sensor data generated by other vehicle onboard sensor(s) 230 may have a lower resolution (e.g., radar sensor data) and thus may need to be correlated and confirmed by LiDAR system(s) 210, which usually has a higher resolution. For example, a sewage cover (also referred to as a manhole cover) may be detected by radar sensor 234 as an object towards which a vehicle is approaching. Due to the low-resolution nature of radar sensor 234, vehicle perception and planning system 220 may not be able to determine whether the object is an obstacle that the vehicle needs to avoid. High-resolution sensor data generated by LiDAR system(s) 210 thus can be used to correlated and confirm that the object is a sewage cover and causes no harm to the vehicle.
Vehicle perception and planning system 220 further comprises an object classifier 223. Using raw sensor data and/or correlated/fused data provided by sensor fusion sub-system 222, object classifier 223 can use any computer vision techniques to detect and classify the objects and estimate the positions of the objects. In some embodiments, object classifier 223 can use machine-learning based techniques to detect and classify objects. Examples of the machine-learning based techniques include utilizing algorithms such as region-based convolutional neural networks (R-CNN), Fast R-CNN, Faster R-CNN, histogram of oriented gradients (HOG), region-based fully convolutional network (R-FCN), single shot detector (SSD), spatial pyramid pooling (SPP-net), and/or You Only Look Once (Yolo).
Vehicle perception and planning system 220 further comprises a road detection sub-system 224. Road detection sub-system 224 localizes the road and identifies objects and/or markings on the road. For example, based on raw or fused sensor data provided by radar sensor(s) 234, camera(s) 232, and/or LiDAR system(s) 210, road detection sub-system 224 can build a 3D model of the road based on machine-learning techniques (e.g., pattern recognition algorithms for identifying lanes). Using the 3D model of the road, road detection sub-system 224 can identify objects (e.g., obstacles or debris on the road) and/or markings on the road (e.g., lane lines, turning marks, crosswalk marks, or the like).
Vehicle perception and planning system 220 further comprises a localization and vehicle posture sub-system 225. Based on raw or fused sensor data, localization and vehicle posture sub-system 225 can determine position of the vehicle and the vehicle's posture. For example, using sensor data from LiDAR system(s) 210, camera(s) 232, and/or GPS data, localization and vehicle posture sub-system 225 can determine an accurate position of the vehicle on the road and the vehicle's six degrees of freedom (e.g., whether the vehicle is moving forward or backward, up or down, and left or right). In some embodiments, high-definition (HD) maps are used for vehicle localization. HD maps can provide highly detailed, three-dimensional, computerized maps that pinpoint a vehicle's location. For instance, using the HD maps, localization and vehicle posture sub-system 225 can determine precisely the vehicle's current position (e.g., which lane of the road the vehicle is currently in, how close it is to a curb or a sidewalk) and predict vehicle's future positions.
Vehicle perception and planning system 220 further comprises obstacle predictor 226. Objects identified by object classifier 223 can be stationary (e.g., a light pole, a road sign) or dynamic (e.g., a moving pedestrian, bicycle, another car). For moving objects, predicting their moving path or future positions can be important to avoid collision. Obstacle predictor 226 can predict an obstacle trajectory and/or warn the driver or the vehicle planning sub-system 228 about a potential collision. For example, if there is a high likelihood that the obstacle's trajectory intersects with the vehicle's current moving path, obstacle predictor 226 can generate such a warning. Obstacle predictor 226 can use a variety of techniques for making such a prediction. Such techniques include, for example, constant velocity or acceleration models, constant turn rate and velocity/acceleration models, Kalman Filter and Extended Kalman Filter based models, recurrent neural network (RNN) based models, long short-term memory (LSTM) neural network based models, encoder-decoder RNN models, or the like.
With reference still to FIG. 2, in some embodiments, vehicle perception and planning system 220 further comprises vehicle planning sub-system 228. Vehicle planning sub-system 228 can include one or more planners such as a route planner, a driving behaviors planner, and a motion planner. The route planner can plan the route of a vehicle based on the vehicle's current location data, target location data, traffic information, etc. The driving behavior planner adjusts the timing and planned movement based on how other objects might move, using the obstacle prediction results provided by obstacle predictor 226. The motion planner determines the specific operations the vehicle needs to follow. The planning results are then communicated to vehicle control system 280 via vehicle interface 270. The communication can be performed through communication paths 227 and 271, which include any wired or wireless communication links that can transfer data.
Vehicle control system 280 controls the vehicle's steering mechanism, throttle, brake, etc., to operate the vehicle according to the planned route and movement. In some examples, vehicle perception and planning system 220 may further comprise a user interface 260, which provides a user (e.g., a driver) access to vehicle control system 280 to, for example, override or take over control of the vehicle when necessary. User interface 260 may also be separate from vehicle perception and planning system 220. User interface 260 can communicate with vehicle perception and planning system 220, for example, to obtain and display raw or fused sensor data, identified objects, vehicle's location/posture, etc. These displayed data can help a user to better operate the vehicle. User interface 260 can communicate with vehicle perception and planning system 220 and/or vehicle control system 280 via communication paths 221 and 261 respectively, which include any wired or wireless communication links that can transfer data. It is understood that the various systems, sensors, communication links, and interfaces in FIG. 2 can be configured in any desired manner and not limited to the configuration shown in FIG. 2.
FIG. 3 is a block diagram illustrating an example LiDAR system 300. LiDAR system 300 can be used to implement LiDAR systems 110, 120A-120I, and/or 210 shown in FIGS. 1 and 2. In one embodiment, LiDAR system 300 comprises a light source 310, a transmitter 320, an optical receiver and light detector 330, a steering system 340, and a control circuitry 350. These components are coupled together using communications paths 312, 314, 322, 332, 342, 352, and 362. These communications paths include communication links (wired or wireless, bidirectional or unidirectional) among the various LiDAR system components, but need not be physical components themselves. While the communications paths can be implemented by one or more electrical wires, buses, or optical fibers, the communication paths can also be wireless channels or free-space optical paths so that no physical communication medium is present. For example, in one embodiment of LiDAR system 300, communication path 314 between light source 310 and transmitter 320 may be implemented using one or more optical fibers. Communication paths 332 and 352 may represent optical paths implemented using free space optical components and/or optical fibers. And communication paths 312, 322, 342, and 362 may be implemented using one or more electrical wires that carry electrical signals. The communications paths can also include one or more of the above types of communication mediums (e.g., they can include an optical fiber and a free-space optical component, or include one or more optical fibers and one or more electrical wires).
In some embodiments, LiDAR system 300 can be a coherent LiDAR system. One example is a frequency-modulated continuous-wave (FMCW) LiDAR. Coherent LiDARs detect objects by mixing return light from the objects with light from the coherent laser transmitter. Thus, as shown in FIG. 3, if LiDAR system 300 is a coherent LiDAR, it may include a route 372 providing a portion of transmission light from transmitter 320 to optical receiver and light detector 330. Route 372 may include one or more optics (e.g., optical fibers, lens, mirrors, etc.) for providing the light from transmitter 320 to optical receiver and light detector 330. The transmission light provided by transmitter 320 may be modulated light and can be split into two portions. One portion is transmitted to the FOV, while the second portion is sent to the optical receiver and light detector of the LiDAR system. The second portion is also referred to as the light that is kept local (LO) to the LiDAR system. The transmission light is scattered or reflected by various objects in the FOV and at least a portion of it forms return light. The return light is subsequently detected and interferometrically recombined with the second portion of the transmission light that was kept local. Coherent LiDAR provides a means of optically sensing an object's range as well as its relative velocity along the line-of-sight (LOS).
LiDAR system 300 can also include other components not depicted in FIG. 3, such as power buses, power supplies, LED indicators, switches, etc. Additionally, other communication connections among components may be present, such as a direct connection between light source 310 and optical receiver and light detector 330 to provide a reference signal so that the time from when a light pulse is transmitted until a return light pulse is detected can be accurately measured.
Light source 310 outputs laser light for illuminating objects in a field of view (FOV). The laser light can be infrared light having a wavelength in the range of 700 nm to 1 mm. Light source 310 can be, for example, a semiconductor-based laser (e.g., a diode laser) and/or a fiber-based laser. A semiconductor-based laser can be, for example, an edge emitting laser (EEL), a vertical cavity surface emitting laser (VCSEL), an external-cavity diode laser, a vertical-external-cavity surface-emitting laser, a distributed feedback (DFB) laser, a distributed Bragg reflector (DBR) laser, an interband cascade laser, a quantum cascade laser, a quantum well laser, a double heterostructure laser, or the like. A fiber-based laser is a laser in which the active gain medium is an optical fiber doped with rare-earth elements such as erbium, ytterbium, neodymium, dysprosium, praseodymium, thulium and/or holmium. In some embodiments, a fiber laser is based on double-clad fibers, in which the gain medium forms the core of the fiber surrounded by two layers of cladding. The double-clad fiber allows the core to be pumped with a high-power beam, thereby enabling the laser source to be a high power fiber laser source.
In some embodiments, light source 310 comprises a master oscillator (also referred to as a seed laser) and power amplifier (MOPA). The power amplifier amplifies the output power of the seed laser. The power amplifier can be a fiber amplifier, a bulk amplifier, or a semiconductor optical amplifier. The seed laser can be a diode laser (e.g., a Fabry-Perot cavity laser, a distributed feedback laser), a solid-state bulk laser, or a tunable external-cavity diode laser. In some embodiments, light source 310 can be an optically pumped microchip laser. Microchip lasers are alignment-free monolithic solid-state lasers where the laser crystal is directly contacted with the end mirrors of the laser resonator. A microchip laser is typically pumped with a laser diode (directly or using a fiber) to obtain the desired output power. A microchip laser can be based on neodymium-doped yttrium aluminum garnet (Y3Al5O12) laser crystals (i.e., Nd:YAG), or neodymium-doped vanadate (i.e., ND:YVO4) laser crystals. In some examples, light source 310 may have multiple amplification stages to achieve a high power gain such that the laser output can have high power, thereby enabling the LiDAR system to have a long scanning range. In some examples, the power amplifier of light source 310 can be controlled such that the power gain can be varied to achieve any desired laser output power.
FIG. 4 is a block diagram illustrating an example fiber-based laser source 400 having a seed laser and one or more pumps (e.g., laser diodes) for pumping desired output power. Fiber-based laser source 400 is an example of light source 310 depicted in FIG. 3. In some embodiments, fiber-based laser source 400 comprises a seed laser 402 to generate initial light pulses of one or more wavelengths (e.g., infrared wavelengths such as 1550 nm), which are provided to a wavelength-division multiplexor (WDM) 404 via an optical fiber 403. Fiber-based laser source 400 further comprises a pump 406 for providing laser power (e.g., of a different wavelength, such as 980 nm) to WDM 404 via an optical fiber 405. WDM 404 multiplexes the light pulses provided by seed laser 402 and the laser power provided by pump 406 onto a single optical fiber 407. The output of WDM 404 can then be provided to one or more pre-amplifier(s) 408 via optical fiber 407. Pre-amplifier(s) 408 can be optical amplifier(s) that amplify optical signals (e.g., with about 10-30 dB gain). In some embodiments, pre-amplifier(s) 408 are low noise amplifiers. Pre-amplifier(s) 408 output to an optical combiner 410 via an optical fiber 409. Combiner 410 combines the output laser light of pre-amplifier(s) 408 with the laser power provided by pump 412 via an optical fiber 411. Combiner 410 can combine optical signals having the same wavelength or different wavelengths. One example of a combiner is a WDM. Combiner 410 provides combined optical signals to a booster amplifier 414, which produces output light pulses via optical fiber 415. The booster amplifier 414 provides further amplification of the optical signals (e.g., another 20-40 dB). The output light pulses can then be transmitted to transmitter 320 and/or steering mechanism 340 (shown in FIG. 3). It is understood that FIG. 4 illustrates one example configuration of fiber-based laser source 400. Laser source 400 can have many other configurations using different combinations of one or more components shown in FIG. 4 and/or other components not shown in FIG. 4 (e.g., other components such as power supplies, lens(es), filters, splitters, combiners, etc.).
In some variations, fiber-based laser source 400 can be controlled (e.g., by control circuitry 350) to produce pulses of different amplitudes based on the fiber gain profile of the fiber used in fiber-based laser source 400. Communication path 312 couples fiber-based laser source 400 to control circuitry 350 (shown in FIG. 3) so that components of fiber-based laser source 400 can be controlled by or otherwise communicate with control circuitry 350. Alternatively, fiber-based laser source 400 may include its own dedicated controller. Instead of control circuitry 350 communicating directly with components of fiber-based laser source 400, a dedicated controller of fiber-based laser source 400 communicates with control circuitry 350 and controls and/or communicates with the components of fiber-based laser source 400. Fiber-based laser source 400 can also include other components not shown, such as one or more power connectors, power supplies, and/or power lines.
Referencing FIG. 3, typical operating wavelengths of light source 310 comprise, for example, about 850 nm, about 905 nm, about 940 nm, about 1064 nm, and about 1550 nm. For laser safety, the upper limit of maximum usable laser power is set by the U.S. FDA (U.S. Food and Drug Administration) regulations. The optical power limit at 1550 nm wavelength is much higher than those of the other aforementioned wavelengths. Further, at 1550 nm, the optical power loss in a fiber is low. There characteristics of the 1550 nm wavelength make it more beneficial for long-range LiDAR applications. The amount of optical power output from light source 310 can be characterized by its peak power, average power, pulse energy, and/or the pulse energy density. The peak power is the ratio of pulse energy to the width of the pulse (e.g., full width at half maximum or FWHM). Thus, a smaller pulse width can provide a larger peak power for a fixed amount of pulse energy. A pulse width can be in the range of nanosecond or picosecond. The average power is the product of the energy of the pulse and the pulse repetition rate (PRR). As described in more detail below, the PRR represents the frequency of the pulsed laser light. In general, the smaller the time interval between the pulses, the higher the PRR. The PRR typically corresponds to the maximum range that a LiDAR system can measure. Light source 310 can be configured to produce pulses at high PRR to meet the desired number of data points in a point cloud generated by the LiDAR system. Light source 310 can also be configured to produce pulses at medium or low PRR to meet the desired maximum detection distance. Wall plug efficiency (WPE) is another factor to evaluate the total power consumption, which may be a useful indicator in evaluating the laser efficiency. For example, as shown in FIG. 1, multiple LiDAR systems may be attached to a vehicle, which may be an electrical-powered vehicle or a vehicle otherwise having limited fuel or battery power supply. Therefore, high WPE and intelligent ways to use laser power are often among the important considerations when selecting and configuring light source 310 and/or designing laser delivery systems for vehicle-mounted LiDAR applications.
It is understood that the above descriptions provide non-limiting examples of a light source 310. Light source 310 can be configured to include many other types of light sources (e.g., laser diodes, short-cavity fiber lasers, solid-state lasers, and/or tunable external cavity diode lasers) that are configured to generate one or more light signals at various wavelengths. In some examples, light source 310 comprises amplifiers (e.g., pre-amplifiers and/or booster amplifiers), which can be a doped optical fiber amplifier, a solid-state bulk amplifier, and/or a semiconductor optical amplifier. The amplifiers are configured to receive and amplify light signals with desired gains.
With reference back to FIG. 3, LiDAR system 300 further comprises a transmitter 320. Light source 310 provides laser light (e.g., in the form of a laser beam) to transmitter 320. The laser light provided by light source 310 can be amplified laser light with a predetermined or controlled wavelength, pulse repetition rate, and/or power level. Transmitter 320 receives the laser light from light source 310 and transmits the laser light to steering mechanism 340 with low divergence. In some embodiments, transmitter 320 can include, for example, optical components (e.g., lens, fibers, mirrors, etc.) for transmitting one or more laser beams to a field-of-view (FOV) directly or via steering mechanism 340. While FIG. 3 illustrates transmitter 320 and steering mechanism 340 as separate components, they may be combined or integrated as one system in some embodiments. Steering mechanism 340 is described in more detail below.
Laser beams provided by light source 310 may diverge as they travel to transmitter 320. Therefore, transmitter 320 often comprises a collimating lens configured to collect the diverging laser beams and produce more parallel optical beams with reduced or minimum divergence. The collimated optical beams can then be further directed through various optics such as mirrors and lens. A collimating lens may be, for example, a single plano-convex lens or a lens group. The collimating lens can be configured to achieve any desired properties such as the beam diameter, divergence, numerical aperture, focal length, or the like. A beam propagation ratio or beam quality factor (also referred to as the M2 factor) is used for measurement of laser beam quality. In many LiDAR applications, it is important to have good laser beam quality in the generated transmitting laser beam. The M2 factor represents a degree of variation of a beam from an ideal Gaussian beam. Thus, the M2 factor reflects how well a collimated laser beam can be focused on a small spot, or how well a divergent laser beam can be collimated. Therefore, light source 310 and/or transmitter 320 can be configured to meet, for example, a scan resolution requirement while maintaining the desired M2 factor.
One or more of the light beams provided by transmitter 320 are scanned by steering mechanism 340 to a FOV. Steering mechanism 340 scans light beams in multiple dimensions (e.g., in both the horizontal and vertical dimension) to facilitate LiDAR system 300 to map the environment by generating a 3D point cloud. A horizontal dimension can be a dimension that is parallel to the horizon or a surface associated with the LiDAR system or a vehicle (e.g., a road surface). A vertical dimension is perpendicular to the horizontal dimension (i.e., the vertical dimension forms a 90-degree angle with the horizontal dimension). Steering mechanism 340 will be described in more detail below. The laser light scanned to an FOV may be scattered or reflected by an object in the FOV. At least a portion of the scattered or reflected light forms return light that returns to LiDAR system 300. FIG. 3 further illustrates an optical receiver and light detector 330 configured to receive the return light. Optical receiver and light detector 330 comprises an optical receiver that is configured to collect the return light from the FOV. The optical receiver can include optics (e.g., lens, fibers, mirrors, etc.) for receiving, redirecting, focusing, amplifying, and/or filtering return light from the FOV. For example, the optical receiver often includes a collection lens (e.g., a single plano-convex lens or a lens group) to collect and/or focus the collected return light onto a light detector.
A light detector detects the return light focused by the optical receiver and generates current and/or voltage signals proportional to the incident intensity of the return light. Based on such current and/or voltage signals, the depth information of the object in the FOV can be derived. One example method for deriving such depth information is based on the direct TOF (time of flight), which is described in more detail below. A light detector may be characterized by its detection sensitivity, quantum efficiency, detector bandwidth, linearity, signal to noise ratio (SNR), overload resistance, interference immunity, etc. Based on the applications, the light detector can be configured or customized to have any desired characteristics. For example, optical receiver and light detector 330 can be configured such that the light detector has a large dynamic range while having a good linearity. The light detector linearity indicates the detector's capability of maintaining linear relationship between input optical signal power and the detector's output. A detector having good linearity can maintain a linear relationship over a large dynamic input optical signal range.
To achieve desired detector characteristics, configurations or customizations can be made to the light detector's structure and/or the detector's material system. Various detector structures can be used for a light detector. For example, a light detector structure can be a PIN based structure, which has an undoped intrinsic semiconductor region (i.e., an “i” region) between a p-type semiconductor and an n-type semiconductor region. Other light detector structures comprise, for example, an APD (avalanche photodiode) based structure, a PMT (photomultiplier tube) based structure, a SiPM (Silicon photomultiplier) based structure, a SPAD (single-photon avalanche diode) based structure, and/or quantum wires. For material systems used in a light detector, Si, InGaAs, and/or Si/Ge based materials can be used. It is understood that many other detector structures and/or material systems can be used in optical receiver and light detector 330.
A light detector (e.g., an APD based detector) may have an internal gain such that the input signal is amplified when generating an output signal. However, noise may also be amplified due to the light detector's internal gain. Common types of noise include signal shot noise, dark current shot noise, thermal noise, and amplifier noise. In some embodiments, optical receiver and light detector 330 may include a pre-amplifier that is a low noise amplifier (LNA). In some embodiments, the pre-amplifier may also include a transimpedance amplifier (TIA), which converts a current signal to a voltage signal. For a linear detector system, input equivalent noise or noise equivalent power (NEP) measures how sensitive the light detector is to weak signals. Therefore, they can be used as indicators of the overall system performance. For example, the NEP of a light detector specifies the power of the weakest signal that can be detected and therefore it in turn specifies the maximum range of a LiDAR system. It is understood that various light detector optimization techniques can be used to meet the requirement of LiDAR system 300. Such optimization techniques may include selecting different detector structures, materials, and/or implementing signal processing techniques (e.g., filtering, noise reduction, amplification, or the like). For example, in addition to, or instead of, using direct detection of return signals (e.g., by using ToF), coherent detection can also be used for a light detector. Coherent detection allows for detecting amplitude and phase information of the received light by interfering the received light with a local oscillator. Coherent detection can improve detection sensitivity and noise immunity.
FIG. 3 further illustrates that LiDAR system 300 comprises steering mechanism 340. As described above, steering mechanism 340 directs light beams from transmitter 320 to scan an FOV in multiple dimensions. A steering mechanism is referred to as a raster mechanism, a scanning mechanism, or simply a light scanner. Scanning light beams in multiple directions (e.g., in both the horizontal and vertical directions) facilitates a LiDAR system to map the environment by generating an image or a 3D point cloud. A steering mechanism can be based on mechanical scanning and/or solid-state scanning. Mechanical scanning uses rotating mirrors to steer the laser beam or physically rotate the LiDAR transmitter and receiver (collectively referred to as transceiver) to scan the laser beam. Solid-state scanning directs the laser beam to various positions through the FOV without mechanically moving any macroscopic components such as the transceiver. Solid-state scanning mechanisms include, for example, optical phased arrays based steering and flash LiDAR based steering. In some embodiments, because solid-state scanning mechanisms do not physically move macroscopic components, the steering performed by a solid-state scanning mechanism may be referred to as effective steering. A LiDAR system using solid-state scanning may also be referred to as a non-mechanical scanning or simply non-scanning LiDAR system (a flash LiDAR system is an example non-scanning LiDAR system).
Steering mechanism 340 can be used with a transceiver (e.g., transmitter 320 and optical receiver and light detector 330) to scan the FOV for generating an image or a 3D point cloud. As an example, to implement steering mechanism 340, a two-dimensional mechanical scanner can be used with a single-point or several single-point transceivers. A single-point transceiver transmits a single light beam or a small number of light beams (e.g., 2-8 beams) to the steering mechanism. A two-dimensional mechanical steering mechanism comprises, for example, polygon mirror(s), oscillating mirror(s), rotating prism(s), rotating tilt mirror surface(s), single-plane or multi-plane mirror(s), or a combination thereof. In some embodiments, steering mechanism 340 may include non-mechanical steering mechanism(s) such as solid-state steering mechanism(s). For example, steering mechanism 340 can be based on tuning wavelength of the laser light combined with refraction effect, and/or based on reconfigurable grating/phase array. In some embodiments, steering mechanism 340 can use a single scanning device to achieve two-dimensional scanning or multiple scanning devices combined to realize two-dimensional scanning.
As another example, to implement steering mechanism 340, a one-dimensional mechanical scanner can be used with an array or a large number of single-point transceivers. Specifically, the transceiver array can be mounted on a rotating platform to achieve 360-degree horizontal field of view. Alternatively, a static transceiver array can be combined with the one-dimensional mechanical scanner. A one-dimensional mechanical scanner comprises polygon mirror(s), oscillating mirror(s), rotating prism(s), rotating tilt mirror surface(s), or a combination thereof, for obtaining a forward-looking horizontal field of view. Steering mechanisms using mechanical scanners can provide robustness and reliability in high volume production for automotive applications.
As another example, to implement steering mechanism 340, a two-dimensional transceiver can be used to generate a scan image or a 3D point cloud directly. In some embodiments, a stitching or micro shift method can be used to improve the resolution of the scan image or the field of view being scanned. For example, using a two-dimensional transceiver, signals generated at one direction (e.g., the horizontal direction) and signals generated at the other direction (e.g., the vertical direction) may be integrated, interleaved, and/or matched to generate a higher or full resolution image or 3D point cloud representing the scanned FOV.
Some implementations of steering mechanism 340 comprise one or more optical redirection elements (e.g., mirrors or lenses) that steer return light signals (e.g., by rotating, vibrating, or directing) along a receive path to direct the return light signals to optical receiver and light detector 330. The optical redirection elements that direct light signals along the transmitting and receiving paths may be the same components (e.g., shared), separate components (e.g., dedicated), and/or a combination of shared and separate components. This means that in some cases the transmitting and receiving paths are different although they may partially overlap (or in some cases, substantially overlap or completely overlap).
With reference still to FIG. 3, LiDAR system 300 further comprises control circuitry 350. Control circuitry 350 can be configured and/or programmed to control various parts of the LiDAR system 300 and/or to perform signal processing. In a typical system, control circuitry 350 can be configured and/or programmed to perform one or more control operations including, for example, controlling light source 310 to obtain the desired laser pulse timing, the pulse repetition rate, and power; controlling steering mechanism 340 (e.g., controlling the speed, direction, and/or other parameters) to scan the FOV and maintain pixel registration and/or alignment; controlling optical receiver and light detector 330 (e.g., controlling the sensitivity, noise reduction, filtering, and/or other parameters) such that it is an optimal state; and monitoring overall system health/status for functional safety (e.g., monitoring the laser output power and/or the steering mechanism operating status for safety).
Control circuitry 350 can also be configured and/or programmed to perform signal processing to the raw data generated by optical receiver and light detector 330 to derive distance and reflectance information, and perform data packaging and communication to vehicle perception and planning system 220 (shown in FIG. 2). For example, control circuitry 350 determines the time it takes from transmitting a light pulse until a corresponding return light pulse is received; determines when a return light pulse is not received for a transmitted light pulse; determines the direction (e.g., horizontal and/or vertical information) for a transmitted/return light pulse; determines the estimated range in a particular direction; derives the reflectivity of an object in the FOV, and/or determines any other type of data relevant to LiDAR system 300.
LiDAR system 300 can be disposed in a vehicle, which may operate in many different environments including hot or cold weather, rough road conditions that may cause intense vibration, high or low humidities, dusty areas, etc. Therefore, in some embodiments, optical and/or electronic components of LiDAR system 300 (e.g., optics in transmitter 320, optical receiver and light detector 330, and steering mechanism 340) are disposed and/or configured in such a manner to maintain long term mechanical and optical stability. For example, components in LiDAR system 300 may be secured and sealed such that they can operate under all conditions a vehicle may encounter. As an example, an anti-moisture coating and/or hermetic sealing may be applied to optical components of transmitter 320, optical receiver and light detector 330, and steering mechanism 340 (and other components that are susceptible to moisture). As another example, housing(s), enclosure(s), fairing(s), and/or window can be used in LiDAR system 300 for providing desired characteristics such as hardness, ingress protection (IP) rating, self-cleaning capability, resistance to chemical and resistance to impact, or the like. In addition, efficient and economical methodologies for assembling LiDAR system 300 may be used to meet the LiDAR operating requirements while keeping the cost low.
It is understood by a person of ordinary skill in the art that FIG. 3 and the above descriptions are for illustrative purposes only, and a LiDAR system can include other functional units, blocks, or segments, and can include variations or combinations of these above functional units, blocks, or segments. For example, LiDAR system 300 can also include other components not depicted in FIG. 3, such as power buses, power supplies, LED indicators, switches, etc. Additionally, other connections among components may be present, such as a direct connection between light source 310 and optical receiver and light detector 330 so that light detector 330 can accurately measure the time from when light source 310 transmits a light pulse until light detector 330 detects a return light pulse.
These components shown in FIG. 3 are coupled together using communications paths 312, 314, 322, 332, 342, 352, and 362. These communications paths represent communication (bidirectional or unidirectional) among the various LiDAR system components but need not be physical components themselves. While the communications paths can be implemented by one or more electrical wires, buses, or optical fibers, the communication paths can also be wireless channels or open-air optical paths so that no physical communication medium is present. For example, in one example LiDAR system, communication path 314 includes one or more optical fibers; communication path 352 represents an optical path; and communication paths 312, 322, 342, and 362 are all electrical wires that carry electrical signals. The communication paths can also include more than one of the above types of communication mediums (e.g., they can include an optical fiber and an optical path, or one or more optical fibers and one or more electrical wires).
As described above, some LiDAR systems use the time-of-flight (ToF) of light signals (e.g., light pulses) to determine the distance to objects in a light path. For example, with reference to FIG. 5A, an example LiDAR system 500 includes a laser light source (e.g., a fiber laser), a steering mechanism (e.g., a system of one or more moving mirrors), and a light detector (e.g., a photodetector with one or more optics). LiDAR system 500 can be implemented using, for example, LiDAR system 300 described above. LiDAR system 500 transmits a light pulse 502 along light path 504 as determined by the steering mechanism of LiDAR system 500. In the depicted example, light pulse 502, which is generated by the laser light source, is a short pulse of laser light. Further, the signal steering mechanism of the LiDAR system 500 is a pulsed-signal steering mechanism. However, it should be appreciated that LiDAR systems can operate by generating, transmitting, and detecting light signals that are not pulsed and derive ranges to an object in the surrounding environment using techniques other than time-of-flight. For example, some LiDAR systems use frequency modulated continuous waves (i.e., “FMCW”). It should be further appreciated that any of the techniques described herein with respect to time-of-flight based systems that use pulsed signals also may be applicable to LiDAR systems that do not use one or both of these techniques.
Referring back to FIG. 5A (e.g., illustrating a time-of-flight LiDAR system that uses light pulses), when light pulse 502 reaches object 506, light pulse 502 scatters or reflects to form a return light pulse 508. Return light pulse 508 may return to system 500 along light path 510. The time from when transmitted light pulse 502 leaves LiDAR system 500 to when return light pulse 508 arrives back at LiDAR system 500 can be measured (e.g., by a processor or other electronics, such as control circuitry 350, within the LiDAR system). This time-of-flight combined with the knowledge of the speed of light can be used to determine the range/distance from LiDAR system 500 to the portion of object 506 where light pulse 502 scattered or reflected.
By directing many light pulses, as depicted in FIG. 5B, LiDAR system 500 scans the external environment (e.g., by directing light pulses 502, 522, 526, 530 along light paths 504, 524, 528, 532, respectively). As depicted in FIG. 5C, LiDAR system 500 receives return light pulses 508, 542, 548 (which correspond to transmitted light pulses 502, 522, 530, respectively). Return light pulses 508, 542, and 548 are formed by scattering or reflecting the transmitted light pulses by one of objects 506 and 514. Return light pulses 508, 542, and 548 may return to LiDAR system 500 along light paths 510, 544, and 546, respectively. Based on the direction of the transmitted light pulses (as determined by LiDAR system 500) as well as the calculated range from LiDAR system 500 to the portion of objects that scatter or reflect the light pulses (e.g., the portions of objects 506 and 514), the external environment within the detectable range (e.g., the field of view between path 504 and 532, inclusively) can be precisely mapped or plotted (e.g., by generating a 3D point cloud or images).
If a corresponding light pulse is not received for a particular transmitted light pulse, then LiDAR system 500 may determine that there are no objects within a detectable range of LiDAR system 500 (e.g., an object is beyond the maximum scanning distance of LiDAR system 500). For example, in FIG. 5B, light pulse 526 may not have a corresponding return light pulse (as illustrated in FIG. 5C) because light pulse 526 may not produce a scattering event along its transmission path 528 within the predetermined detection range. LiDAR system 500, or an external system in communication with LiDAR system 500 (e.g., a cloud system or service), can interpret the lack of return light pulse as no object being disposed along light path 528 within the detectable range of LiDAR system 500.
In FIG. 5B, light pulses 502, 522, 526, and 530 can be transmitted in any order, serially, in parallel, or based on other timings with respect to each other. Additionally, while FIG. 5B depicts transmitted light pulses as being directed in one dimension or one plane (e.g., the plane of the paper), LiDAR system 500 can also direct transmitted light pulses along other dimension(s) or plane(s). For example, LiDAR system 500 can also direct transmitted light pulses in a dimension or plane that is perpendicular to the dimension or plane shown in FIG. 5B, thereby forming a 2-dimensional transmission of the light pulses. This 2-dimensional transmission of the light pulses can be point-by-point, line-by-line, all at once, or in some other manner. That is, LiDAR system 500 can be configured to perform a point scan, a line scan, a one-shot without scanning, or a combination thereof. A point cloud or image from a 1-dimensional transmission of light pulses (e.g., a single horizontal line) can generate 2-dimensional data (e.g., (1) data from the horizontal transmission direction and (2) the range or distance to objects). Similarly, a point cloud or image from a 2-dimensional transmission of light pulses can generate 3-dimensional data (e.g., (1) data from the horizontal transmission direction, (2) data from the vertical transmission direction, and (3) the range or distance to objects). In general, a LiDAR system performing an n-dimensional transmission of light pulses generates (n+1) dimensional data. This is because the LiDAR system can measure the depth of an object or the range/distance to the object, which provides the extra dimension of data. Therefore, a 2D scanning by a LiDAR system can generate a 3D point cloud for mapping the external environment of the LiDAR system.
The density of a point cloud refers to the number of measurements (data points) per area performed by the LiDAR system. A point cloud density relates to the LiDAR scanning resolution. Typically, a larger point cloud density, and therefore a higher resolution, is desired at least for the region of interest (ROI). The density of points in a point cloud or image generated by a LiDAR system is equal to the number of pulses divided by the field of view. In some embodiments, the field of view can be fixed. Therefore, to increase the density of points generated by one set of transmission-receiving optics (or transceiver optics), the LiDAR system may need to generate a pulse more frequently. In other words, a light source in the LiDAR system may have a higher pulse repetition rate (PRR). On the other hand, by generating and transmitting pulses more frequently, the farthest distance that the LiDAR system can detect may be limited. For example, if a return signal from a distant object is received after the system transmits the next pulse, the return signals may be detected in a different order than the order in which the corresponding signals are transmitted, thereby causing ambiguity if the system cannot correctly correlate the return signals with the transmitted signals.
To illustrate, consider an example LiDAR system that can transmit laser pulses with a pulse repetition rate between 500 kHz and 1 MHz. Based on the time it takes for a pulse to return to the LiDAR system and to avoid mix-up of return pulses from consecutive pulses in a typical LiDAR design, the farthest distance the LiDAR system can detect may be 300 meters and 150 meters for 500 kHz and 1 MHz, respectively. The density of points of a LiDAR system with 500 kHz repetition rate is half of that with 1 MHz. Thus, this example demonstrates that, if the system cannot correctly correlate return signals that arrive out of order, increasing the repetition rate from 500 kHz to 1 MHz (and thus improving the density of points of the system) may reduce the detection range of the system. Various techniques are used to mitigate the tradeoff between higher PRR and limited detection range. For example, multiple wavelengths can be used for detecting objects in different ranges. Optical and/or signal processing techniques (e.g., pulse encoding techniques) are also used to correlate between transmitted and return light signals.
Various systems, apparatus, and methods described herein may be implemented using digital circuitry, or using one or more computers using well-known computer processors, memory units, storage devices, computer software, and other components. Typically, a computer includes a processor for executing instructions and one or more memories for storing instructions and data. A computer may also include, or be coupled to, one or more mass storage devices, such as one or more magnetic disks, internal hard disks and removable disks, magneto-optical disks, optical disks, etc.
Various systems, apparatus, and methods described herein may be implemented using computers operating in a client-server relationship. Typically, in such a system, the client computers are located remotely from the server computers and interact via a network. The client-server relationship may be defined and controlled by computer programs running on the respective client and server computers. Examples of client computers can include desktop computers, workstations, portable computers, cellular smartphones, tablets, or other types of computing devices.
Various systems, apparatus, and methods described herein may be implemented using a computer program product tangibly embodied in an information carrier, e.g., in a non-transitory machine-readable storage device, for execution by a programmable processor; and the method processes and steps described herein, including one or more of the steps of at least some of the FIGS. 1-13, may be implemented using one or more computer programs that are executable by such a processor. A computer program is a set of computer program instructions that can be used, directly or indirectly, in a computer to perform a certain activity or bring about a certain result. A computer program can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment.
A high-level block diagram of an example apparatus that may be used to implement systems, apparatus and methods described herein is illustrated in FIG. 6. Apparatus 600 comprises a processor 610 operatively coupled to a persistent storage device 620 and a main memory device 630. Processor 610 controls the overall operation of apparatus 600 by executing computer program instructions that define such operations. The computer program instructions may be stored in persistent storage device 620, or other computer-readable medium, and loaded into main memory device 630 when execution of the computer program instructions is desired. For example, processor 610 may be used to implement one or more components and systems described herein, such as control circuitry 350 (shown in FIG. 3), vehicle perception and planning system 220 (shown in FIG. 2), and vehicle control system 280 (shown in FIG. 2). Thus, the method steps of at least some of FIGS. 1-13 can be defined by the computer program instructions stored in main memory device 630 and/or persistent storage device 620 and controlled by processor 610 executing the computer program instructions. For example, the computer program instructions can be implemented as computer executable code programmed by one skilled in the art to perform an algorithm defined by the method steps discussed herein in connection with at least some of FIGS. 1-13. Accordingly, by executing the computer program instructions, the processor 610 executes an algorithm defined by the method steps of these aforementioned figures. Apparatus 600 also includes one or more network interfaces 680 for communicating with other devices via a network. Apparatus 600 may also include one or more input/output devices 690 that enable user interaction with apparatus 600 (e.g., display, keyboard, mouse, speakers, buttons, etc.).
Processor 610 may include both general and special purpose microprocessors and may be the sole processor or one of multiple processors of apparatus 600. Processor 610 may comprise one or more central processing units (CPUs), and one or more graphics processing units (GPUs), which, for example, may work separately from and/or multi-task with one or more CPUs to accelerate processing, e.g., for various image processing applications described herein. Processor 610, persistent storage device 620, and/or main memory device 630 may include, be supplemented by, or incorporated in, one or more application-specific integrated circuits (ASICs) and/or one or more field programmable gate arrays (FPGAs).
Persistent storage device 620 and main memory device 630 each comprise a tangible non-transitory computer readable storage medium. Persistent storage device 620, and main memory device 630, may each include high-speed random access memory, such as dynamic random access memory (DRAM), static random access memory (SRAM), double data rate synchronous dynamic random access memory (DDR RAM), or other random access solid state memory devices, and may include non-volatile memory, such as one or more magnetic disk storage devices such as internal hard disks and removable disks, magneto-optical disk storage devices, optical disk storage devices, flash memory devices, semiconductor memory devices, such as erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), compact disc read-only memory (CD-ROM), digital versatile disc read-only memory (DVD-ROM) disks, or other non-volatile solid state storage devices.
Input/output devices 690 may include peripherals, such as a printer, scanner, display screen, etc. For example, input/output devices 690 may include a display device such as a cathode ray tube (CRT), plasma or liquid crystal display (LCD) monitor for displaying information to a user, a keyboard, and a pointing device such as a mouse or a trackball by which the user can provide input to apparatus 600.
Any or all of the functions of the systems and apparatuses discussed herein may be performed by processor 610, and/or incorporated in, an apparatus or a system such as LiDAR system 300. Further, LiDAR system 300 and/or apparatus 600 may utilize one or more neural networks or other deep-learning techniques performed by processor 610 or other systems or apparatuses discussed herein.
One skilled in the art will recognize that an implementation of an actual computer or computer system may have other structures and may contain other components as well, and that FIG. 6 is a high-level representation of some of the components of such a computer for illustrative purposes.
A LiDAR system comprises a plurality of transmitter channels configured to transmit a plurality of transmission beams. When the transmission beams travel to illuminate one or more objects in a FOV, at least a portion of the transmission beams is reflected or scattered to form return light. The LiDAR system further comprises a plurality of detector elements on the receiver side configured to detect the return light. In one example, the plurality of the detector elements can be an avalanche photodiode (APD) array. The plurality of transmitter channels and the plurality of the detector elements are parts of a transceiver and sometimes collectively referred to as transceiver. It is desired to have a transceiver alignment in the LiDAR system, so that the plurality of detector elements can collect as much as possible the return light formed based on the transmission beams, thereby achieving a high sensitivity for the LiDAR system.
FIGS. 7A and 7B are diagrams illustrating examples of devices 700 and 710 for transceiver alignment in the LiDAR system according to some embodiments. As shown in FIG. 7A, the device 700 comprises a detector package 701, and a plurality of detector elements 702 mounted to the detector package 701. FIG. 7A only illustrates four detector elements 702 in the detector package 701, but it is understood that more or fewer detector elements can be included in a detector package. The plurality of detector elements 702 are configured to detect the return light and can be used to implement the optical receiver and light detector 330 shown in FIG. 3. In one example, the plurality of the detector elements 702 can be an APD array of a group of APDs. The term “array” in this disclosure refers to the detector element 702 are arranged in a particular way, which may or may not correspond to that the detector elements 702 line up with each other (e.g., in a straight line). In some embodiments, as shown in FIG. 7A, the plurality of detector elements 702 forms a one-dimensional array of detector elements. The device 700 further comprise light forming markers 703 mounted to the detector package 701. In some embodiments, the detector package 701 further comprises a printed circuit board (PCB). The light forming markers 703 are disposed on the PCB. As shown in FIG. 7A, the light forming markers 703 comprise rectangular-shaped markers. In some embodiments, the light forming markers 703 comprise markers with one or more designs including a line shape design, a rectangular shape design, a circular shape design, an elliptical shape design, a polygon shape design, a bar code design, a QR code design, and any free form shape design. As shown in FIG. 7A, the light forming markers 703 are disposed at predetermined positions with respect to the plurality of detector elements 702. The predetermined positions of the light forming markers 703 are pre-determined to facilitate alignment of each of the plurality of detector elements 702 to a corresponding transmitter channel of a plurality of transmitter channels (not shown in FIG. 7A). This is described in detail further below with reference to FIGS. 8A-8C.
FIG. 7B illustrates another example device 710 for transceiver alignment in the LiDAR system. Similar to FIG. 7A, the device 710 comprises a detector package 701 and a plurality of detector elements 702 mounted to the detector package 701. As shown in FIG. 7B, the plurality of detector elements 702 forms a two-dimensional array of detector elements. The device 710 further comprises a light forming marker 703 disposed at a predetermined position with respect to the plurality of detector elements 702. The predetermined position is configured to facilitate the transceiver alignment.
FIGS. 8A-8C are diagrams illustrating examples of transceiver alignments using light forming markers according to some embodiments. As shown in FIGS. 8A-8C, the LiDAR system comprises a transceiver 820. The transceiver 820 comprises a plurality of transmitter channels 822 configured to transmit a plurality of transmission beams 830. The plurality of transmitter channels 822 can be used to implement the transmitter 320 shown in FIG. 3. The plurality of transmission beams 830 has a wavelength λt, which is the operating wavelength of the transceiver 820. In one example, during manufacturing or testing of the transceiver and/or the LiDAR system, one or more imaging devices can be disposed in the transmission light path of the transceiver 820. The one or more imaging devices can be used for facilitating transceiver alignment. During normal operations of the LiDAR system, imaging devices may not be needed. As shown in FIG. 8A-8C, the plurality of transmission beams 830 are directed towards an imaging device 850 (shown in FIGS. 8A-8B) or imaging device 850a (shown in FIG. 8C). As a result, imaging device 850 (or imaging device 850a shown in FIG. 8C) receives the transmission beams 830 and forms images 853. As shown in FIGS. 8A-8C, the transceiver 820 further comprises an optic 823. In some embodiments as shown in FIGS. 8A and 8B, the optic 823 having an opening 824. In some embodiments, the opening 824 may be a rectangular-shaped opening, a circular-shaped opening, a square shaped opening, a slot, a hole, a slit, or any other shaped opening. As shown in FIGS. 8A and 8B, the opening 824 is made from the curved frontside surface to the flat backside surface of the optic 823. The plurality of transmitter channels 822 optically coupled to the optic 823 is at least partially disposed in the opening 824 or near opening 824. Because of the opening 824, the plurality of transmission beams 830 can be transmitted through the optic 823 towards the imaging device 850 (or imaging device 850a shown in FIG. 8C). In some embodiments as shown in FIG. 8C, the optic 823 can have a small size and thus not positioned in the transmission light path. Other arrangements of optics 823 and transmitter channels 822 can also be configured such that the optic 823 does not interfere with beams 830.
As shown in FIGS. 8A-8C, the transceiver 820 further comprises a plurality of detector elements 811 mounted to a detector package 810. Detector elements 811 and package 810 can be substantially the same or similar to detector element 702 and detector package 701, respectively, shown in FIGS. 7A and 7B. When the LiDAR system operates to scan an FOV, the transmission beams 830 travel to illuminate one or more objects in the FOV. At least a portion of the transmission beams 830 is reflected or scattered to form return light (not shown). The plurality of detector elements 811 are configured to detect the return light formed based on the transmission beams 830. The plurality of detector elements 811 can be used to implement, or be a part of, the optical receiver and light detector 330 shown in FIG. 3. When the transceiver alignment is performed, however, the transmission beams 830 are directed to the imaging device 850 shown in FIGS. 8A-8B or imaging device 850a shown in FIG. 8C. During the transceiver alignment process, the LiDAR system does not scan and therefore, there is no return light shown in FIGS. 8A-8C. After the transceiver alignment process is performed, the LiDAR system operates to scan the FOV and receive return light by the detector elements 811. In some examples, the plurality of detector elements 811 senses light but does not emit light, the detector elements 811. Therefore, during the transceiver alignment process, the detector elements 811 do not form images in the imaging device 850. As shown in FIGS. 8A-8B, a plurality of dashed boxes 851 illustrates possible positions of the plurality of detector elements 811 imaged in the imaging device 850 (or imaging device 850a shown in FIG. 8C), as if they could be imaged. As shown in FIGS. 8A-8C, the LiDAR system further comprise one or more light forming markers mounted to the detector package 810 for the transceiver alignments. In some embodiments, the detector package 810 further comprises a PCB. The light forming markers are disposed on the PCB. Examples of the transceiver alignment process using the light forming markers are described in more detail below.
FIG. 8A illustrates one example of transceiver alignment in the LiDAR system according to some embodiments. As shown in FIG. 8A, light forming markers 812 (e.g., light forming marker 703 shown in FIGS. 7A and 7B) are mounted to the detector package 810. FIG. 8A only illustrates two such light forming markers 812a and 812b, but it is understood that more or fewer light forming markers 812 can be included. The light forming markers 812a and 812b are collectively referred to as light forming markers 812. As shown in FIG. 8A, the light forming markers 812 comprise rectangular-shaped markers. In some embodiments, the light forming markers 812 comprise markers with one or more designs including a line shape design, a rectangular shape design, a circular shape design, an elliptical shape design, a polygon shape design, a bar code design, a QR code design, and any free form shape design. In some embodiments as shown in FIG. 8A, the light forming markers 812 comprise light emitting devices electrically coupled to one or more electrodes 813a and 813b (collectively as electrodes 813). The electrodes 813 are configured to provide electrical signals that cause the light forming markers 812a and 812b to emit light 840a and 840b (collectively as light 840), respectively, during the transceiver alignment process. Such light forming markers 812 are thus referred to as active light forming markers. In some embodiments, when the LiDAR system is performing a scan, the electrodes 813 are turned off and thus do not provide electrical signals to the light forming markers 812. Therefore, during the normal operation of the LiDAR system, the light forming markers 812 does not emit light, which may disturb the LiDAR's light detection. In some embodiments, the light emitting device used for the light forming markers 812 comprises one or more of an edge-emitting laser (EEL), a vertical cavity surface-emitting laser (VCSEL), a light emitting diode (LED), and a photonic crystal surface emitting laser (PCSEL). As shown in FIG. 8A, the light forming markers 812 emit light 840 toward the imaging device 850. As a result, images 852a and 852b of the light forming markers 812a and 812b (collectively referred to as images 852) are formed in the imaging device 850. In some embodiments, the optic 823 can be used for one or both of collimation and focusing, depending on the optical path. For instance, for the optical path used in the transceiver alignment, optic 823 can be a collimation lens configured to collimate the light 840. During the LiDAR system's normal operation, optic 823 can be a collection lens or focusing lens configured to focus the return light to detector elements 811. FIG. 8A illustrates two images 852a and 852b corresponding to the two light forming markers 812a and 812b, respectively. It is understood that if more or fewer light forming markers 812 are included in detect package 810, accordingly the more or fewer images 852 are formed in the imaging device 850.
As shown in FIG. 8A, the light 840a provided by the light forming markers 812a has a wavelength λma. The light 840b provided by the light forming markers 812b has a wavelength λmb. In some embodiments, the wavelength λma of the light 840a is different from the wavelength λmb of the light 840b (i.e., λma≠λmb). Because the light 840a and 840b have different wavelengths, they have different focal lengths. In one example, to properly form images of the light 840a and 840b with different wavelengths on the same imaging device 850, the light forming markers 812a and the light forming markers 812b may be placed at different heights or different distances from the imaging device 850. As shown in FIG. 8A, the axis h in the coordinate system represents the horizontal direction, axis y represents the vertical direction, and axis x represents the direction perpendicular to the paper surface. The height difference or the distance difference between the light forming markers 812a and 812b are shown as the different positions of the markers 812a and 812b along the axis h. When placing in different positions or distances from imaging device 850, light 840a and 840b, while having different wavelengths, can be properly focused onto imaging device 850 and thus form sharp and clear images. In some embodiments as shown in FIG. 8A, the LiDAR system can further comprise an optics 870 (e.g., a lens or a lens group) configured to facilitate image forming in the imaging device 850. Alternatively, the optics 823 and/or 870 can be an achromatic lens configured to direct the light 840a and 840b with different wavelengths to properly form images on the same imaging device 850.
In some embodiments, the light 840 (either 840a or 840b) formed by the light forming marker 812 may have a different wavelength from the operating wavelength of the transceiver 820 (i.e., for a wavelength λt of the plurality of transmission beams 830, λma≠λt, and/or λmb≠ λt). To properly form images of the light 830 and 840 with different wavelengths onto the same imaging device 850, the light forming markers 812 and the plurality of detector elements 811 may have different heights or different distances from imaging device 850. As shown in FIG. 8A, height difference or distance difference among the light forming markers 812 and the plurality of detector elements 811 are shown as their different positions along the axis h. For example, the markers 812 may be placed closer to imaging device 850 compared to detector elements 811, or vice versa. Alternatively, the optic 823 and/or 870 can be an achromatic lens configured to direct the light 830 and 840 with different wavelengths to form images on the same imaging device 850. In some embodiments, the light 840 (light 840a and 840b) formed by the light forming markers 812 has substantially the same wavelength as the operating wavelength of the transceiver 820 (i.e., wavelength λt of the plurality of transmission beams 830; λma=λmb=λt). In this scenario, the light forming markers 812 and the plurality of detector elements 811 can be placed at a same height or a same distance from the imaging device 850.
As shown in FIG. 8A, based on an alignment requirement of the plurality of detector elements 811, the light forming markers 812 are disposed at predetermined positions with respect to the plurality of detector elements 811. The predetermined positions of the light forming markers 812 are configured to facilitate alignment of each of the plurality of detector elements 811 to a corresponding transmitter channel of the plurality of transmitter channels 822. Based on the images 853 of transmission beams 830 and the images 852 of the light forming markers 812, the plurality of transmitter channels 822 can be aligned with respect to the plurality of detector elements 811. As shown in FIG. 8A, if the images 853 of transmission beams 830 are at corresponding expected positions 851 (as if the plurality of detector elements 811 were imaged) in the imaging device 850, each of the plurality of detector elements 811 is aligned to a corresponding transmitter channel of the plurality of transmitter channels 822. The corresponding expected positions 851 can be determined based on the images 852 of the light forming markers 812, because the relation between the markers 812 and detector elements 811 are known and because the light path configurations are also known (e.g., the focus lengths of optics 823 and 870). For instance, as shown in FIG. 8A, if the expected positions 851 overlap with images 853 (e.g., each image 853 is at position 851 within a threshold distance), the transmitter channels and detector elements are considered aligned. If the images 853 deviate from the expected positions 851 more than a threshold distance, the transmitter channels and the corresponding detector elements are not aligned. In some embodiments, it is also determined if the images 852 of the light forming markers 812 are focused images. When sharpness of the images 852 are large than a threshold, it is determined the images 852 are focused images. If the images 852 are not focused images, and/or if the images 853 deviates from the expected positions 851, it indicates that the detector elements positions may need to be adjusted for proper alignment with the transmitter channels. In some embodiments, it is also determined if the images 853 of the transmission beams 830 are focused images, whose sharpness are larger than the threshold. In some embodiments, if the images 852 of the light forming markers 812 are focused images, and images 853 of the transmission beams 830 are not focused on expected position 851, it indicates that the detector elements positions may need to be adjusted for proper alignment with the transmitter channels in a direction perpendicular to the imaging device 850. In some embodiments, if both the images 852 and images 853 are focused images, but the images 853 deviates from the expected positions 851, it indicates that the corresponding detector elements positions may need to be adjusted for proper alignment with the transmitter channels in a direction parallel to the imaging device 850. After the detector elements positions are adjusted, the process can be repeated to re-evaluate the alignment. The process can be repeated many times until the transceiver is properly aligned. As a result, including light forming markers in a detector package can achieve a transceiver alignment in the LiDAR system and improve the efficiency of light collection. Further, by using the light forming markers 812 and the imaging device 850 to facilitate alignment of the plurality of detector elements 811 to the plurality of transmitter channels 822, the LiDAR system's production process can be improved, resulting in time-saving and achieving an efficient high-volume production.
FIG. 8B illustrates another example of transceiver alignment in the LiDAR system. Similar to FIG. 8A, the transceiver 820 in FIG. 8B further comprises two light forming markers 814a and 814b (collectively referred as light forming markers 814) mounted to the detector package 810. As shown in FIG. 8B, the light forming markers 814 comprise rectangular-shaped markers. In some embodiments, the light forming markers 814 comprise markers with one or more designs including a line shape design, a rectangular shape design, a circular shape design, an elliptical shape design, a polygon shape design, a bar code design, a QR code design, and any free form shape design. In some embodiments, the light forming markers 814 are passive light marker that do not emit light themselves. Such light forming markers comprise at least one of: a light reflective marker or a light scattering marker. As shown in FIG. 8B, a light source 862 is configured to emit light 860. Light source 862 is used to provide light to the light forming markers 814, such that they can reflect or scatter light. In the example shown in FIG. 8B, one or more optics 864 is coupled to the light source 862. The one or more optics 864 are configured to direct light 860 emitted by the light source 862 to the light forming markers 814. In turn, the light forming markers 814 reflect or scatter the light 860 toward the imaging device 850. As a result, images 854 of the light forming markers 814 are formed in the imaging device 850. There are two light forming markers 814 and accordingly two images 854 shown in FIG. 8B, but it is understood that more or fewer light forming markers 814 can be included in detect package 810, and more or fewer images 854 can be formed in the imaging device 850 accordingly. As shown in FIG. 8B, the one or more optics 864 comprise a light splitter. The light splitter is configured to reflect the light 860 emitted by the light source 862 to the light forming markers 814. The light splitter further passes a substantial portion of the light 860 reflected or scattered by the light forming markers 814 toward the imaging device 850. In some embodiments, when performing a transceiver alignment process, the optic 823 is used as a collimation lens configured to collimate the light 860 and direct collimated light 860 toward the imaging device 850. In some embodiments, when the LiDAR system is under normal operation to perform a scan, the light source 862 is removed from the LiDAR system and light forming markers 814 can be covered or shielded such that they do not reflect/scatter any light. For instance, the LiDAR system may include one or more windows (not shown) facing the light forming markers 814. The windows may be blackened (e.g., after the alignment is completed) to prevent the light forming markers 814 from reflecting or scattering any light to disturb light detection. Compared with the scenario shown in FIG. 8A, the embodiment shown in FIG. 8B uses passive light forming markers. Thus, it can result in more energy saving and can be more cost efficient because no electrodes are needed to provide electrical signals.
As shown in FIG. 8B, based on an alignment requirement of the plurality of detector elements 811, the light forming markers 814 are disposed at predetermined positions with respect to the plurality of detector elements 811. Images 853 represent the images formed by the transmission beams 830. The geometric relation between the markers 814 and the detector elements 811 are known. The expected positions 851 represent the location of images detector elements 811 as if they were imaged in imaging device 850. In reality, since detector elements 811 do not emit any light, they are not imaged. Expected positions 851 can be calculated using the positions of images 854 of the light forming markers 814 and other known data. The known data include the geometric relation between the markers 814 and the detector elements 811; and the optical path parameters such as focal lengths of optics 823 and 870. Therefore, based on the images 853 of transmission beams 830 and the images 854 of the light forming markers 814, it can be determined if each of the plurality of detector elements 811 is aligned to a corresponding transmitter channel of the plurality of transmitter channels 822. For instance, as shown in FIG. 8B, if the expected positions 851 overlap with images 853 (e.g., each image 853 is at position 851 within a threshold distance), the transmitter channels and detector elements are considered aligned. If the images 853 deviate from the expected positions 851 more than a threshold distance, the transmitter channels and the detector elements are not aligned. In some embodiments, it is also determined if the images 854 of the light forming markers 814 are focused images, whose sharpness are larger than a threshold. If the images 853 are not focused images, and/or if the images 853 deviates from the expected positions 851, it indicates that the detector elements positions may need to be adjusted for proper alignment with the transmitter channels. In some embodiments, it is also determined if the images 853 of the transmission beams 830 are focused images, whose sharpness are larger than the threshold. In some embodiments, if the images 854 of the light forming markers 814 are focused images, and images 853 of the transmission beams 830 are not focused on expected position 851, it indicates that the detector elements positions may need to be adjusted for proper alignment with the transmitter channels in a direction perpendicular to the imaging device 850. In some embodiments, if both the images 854 and images 853 are focused images, but the images 853 deviates from the expected positions 851, it indicates that the detector elements positions may need to be adjusted for proper alignment with the transmitter channels in a direction parallel to the imaging device 850. After the detector elements positions are adjusted, the process can be repeated to re-evaluate the alignment. The process can be repeated many times until the transceiver is properly aligned.
The light forming markers therefore facilitate the transceiver alignment in the LiDAR system and improve the efficiency of light collection. Further, by using the light forming markers 814 and the imaging device 850 to facilitate alignment of the plurality of detector elements 811 to the plurality of transmitter channels 822, it results in time-saving and improving the efficiency of high-volume production.
As shown in FIG. 8B, the light source 862 emits the light 860 having a wavelength λm. The light reflected or scattered by the light forming markers 814a and 814b also has the same wavelength λm. In some embodiments, the wavelength λm of light 860 is different from the operating wavelength of the transceiver 820 (i.e., for wavelength λt of the plurality of transmission beams 830, λm≠λt). To properly form images of the light 830 and reflected/scattered light from light 860, which have different wavelengths, onto the same imaging device 850, the light forming markers 814 and the plurality of detector elements 811 may have different heights or different distances from the imaging device 850. As shown in FIG. 8B, height difference or distance difference among the light forming markers 814 and the plurality of detector elements 811 are shown as their different positions along the axis h. For example, the markers 814 may be placed closer to imaging device 850 compared to detector elements 811, or vice versa. Alternatively, the optic 823 and/or 870 can be an achromatic lens configured to direct the light 830 and 860 with different wavelengths to properly form images on the same imaging device 850. The images formed in this manner are focused and clear, despite the different wavelengths. In some embodiments, the light 860 reflected/scattered by the light forming markers 814 has substantially the same wavelength as the operating wavelength of the transceiver 820 (i.e., for wavelength λt of the plurality of transmission beams 830, λm=λt). In this scenario, the light forming markers 814 and the plurality of detector elements 811 can be placed at a same height or a same distance from the imaging device 850. In some embodiments, light provided by the light forming markers 814a and light provided by the light forming markers 814b may have different wavelengths. In this scenario, the light forming markers 814a and 814b reflects or scatters light from different light sources having different wavelengths. To properly form images of the light with different wavelengths onto the same imaging device 850, the light forming markers 814a and 814b may have different heights or different distances from the imaging device 850. Additionally or alternatively, the optic 823 and/or 870, (e.g., an achromatic lens) can be used to properly form the images in imaging device 850.
FIG. 8C illustrates an alternative way to address wavelength differences in the transceiver alignment process for a LiDAR system. As shown in FIG. 8C, a plurality of transmitter channels 822 transmits a plurality of transmission beams 830. The plurality of transmission beams 830 has a wavelength λt, which is the operating wavelength of the transceiver 820. The transceiver 820 further comprises a plurality of detector elements 811 and a light forming marker 812 mounted to a detector package 810. As shown in FIG. 8C, light 840 formed by the light forming marker 812 (either an active marker or a passive marker) has a wavelength λm, which is different from the wavelength λt (i.e., λm≠λt). In some embodiments, the light forming marker 812 comprises a light emitting device electrically coupled to an electrode (e.g., electrodes 813 shown in FIG. 8A). The electrode is configured to provide electrical signals that cause the light emitting device to emit the light 840. In some embodiments, the light forming markers 812 comprises a light reflective marker or light scattering marker. The light forming marker 812 reflects or scatters the light 840 emitted from a light source (e.g., light source 862 shown in FIG. 8B).
As shown in FIG. 8C, the transmission beams 830 and the light 840 formed by the light forming marker 812 are separated by a wavelength-based beam splitter 880. Wavelength-based beam splitter 880 can be, for example, a dielectric beam splitter with wavelength-dependent reflectance, a beam splitter with wavelength-dependent geometric splitting, a fiber coupler with a wavelength-dependent splitting ratio, or the like. The separated light having different wavelengths is directed to individual imaging devices 850a and 850b, respectively. As a result, images 853 of the plurality of transmission beams 830 are formed in the imaging device 850a. Image 852 of the light forming marker 812 is formed in the imaging device 850b. FIG. 8C illustrates the light having two different wavelengths is directed to two different imaging devices, respectively. The images are formed in the two imaging devices, respectively. It is understood if light has three or more different wavelengths, accordingly the light can be directed to three or more imaging devices, respectively, and images can be formed in the three or more individual imaging devices, respectively.
Based on an alignment requirement of the plurality of detector elements 811, the light forming marker 812 is at a predetermined position with respect to the plurality of detector elements 811. The predetermined position of the light forming marker 812 is configured to facilitate alignment of each of the plurality of detector elements 811 to a corresponding transmitter channel of the plurality of transmitter channels 822. Based on the images 853 of transmission beams 830 formed in the imaging device 850a and the image 852 of the light forming marker 812 formed in the imaging device 850b, each of the plurality of detector elements 811 can be aligned to a corresponding transmitter channel of the plurality of transmitter channels 822. As shown in FIG. 8C, if the images 853 of transmission beams 830 are at corresponding expected positions 851 (as if the plurality of detector elements 811 were imaged) in the imaging device 850a, each of the plurality of detector elements 811 is aligned to a corresponding transmitter channel of the plurality of transmitter channels 822. Because the relation between the marker 812 and detector elements 811 are known and because the light path configurations are also known (e.g., the focus length of optics 823), the corresponding expected positions 851 on the imaging 850a can be determined. Positions of the imaging devices 850a and 850b are calibrated and displacement data between the imaging devices 850a and 850b are also known. Therefore, the corresponding expected positions 851 on the imaging 850a are determined based on the position of the image 852 on the imaging 850b and the displacement data between the imaging devices 850a and 850b. For instance, as shown in FIG. 8C, if the expected positions 851 overlap with images 853 (e.g., each image 853 is at position 851 within a threshold distance), the transmitter channels and detector elements are considered aligned. If the images 853 deviate from the expected positions 851 more than a threshold distance, the transmitter channels and the detector elements are not aligned. In some embodiments, it is also determined if the image 852 of the light forming marker 812 is a focused image, whose sharpness is larger than a threshold. If the image 852 and/or images 853 are not focused images on the respective imaging devices 850a and 850b, and/or if the images 853 deviates from the expected positions 851, it indicates that the detector elements positions may need to be adjusted for proper alignment with the transmitter channels. After the detector elements positions are adjusted, the process can be repeated to re-evaluate the alignment. The process can be repeated many times until the transceiver is properly aligned. As a result, including the light forming marker in a detector package can achieve a transceiver alignment in the LiDAR system and improve the efficiency of light collection.
As described above, light forming markers can have various different shapes, sizes, orientations, etc. FIGS. 9A-9G are diagrams illustrating examples of light forming markers 900-960 according to some embodiments. The light forming markers 900-960 can be used to implement the light forming markers 703 shown in FIGS. 7A and 7B, the light forming markers 812 shown in FIGS. 8A and 8C, and the light forming markers 814 shown in FIG. 8B. As shown in FIGS. 9A-9G, the light forming markers 900-960 comprise markers with one or more designs including a line shape design (e.g., light forming marker 900 shown in FIG. 9A), a rectangular shape design (e.g., light forming marker 910 shown in FIG. 9B), a circular shape design (e.g., light forming marker 920 shown in FIG. 9C), an elliptical shape design (e.g., light forming marker 930 shown in FIG. 9D), a polygon shape design (e.g., light forming marker 940 shown in FIG. 9E), a bar code design (e.g., light forming marker 950 shown in FIG. 9F), and a QR code design (e.g., light forming marker 960 shown in FIG. 9G). In some embodiments, a light forming marker can be any free form shape, which is not limited to the shapes shown in FIGS. 9A-9G. Each of the light forming markers shown in FIGS. 9A-9G have known or predetermined sizes and geometrical shapes. They are disposed at predetermined positions with respect to the detector elements, and therefore the geometrical relation between the markers and the detector elements are known. These data can be used to calculate the positions of the images of the detector elements as if they were imaged onto an imaging device. Based on the calculations, it can be determined if the transmitter channels are aligned with the detector elements. When they are aligned, the return light formed by reflecting/scatter beams of each transmitter channel can be properly received by the detector element, increasing the detection efficiency. It is understood that the number of light forming markers and the positions of the light forming markers can be selected as desired. For example, in one LiDAR system, two markers 900 may be used, and in another system, one marker 910 may be used. Different types of light forming markers can also be mixed. For example, in another LiDAR system, a light forming marker 910 and a light forming marker 930 may both be used.
FIGS. 10A-10I are diagrams illustrating examples of positions of light forming markers 1030 with respect to detector elements 1020 according to some embodiments. As shown in FIGS. 10A-10I, each device 1000-1008 comprises a detector package 1010, and a plurality of detector elements 1020 mounted to the detector package 1010. The plurality of detector elements 1020 are configured to detect return light and can be used to implement the optical receiver and light detector 330 shown in FIG. 3, the detector elements 702 shown in FIGS. 7A and 7B, the detector elements 811 shown in FIGS. 8A-8C. In some embodiments as shown in FIGS. 10A-10D, 10F, 10H and 10I, a plurality of the detector elements 1020 forms a one-dimensional array of detector elements. In some embodiments as shown in FIGS. 10E and 10G, the plurality of detector elements 1020 forms a two-dimensional array of detector elements. Other arrangements of the detector elements 1020 can also be implemented (e.g., forming a circle, a disk, a polygon, etc.). As shown in FIGS. 10A-10I, each device 1000-1008 further comprise one or more light forming markers 1030 mounted to the detector package 1010. The light forming markers 1030 can be substantially the same as the light forming markers 703 shown in FIGS. 7A and 7B, the light forming markers 812 shown in FIGS. 8A and 8C, the light forming markers 814 shown in FIG. 8B. And they can be implemented by the light forming markers 900-960 shown in FIGS. 9A-9G. In some embodiments, the detector package 1010 further comprises a PCB. The light forming markers 1030 are disposed on the PCB. As shown in FIGS. 10A-10I, the light forming markers 1030 are at predetermined positions with respect to the plurality of detector elements 1020. As described above, the predetermined positions of the light forming markers 1030 are configured to facilitate alignment of each of the plurality of detector elements 1020 to a corresponding transmitter channel of a plurality of transmitter channels. FIGS. 10A-10I illustrate that the light forming markers 1030 are arranged in a manner such that the light forming markers 1030 have fixed spatial relations with respect to the plurality of detector elements 1020.
As shown in FIGS. 10A and 10B, at least two of the light forming markers 1030 are positioned at two opposite sides of an array formed by the plurality of detector elements 1020 and are external to the array. The array formed by the plurality of detector elements 1020 has a lateral direction and longitudinal direction. In FIGS. 10A and 10B, the lateral direction of the array is the horizontal direction and the longitudinal direction is the vertical direction. In some embodiments as shown in FIG. 10A, the two opposite sides (e.g., left side and right side) of the array are along the lateral direction of the array formed by the plurality of detector elements 1020. As shown in FIG. 10A, the two light forming markers 1030 are aligned horizontally at the opposite sides of the array of detector elements 1020. In some embodiments as shown in FIG. 10B, the two opposite sides (e.g., a top side and a bottom side) of the array are along the longitudinal direction of the array formed by the plurality of detector elements 1020. As shown in FIG. 10B, the two light forming markers 1030 are aligned vertically at the two opposite sides of the array.
As shown in FIGS. 10C-10E, at least two of the light forming markers 1030 are positioned at the same side of an array formed by the plurality of detector elements 1020 or at the same corner of the detector package 1010. For instance, the embodiments of FIGS. 10C and 10E show that the markers 1030 are located at the same left side of the array of elements 1020. And the embodiment of FIG. 10D shows that the markers 1030 are located at the same bottom side of the array of elements 1020. In some embodiments, the at least two of the light forming markers 1030 are aligned horizontally or vertically. As shown in FIGS. 10C and 10D, the two light forming markers 1030 are aligned horizontally. As shown in FIG. 10E, the two light forming markers 1030 are aligned vertically. It is understood that the marks do not have to be aligned horizontally or vertically, or aligned at all. They can form any geometrical relations with respect to each other, as long as the relation is known and can be used for calculations of the positions of the images of detector elements as if they were imaged onto an imaging device.
As shown in FIGS. 10F and 10G, in some embodiments, at least one of the light forming markers 1030 can be positioned between two detector elements 1020 of the plurality of detector elements 1020. As shown in FIG. 10G, two light forming markers 1030 are positioned between two detector elements of a two dimensional array of elements 1020. The two markers 1030 May be aligned horizontally.
As shown in FIG. 10H, in some embodiments, at least two of the light forming markers 1030 are positioned parallel to each other. As shown in FIG. 10I, in some embodiments, at least two of the light forming markers 1030 are positioned non-parallel to each other. Other arrangements of the markers can also be made, as a person of ordinary skill in the art would understand.
FIG. 11 shows a flowchart illustrating an example method 1100 for transceiver alignment in a LiDAR system according to some embodiments. The LiDAR system comprises a transceiver (e.g., transceiver 820 shown in FIGS. 8A-C). The transceiver comprises a plurality of transmitter channels (e.g., transmitter 320 shown in FIG. 3 and transmitter channels 822 shown in FIGS. 8A-C) configured to transmit a plurality of transmission beams (e.g., transmission beams 830 shown in FIGS. 8A-8C). The LiDAR system further comprises a controller (e.g., control circuitry 350 shown in FIG. 3) configured to control the plurality of transmitter channels. The transceiver further comprises a plurality of detector elements (e.g., optical receiver and light detector 330 shown in FIG. 3, detector element 702 shown in FIGS. 7A and 7B, detector element 811 shown in FIGS. 8A-8C, and detector element 1020 shown in FIGS. 10A-10G) configured to detect return light formed based on the plurality of transmission beams. One or more imaging devices (e.g., imaging device 850 shown in FIGS. 8A and 8B, and imaging devices 850a and 850b shown in FIG. 8C) can be disposed in the transmission light path of the transceiver. The one or more imaging devices are configured to form images and facilitate the transceiver alignment.
In step 1110 of the method 1100, the controller controls the plurality of transmitter channels to transmit the plurality of transmission beams toward the imaging device.
In step 1120 of the method 1100, the controller causes one or more light forming markers (e.g., light forming markers 703 shown in FIGS. 7A and 7B, the light forming markers 812 shown in FIGS. 8A and 8C, the light forming markers 814 shown in FIG. 8B, the light forming markers 900-960 shown in FIGS. 9A-9G, and the light forming markers 1030 shown in FIGS. 10A-10G) to emit light toward the imaging device. The light forming markers are positioned with respect to the plurality of detector elements at locations predetermined based on an alignment requirement of the plurality of detector elements. For example, depending on the number of detector elements, the shape/size of the detector elements, and the location of the detector elements, the size/shape/number/positions of the light forming markers can be configured accordingly. In some embodiments, the plurality of detector elements comprises a one-dimensional array of detector elements. In some embodiments, the plurality of detector elements comprises a two-dimensional array of detector elements.
In some embodiments, the one or more light forming markers comprise rectangular-shaped markers. In some embodiments, the one or more light forming markers comprise markers with one or more designs including a line shape design, a rectangular shape design, a circular shape design, an elliptical shape design, a polygon shape design, a bar code design, a QR code design, and any free form shape design.
In some embodiments, the one or more light forming markers are arranged in a manner such that the light forming markers have fixed spatial relations with the plurality of detector elements. In some embodiments, at least two of the light forming markers are positioned at two opposing sides of an array formed by the plurality of detector elements and are external to the array. In one embodiment, the two opposing sides of the array are along a longitudinal direction of the array formed by the plurality of detector elements. In one embodiment, the two opposing sides of the array are along a lateral direction of the array formed by the plurality of detector elements. In some embodiments, at least two of the light forming markers are positioned at the same side of an array formed by the plurality of detector elements or at the same corner of detector package. The plurality of detector elements and one or more light forming markers are mounted to the detector package. In some embodiments, at least one of the light forming markers is positioned between two detector elements of the plurality of detector elements. In some embodiments, at least two of the light forming markers are aligned horizontally or vertically. In some embodiments, at least two of the light forming markers are parallel to each other. In some embodiments, at least two of the light forming markers are non-parallel to each other.
In some embodiments, light formed by the one or more light forming markers has substantially the same wavelength as an operating wavelength of the transceiver. In some embodiments, the one or more light forming markers have a same height as a height of the plurality of detector elements. In some embodiments, light formed by the one or more light forming markers has a different wavelength from an operating wavelength of a transceiver. In one embodiment, the light having the different wavelength from the operating wavelength is separated by a wavelength-based beam splitter and directed to individual imaging devices. In one embodiment, the one or more light forming markers has a different height from a height of the plurality of detector elements. In some embodiments, light formed by at least two of the light forming markers have different wavelengths. The at least two of the light forming markers have different heights.
In step 1130 of the method 1100, the imaging device forms images of the plurality of transmission beams and images of the one or more light forming markers.
In step 1140 of the method 1100, the controller aligns the plurality of transmitter channels with respect to the plurality of detector elements based on the images of transmission beams and the images of the one or more light forming markers. Based on an alignment requirement of the plurality of detector elements, the one or more light forming markers are positioned at predetermined positions with respect to the plurality of detector elements. Therefore, the geometric relation between the markers and the detector elements are known. Expected positions of images of the detector elements (as if they were imaged in the imaging device) can be calculated using the positions of images of the light forming markers and the known geometric relation between the markers and the detector elements. Therefore, based on the images of transmission beams and the images of the light forming markers, it can be determined if each of the plurality of detector elements is aligned to a corresponding transmitter channel of the plurality of transmitter channels. For instance, if the expected positions overlap with images of transmission beams, the transmitter channels and detector elements are considered aligned. If the images of transmission beams deviate from the expected positions more than a threshold distance, the transmitter channels and the detector elements are not aligned. After the detector elements positions are adjusted, the process can be repeated to re-evaluate the alignment. The process can be repeated many times until the transceiver is properly aligned. By using the method 1100 for transceiver alignment, it results in time-saving and improving the efficiency of high-volume production.
FIG. 12 shows an illustrative method 1120 for causing light forming marks to emit light according to some embodiments. The step 1120 in FIG. 12 is the same step 1120 in FIG. 11. The controller causes one or more light forming markers to emit light toward the imaging device.
In some embodiments, the one or more light forming markers comprise an active marker such as at least one light emitting device electrically coupled to one or more electrodes. In step 1210 of the method 1200, the one or more electrodes provides electrical signals to the at least one light emitting device. The at least one light emitting device causes the at least one light emitting device to emit light toward the imaging device. In some embodiments, the at least one light emitting device comprises one or more of an edge-emitting laser (EEL), a vertical cavity surface-emitting laser (VCSEL), a light emitting diode (LED), and a photonic crystal surface emitting laser (PCSEL).
In some embodiments, the one or more light forming markers comprise a passive marker such as at least one light reflective marker or light scattering marker. In step 1220 of the method 1200, the controller controls a light source to emit light. In step 1230 of the method 1200, one or more optics are optically coupled to the light source. The one or more optics direct the light emitted by the light source to the at least one light reflective marker or light scattering markers. The at least one light reflective marker of light scattering marker reflects or scatters the light toward the imaging device. In some embodiments, the one or more optics comprise a light splitter. The light splitter is configured to reflect the light emitted by the light source to the at least one light reflective marker or light scattering marker. The light splitter further passes a substantial portion of the light reflected or scattered by the at least one light reflective marker or light scattering marker toward the imaging device.
FIG. 13 shows an illustrative method 1140 for aligning a plurality of transmitter channels according to some embodiments. The step 1140 in FIG. 13 is the same step 1140 in FIG. 11. Based on the images of transmission beams and the images of the one or more light forming markers, the controller aligns the plurality of transmitter channels with respect to the plurality of detector elements.
In step 1310 of the method 1300, the controller determines whether the images of the one or more light forming markers are located at expected positions with respect to the images of transmission beams.
In step 1320 of the method 1300 the controller determines whether the images of the one or more light forming markers are focused images.
In step 1330 of the method 1300, in accordance with a determination that at least one of the images of at least one of the one or more light forming markers is not located at expected positions with respect to the images of transmission beams, or a determination that at least one of the images of at least one of the one or more light forming markers is not a focused image, or both, the controller adjusts at least one of the plurality of detector elements with respect to a corresponding transmitter channel.
Additional embodiments of the present invention are described as follows.
1. A device for transceiver alignment in a light ranging and detection (LiDAR) system, the device comprising:
- a detector package;
- a plurality of detector elements mounted to the detector package; and
- one or more light forming markers mounted to the detector package at predetermined positions with respect to the plurality of detector elements, the predetermined positions of the one or more light forming markers being configured to facilitate alignment of each of the plurality of detector elements to a corresponding transmitter channel of a plurality of transmitter channels.
2. The device of embodiment 1, wherein the plurality of detector elements forms a one-dimensional array of detector elements or a two-dimensional array of detector elements.
3. The device of any of embodiments 1-2, wherein the one or more light forming markers comprise markers with one or more designs including a line shape design, a polygon shape design, a circular shape design, an elliptical shape design, a bar code design, and a QR code design.
4. The device of any of embodiments 1-3, wherein the one or more light forming markers are arranged in a manner such that the light forming markers have fixed spatial relations with the plurality of detector elements.
5. The device of any of embodiments 1-4, wherein the one or more light forming markers comprise rectangular-shaped markers.
6. The device of any of embodiments 1-5, wherein at least two of the light forming markers are positioned at two opposite sides of an array formed by the plurality of detector elements and are external to the array.
7. The device of embodiment 6, wherein the two opposite sides of the array are along a longitudinal direction of the array formed by the plurality of detector elements.
8. The device of embodiment 6, wherein the two opposite sides of the array are along a lateral direction of the array formed by the plurality of detector elements.
9. The device of any of embodiments 1-8, wherein at least two of the light forming markers are positioned at the same side of an array formed by the plurality of detector elements or at the same corner of the detector package.
10. The device of any of embodiments 1-9, wherein at least one of the light forming markers is positioned between two detector elements of the plurality of detector elements.
11. The device of any of embodiments 1-10, wherein at least two of the light forming markers are aligned horizontally or vertically.
12. The device of any of embodiments 1-11, wherein at least two of the light forming markers are parallel to each other.
13. The device of any of embodiments 1-12, wherein at least two of the light forming markers are non-parallel to each other.
14. The device of any of embodiments 1-13, wherein the one or more light forming markers comprise at least one light emitting device electrically coupled to one or more electrodes, the one or more electrodes being configured to provide electrical signals that cause the at least one light emitting device to emit light toward an imaging device.
15. The device of embodiment 14, wherein the at least one light emitting device comprises one or more of an edge-emitting laser (EEL), a vertical cavity surface-emitting laser (VCSEL), a light emitting diode (LED), and a photonic crystal surface emitting laser (PCSEL).
16. The device of any of embodiments 1-15, wherein the one or more light forming markers comprise at least one light reflective marker or light scattering marker.
17. The device of embodiment 16, further comprising:
- a light source configured to emit light; and
- one or more optics optically coupled to the light source, the one or more optics being configured to direct light emitted by the light source to the at least one light reflective marker or light scattering marker, wherein the at least one light reflective marker or light scattering marker reflects or scatters the light toward an imaging device.
18. The device of embodiment 17, wherein the one or more optics comprise a light splitter configured to reflect the light emitted by the light source to the at least one light reflective marker or light scattering marker and pass a substantial portion of the light reflected or scattered by the at least one light reflective marker or light scattering marker toward the imaging device.
19. The device of any of embodiments 1-18, wherein light formed by the one or more light forming markers has substantially the same wavelength as an operating wavelength of a transceiver.
20. The device of any of embodiments 1-19, wherein the one or more light forming markers and the plurality of detector elements are placed at a same height or a same distance from an imaging device.
21. The device of any of embodiments 1-18, wherein light formed by the one or more light forming markers has a different wavelength from an operating wavelength of a transceiver.
22. The device of embodiment 21, wherein the light having the different wavelength from the operating wavelength is separated by a wavelength based beam splitter and directed to individual imaging devices.
23. The device of any of embodiments 1-18 or 21, wherein the one or more light forming markers and the plurality of detector elements are placed at different heights or different distances from an imaging device.
24. The device of any of embodiments 1-18, wherein light formed by at least two of the light forming markers have different wavelengths.
25. The device of any of embodiments 1-18 or 24, wherein at least two of the light forming markers are placed at different heights or different distances from an imaging device.
26. A method for transceiver alignment in a light ranging and detection (LiDAR) system, the method comprising:
- controlling a plurality of transmitter channels to transmit a plurality of transmission beams toward an imaging device;
- causing one or more light forming markers to emit light toward the imaging device, wherein the one or more light forming markers are positioned with respect to a plurality of detector elements at locations predetermined based on an alignment requirement of the plurality of detector elements;
- forming images of the plurality of transmission beams and images of the one or more light forming markers; and
- aligning the plurality of transmitter channels with respect to the plurality of detector elements based on the images of transmission beams and the images of the one or more light forming markers.
27. The method of embodiment 26, wherein the plurality of detector elements comprise a one-dimensional array of detector elements or a two-dimensional array of detector elements.
28. The method of any of embodiments 26-27, wherein the one or more light forming markers comprise markers with one or more designs including a line shape design, a polygon shape design, a circular shape design, an elliptical shape design, a bar code design, and a QR code design.
29. The method of any of embodiments 26-28, wherein the one or more light forming markers are arranged in space, so that the light forming markers have fixed spatial relations with the plurality of detector elements.
30. The method of any of embodiments 26-29, wherein the one or more light forming markers comprise rectangular-shaped markers.
31. The method of any of embodiments 26-30, wherein at least two of the light forming markers are positioned at two opposing sides of an array formed by the plurality of detector elements and are external to the array.
32. The method of embodiment 31, wherein the two opposing sides of the array are along a longitudinal direction of the array formed by the plurality of detector elements.
33. The method of embodiment 31, wherein the two opposing sides of the array are along a lateral direction of the array formed by the plurality of detector elements.
34. The method of any of embodiments 26-33, wherein at least two of the light forming markers are positioned at the same side of an array formed by the plurality of detector elements or at the same corner of the detector package.
35. The method of any of embodiments 26-34, wherein at least one of the light forming markers is positioned between two detector elements of the plurality of detector elements.
36. The method of any of embodiments 26-35, wherein at least two of the light forming markers are aligned horizontally or vertically.
37. The method of any of embodiments 26-36, wherein at least two of the light forming markers are parallel to each other.
38. The method of any of embodiments 26-36, wherein at least two of the light forming markers are non-parallel to each other.
39. The method of any of embodiments 26-38, wherein the one or more light forming markers comprise at least one light emitting device electrically coupled to one or more electrodes, wherein causing the one or more light forming markers to emit light toward the imaging device comprises:
- providing, via the one or more electrodes, electrical signals to the at least one light emitting device that causes the at least one light emitting device to emit light toward the imaging device.
40. The method of embodiment 39, wherein the at least one light emitting device comprises one or more of an edge-emitting laser (EEL), a vertical cavity surface-emitting laser (VCSEL), a light emitting diode (LED), and a photonic crystal surface emitting laser (PCSEL).
41. The method of any of embodiments 26-40, wherein the one or more light forming markers comprise at least one light reflective marker or light scattering marker.
42. The method of embodiment 41, wherein causing the one or more light forming markers to emit light toward the imaging device comprises:
- controlling a light source to emit light; and
- directing, by one or more optics optically coupled to the light source, the light emitted by the light source to the at least one light reflective marker or light scattering markers, wherein the at least one light reflective marker of light scattering marker reflects or scatters the light toward the imaging device.
43. The method of embodiment 42, wherein the one or more optics comprise a light splitter configured to reflect the light emitted by the light source to the at least one light reflective marker and pass a substantial portion of the light reflected or scattered by the at least one light reflective marker or light scattering marker toward the imaging device.
44. The method of any of embodiments 26-43, wherein light formed by the one or more light forming markers has substantially the same wavelength as an operating wavelength of a transceiver.
45. The method of any of embodiments 26-44, wherein the one or more light forming markers and the plurality of detector elements are placed at a same height or a same distance from the imaging device.
46. The method of any of embodiments 26-43, wherein light formed by the one or more light forming markers has a different wavelength from an operating wavelength of a transceiver.
47. The method of embodiment 46, further comprising:
- separating the light having the different wavelength from light having the operating wavelength by a wavelength based beam splitter; and
- directing the separated light to individual imaging devices.
48. The method of any of embodiments 26-43, or 46, wherein the one or more light forming markers and the plurality of detector elements are placed at different heights or different distances from the imaging device.
49. The method of any of embodiments 26-43, wherein light formed by at least two of the light forming markers have different wavelengths.
50. The method of any of embodiments 26-43 or 49, wherein at least two of the light forming markers are placed at different heights or different distances from the imaging device.
51. The method of any of embodiments 26-50, wherein aligning the plurality of transmission channels with respect to the plurality of detector elements based on the images of transmission beams and the images of the one or more light forming markers comprises:
- determining whether the images of the one or more light forming markers are located at expected positions with respect to the images of transmission beams; and
- determining whether the images of the one or more light forming markers are focused images.
52. The method of embodiment 51, further comprising:
- in accordance with a determination that at least one of the images of at least one of the one or more light forming markers is not located at expected positions with respect to the images of transmission beams or a determination that at least one of the images of at least one of the one or more light forming markers is not a focused image, or both, adjusting at least one of the plurality of detector elements with respect to a corresponding transmitter channel.
53. A light ranging and detection (LiDAR) system comprising a device of any of embodiments 1-25 or a device that performs any of methods 26-52.
54. A vehicle comprising a light ranging and detection (LiDAR) system comprising a device of any of embodiments 1-25 or a device that performs any of methods 26-52.
The foregoing specification is to be understood as being in every respect illustrative and exemplary, but not restrictive, and the scope of the invention disclosed herein is not to be determined from the specification, but rather from the claims as interpreted according to the full breadth permitted by the patent laws. It is to be understood that the embodiments shown and described herein are only illustrative of the principles of the present invention and that various modifications may be implemented by those skilled in the art without departing from the scope and spirit of the invention. Those skilled in the art could implement various other feature combinations without departing from the scope and spirit of the invention.
Patent Application
20240210541
