Synchronous transmitter and receiver filtering for reducing stray light in LiDAR systems

Abstract

Systems and methods for reducing stray light using synchronous filtering are provided. The system includes an emitter and a light source that emits laser light having a first wavelength range. The emitter is configured to provide transmitted light based on laser light having a first wavelength range. The system further includes a receiver configured to receive return light including stray light and a light signal formed based on the transmitted light. The system further includes a synchronization filter structure including one or more bandpass filters having substantially the same pass band. The synchronous filter structure reduces the bandwidth of the laser from a first wavelength range to a second wavelength range; filtering at least one part of stray light with the wavelength outside the second wavelength range; and transmitting a majority of the light signal formed based on the transmitted light to a detector.

Description

Cross-references to related applications

[0001] This application claims priority to U.S. Provisional Patent Application Serial No. 63 / 541,274, filed September 28, 2023, entitled “SYNCHRONIZED TRANSMITTER AND RECEIVER FILTERING FORREDUCING STRAYLIGHT IN LIDAR SYSTEMS,” the contents of which are incorporated herein by reference in their entirety for all purposes. Technical Field

[0002] This disclosure generally relates to light emission and detection, and more specifically to an optical ranging and detection (LiDAR) system that uses synchronous filtering to reduce stray light. Background Technology

[0003] Light detection and ranging (LiDAR) systems use light pulses to create images or point clouds of the external environment. LiDAR systems can be scanning or non-scanning. Some typical scanning LiDAR systems include a light source, a light emitter, a light steering system, and a photodetector. The light source generates a light beam, which, when emitted from the LiDAR system, is guided in a specific direction by the light steering system. When the emitted beam is scattered or reflected by an object, a portion of the scattered or reflected light returns to the LiDAR system as a returned light pulse. The photodetector detects the returned light pulse. Using the difference between the time it takes to detect the returned light pulse and the time it takes for the corresponding light pulse in the beam to be emitted, the LiDAR system can determine the distance to an object based on the speed of light. This distance determination technique is called Time-of-Flight (ToF). The light steering system can guide the light beam along different paths to allow the LiDAR system to scan the surrounding environment and generate images or point clouds. Typical non-scanning LiDAR systems illuminate the entire field of view (FOV) rather than scanning it. An example of a non-scanning LiDAR system is a flash LiDAR, which can also use ToF technology to measure the distance to objects. The LiDAR system can also use techniques other than time-of-flight and scanning to measure the surrounding environment. Summary of the Invention

[0004] Typically, a LiDAR system has a transmitter (TX) and a receiver (RX). The transmitter emits laser light to form transmitted light. The receiver receives the returned light from the field of view (FOV). At least a portion of the returned light is formed by reflected or scattered laser light from one or more target objects within the FOV. The returned light may also include stray light, which can be noise and / or interference light. LiDAR systems typically operate at a specific center wavelength with a certain bandwidth, such as 905 nm (center wavelength) + / - 5 nm (bandwidth) for semiconductor lasers. In existing LiDAR systems, bandpass filters (BPFs) are widely used in the receiver to filter out stray light from the returned light received by the LiDAR system. The wavelength of the stray light may be the same as or different from the wavelength of the transmitted light.

[0005] However, bandpass filters are typically configured with a wide passband to allow all signal laser power to pass through. Using this type of wide-passband BPF, stray light with the same wavelength or wavelength range as the transmitted light cannot be filtered out. One way to reduce such stray light is to narrow the passband of the BPF (e.g., to 2 nm or even smaller) and only allow return light with the same wavelength as the center wavelength of the transmitted light to pass through. The problem with this method is that a significant amount of signal power from the return light may also be lost because the signal bandwidth is narrower than the passband of the BPF. To compensate for the return light signal power loss caused by the BPF, the signal power of the transmitted light must be increased. However, increasing the signal power of the transmitted laser is limited by the eye safety requirements of LiDAR systems. Therefore, simply increasing the laser power to increase the signal power of the transmitted light, and thus consequently the return light signal power passing through the narrow passband of the BPF in the receiver, may be infeasible or impractical.

[0006] This disclosure provides systems and methods for reducing stray light using synchronous filtering. In one embodiment, an optical ranging and detection (LiDAR) system for reducing stray light using synchronous filtering is provided. The system includes a light source and an emitter that emits laser light having a first wavelength range, the emitter including one or more emitting optics disposed in a transmitted light path. The emitter is configured to provide transmitted light based on the laser light having the first wavelength range. The system also includes a receiver that includes a detector and one or more receiving optics disposed in a receiving light path. The receiver is configured to receive return light including stray light and an optical signal formed based on the transmitted beam. The system further includes a synchronous filter structure including one or more bandpass filters having substantially the same passband. The synchronous filter structure is coupled to both the emitter and the receiver. The synchronous filter structure is configured to perform the following operations: reduce the bandwidth of the laser light from the first wavelength range to a second wavelength range, such that the transmitted beam has the second wavelength range; filter out at least a portion of stray light with wavelengths outside the second wavelength range; and transmit the majority of the optical signal formed based on the transmitted beam to the detector.

[0007] By utilizing a synchronous filter structure, stray light in the returned light can be significantly filtered out or reduced (e.g., by 60%) without much loss of signal power. Furthermore, due to the synchronous filter structure, the laser power within the LiDAR system can be increased to compensate for signal power loss, so the signal power of the transmitted light can still meet the laser eye safety requirements. Attached Figure Description

[0008] This application can be best understood by referring to the embodiments described below in conjunction with the accompanying drawings, in which the same parts are indicated by the same reference numerals.

[0009] Figure 1 The illustration shows one or more exemplary LiDAR systems that are set up or included in a motor vehicle.

[0010] Figure 2 This is a block diagram illustrating the interaction between an exemplary LiDAR system and several other systems, including a vehicle perception and planning system.

[0011] Figure 3 This is a block diagram illustrating an exemplary LiDAR system.

[0012] Figure 4A This is a block diagram illustrating an exemplary fiber-optic-based laser source.

[0013] Figure 4B This is a block diagram illustrating an exemplary semiconductor-based laser source.

[0014] Figures 5A to 5CThe illustration shows an exemplary LiDAR system that uses pulse signals to measure the distance to an object positioned in the field of view (FOV).

[0015] Figure 6 This is a block diagram illustrating exemplary apparatus for implementing systems, devices, and methods in various embodiments.

[0016] Figure 7 This is a block diagram illustrating a prior art LiDAR device with a bandpass filter in the receiving optical path.

[0017] Figures 8A to 8B These are examples of LiDAR systems for reducing stray light using synchronous filtering, according to various embodiments.

[0018] Figures 9A to 9D Examples of transmitters for LiDAR systems that use synchronous filtering to reduce stray light, according to various embodiments.

[0019] Figures 10A to 10D These are examples of receivers for LiDAR systems that use synchronization filtering to reduce stray light, according to various embodiments.

[0020] Figures 11A to 11C Examples of LiDAR systems according to various embodiments for reducing stray light by using a single bandpass filter for synchronous filtering.

[0021] Figure 12 This is a flowchart of an exemplary method for reducing stray light using a synchronous filtering structure, according to various embodiments. Detailed Implementation

[0022] To provide a more thorough understanding of the various embodiments of the present invention, numerous specific details, such as specific configurations, parameters, and examples, are set forth in the following description. However, it should be understood that this description is not intended to limit the scope of the invention, but rather to provide a better description of exemplary embodiments.

[0023] Throughout the specification and claims, unless the context clearly indicates otherwise, the following terms shall have the meaning explicitly associated herein: As used herein, the phrase "in one embodiment" does not necessarily refer to the same embodiment, although it may be the same embodiment. Therefore, as described below, various embodiments of the invention can be readily combined without departing from the scope or spirit of this disclosure.

[0024] As used herein, the term “or” is an inclusive “or” operator and is equivalent to the term “and / or”, unless the context clearly indicates otherwise.

[0025] The term "based on" is not exclusive and allows for the use of additional factors not described unless explicitly stated in the context.

[0026] As used herein, unless the context otherwise requires, the term "coupled to" is intended to include both direct coupling (where two coupled elements are in contact with each other) and indirect coupling (where at least one additional element is located between the two elements). Therefore, the terms "coupled to" and "coupled with" are used synonymously. In the context of a networked environment where two or more components or devices are capable of exchanging data, the terms "coupled to" and "coupled with" are also used to indicate possible "communicable coupling" with via one or more intermediate devices. Components or devices can be optical, mechanical, and / or electrical.

[0027] Although the following description uses the terms "first," "second," etc., to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of the various descriptive examples, a first bandpass filter may be referred to as a second bandpass filter, and similarly, a second bandpass filter may be referred to as a first bandpass filter. Both the first and second bandpass filters can be sensors, and in some cases, they can be separate and different bandpass filters.

[0028] Furthermore, throughout the specification, the meanings of “an,” “a,” and “the” include the plural, and the meaning of “in” can include both “in” and “on”.

[0029] While some embodiments given herein constitute a single combination of inventive elements, it should be understood that the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus, if one embodiment includes elements A, B, and C, and another embodiment includes elements B and D, the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly discussed herein. Furthermore, the transitional term "comprising" means having a component or element, or those components or elements. As used herein, the transitional term "comprising" is inclusive or open-ended and does not exclude additional, unlisted elements or method steps.

[0030] As used in the description herein and throughout the claims thereafter, when a system, engine, server, device, module or other computing element is described as being configured to perform or execute functions on data in memory, the meaning of “configured to” or “programmed to” is defined as one or more processors or cores of the computing element being programmed with a set of software instructions stored in the memory of the computing element to perform that set of functions on target data or data objects stored in memory.

[0031] It should be noted that any language designed for computers should be understood 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, individually or in combination. It should be understood that computing devices include processors configured to execute software instructions stored on tangible, non-transitory computer-readable storage media, such as hard disk drives, FPGAs, PLAs, solid-state drives, RAM, flash memory, ROM, or any other volatile or non-volatile storage devices. These software instructions configure or program the computing device to provide roles, responsibilities, or other functions, as discussed below with respect to the disclosed apparatus. Furthermore, the disclosed technology can be embodied as a computer program product comprising a non-transitory computer-readable medium storing software instructions that cause a processor to perform the disclosed steps associated with an implementation of a computer-based algorithm, process, method, or other instructions. In some embodiments, various servers, systems, databases, or interfaces exchange data using standardized protocols or algorithms, possibly based on HTTP, HTTPS, AES, public-key exchange, web service APIs, known financial transaction protocols, or other electronic information exchange methods. Data exchange between devices can be carried out through the following: packet-switched networks, the Internet, LAN, WAN, VPN or other types of packet-switched networks; circuit-switched networks; cell-switched networks; or other types of networks.

[0032] Typically, a LiDAR system has a transmitter (TX) and a receiver (RX). The transmitter emits laser light to form transmitted light. The receiver receives the reflected light from one or more target objects in the field of view. At least a portion of the reflected light is formed by laser light reflected or scattered by the target objects. The reflected light may also include stray light, which can be noise and / or interference light. LiDAR systems typically operate at a specific center wavelength with a certain bandwidth, such as 905 nm (center wavelength) + / - 5 nm (bandwidth) for semiconductor lasers. In existing LiDAR systems, bandpass filters (BPFs) are widely used in the receiver to filter out stray light from the reflected light received by the LiDAR system. The wavelength of the stray light may be the same as or different from the wavelength of the transmitted light.

[0033] However, bandpass filters are typically configured with a wide passband to allow all signal laser power to pass through. With this type of BPF, stray light with the same wavelength or wavelength range as the transmitted light cannot be filtered out. One way to reduce such stray light is to narrow the passband of the BPF (e.g., to 2 nm or even smaller) and only allow return light with the same wavelength as the center wavelength of the transmitted light to pass through. The problem with this method of reducing stray light is that a significant amount of signal power in the return light may be lost because the signal bandwidth is narrower than the passband of the BPF. To compensate for the loss of return light signal power caused by the BPF, the signal power of the transmitted light must be increased. However, increasing the signal power of the transmitted laser is limited by the eye safety requirements of LiDAR systems. Therefore, simply increasing the laser power to increase the signal power of the transmitted laser, and thus consequently increasing the return light signal power passing through the narrow passband of the BPF in the receiver, may be infeasible or impractical.

[0034] This disclosure provides systems and methods for reducing stray light using synchronous filtering. In one embodiment, an optical ranging and detection (LiDAR) system for reducing stray light using synchronous filtering is provided. The system includes a light source and an emitter that emits laser light having a first wavelength range, the emitter including one or more emitting optics disposed in a transmitted light path. The emitter is configured to provide transmitted light based on the laser light having the first wavelength range. The system also includes a receiver that includes a detector and one or more receiving optics disposed in a receiving light path. The receiver is configured to receive return light including stray light and an optical signal formed based on the transmitted beam. The system further includes a synchronous filter structure including one or more bandpass filters having substantially the same passband. The synchronous filter structure is coupled to both the emitter and the receiver. The synchronous filter structure is configured to perform the following operations: reduce the bandwidth of the laser light from the first wavelength range to a second wavelength range, such that the transmitted beam has the second wavelength range; filter out at least a portion of stray light with wavelengths outside the second wavelength range; and transmit the majority of the optical signal formed based on the transmitted beam to the detector.

[0035] By utilizing a synchronous filter structure, stray light in the returned light can be significantly filtered out or reduced (e.g., by 60%) without much loss of signal power. Furthermore, due to the synchronous filter structure, the laser power within the LiDAR system is increased to compensate for signal power loss, thus ensuring that the transmitted light signal power still meets laser eye safety requirements.

[0036] Figure 1The illustration shows one or more exemplary LiDAR systems 110 and 120A to 120I set up or included in a motor vehicle 100. The vehicle 100 can be a car, SUV, truck, train, van, bicycle, motorcycle, tricycle, bus, motorized scooter, tram, ship, boat, underwater vehicle, airplane, helicopter, unmanned aerial vehicle (UAV), spacecraft, etc. The motor vehicle 100 can be a vehicle with any level of automation. For example, the 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 human driver intervention. For example, a partially automated vehicle can perform blind spot monitoring, lane keeping and / or lane changing operations, automatic emergency braking, intelligent cruise control and / or traffic following, etc. Some operations of a partially automated vehicle may be limited to specific applications or driving scenarios (e.g., limited to highway driving). A highly automated vehicle can generally perform all the operations of a partially automated vehicle, but with fewer limitations. Highly automated vehicles can also detect their own limits while operating the vehicle and, if necessary, request the driver to take over control. Fully automated vehicles can perform all vehicle operations without driver intervention, but can also detect their own limits and, if necessary, request driver intervention. Driverless vehicles can operate autonomously without any driver intervention.

[0037] In a typical configuration, the motor vehicle 100 includes one or more LiDAR systems 110 and 120A to 120I. Each of the LiDAR systems 110 and 120A to 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 beams in one or more directions (e.g., horizontal and vertical) to detect objects in the field of view (FOV). A non-scanning-based LiDAR system emits a laser to illuminate the FOV without scanning. For example, a flash LiDAR is a type of non-scanning-based LiDAR system. A flash LiDAR can emit a laser, illuminating the FOV simultaneously using a single light pulse or a beam of light.

[0038] LiDAR systems are commonly used sensors in at least partially automated vehicles. In one embodiment, such as... Figure 1As shown, a motor vehicle 100 may include a single LiDAR system 110 (e.g., without LiDAR systems 120A to 120I) positioned at the highest point of the vehicle (e.g., on the top of the vehicle). Positioning the LiDAR system 110 on the top of the vehicle facilitates 360-degree scanning around the vehicle 100. In some other embodiments, the motor vehicle 100 may include multiple LiDAR systems, including two or more of systems 110 and / or 120A to 120I. Figure 1 As shown, in one embodiment, multiple LiDAR systems 110 and / or 120A to 120I are attached to vehicle 100 at different locations on the vehicle. For example, LiDAR system 120A is attached to vehicle 100 at the right front corner; LiDAR system 120B is attached to vehicle 100 at the front center position; LiDAR system 120C is attached to vehicle 100 at the left front corner; LiDAR system 120D is attached to vehicle 100 at the right rearview mirror; LiDAR system 120E is attached to vehicle 100 at vehicle 100 at the left rearview mirror; LiDAR system 120F is attached to vehicle 100 at vehicle 100 at the rear center position; LiDAR system 120G is attached to vehicle 100 at the right rear corner; LiDAR system 120H is attached to vehicle 100 at vehicle 100 at the left rear corner; and / or LiDAR system 120I is attached to vehicle 100 at the center towards the rear end (e.g., the rear end of the top of the vehicle). It should be understood that one or more LiDAR systems can be distributed and attached to vehicles in any desired manner, and Figure 1 Only one embodiment is illustrated. As another example, LiDAR systems 120D and 120E may be attached to the B-pillar of vehicle 100 instead of the rearview mirror. As another example, LiDAR system 120B may be attached to the windshield of vehicle 100 instead of the front bumper.

[0039] In some embodiments, LiDAR systems 110 and 120A through 120I are independent LiDAR systems, each with its own laser source, control electronics, transmitter, receiver, and / or steering mechanism. In other embodiments, some of LiDAR systems 110 and 120A through 120I may share one or more components, thereby forming a distributed sensor system. In one example, optical fiber is used to deliver laser light from a centralized laser source to all LiDAR systems. For example, system 110 (or another system located at the center of vehicle 100 or any other location) includes a light source, transmitter, and photodetector, but no steering mechanism. System 110 may distribute transmitted light to each of systems 120A through 120I. The transmitted light may be distributed via optical fiber. Optical connectors may be used to couple optical fiber to each of systems 110 and 120A through 120I. In some examples, one or more of systems 120A through 120I include a steering mechanism, but no light source, transmitter, or photodetector. The steering mechanism may include one or more movable mirrors, such as one or more polygonal mirrors, one or more single-plane mirrors, one or more multi-plane mirrors, etc. Embodiments of the light source, emitter, steering mechanism, and photodetector will be described in more detail below. Via the steering mechanism, one or more of systems 120A to 120I scan light into one or more corresponding fields of view (FOVs) and receive the corresponding return light. The return light is formed by the scattering or reflection of transmitted light by one or more objects in the FOV. Systems 120A to 120I may also include collecting lenses and / or other optics to focus and / or guide the return light into an optical fiber, which delivers the received return light to system 110. System 110 includes one or more photodetectors for detecting the received return light. In some examples, system 110 is located inside a vehicle, thus placing it in a temperature-controlled environment, while one or more systems 120A to 120I may be at least partially exposed to the external environment.

[0040] Figure 2 This is a block diagram 200 illustrating the interaction between an onboard LiDAR system 210 and several other systems, including a vehicle perception and planning system 220. The LiDAR system 210 can be mounted on or integrated into a vehicle. The LiDAR system 210 includes sensors that scan the surrounding environment with laser light to measure the distance, angle, and / or velocity of objects. Based on the scattered light returning to the LiDAR system 210, it can generate sensor data (e.g., image data or 3D point cloud data) representing the perceived external environment.

[0041] LiDAR system 210 may include one or more of short-range LiDAR sensors, mid-range LiDAR sensors, and long-range LiDAR sensors. Short-range LiDAR sensors measure objects up to approximately 20 to 50 meters away from the LiDAR sensor. Short-range LiDAR sensors can be used, for example, to monitor nearby moving objects (e.g., pedestrians crossing the street in a school zone), parking assistance applications, etc. Mid-range LiDAR sensors measure objects up to approximately 70 to 200 meters away from the LiDAR sensor. Mid-range LiDAR sensors can be used, for example, to monitor road intersections, assist merging or exiting highways, etc. Long-range LiDAR sensors measure objects located at 200 meters and above. Long-range LiDAR sensors are typically used when vehicles are traveling at high speeds (e.g., on highways), allowing the vehicle's control system only a few seconds (e.g., 6 to 8 seconds) to respond to any situation detected by the LiDAR sensor. Figure 2 As shown, in one embodiment, LiDAR sensor data can be provided to the vehicle perception and planning system 220 via communication path 213 for further processing and control of vehicle operation. Communication path 213 can be any wired or wireless communication link capable of transmitting data.

[0042] Still referencing Figure 2 In some embodiments, other vehicle sensors 230 are configured to provide additional sensor data, either alone or in conjunction with the LiDAR system 210. These other vehicle sensors 230 may include, for example, one or more cameras 232, one or more radars 234, one or more ultrasonic sensors 236, and / or other sensors 238. Cameras 232 may capture images and / or video of the vehicle's external environment. Cameras 232 may capture, for example, high-definition (HD) video with millions of pixels per frame. Cameras include image sensors that facilitate the generation of monochrome or color images and videos. Color information may be important in interpreting data in certain situations (e.g., interpreting images of traffic lights). Color information may not be available from other sensors, such as LiDAR or radar sensors. Cameras 232 may include one or more of narrow-focal-length cameras, wide-focal-length cameras, side-mounted cameras, infrared cameras, fisheye cameras, etc. Image and / or video data generated by cameras 232 may also be provided to the vehicle perception and planning system 220 via communication path 233 for further processing and control of vehicle operation. Communication path 233 may be any wired or wireless communication link capable of transmitting data. The camera 232 can be mounted or integrated into the vehicle in any location (e.g., rearview mirror, pillar, front grille and / or rear bumper, etc.).

[0043] Other vehicle-mounted sensors 230 may also include a radar sensor 234. The radar sensor 234 uses radio waves to determine the distance, angle, and speed of an object. The radar sensor 234 generates electromagnetic waves in the radio or microwave spectrum. These electromagnetic waves are reflected by the object, and some of the reflected waves return to the radar sensor, providing information about the object's position and speed. The radar sensor 234 may include one or more of short-range, medium-range, and long-range radars. Short-range radar measures objects at a distance of approximately 0.1 meters to 30 meters from the radar. Short-range radar is useful for detecting objects located near vehicles (such as other vehicles, buildings, walls, pedestrians, cyclists, etc.). Short-range radar can be used for blind spot detection, lane change assistance, providing rear-end collision warnings, parking assistance, and emergency braking. Medium-range radar measures objects at a distance of approximately 30 meters to 80 meters from the radar. Long-range radar measures objects located at a distance of approximately 80 meters to 200 meters. Medium-range and / or long-range radar can be used for, for example, traffic tracking, adaptive cruise control, and / or automatic braking on highways. Sensor data generated by radar sensor 234 can also be provided to vehicle perception and planning system 220 via communication path 233 for further processing and control of vehicle operation. Radar sensor 234 can be installed or integrated into any location on the vehicle (e.g., rearview mirror, pillar, front grille and / or rear bumper, etc.).

[0044] Other onboard sensors 230 may also include ultrasonic sensors 236. Ultrasonic sensors 236 use sound waves or pulses to measure objects located outside the vehicle. Sound waves generated by ultrasonic sensors 236 are emitted into the surrounding environment. At least some of the emitted waves are reflected by objects and return to ultrasonic sensors 236. Based on the returned signals, the distance to the object can be calculated. Ultrasonic sensors 236 can be used, for example, to check blind spots, identify parking spaces, and provide lane change assistance in traffic. Sensor data generated by ultrasonic sensors 236 can also be provided via communication path 233 to the vehicle perception and planning system 220 for further processing and control of vehicle operation. Ultrasonic sensors 236 can be mounted or integrated into any location on the vehicle (e.g., rearview mirrors, pillars, front grille, and / or rear bumper, etc.).

[0045] In some embodiments, one or more other sensors 238 may be attached to the vehicle and may also generate sensor data. Other sensors 238 may include, for example, a Global Positioning System (GPS), an Inertial Measurement Unit (IMU), etc. The sensor data generated by the other sensors 238 may also be provided to the vehicle perception and planning system 220 via communication path 233 for further processing and control of vehicle operation. It should be understood that communication path 233 may include one or more communication links for transmitting data between the various sensors 230 and the vehicle perception and planning system 220.

[0046] In some embodiments, such as Figure 2 As shown, sensor data from other vehicle-mounted sensors 230 can be provided to the vehicle-mounted LiDAR system 210 via communication path 231. The LiDAR system 210 can process the sensor data from the other vehicle-mounted sensors 230. For example, sensor data from camera 232, radar sensor 234, ultrasonic sensor 236, and / or other sensors 238 can be correlated or fused with sensor data from the LiDAR system 210, thereby at least partially offloading the sensor fusion process performed by the vehicle perception and planning system 220. It should be understood that other configurations can also be implemented to transmit and process sensor data from various sensors (e.g., data can be transmitted to a cloud or edge computing service provider for processing, and the processing results can then be transmitted back to the vehicle perception and planning system 220 and / or the LiDAR system 210).

[0047] Still referencing Figure 2 In some embodiments, sensors on other vehicles 250 are used individually or in conjunction with the LiDAR system 210 to provide additional sensor data. For example, two or more nearby vehicles may have their own LiDAR sensors, cameras, radar sensors, ultrasonic sensors, etc. Nearby vehicles can transmit and share sensor data with each other. Communication between vehicles is also referred to as V2V (vehicle-to-vehicle) communication. For example, as... Figure 2 As shown, sensor data generated by other vehicles 250 can be transmitted to the vehicle perception and planning system 220 and / or the onboard LiDAR system 210 via communication path 253 and / or communication path 251, respectively. Communication paths 253 and 251 can be any wired or wireless communication links capable of transmitting data.

[0048] Sharing sensor data facilitates better perception of the external environment of a vehicle. For example, the first vehicle may not detect a pedestrian approaching it from behind a second vehicle. The second vehicle can share sensor data related to the pedestrian with the first vehicle, allowing the first vehicle additional reaction time to avoid a collision. In some embodiments, data generated by sensors on other vehicles 250, similar to data generated by sensor 230, can be correlated or fused with sensor data generated by LiDAR system 210 (or other LiDAR systems located in other vehicles), thereby at least partially offloading the sensor fusion process performed by vehicle perception and planning system 220.

[0049] In some embodiments, the intelligent infrastructure system 240 is used to provide sensor data, either alone or in conjunction with the LiDAR system 210. Certain infrastructure can be configured to communicate with vehicles to relay information, and vice versa. Communication between vehicles and infrastructure is generally referred to as V2I (vehicle-to-infrastructure) communication. For example, the intelligent infrastructure system 240 may include intelligent traffic lights that can communicate their status to approaching vehicles with messages such as "turns yellow in 5 seconds." The intelligent infrastructure system 240 may also include its own LiDAR system installed near an intersection, enabling it to transmit traffic monitoring information to vehicles. For example, a vehicle turning left at an intersection may not have sufficient sensing capabilities because some of its own sensors may be blocked by traffic from the opposite direction. In this case, the sensors of the intelligent infrastructure system 240 can provide useful data to the left-turning vehicle. This data may include, for example, traffic conditions, information about objects in the direction the vehicle is turning, traffic light status, and predictions. The sensor data generated by the intelligent infrastructure system 240 can be provided to the vehicle perception and planning system 220 and / or the onboard LiDAR system 210 via communication paths 243 and / or 241, respectively. Communication paths 243 and / or 241 can include any wired or wireless communication links capable of transmitting data. For example, sensor data from the intelligent infrastructure system 240 can be transmitted to the LiDAR system 210 and correlated or fused with the sensor data generated by the LiDAR system 210, thereby at least partially offloading the sensor fusion process performed by the vehicle perception and planning system 220. The above-described V2V and V2I communications are examples of vehicle-to-X (V2X) communications, where “X” represents any other device, system, sensor, infrastructure, etc., that can share data with the vehicle.

[0050] Still referencing Figure 2The vehicle perception and planning system 220 receives sensor data from one or more of the LiDAR system 210, other onboard sensors 230, other vehicles 250, and / or intelligent infrastructure systems 240 via various communication paths. In some embodiments, different types of sensor data are correlated and / or fused by a sensor fusion subsystem 222. For example, the sensor fusion subsystem 222 can generate a 360-degree model using multiple images or videos captured by multiple cameras located at different locations on the vehicle. The sensor fusion subsystem 222 obtains sensor data from different types of sensors and uses the combined data to perceive the environment more accurately. For example, the onboard camera 232 may not capture a clear image because it is directly facing the sun or a light source (e.g., the headlight of another vehicle at night). The LiDAR system 210 may not be significantly affected, and therefore the sensor fusion subsystem 222 can combine the sensor data provided by the camera 232 and the LiDAR system 210, and use the sensor data provided by the LiDAR system 210 to compensate for the unclear image captured by the camera 232. As another example, in rainy or foggy weather, radar sensor 234 may perform better than camera 232 or LiDAR system 210. Accordingly, sensor fusion subsystem 222 can use sensor data provided by radar sensor 234 to compensate for sensor data provided by camera 232 or LiDAR system 210.

[0051] In other examples, sensor data generated by other onboard sensors 230 may have lower resolution (e.g., radar sensor data) and therefore may need to be correlated and verified by a LiDAR system 210, which typically has higher resolution. For example, radar sensor 234 may detect a manhole cover (also known as a maintenance hatch cover) as an object approaching a vehicle. Due to the low resolution 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. Therefore, high-resolution sensor data generated by LiDAR system 210 can be used to correlate and verify that the object is a manhole cover and will not cause damage to the vehicle.

[0052] The vehicle perception and planning system 220 further includes an object classifier 223. Using raw sensor data and / or related / fused data provided by the sensor fusion subsystem 222, the object classifier 223 can use any computer vision technique to detect and classify objects and estimate their positions. In some embodiments, the object classifier 223 can use machine learning-based techniques to detect and classify objects. Examples of machine learning-based techniques include algorithms such as region-based convolutional neural networks (R-CNN), fast R-CNN, faster R-CNN, oriented gradient histogram (HOG), region-based fully convolutional networks (R-FCN), single-shot detectors (SSD), spatial pyramid pooling (SPP-net), and / or You Only Look Once (Yolo).

[0053] The vehicle perception and planning system 220 further includes a road detection subsystem 224. The road detection subsystem 224 locates the road and identifies objects and / or markings on the road. For example, based on raw or fused sensor data provided by radar sensor 234, camera 232, and / or LiDAR system 210, the road detection subsystem 224 can construct a 3D model of the road based on machine learning techniques (e.g., pattern recognition algorithms for lane identification). Using the 3D model of the road, the road detection subsystem 224 can identify objects (e.g., obstacles or debris) and / or markings (e.g., lane lines, turning signs, pedestrian crossing signs, etc.) on the road.

[0054] The vehicle perception and planning system 220 further includes a localization and vehicle attitude subsystem 225. Based on raw or fused sensor data, the localization and vehicle attitude subsystem 225 can determine the vehicle's position and attitude. For example, using sensor data from LiDAR system 210, camera 232, and / or GPS data, the localization and vehicle attitude subsystem 225 can determine the vehicle's precise location on the road and its six degrees of freedom (e.g., whether the vehicle is moving forward or backward, up or down, left or right). In some embodiments, a high-definition (HD) map is used for vehicle localization. The HD map can provide a very detailed three-dimensional computer map that accurately locates the vehicle's position. For example, using an HD map, the localization and vehicle attitude subsystem 225 can accurately determine the vehicle's current position (e.g., which lane the vehicle is currently in on the road, and how close it is to the curb or sidewalk) and predict the vehicle's future position.

[0055] The vehicle perception and planning system 220 further includes an obstacle predictor 226. Objects identified by the object classifier 223 can be stationary (e.g., lampposts, road signs) or dynamic (e.g., moving pedestrians, bicycles, another vehicle). For moving objects, predicting their movement paths or future positions is important for collision avoidance. The obstacle predictor 226 can predict obstacle trajectories and / or warn the driver or vehicle planning subsystem 228 of potential collisions. For example, if there is a high probability that the obstacle's trajectory will intersect with the vehicle's current movement path, the obstacle predictor 226 can generate such a warning. The obstacle predictor 226 can use various techniques to make such predictions. These techniques include, for example, constant speed or acceleration models, constant turning rate and speed / acceleration models, Kalman filter-based 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, etc.

[0056] Still referencing Figure 2 In some embodiments, the vehicle perception and planning system 220 further includes a vehicle planning subsystem 228. The vehicle planning subsystem 228 may include one or more planners, such as a route planner, a driving behavior planner, and a motion planner. The route planner may plan the vehicle's route based on the vehicle's current location data, target location data, traffic information, etc. The driving behavior planner uses obstacle prediction results provided by obstacle predictor 226 to adjust the timing and planned movement based on how other objects might move. The motion planner determines the specific actions the vehicle needs to follow. The planning results are then transmitted to the vehicle control system 280 via vehicle interface 270. Communication can be performed via communication paths 227 and 271, which include any wired or wireless communication links capable of transmitting data.

[0057] The vehicle control system 280 controls the vehicle's steering mechanism, throttle, brakes, etc., to operate the vehicle according to a planned route and movement. In some examples, the vehicle perception and planning system 220 may further include a user interface 260 that provides access to the vehicle control system 280 to a user (e.g., a driver) to, for example, overtake or take over control of the vehicle when necessary. The user interface 260 may also be separate from the vehicle perception and planning system 220. The user interface 260 may communicate with the vehicle perception and planning system 220, for example, to acquire and display raw or fused sensor data, identified objects, the vehicle's position / attitude, etc. This displayed data can help the user better operate the vehicle. The user interface 260 may communicate with the vehicle perception and planning system 220 and / or the vehicle control system 280 via communication paths 221 and 261, respectively, which include any wired or wireless communication links capable of transmitting data. It should be understood that... Figure 2 The various systems, sensors, communication links, and interfaces within can be configured in any desired manner, and are not limited to... Figure 2 The configuration shown.

[0058] Figure 3 This is a block diagram illustrating an exemplary LiDAR system 300. The LiDAR system 300 can be used to implement... Figure 1 and Figure 2 The LiDAR systems 110, 120A to 120I and / or 210 are shown. In one embodiment, LiDAR system 300 includes a light source 310, a transmitter 320, an optical receiver and photodetector 330, a steering system 340, and a control circuitry system 350. These components are coupled together using communication paths 312, 314, 322, 332, 342, 352, 362, and 372. These communication paths include communication links (wired or wireless, bidirectional or unidirectional) between various LiDAR system components, but do not necessarily have to be the physical components themselves. While communication paths can be implemented by one or more wires, buses, or optical fibers, they can also be wireless channels or free-space optical paths, thus eliminating the need for a physical communication medium. For example, in one embodiment of LiDAR system 300, communication path 314 between light source 310 and transmitter 320 can be implemented using one or more optical fibers. Communication paths 332 and 352 can represent optical paths implemented using free-space optical components and / or optical fibers. Furthermore, communication paths 312, 322, 342, and 362 can be implemented using one or more wires carrying electrical signals. The communication paths may also include one or more of the communication media of the types described above (for example, they may include optical fibers and free-space optical components, or include one or more optical fibers and one or more wires).

[0059] In some embodiments, LiDAR system 300 can be a coherent LiDAR system. Frequency-modulated continuous wave (FMCW) LiDAR is one example. Coherent LiDAR detects objects by mixing the reflected light from the object with light from a coherent laser emitter. Therefore, as... Figure 3 As shown, if LiDAR system 300 is a coherent LiDAR, it may include a route 372 that provides a portion of the transmitted light from transmitter 320 to optical receiver and photodetector 330. Route 372 may include one or more optical components (e.g., optical fibers, lenses, mirrors, etc.) for providing light from transmitter 320 to optical receiver and photodetector 330. The transmitted light provided by transmitter 320 may be modulated light and may be split into two parts. One part is emitted to the field of view (FOV), while the second part is sent to the optical receiver and photodetector 330 of LiDAR system 300. The second part is also referred to as light retained locally (LO) in LiDAR system 300. The transmitted light is scattered or reflected by various objects in the FOV, and at least a portion of it forms returned light. The returned light is then detected and interferes with and reconstitutes with the second part of the locally retained transmitted light. Coherent LiDAR provides a mechanism for optically sensing the range of objects and their relative velocity along the line of sight (LOS).

[0060] The LiDAR system 300 may also include Figure 3 Other components not shown include power buses, power supplies, LED indicators, and switches. Additionally, other communication connections between components may exist, such as a direct connection between the light source 310 and the optical receiver and photodetector 330, to provide a reference signal that allows for accurate measurement of the time from the emission of a light pulse to detection and the return of the light pulse.

[0061] Light source 310 outputs laser light to illuminate objects within the field of view (FOV). The laser light can be infrared light with wavelengths ranging from 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. Semiconductor-based lasers can be, for example, edge-emitting lasers (EELs), vertical-cavity surface-emitting lasers (VCSELs), external-cavity diode lasers, vertical-external-cavity surface-emitting lasers, distributed feedback (DFB) lasers, distributed Bragg reflector (DBR) lasers, interband cascade lasers, quantum cascade lasers, quantum well lasers, dual heterostructure lasers, etc. Fiber-based lasers are lasers 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, the fiber laser is based on double-clad fiber, wherein the gain medium forms the core of the fiber surrounded by two cladding layers. Double-clad fiber allows the fiber core to be pumped with a high-power beam, thus enabling the laser source to become a high-power fiber laser source.

[0062] In some embodiments, the light source 310 includes a master oscillator (also referred to as a seed laser) and a power amplifier (MOPA). The power amplifier amplifies the output power of the seed laser. The power amplifier can be an 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 an external cavity tunable diode laser. In some embodiments, the light source 310 can be an optically pumped microchip laser. A microchip laser is an alignment-free monolithic solid-state laser in which the laser crystal is in direct contact with the end mirror of the laser resonator. Microchip lasers are typically pumped by laser diodes (directly or using fiber) to obtain the desired output power. Microchip lasers 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, the light source 310 may have multiple amplification stages to achieve high power gain, enabling the laser output to have high power and thus allowing the LiDAR system to have a long scan range. In some examples, the power amplifier of the light source 310 can be controlled, allowing the power gain to be varied to achieve any desired laser output power.

[0063] Figure 4A This is a block diagram illustrating an exemplary fiber-optic-based laser source 400, which includes a seed laser and one or more pumps (e.g., laser diodes) for pumping a desired output power. The fiber-optic-based laser source 400 is... Figure 3An example of the depicted light source 310. In some embodiments, the fiber-based laser source 400 includes a seed laser 402 configured to generate initial optical pulses of one or more wavelengths (e.g., infrared wavelengths such as 1550 nm), which are provided to a wavelength division multiplexer (WDM) 404 via fiber 403. The fiber-based laser source 400 further includes a pump 406 for providing laser power (e.g., different wavelengths, such as 980 nm) to the WDM 404 via fiber 405. The WDM 404 multiplexes the optical pulses provided by the seed laser 402 and the laser power provided by the pump 406 onto a single fiber 407. The output of the WDM 404 can then be provided to one or more preamplifiers 408 via fiber 407. The preamplifier 408 may be an optical amplifier that amplifies the optical signal (e.g., with a gain of about 10 dB to 30 dB). In some embodiments, the preamplifier 408 is a low-noise amplifier. The preamplifier 408 outputs to an optical combiner 410 via fiber 409. Combiner 410 combines the output laser from preamplifier 408 with laser power supplied by pump 412 via fiber optic 411. Combiner 410 can combine optical signals with the same or different wavelengths. An example of a combiner is a WDM. Combiner 410 provides the combined optical signal to boost amplifier 414, which generates an output optical pulse via fiber optic 415. Boost amplifier 414 provides further amplification of the optical signal (e.g., another 20 dB to 40 dB). The output optical pulse can then be transmitted to transmitter 320 and / or steering mechanism 340 (e.g., ...). Figure 3 (As shown). It should be understood that, Figure 4A The illustration shows an exemplary configuration of a fiber-optic laser source 400. The laser source 400 may have the following characteristics: Figure 4A One or more components shown and / or Figure 4A Many other configurations of different combinations of other components not shown (e.g., power supplies, lenses, filters, beam splitters, combiners, etc.).

[0064] In some variations, the fiber-based laser source 400 can be controlled (e.g., via control circuitry 350) to generate pulses of different amplitudes based on the fiber gain distribution of the fiber used in the fiber-based laser source 400. Communication path 312 couples the fiber-based laser source 400 to the control circuitry 350 (e.g., via control circuitry 350). Figure 3As shown, components of the fiber-based laser source 400 can be controlled by or otherwise communicate with the control circuitry system 350. Alternatively, the fiber-based laser source 400 may include its own dedicated controller. Instead of the control circuitry system 350 communicating directly with the components of the fiber-based laser source 400, the dedicated controller of the fiber-based laser source 400 communicates with and controls the components of the fiber-based laser source 400 and / or communicates with them. The fiber-based laser source 400 may also include other components not shown, such as one or more power connectors, power supplies, and / or transmission lines.

[0065] Figure 4B This is a block diagram illustrating an exemplary semiconductor-based laser source 440. The semiconductor-based laser source 440 is... Figure 3 An example of light source 310 is shown. In Figure 4B In the example shown, laser source 440 is a vertical-cavity surface-emitting laser (VCSEL), a type of semiconductor laser diode with a unique structure that allows it to emit light vertically from the surface of the chip, rather than through the edge of the chip as in edge-emitting laser (EEL) diodes. VCSELs offer advantages such as high-speed operation and ease of integration into semiconductor devices. Figure 4BA cross-sectional view of an exemplary VCSEL 440 is shown. In this example, the VCSEL 440 includes a metal contact layer 442, an upper Bragg reflector 444, an active region 446, a lower Bragg reflector 448, a substrate 450, and another metal contact layer 452. In the VCSEL 440, the metal contact layers 442 and 452 are used to form electrical contacts, thereby allowing current and / or voltage to be supplied to the VCSEL 440 to generate laser light. The substrate layer 450 is a semiconductor substrate, which may be, for example, a gallium arsenide (GaAs) substrate. The VCSEL 440 uses a laser resonator that includes two distributed Bragg reflectors (DBRs) (i.e., the upper Bragg reflector 444 and the lower Bragg reflector 448), with the active region 446 sandwiched between the DBR reflectors. The active region 446 includes, for example, one or more quantum wells for laser generation. The planar DBR reflector may be a mirror with alternating high and low refractive index layers. Each layer has a thickness equivalent to one-quarter of the laser wavelength in the material, producing an intensity reflectivity of, for example, 99%. High-reflectivity mirrors in the VCSEL balance the short axial length of the gain region. In one example of the VCSEL 440, the upper DBR reflector 444 and the lower DBR reflector 448 can be doped with p-type and n-type materials, respectively, to form a diode junction. In another example, the p-type and n-type regions can be embedded between the reflectors, requiring more complex semiconductor processes to fabricate electrical contacts with the active region, but eliminating power losses in the DBR structure. The active region 446 is sandwiched between the DBR reflectors 444 and 448 of the VCSEL 440. The active region is where the laser light is generated. The active region 446 typically has a quantum well or quantum dot structure containing the gain medium responsible for optical amplification. When current is applied to the active region 446, it generates photons through stimulated emission. The distance between the upper DBR reflector 444 and the lower DBR reflector 448 defines the cavity length of the VCSEL 440. The cavity length, in turn, determines the wavelength of the emitted light and affects the laser's performance characteristics. When current is applied to the VCSEL 440, it generates light that bounces between the DBR reflectors 444 and 448 and exits the VCSEL 440 through, for example, the lower DBR reflector 448, thereby producing a highly coherent and vertically emitted laser beam 454. The VCSEL 440 can provide improved beam quality, low threshold current, and the ability to produce single-mode or multimode output.

[0066] In some variations, VCSEL 440 can be controlled (e.g., via control circuitry 350) to generate pulses of varying amplitudes. Communication path 312 couples VCSEL 440 to control circuitry 350 (e.g., via control circuitry 350). Figure 3As shown, components of the VCSEL 440 can be controlled by or otherwise communicate with the control circuitry system 350. Alternatively, the VCSEL 440 may include its own dedicated controller. Instead of the control circuitry system 350 communicating directly with the components of the VCSEL 440, the dedicated controller of the VCSEL 440 communicates with and controls the components of the VCSEL 440 and / or communicates with them. The VCSEL 440 may also include other components not shown, such as one or more power connectors, power supplies, and / or power lines.

[0067] The VCSEL 440 can be used to generate laser pulses or continuous wave (CW) lasers. To generate laser pulses, the control circuitry 350 modulates the current supplied to the VCSEL 440. Laser pulses can be generated by rapidly switching the power supply current on and off. The pulse duration, repetition rate, and shape can be controlled by adjusting the modulation parameters. As another example, the VCSEL 440 can also be a mode-locked VCSEL, which uses a combination of current modulation and optical feedback to obtain ultrashort pulses. Mode-locked VCSELs can also be controlled to synchronize the phase of the laser mode to produce very short and high-intensity pulses. As another example, the VCSEL 440 can use Q-switching technology, which includes an optical switch in the laser cavity that temporarily blocks laser action and allows energy to accumulate in the cavity. When the switch is open, a high-intensity pulse is emitted. As another example, the VCSEL 440 can also have external modulation performed by an external modulator (not shown), such as an electro-optic or acousto-optic modulator. External modulation can be used in conjunction with the VCSEL itself to produce pulse output. The external modulator can be used to control the pulse duration and repetition rate. The type of VCSEL used as at least a part of the light source 310 depends on the application and the required pulse characteristics, such as pulse duration, repetition rate and peak power.

[0068] refer to Figure 3Typical operating wavelengths of the light source 310 include, for example, approximately 850 nm, approximately 905 nm, approximately 940 nm, approximately 1064 nm, and approximately 1550 nm. For laser safety, the maximum usable laser power is capped by regulations set by the U.S. Food and Drug Administration (FDA). The optical power limit at 1550 nm is significantly higher than the power limits at the other wavelengths mentioned above. Furthermore, at 1550 nm, optical power loss in the fiber is very low. These characteristics of the 1550 nm wavelength make it more advantageous for long-range LiDAR applications. The amount of optical power output from the light source 310 can be characterized by its peak power, average power, pulse energy, and / or pulse energy density. Peak power is the ratio of pulse energy to pulse width (e.g., full width at half maximum or FWHM). Therefore, for a fixed amount of pulse energy, a smaller pulse width can provide a larger peak power. Pulse widths can range from nanoseconds to picoseconds. Average power is the product of pulse energy and pulse repetition rate (PRR). As described in more detail below, PRR represents the frequency of the pulsed laser. Generally, the smaller the time interval between pulses, the higher the PRR. PRR typically corresponds to the maximum range that a LiDAR system can measure. The light source 310 can be configured to generate pulses with a high PRR to meet the desired number of data points in the point cloud generated by the LiDAR system. The light source 310 can also be configured to generate pulses with a medium or low PRR to meet the desired maximum detection range. Wall insertion efficiency (WPE) is another factor for evaluating total power consumption and can be a useful metric for assessing laser efficiency. For example, as... Figure 1 As shown, multiple LiDAR systems can be attached to vehicles, which can be electric vehicles or vehicles with limited fuel or battery power. Therefore, high WPE and intelligent methods of using laser power are often important considerations when selecting and configuring the light source 310 and / or designing laser delivery systems for vehicle-mounted LiDAR applications.

[0069] It should be understood that the above description provides a non-limiting example of 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 external-cavity tunable diode lasers) configured to generate one or more optical signals of various wavelengths. In some examples, light source 310 includes amplifiers (e.g., preamplifiers and / or boost amplifiers), which can be doped fiber amplifiers, solid-state amplifiers, and / or semiconductor optical amplifiers. The amplifiers are configured to receive and amplify the optical signals at a desired gain.

[0070] Return to reference Figure 3The LiDAR system 300 further includes a transmitter 320. A light source 310 supplies laser light (e.g., in the form of a laser beam) to the transmitter 320. The laser light supplied by the light source 310 may be an amplified laser with a predetermined or controlled wavelength, pulse repetition rate, and / or power level. The transmitter 320 receives the laser light from the light source 310 and transmits it to a steering mechanism 340 with low divergence. In some embodiments, the transmitter 320 may include, for example, optical components (e.g., lenses, optical fibers, mirrors, etc.) for transmitting one or more laser beams directly or via the steering mechanism 340 to the field of view (FOV). Although Figure 3 The transmitter 320 and the steering mechanism 340 are illustrated as separate components, but in some embodiments, they may be combined or integrated into a system. The steering mechanism 340 is described in more detail below.

[0071] The laser beam provided by light source 310 may diverge as it propagates to emitter 320. Therefore, emitter 320 typically includes a collimating lens or lens group configured to collect the diverging laser beam and produce a more parallel beam with reduced or minimal divergence. The collimated beam can then be further guided through various optical devices, such as mirrors and lenses. The collimating lens can be, for example, a single plano-convex lens or a lens group. The collimating lens can be configured to achieve any desired characteristics, such as beam diameter, divergence, numerical aperture, focal length, etc. Beam propagation ratio or beam quality factor (also known as M) is also considered. 2 The laser beam quality factor (M) is used to measure the quality of the laser beam. In many LiDAR applications, good laser beam quality is crucial in the generated emitted laser beam. 2 The factor represents the degree of variation of the beam relative to an ideal Gaussian beam. Therefore, the M² factor reflects how well a collimated laser beam can be focused on a small point, or how well a diverging laser beam can be collimated. Thus, the light source 310 and / or emitter 320 can be configured to meet, for example, scanning resolution requirements while maintaining the desired M² factor.

[0072] One or more beams of light provided by transmitter 320 are scanned onto the field of view (FOV) by steering mechanism 340. Steering mechanism 340 scans the beams in multiple dimensions (e.g., horizontal and vertical) to allow LiDAR system 300 to map the environment by generating a 3D point cloud. The horizontal dimension may be parallel to the horizon or a surface associated with the LiDAR system or vehicle (e.g., a road surface). The 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 onto the FOV may be scattered or reflected by objects within the FOV. At least a portion of the scattered or reflected light forms a return beam that returns to LiDAR system 300. Figure 3Further illustration shows an optical receiver and photodetector 330 configured to receive returned light. The optical receiver and photodetector 330 include an optical receiver configured to collect returned light from the field of view (FOV). The optical receiver may include optics (e.g., lenses, optical fibers, mirrors, etc.) for receiving, redirecting, focusing, amplifying, and / or filtering the returned light from the FOV. For example, the optical receiver typically includes a collecting lens (e.g., a single plano-convex lens or a group of lenses) to collect the returned light and / or focus the collected returned light onto the photodetector.

[0073] A photodetector detects the returned light focused by an optical receiver and generates a current and / or voltage signal proportional to the incident intensity of the returned light. Based on such current and / or voltage signals, depth information of the object within the field of view (FOV) can be derived. An exemplary method for deriving this depth information is based on direct time-of-flight (TOF), which will be described in more detail below. A photodetector can be characterized by its detection sensitivity, quantum efficiency, detector bandwidth, linearity, signal-to-noise ratio (SNR), overload immunity, interference immunity, etc. Depending on the application, a photodetector can be configured or customized to have any desired characteristics. For example, the optical receiver and photodetector 330 can be configured such that the photodetector has a large dynamic range while maintaining good linearity. Photodetector linearity indicates the detector's ability to maintain a linear relationship between the input optical signal power and the detector output. A detector with good linearity can maintain a linear relationship over a large dynamic range of input optical signals.

[0074] To achieve the desired detector characteristics, the structure and / or material system of the photodetector can be configured or customized. Various detector structures can be used for photodetectors. For example, a photodetector structure can be a PIN-based structure with an undoped intrinsic semiconductor region (i.e., the "I" region) between the p-type and n-type semiconductor regions. Other photodetector structures include, for example, APD (avalanche photodiode) based structures, PMT (photomultiplier tube) based structures, SiPM (silicon photomultiplier tube) based structures, SPAD (single-photon avalanche diode) based structures, and / or quantum wires. For the material system used in the photodetector, Si, InGaAs, and / or Si / Ge-based materials can be used. It should be understood that many other detector structures and / or material systems can be used in the optical receiver and photodetector 330.

[0075] Photodetectors (e.g., APD-based detectors) can have internal gain, amplifying the input signal when an output signal is generated. However, noise can also be amplified due to the photodetector's internal gain. Common noise types include signal shot noise, dark current shot noise, thermal noise, and amplifier noise. In some embodiments, the optical receiver and photodetector 330 may include a preamplifier for a low-noise amplifier (LNA). In some embodiments, the preamplifier may also include a transimpedance amplifier (TIA) that converts a current signal into a voltage signal. For linear detector systems, input equivalent noise or noise equivalent power (NEP) measures the photodetector's sensitivity to weak signals. Therefore, they can be used as indicators of overall system performance. For example, the photodetector's NEP specifies the power of the weakest signal that can be detected, and thus it specifies the maximum range of the LiDAR system. It should be understood that various photodetector optimization techniques can be used to meet the requirements of the 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, etc.). For example, coherent detection can be used in photodetectors in addition to or instead of direct detection using a returned signal (e.g., by using Time-of-Flight). Coherent detection allows the detection of the amplitude and phase information of received light by interfering the received light with a local oscillator. Coherent detection can improve detection sensitivity and noise immunity.

[0076] Figure 3 Further illustration shows the LiDAR system 300 including a steering mechanism 340. As described above, the steering mechanism 340 guides the beam from the transmitter 320 to scan the field of view (FOV) in multiple dimensions. The steering mechanism is also referred to as a grating mechanism, a scanning mechanism, or simply a light scanner. Scanning the beam in multiple directions (e.g., horizontal and vertical) facilitates the LiDAR system in mapping the environment by generating images or 3D point clouds. The 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 rotates the LiDAR transmitter and receiver (collectively referred to as transceivers) to scan the laser beam. Solid-state scanning guides the laser beam to various locations within the FOV without mechanically moving any macroscopic components, such as transceivers. Solid-state scanning mechanisms include, for example, steering based on optical phased arrays and steering based on flash LiDAR. In some embodiments, steering performed by a solid-state scanning mechanism can be referred to as effective steering because the solid-state scanning mechanism does not physically move macroscopic components. LiDAR systems using solid-state scanning can also be referred to as non-mechanical scanning or simple non-scanning LiDAR systems (flash LiDAR systems are exemplary non-scanning LiDAR systems).

[0077] The steering mechanism 340 can be used with transceivers (e.g., transmitter 320 and optical receiver and photodetector 330) to scan the field of view (FOV) for generating images or 3D point clouds. As an example, to implement the steering mechanism 340, a 2D mechanical scanner can be used with a single-point or several single-point transceivers. The single-point transceivers transmit a single beam or a small number of beams (e.g., 2 to 8 beams) to the steering mechanism. 2D mechanical steering mechanisms include, for example, polygonal mirrors, oscillating mirrors, rotating prisms, rotating tilting mirrors, single-plane or multi-plane mirrors, or combinations thereof. In some embodiments, the steering mechanism 340 can include a non-mechanical steering mechanism, such as a solid-state steering mechanism. For example, the steering mechanism 340 can be based on the tuned wavelength of a laser incorporating refractive effects, and / or on a reconfigurable grating / phase array. In some embodiments, the steering mechanism 340 can implement 2D scanning using a single scanning device or by using a combination of multiple scanning devices.

[0078] As another example, to implement steering mechanism 340, a one-dimensional mechanical scanner can be used in conjunction with an array or a large number of single-point transceivers. Specifically, the transceiver array can be mounted on a rotating platform to achieve a 360-degree horizontal field of view. Alternatively, a static transceiver array can be combined with a one-dimensional mechanical scanner. One-dimensional mechanical scanners include polygonal mirrors, oscillating mirrors, rotating prisms, rotating tilting mirrors, or combinations thereof, for obtaining a forward-looking horizontal field of view. Steering mechanisms using mechanical scanners can provide robustness and reliability in mass production for automotive applications.

[0079] As another example, to implement the steering mechanism 340, a two-dimensional transceiver can be used to directly generate scanned images or 3D point clouds. In some embodiments, stitching or micro-displacement methods can be used to improve the resolution of the scanned image or the scanned field of view. For example, using a two-dimensional transceiver, signals generated in one direction (e.g., horizontal) and signals generated in another direction (e.g., vertical) can be integrated, interleaved, and / or matched to generate a higher or full-resolution image or 3D point cloud representing the scanned FOV.

[0080] Some embodiments of the redirection mechanism 340 include one or more optical redirection elements (e.g., mirrors or lenses) that redirect the returning optical signal along the receiving path (e.g., by rotation, vibration, or guidance) to direct the returning optical signal to the optical receiver and photodetector 330. The optical redirection elements that guide the optical signal along the transmission and receiving paths can be identical 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 transmission and receiving paths are different, although they may partially overlap (or in some cases, substantially overlap or completely overlap).

[0081] Still referencing Figure 3 The LiDAR system 300 further includes a control circuitry system 350. The control circuitry system 350 can be configured and / or programmed to control various parts of the LiDAR system 300 and / or perform signal processing. In a typical system, the control circuitry system 350 can be configured and / or programmed to perform one or more control operations, including, for example, controlling the light source 310 to obtain desired laser pulse timing, pulse repetition rate, and power; controlling the steering mechanism 340 (e.g., controlling speed, direction, and / or other parameters) to scan the field of view (FOV) and maintain pixel registration and / or alignment; controlling the optical receiver and photodetector 330 (e.g., controlling sensitivity, noise reduction, filtering, and / or other parameters) to optimize their operation; and monitoring the overall system health / functional safety status (e.g., monitoring the laser output power and / or the safety of the steering mechanism's operating status).

[0082] The control circuit system 350 can also be configured and / or programmed to perform signal processing on the raw data generated by the optical receiver and photodetector 330 to obtain distance and reflectivity information, and to perform data packaging and communication with the vehicle perception and planning system 220 (such as...). Figure 2 The communication (as shown) involves, for example, the control circuitry 350 determining the time taken from the transmission of a light pulse to the receipt of a corresponding return light pulse; determining when a return light pulse is not received for the transmitted light pulse; determining the direction of the transmitted / return light pulse (e.g., horizontal and / or vertical information); determining an estimated range in a specific direction; deriving the reflectivity of objects in the field of view (FOV); and / or determining any other types of data relevant to the LiDAR system 300.

[0083] The LiDAR system 300 can be incorporated into a vehicle that operates in a variety of environments, including hot or cold weather, rough road conditions that may cause severe vibrations, high or low humidity, dusty areas, etc. Therefore, in some embodiments, the optical and / or electronic components of the LiDAR system 300 (e.g., the optics, optical receivers, and photodetectors 330 in the transmitter 320, and the steering mechanism 340) are positioned and / or configured to maintain long-term mechanical and optical stability. For example, components in the LiDAR system 300 can be secured and sealed so that they can operate under all conditions the vehicle may encounter. As an example, a moisture-proof coating and / or an airtight seal can be applied to the optics, optical receivers, and photodetectors 330 of the transmitter 320, and the steering mechanism 340 (as well as other components susceptible to moisture). As another example, housings, enclosures, fairings, and / or windows can be used in the LiDAR system 300 to provide desired properties such as hardness, foreign object protection rating (IP), self-cleaning capability, chemical resistance, and impact resistance. In addition, the efficient and economical method for assembling the LiDAR system 300 can be used to meet the operational requirements of LiDAR while maintaining low cost.

[0084] Those skilled in the art should understand that Figure 3 The above description is for illustrative purposes only, and a LiDAR system may include other functional units, blocks, or segments, and may include variations or combinations of these functional units, blocks, or segments. For example, LiDAR system 300 may also include Figure 3 Other components not shown include power buses, power supplies, LED indicators, and switches. Additionally, other connections between components may exist, such as direct connections between the light source 310 and the optical receiver and photodetector 330, allowing the photodetector 330 to accurately measure the time from the emission of a light pulse by the light source 310 to the detection of the returning light pulse by the photodetector 330.

[0085] Figure 3The components shown are coupled together using communication paths 312, 314, 322, 332, 342, 352, 362, and 372. These communication paths represent communication paths (bidirectional or unidirectional) between various LiDAR system components, but do not necessarily have to be the physical components themselves. While communication paths can be implemented by one or more wires, buses, or optical fibers, they can also be wireless channels or open-air optical paths, thus eliminating the need for a physical communication medium. For example, in an exemplary 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 wires carrying electrical signals. Communication paths can also include more than one of the communication media of the types described above (e.g., they can include optical fibers and optical paths, or one or more optical fibers and one or more wires).

[0086] As mentioned above, some LiDAR systems use the time-of-flight (ToF) of an optical signal (e.g., a light pulse) to determine the distance to an object in the optical path. For example, reference... Figure 5A An exemplary LiDAR system 500 includes a laser source (e.g., a fiber laser), a steering mechanism (e.g., a system with one or more moving mirrors), and a photodetector (e.g., a photodetector with one or more optics). The LiDAR system 500 can be implemented using, for example, the LiDAR system 300 described above. The LiDAR system 500 emits light pulses 502 along an optical path 504 defined by the steering mechanism of the LiDAR system 500. In the depicted example, the light pulses 502 generated by the laser source are short pulses of laser light. Furthermore, the signal manipulation mechanism of the LiDAR system 500 is a pulse signal steering mechanism. However, it should be understood that LiDAR systems can operate by generating, emitting, and detecting non-pulsed light signals and using techniques other than time-of-flight to derive the distance to objects in the surrounding environment. For example, some LiDAR systems use frequency-modulated continuous wave (i.e., "FMCW"). It should also be understood that any techniques described herein for time-of-flight based systems using pulsed signals can also be applied to LiDAR systems that do not use one or both of these techniques.

[0087] Return to reference Figure 5A(For example, a time-of-flight LiDAR system using light pulses is illustrated.) When light pulse 502 reaches object 506, it is scattered or reflected to form a returning light pulse 508. The returning light pulse 508 can return to system 500 along optical path 510. The time from when the emitted light pulse 502 leaves LiDAR system 500 to when the returning light pulse 508 returns to LiDAR system 500 can be measured (e.g., via a processor or other electronic device within the LiDAR system, such as control circuitry system 350). This time-of-flight, combined with knowledge of the speed of light, can be used to determine the distance / range from LiDAR system 500 to the portion of object 506 where the light pulse 502 is scattered or reflected.

[0088] By guiding many light pulses, such as Figure 5B As depicted, the LiDAR system 500 scans the external environment (e.g., by guiding optical pulses 502, 522, 526, and 530 along optical paths 504, 524, 528, and 532, respectively). Figure 5C As depicted, the LiDAR system 500 receives returned light pulses 508, 542, and 548 (corresponding to emitted light pulses 502, 522, and 530, respectively). The returned light pulses 508, 542, and 548 are formed by scattering or reflecting the emitted light pulses by one of objects 506 and 514. The returned light pulses 508, 542, and 548 can return to the LiDAR system 500 along optical paths 510, 544, and 546, respectively. Based on the direction of the emitted light pulses (as determined by the LiDAR system 500) and the calculated distance from the LiDAR system 500 to the portion of the object scattering or reflecting the light pulses (e.g., portions of objects 506 and 514), the external environment within the detectable range (e.g., the field of view between paths 504 and 532, included) can be precisely mapped or plotted (e.g., by generating a 3D point cloud or image).

[0089] If no corresponding light pulse is received for a specific emitted light pulse, the LiDAR system 500 can determine that there is no object within its detectable range (e.g., the object is beyond the maximum scanning distance of the LiDAR system 500). For example, in Figure 5B In the middle, optical pulse 526 may not have a corresponding return optical pulse (e.g. Figure 5C As illustrated, the light pulse 526 may not generate a scattering event along its transmission path 528 within a predetermined detection range. The LiDAR system 500 or an external system (e.g., a cloud system or service) communicating with the LiDAR system 500 may interpret the lack of a returning light pulse as the absence of an object positioned along the light path 528 within the detectable range of the LiDAR system 500.

[0090] exist Figure 5B In this process, optical pulses 502, 522, 526, and 530 can be emitted in any order, serially, in parallel, or based on other timing relative to each other. Additionally, although... Figure 5B The emitted light pulse can be depicted as being guided in one dimension or one plane (e.g., the plane of paper), but the LiDAR system 500 can also guide the emitted light pulse along other dimensions or planes. For example, the LiDAR system 500 can also guide the emitted light pulse perpendicular to... Figure 5B The emitted light pulse is guided in the dimension or plane shown, thereby forming a 2D transmission of the light pulse. This 2D transmission of the light pulse can be point-by-point, line-by-line, one-time, or otherwise. That is, the LiDAR system 500 can be configured to perform point scans, line scans, single scans without scanning, or combinations thereof. Point clouds or images (e.g., a single horizontal line) from 1D transmission of the light pulse can generate 2D data (e.g., (1) data from the horizontal transmission direction and (2) the range or distance to the object). Similarly, point clouds or images from 2D transmission of the light pulse can generate 3D data (e.g., (1) data from the horizontal transmission direction, (2) data from the vertical transmission direction, and (3) the range or distance to the object). Typically, the transmission of the light pulse is performed by... n Generation of LiDAR systems using 3D transmission ( n +1) Dimensional data. This is because LiDAR systems can measure the depth of objects or the distance to objects, providing an additional dimension of data. Therefore, 2D scans performed by a LiDAR system can generate 3D point clouds for mapping the external environment of the LiDAR system.

[0091] Point cloud density refers to the number of measurements (data points) performed by a LiDAR system for each region. Point cloud density is related to the LiDAR scan resolution. Generally, at least for the region of interest (ROI), a higher point cloud density is desired, and therefore a higher resolution is required. The point density 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 a set of transmit-receive optics (or transceiver optics), a LiDAR system may need to generate pulses more frequently. In other words, the light source in a LiDAR system can have a higher pulse repetition rate (PRR). On the other hand, by generating and transmitting pulses more frequently, the maximum distance that a 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 signal may be detected in a different order than the corresponding transmitted signal, resulting in ambiguity if the system cannot correctly correlate the return signal with the transmitted signal.

[0092] To illustrate, consider an exemplary LiDAR system capable of emitting laser pulses with repetition rates between 500 kHz and 1 MHz. Based on the time it takes for the pulse to return to the LiDAR system, and to avoid confusion between return pulses from continuous pulses in a typical LiDAR design, the maximum detection range of the LiDAR system could be 300 meters for 500 kHz and 150 meters for 1 MHz. The point density of a LiDAR system with a repetition rate of 500 kHz is half that of a 1 MHz system. Therefore, this example shows that increasing the repetition rate from 500 kHz to 1 MHz (and thus increasing the point density) may reduce the system's detection range if the system cannot properly correlate out-of-order arriving return signals. Various techniques are used to mitigate the trade-off between a higher PRR and limited detection range. For example, multiple wavelengths can be used to detect objects within different ranges. Optical and / or signal processing techniques (e.g., pulse coding techniques) are also used to correlate the emitted and returned optical signals.

[0093] The various systems, apparatuses, and methods described herein can be implemented using digital circuit systems or using one or more computers that utilize 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 disks, internal hard disks and removable disks, magneto-optical disks, optical disks, etc.

[0094] The various systems, apparatuses, and methods described herein can be implemented using computers operating in a client-server relationship. Typically, in such a system, the client computer is located remotely from the server computer and interacts via a network. The client-server relationship can be defined and controlled by computer programs running on the respective client and server computers. Examples of client computers may include desktop computers, workstations, laptops, cellular smartphones, tablets, or other types of computing devices.

[0095] The various systems, apparatuses, and methods described herein can be implemented using a computer program product tangibly contained in an information carrier, such as a non-transitory machine-readable storage device, for execution by a programmable processor; and the methods, processes, and steps described herein (including...) Figures 1 to 12At least some of the steps in a computer program (or at least one step in a computer program) can be implemented using one or more computer programs 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 specific activity or produce a specific 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 standalone program or as a module, component, subroutine, or other unit suitable for use in a computing environment.

[0096] Figure 6 A simplified block diagram of an exemplary apparatus that can be used to implement the systems, devices, and methods described herein is illustrated. Apparatus 600 includes a processor 610 operatively coupled to persistent storage device 620 and main memory device 630. Processor 610 controls the overall operation of apparatus 600 by executing computer program instructions that define these 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 system 350 (… Figure 3 As shown), the vehicle perception and planning system 220 ( Figure 2 (as shown) and vehicle control system 280 ( Figure 2 (As shown). Therefore, Figures 1 to 12 At least some of the method steps can be defined by computer program instructions stored in main memory device 630 and / or persistent storage device 620, and controlled by processor 610 that executes the computer program instructions. For example, the computer program instructions can be implemented as computer executable code programmed by those skilled in the art to perform the actions described herein. Figures 1 to 12 The algorithm is defined by at least some of the method steps discussed in the foregoing figures. Accordingly, by executing computer program instructions, processor 610 executes the algorithm defined by the method steps in these foregoing figures. Device 600 also includes one or more network interfaces 680 for communicating with other devices via a network. Device 600 may also include one or more input / output devices 690 that enable a user to interact with device 600 (e.g., a display, keyboard, mouse, speaker, buttons, etc.).

[0097] Processor 610 may include both general-purpose microprocessors and special-purpose microprocessors, and may be the sole processor of device 600 or one of multiple processors. Processor 610 may include one or more central processing units (CPUs) and one or more graphics processing units (GPUs), the GPUs of which may, for example, operate independently of one or more CPUs and / or perform multitasking with one or more CPUs to accelerate processing, for example, for the various image processing applications described herein. Processor 610, persistent storage device 620, and / or main memory device 630 may include one or more application-specific integrated circuits (ASICs) and / or one or more field-programmable gate arrays (FPGAs), or be supplemented by one or more ASICs and / or one or more FPGAs, or incorporated into one or more ASICs and / or one or more FPGAs.

[0098] Persistent storage device 620 and main memory device 630 each include 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 disk storage devices, such as internal hard disks and removable disks, magneto-optical disk storage devices, optical disk storage devices, flash memory devices, semiconductor storage devices (such as erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM)), optical disc read-only memory (CD-ROM), digital universal optical disc read-only memory (DVD-ROM), or other non-volatile solid-state storage devices.

[0099] Input / output device 690 may include peripheral devices such as printers, scanners, displays, etc. For example, input / output device 690 may include display devices for displaying information to a user (such as cathode ray tube (CRT), plasma or liquid crystal display (LCD) monitors, keyboards) and pointing devices (such as mice or trackballs) that a user can use to provide input to device 600.

[0100] Any or all of the functions of the systems and apparatuses discussed herein may be executed by processor 610 and / or incorporated into an apparatus or system such as LiDAR system 300. Furthermore, LiDAR system 300 and / or apparatus 600 may utilize one or more neural networks or other deep learning techniques executed by processor 610 or other systems or apparatuses discussed herein.

[0101] Those skilled in the art will recognize that the implementation of an actual computer or computer system may have other structures and may include other components, and Figure 6 This is a brief representation of some of the components of this computer for illustrative purposes.

[0102] Figure 7 This is a block diagram illustrating a prior art LiDAR device 700 with a bandpass filter in the receiving optical path. Figure 7 As shown, the LiDAR device 700 includes a light source 702 (e.g., a laser source) that emits a laser 703 with a wide bandwidth. For example, if the light source 702 is a semiconductor laser, the center wavelength of the laser 703 may be 905 nm, and the bandwidth may be ±5 nm (i.e., a total of 10 nm). The LiDAR device 700 may also include an emitter lens (or lens group) 704 that transmits the laser 703 to downstream components or the field of view (FOV) of the LiDAR system. In either case, the transmitted laser 705 provided by the LiDAR device 700 has a wide bandwidth (e.g., the same as the wide bandwidth of the laser 703 emitted by the light source 702).

[0103] The transmitted laser 705 illuminates one or more target objects within the field of view (FOV) of the LiDAR device 700. The target objects reflect and / or scatter the transmitted laser 705 to form a portion of the reflected light. For example... Figure 7 As shown, the returned light typically includes not only the desired returned light signal 707 formed based on the transmitted laser 705, but also stray light 709. The light signal 707 typically has a wide bandwidth similar to that of the transmitted laser 705 because it is formed by the reflection / scattering of the transmitted laser 705. For example, if the center wavelength of the transmitted laser 705 is 905 nm and its bandwidth is ±5 nm, the light signal 707 in the returned light may also have a wide bandwidth of approximately 10 nm. The stray light 709 can include any type of noise and / or interfering light, such as sunlight, streetlights, lasers from other lidar devices, moonlight, headlights, taillights, etc. Therefore, the stray light 709 can have a very wide bandwidth.

[0104] In the LiDAR device 700, a bandpass filter 706 is used in the receiving optical path to reduce the impact of stray light 709. The bandpass filter 706 filters out the portion of the stray light 709 whose wavelength is outside the passband of the filter 706. To retain as much signal power as possible of the desired optical signal 707 (i.e., the desired return light) formed based on the transmitted laser 705, the filter 706 is typically configured to have a wide passband corresponding to the bandwidth of the transmitted laser 705, allowing all or most of the optical signal 707 to pass through the filter 706. For example, the bandpass filter 706 can filter out any light with a center wavelength of 905 nm and a passband of 10 nm.

[0105] However, this bandpass filter 706 cannot filter out the portion of stray light 709 whose wavelength falls within the same wavelength range as the transmitted laser 705, because this portion of stray light 709 falls within the passband of the filter 706. Therefore, as Figure 7 As shown, the receiving lens (or lens group) 710 of device 700 provides filtered return light including signal 713 and stray light 711. All or most of the desired optical signal 707, based on the target object, passes through filter 706 and is received by receiving lens 710. Receiver lens 710 redirects the received signal to form optical signal 713, which has the same wide bandwidth as the transmitted laser 705. For stray light 709, the portion falling outside the passband of filter 706 is filtered out. The remaining portion of stray light 709 with wavelengths within the passband of filter 706 passes through filter 706 and is received by receiving lens 710. Receiver lens 710 redirects the remaining stray light to form stray light 711. The wide wavelength range of stray light 711 may be the same as or substantially the same as the wide wavelength range of transmitted laser 705 (and optical signal 707). Therefore, a considerable amount of stray light remains after filter 706. The remaining stray light 711 is noise, which may cause false detection by the photodetector 714, may interfere with the required optical signal 713, and / or may cause errors in downstream processing (e.g., misidentification of objects).

[0106] One way to reduce such residual stray light 711 is to reduce the bandwidth of filter 706 to, for example, 2 nm or even smaller, and allow only light signals with a essentially center wavelength to pass through. The problem with this solution is that a significant amount of signal power in the desired signal 707 may also be lost because the bandwidth of the filtered signal is narrower than that of the bandpass filter 706. For example, if the passband of the bandpass filter is only 2 nm, the bandwidth of the filtered signal may be only 1 nm or less, depending on the filter characteristics. Therefore, a significant amount of signal power may be lost due to filtering. When detector 714 receives the filtered signal, it may or may not be detected due to the lower signal power, thus reducing the detectability of detector 714. To compensate for the signal power loss, the power of laser source 702 must be increased. However, this means that the power of transmitted laser 705 will also increase. The power of transmitted laser cannot be increased indefinitely because laser emitting devices have eye safety requirements. Excessively increasing the power of transmitted laser poses an eye safety risk. Therefore, simply increasing the laser power to improve the signal power of the narrow passband signal passing through the filter 706 in the device 700 may be infeasible or impractical.

[0107] Figures 8A to 8BThis is an example of a novel LiDAR system 800 for reducing stray light using synchronous filtering, according to various embodiments. The LiDAR system 800 includes a light source 802, transmitter optics 804, receiver optics 810, and detector 814. These components of the system 800 may be the same as or substantially the same as the optics in the light source 310, transmitter 320, and optical receiver and photodetector 330, respectively. For example, transmitter optics 804 may include one or more of the following: collimating lens, filter, beam shifting device, fiber array, movable or fixed mirror, lens group, prism, or combinations thereof. Receiver optics 810 may include one or more of the following: collecting lens, filter, fiber array, beam homogenizer, movable or fixed mirror, lens group, prism, or combinations thereof.

[0108] like Figure 8A As shown, light source 802 emits laser light 803 having a first wavelength range. The first wavelength range can be a wide wavelength range such as 10 nm (e.g., a center wavelength in the range of 700 nm to 20,000 nm with a bandwidth of + / - 5 nm). An example of a center wavelength is 905 nm. Emitter optics 804 are positioned in the transmission optical path and receive the laser light 803. The transmission optical path is the optical path from light source 802 to the field of view (FOV) of the LiDAR system 800 used to emit laser light to illuminate one or more target objects within the field of view. Therefore, emitter optics 804 is configured to provide transmitted light 805 based on the laser light 803 having the first wavelength range. However, due to the synchronization filter structure 806, the transmitted light 805 has a second wavelength range. Typically, the second wavelength range is narrower than the first wavelength range. For example, the center wavelength of the second wavelength range is in the range of 700 nm to 20,000 nm (e.g., at 905 nm), and the bandwidth is + / - 2 nm. Therefore, using the synchronization filter structure 806, if the first wavelength range is centered at 905 nm with a bandwidth of 10 nm, then the second wavelength range can also be centered at 905 nm, but with a narrower bandwidth of 4 nm. The synchronization filter structure 806 will be described in more detail below.

[0109] Continue to refer to Figure 8AOn the receiver side, the receiver may include receiver optics 810 and detector 814, which may be the same as or similar to those in the optical receiver and photodetector 330 of the LiDAR system 300 described above. Receiver optics 810 and detector 814 are arranged in the receiving optical path to receive returned light. The returned light may include an optical signal 807 formed based on transmitted light 805 and stray light 809. The optical signal 807 is formed based on transmitted light 805, and therefore includes light scattered and / or reflected from one or more objects in the FOV. Therefore, the wavelengths of these optical signals 807 are the same as those of the transmitted light 805. As described above, the transmitted light 805 has a second wavelength range with a bandwidth narrower than the first wavelength range (e.g., a 4 nm bandwidth compared to a 10 nm bandwidth). Therefore, the optical signal 807 also has a narrower bandwidth (e.g., a bandwidth of + / - 2 nm with a center wavelength in the range of 700 nm to 20000 nm (e.g., at 905 nm)).

[0110] Stray light 809 can be noise and / or interfering light, such as sunlight, moonlight, streetlights, LiDAR transmitted light from other vehicles, headlights and taillights of vehicles, and reflected / scattered light from internal components of this LiDAR system. Stray light 809 typically has a wide bandwidth and therefore requires filtering. Figure 8AIn the configuration shown, at least most of the returned light (including the desired optical signal 807 and unwanted stray light 809) passes through the synchronization filter structure 806. The filtered optical signal is received by the receiver optics 810 and transmitted to the photodetector 814. The filtered optical signal received by the photodetector 814 may include a filtered optical signal 813 and filtered stray light 811. Optical signal 813 is the filtered signal of optical signal 807. Because optical signal 807 already has a narrow bandwidth (e.g., a second wavelength range), there is little or no loss of signal power when optical signal 807 passes through the synchronization filter structure 806. In other words, the synchronization filter structure 806 transmits most of the desired optical signal 807, formed based on transmitted light 805, to the detector 814. Therefore, optical signal 813 can have good signal strength and a narrow bandwidth, thereby improving the detectability of the detector 814. As described above, typically when the transmitted light 805 is filtered to reduce its bandwidth, the signal power also decreases. Therefore, to compensate for the signal power loss, the light source power needs to be increased. This can potentially cause eye safety issues. In this example, by using the synchronization filter structure 806, the bandwidth of the transmitted light 805 is reduced (e.g., from 10 nm to 4 nm). Therefore, even with the increased light source power, eye safety requirements can still be met because the power increase occurs within the LiDAR system prior to the synchronization filter structure 806. The transmitted light 805 is filtered light with a narrow bandwidth, so the power increase does not cause eye safety issues as seen in the prior art LiDAR system 700 described above.

[0111] For stray light 809, the synchronization filter structure 806 can also filter out at least a portion of the stray light whose wavelength is outside the second wavelength range. For example, if the transmitted light 805 has a second wavelength range (e.g., a center wavelength in the range of 700 nm to 20000 nm (e.g., at 905 nm), and a bandwidth of + / - 2 nm), then the synchronization filter structure 806 can be configured to remove most of the stray light 809 that falls outside this second wavelength range. For example, if the bandwidth of stray light 809 is 10 nm, then after passing through the synchronization filter structure 806, its bandwidth is reduced to 4 nm.

[0112] Still referencing Figure 8A In some embodiments, the synchronization filter structure includes one or more bandpass filters having substantially the same passband; and the synchronization filter structure 806 is coupled to both the transmitter and the receiver. For example, as Figure 8AAs shown, in this example, the synchronization filter structure 806 includes a first bandpass filter 806A and a second bandpass filter 806B. The first bandpass filter 806A is disposed in the transmission optical path, and the second bandpass filter is disposed in the receiving optical path. In some examples, the first bandpass filter 806A and the second bandpass filter 806B have substantially the same passband. For example, they can both allow light with a center wavelength of 905 nm and a bandwidth of + / - 2 nm to pass through, but will filter out any optical signals falling outside this wavelength range.

[0113] Figure 8A An example of a synchronization filter structure 806 is shown, which uses two separate bandpass filters 806A and 806B, one for the transmission optical path and one for the receiving optical path. By using two bandpass filters, the synchronization filter structure 806 provides flexibility in the placement of the two bandpass filters, the size of each filter, the type of filter, and other aspects. For example, although Figure 8A The illustrated filter 806A is positioned downstream of the transmitter optics 804 in the transmission optical path, but it can also be positioned elsewhere in the transmission optical path, as described below. Similarly, filter 806B is not necessarily positioned upstream of the receiver optics 810; it can also be positioned elsewhere in the receiver optical path. The sizes of filters 806A and 806B can be the same or different, depending on factors such as the optical aperture requirements of the transmission and receiver optical paths, the type of filter used, etc. In one example, the LiDAR system 800 may be large; the transmission and receiver optical paths may be far apart, and / or the optical components in the transmission and receiver optical paths may be arranged at specific angles / or orientations (e.g., not as...). Figure 8A (as in parallel). In these configurations, using two bandpass filters provides flexibility to incorporate them independently into their respective desired locations in the transmission and receiving optical paths.

[0114] Figure 8B Another embodiment is illustrated, in which the synchronization filter structure 806 includes a single bandpass filter shared between the transmission optical path and the receiving optical path. Figure 8B and Figure 8A The similarities and differences lie in that the synchronization filter structure 806 is formed by a single bandpass filter. This single bandpass filter is placed on both the transmission and receiving optical paths. The advantage of using a single bandpass filter is that there is no passband mismatch problem compared to using two filters. If two bandpass filters are used (such as...),... Figure 8AAs shown), ideally, the passband and other optical characteristics of the two bandpass filters should be perfectly matched. Sometimes, mismatches may occur between the two filters, but these should be minimized or tolerated. Using a single passband filter eliminates the need to match the characteristics of the two bandpass filters. In some examples, if the LiDAR system 800 is small and compact, or in a coaxial configuration where the transmission and receiving optical paths are close to or at least partially overlap, a single bandpass filter in structure 806 can be used.

[0115] Figures 9A to 9D These are various examples of transmitters for LiDAR systems using synchronization filtering to reduce stray light, according to various embodiments. As described above, if the synchronization filter structure 806 includes two separate bandpass filters, one can be placed at a different location in the transmission optical path, and the other can be placed at a different location in the receiving optical path. Figure 9A An example is illustrated in which the first bandpass filter 806A1 of the synchronous filter structure is positioned downstream of the light source 802, between the light source 802 and the transmitter optics 804. Figure 9B Another example is illustrated, in which the first bandpass filter 806A2 of the synchronization filter structure is positioned downstream of the light source 802, between any two transmitter optics 804A and 804B. The transmitter optics 804 may include, for example, lenses, lens groups, mirrors, prisms, optical fibers, etc., for redirecting light 803 from the light source 802. Therefore, the first bandpass filter 806A2 can be placed anywhere within the transmitter optics 804 between two optical components (e.g., between the optical fiber and the collimating lens).

[0116] Figure 9C Another example is illustrated, in which the first bandpass filter 806A3 of the synchronization filter structure is positioned downstream of the light source 802, between one or more transmitter optics 804 and the steering mechanism 840. Steering Mechanism 840 receives transmitted light 805 from the first bandpass filter 806A3 and scans the transmitted light 805 into the field of view (FOV) along one or more directions. The steering mechanism 840 may be substantially the same as or similar to the steering mechanism 340 described above. For example, steering mechanism 840 may include one or more faceted mirrors, one or more galvanometers, one or more folding mirrors, lenses, prisms, etc., for scanning the transmitted light 805 in two dimensions (e.g., horizontal and vertical dimensions).

[0117] Figure 9DAnother example is illustrated, in which the first bandpass filter 806A4 of the synchronization filter structure is positioned downstream of the light source 802 and downstream of the steering mechanism 840 in the transmission optical path. In one example, the first bandpass filter 806A4 may have a sufficiently large optical aperture to cover the entire scanning area as the steering mechanism 840 moves. In another example, the first bandpass filter 806A4 and the steering mechanism 840 may be mounted on the same movable platform, such that the first bandpass filter 806A4 moves together with the steering mechanism 840.

[0118] Figures 10A to 10D These are examples of receivers for LiDAR systems using synchronization filtering to reduce stray light, according to various embodiments. Similar to filters positioned in the transmission optical path, filters positioned in the receiving optical path can also be located in different locations. Figure 10A An example is illustrated where a second bandpass filter 806B1 is positioned upstream of detector 814 in the receiving optical path and upstream of steering mechanism 840 in the receiving optical path. In this example, steering mechanism 840 is substantially the same as or similar to steering mechanism 340 in LiDAR system 300. Steering mechanism 840 receives filtered return light and directs the filtered return light to one or more receiver optics 810. As described above, the return light includes a desired optical signal 807 and unwanted stray light 809. Optical signal 807 has a second wavelength range, which is the same as the wavelength range of transmitted light 805. Therefore, optical signal 807, or most of it, can pass through filter 806B1, which has a narrow passband corresponding to the second wavelength range. Stray light 809 can be filtered out after passing through filter 806B1, except for a portion within the narrow passband corresponding to the second wavelength range. In one example, the second bandpass filter 806B1 may have a sufficiently large optical aperture to cover the entire scanning area as the steering mechanism 840 moves, allowing the second bandpass filter to filter return light from all scanning angles. In another example, the second bandpass filter 806B1 and the steering mechanism 840 may be mounted on the same movable platform, allowing the second bandpass filter 806B1 to move together with the steering mechanism 840.

[0119] Figure 10BAn example is illustrated where a second bandpass filter 806B2 is positioned upstream of detector 814 in the receiving optical path, between steering mechanism 840 and receiver optics 810. In this example, steering mechanism 840 directs unfiltered return light to the second bandpass filter 806B2. The second bandpass filter 806B2 filters the return light, which includes the desired optical signal 807 and unwanted stray light 809, and directs the filtered return light to receiver optics 810, which in turn transmits the filtered return light to detector 814.

[0120] Figure 10C Another example is illustrated, in which the second bandpass filter 806B3 of the synchronization filter structure is positioned upstream of the detector 814 in the receiving optical path, between any two receiver optics 810A and 810B. The receiver optics 810 may include, for example, lenses, lens groups, mirrors, prisms, optical fibers, etc., for redirecting returned light from the redirection mechanism to the photodetector 814. Therefore, the second bandpass filter 810B3 can be placed anywhere within the receiver optics 810 between two optical components (e.g., between the collecting lens and the folding mirror).

[0121] Figure 10D Another example is illustrated, in which the second bandpass filter 806B4 of the synchronization filter structure is positioned upstream of detector 814 in the receiving optical path, between receiver optics 810 and detector 814. In this example, the returning light passes through the steering mechanism ( Figure 10D (Not shown in the image) and the receiver optics 810 are filtered, but before reaching the detector 814. Therefore, the filter 806B4 can be placed close to the detector 814, and in some examples, it can be integrated with the detector 814.

[0122] It should be understood that Figures 9A to 9D and Figures 10A to 10D Examples of the positions of the first and second bandpass filters are provided. The filters can also be placed in other locations, not limited to the examples shown above.

[0123] Figures 11A to 11C These are various examples of LiDAR systems for reducing stray light using synchronization filtering with a single bandpass filter, according to various embodiments. As described above, the synchronization filter structure 806 may include a single bandpass filter (instead of two) for both the transmission and receiving optical paths. Figure 11AAn example is illustrated where a single bandpass filter 8061 is positioned downstream of a light source 802 in the transmission path and upstream of a detector 814 in the receiving path, between one or more transmitter optics 804 and a steering mechanism 840, and between the steering mechanism 840 and one or more receiver optics 810. Thus, the steering mechanism 840 (e.g., substantially the same as or similar to steering mechanism 340) scans the filtered transmission light 805 to have a second wavelength range (e.g., a narrow bandwidth of 4 nm). The steering mechanism 840 receives the desired return light signal 807 and stray light 809 and forwards them to the same filter 8061 for filtering. In this way, the receiver optics 810 can receive the filtered return light, which includes a signal 813 having a second wavelength range (e.g., substantially the same as the transmission light 805 and the return light signal 807) and filtered stray light 811. The noise and interference of the filtered stray light 811 are significantly reduced because the return light outside the second wavelength range has been filtered out. In one example, the bandpass filter 8061 may have a sufficiently large optical aperture to cover the entire scanning area as the steering mechanism 840 moves, allowing the bandpass filter to filter return light from all scanning angles. In another example, the bandpass filter 8061 and the steering mechanism 840 may be mounted on the same moving platform, allowing the bandpass filter 8061 to move together with the steering mechanism 840.

[0124] Figure 11B An example is illustrated where a single bandpass filter 8061 is positioned downstream of the light source 802 in the transmission optical path and upstream of the detector 814 in the receiving optical path, and upstream of the steering mechanism 840 in the transmission optical path. For example, in Figure 11B In the example shown, a single bandpass filter 8062 can be placed between the light source 802 and the transmitter optics 804, and between the receiver optics 810 and the photodetector 814. Therefore, light 803 from the light source 802 is filtered to produce transmitted light 805 with a second wavelength range (e.g., a narrow bandwidth of 4 nm). Simultaneously, the returned light (including the desired returned light signal 807 and stray light 809) is filtered before reaching the photodetector 814, thereby eliminating noise and interference as much as possible. The photodetector 814 still receives the filtered light signal 813 with the second wavelength range and the filtered stray light 811 (which is a small portion of noise or interference falling within the passband of filter 8062).

[0125] Figure 11CAn example is illustrated where a single bandpass filter 8063 is positioned downstream of the light source 802 in the transmission optical path and upstream of the detector 814 in the receiving optical path, and upstream of the steering mechanism 840 in the receiving optical path. In this example, the single bandpass filter 8063 is positioned downstream of the steering mechanism 840 in the transmission optical path but upstream of the steering mechanism 840 in the receiving optical path. Therefore, light 803 from the light source 802 and scanned by the steering mechanism 840 is filtered to produce transmitted light 805 with a second wavelength range (e.g., a narrow bandwidth of 4 nm). Simultaneously, the return light (including the desired return light signal 807 and stray light 809) is filtered before reaching the steering mechanism 840, thereby eliminating noise and interference as much as possible. The photodetector 814 still receives the filtered light signal 813 with the second wavelength range and the filtered stray light 811 (which is a small portion of noise or interference falling within the passband of filter 8062). In this example, the bandpass filter 8063 can have a sufficiently large optical aperture to cover the entire scanning area as the steering mechanism 840 moves, allowing the bandpass filter to filter return light from all scanning angles. In another example, the bandpass filter 8063 and the steering mechanism 840 can be mounted on the same moving platform, allowing the bandpass filter 8063 to move together with the steering mechanism 840.

[0126] Figures 11A to 11C For example, the location of a single bandpass filter is not limited. As long as the single bandpass filter is positioned to provide narrowband transmitted light for scanning the field of view (FOV) and narrowband returned light for detection, it can be placed anywhere in the LiDAR system. In this description, "upstream" and "downstream" refer to the relative positions between optical components in the optical path. For example, for any given optical path, if light flows from component A to component B, component A is located upstream of component B, and component B is located downstream of component A.

[0127] In the above example, the steering mechanism (e.g., 840) may include one or more of the following: a rotatable polygonal mirror, an oscillating mirror, an oscillating prism, or a combination thereof. The steering mechanism can be controlled to perform a two-dimensional scan (e.g., horizontal and vertical directions). The controller may be, for example, Figure 3 The control circuit 350 shown and described above.

[0128] In some embodiments, the controller may also be configured to set the power level of the laser emitted by the light source to compensate for the power loss of the transmitted light caused by the synchronization filter structure. As described above, the synchronization filter structure can reduce the bandwidth of the transmitted light (e.g., from a bandwidth of 10 nm to a bandwidth of 4 nm). During filtering, some signal power may be lost. Therefore, the power of the transmitted light 805 may be lower than that of the light 803 emitted by the light source 802 (e.g., ...). Figure 8A and Figure 9A (As shown). Because the power of the transmitted light 805 may be relatively low, the detection range of the LiDAR system may be affected. For example, the detection range may decrease from 250 m to only 100 m. To compensate for this signal power loss, the controller can increase the power level of the laser emitted by the light source by a level that is set higher than the power level of the laser emitted by the light source without the synchronous filter structure. In one example, the amount of power level increased by the controller is inversely proportional to the power loss caused by the synchronous filter structure. Therefore, the greater the signal loss caused by the synchronous filter structure, the greater the increase in power level the controller needs to set. However, the controller can still set the power level of the transmitted light, after compensating for the power loss, to be within the laser power threshold range safe for human eyes. In other words, the controller cannot increase the power level of the laser 803 emitted by the light source 802 too much, lest the transmitted light 805 (the light filtered by the synchronous filter structure 806) become unsafe according to laser eye safety standards. In some examples, the laser eye safety standards are set based on the scanning speed of the LiDA system and the exposure time and power of the transmitted light relative to the biological eye.

[0129] Figure 12 This is a flowchart of an exemplary method 1200 for reducing stray light using a synchronous filtering structure according to various embodiments. In block 1202, a light source (e.g., 802) emits laser light having a first wavelength range. In block 1204, a transmitter provides transmitted light (e.g., 805) based on the laser light having the first wavelength range, the transmitter including one or more transmitter optics (e.g., 804) arranged in the transmitted light path. In block 1206, a receiver receives returned light including stray light (e.g., 809) and an optical signal formed based on the transmitted light (e.g., 807), the receiver including a detector (e.g., 814) and one or more receiver optics (e.g., 810) arranged in the receiving light path.

[0130] In some examples, blocks 1206 through 1210 are implemented by a synchronization filter structure (e.g., 806) comprising one or more bandpass filters having substantially the same passband. The synchronization filter structure is coupled to both the transmitter and the receiver. In block 1206, the synchronization filter structure reduces the bandwidth of the laser from a first wavelength range to a second wavelength range, such that the transmitted light has a second wavelength range. In block 1208, the synchronization filter structure filters out at least a portion of stray light with wavelengths outside the second wavelength range. In block 1210, the synchronization filter structure delivers the majority of the optical signal formed based on the transmitted light to the detector.

[0131] The foregoing description should be understood as illustrative and exemplary in all respects, not restrictive, and the scope of the invention disclosed herein is not determined by the description, but by the claims as interpreted in the fullest extent permitted by patent law. It should be understood that the embodiments shown and described herein are merely illustrative of the principles of the invention, and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention. Various other combinations of features can be implemented by those skilled in the art without departing from the scope and spirit of the invention.

Claims

1. A LiDAR (Light Detection and Ranging) system for reducing stray light using synchronous filtering, the system comprising: A light source that emits laser light having a first wavelength range; A transmitter comprising one or more transmitter optics disposed in a transmitted light path, the transmitter being configured to provide transmitted light based on the laser having the first wavelength range; A receiver, comprising a detector and one or more receiver optics disposed in a receiving optical path, the receiver being configured to receive return light including stray light and an optical signal formed based on the transmitted light; and A synchronization filter structure comprising one or more bandpass filters having substantially the same passband, wherein the synchronization filter structure is coupled to both the transmitter and the receiver, and the synchronization filter structure is configured to perform: The bandwidth of the laser is reduced from the first wavelength range to the second wavelength range, so that the transmitted light has the second wavelength range. Filtering out at least a portion of the stray light whose wavelength is outside the second wavelength range, and Most of the optical signal formed based on the transmitted light is transmitted to the detector.

2. The system of claim 1, wherein the center wavelength of the first wavelength range is in the range of 700 nm to 20000 nm, and the bandwidth is at least + / - 5 nm.

3. The system according to any one of claims 1 to 2, wherein the center wavelength of the second wavelength range is in the range of 700 nm to 20000 nm and the bandwidth is + / - 2 nm.

4. The system according to any one of claims 1 to 2, wherein the one or more bandpass filters of the synchronization filter structure comprise: A first bandpass filter is disposed in the transmitted light path; and A second bandpass filter is disposed in the received optical path, wherein the first bandpass filter and the second bandpass filter have substantially the same passband.

5. The system of claim 4, wherein the first bandpass filter is disposed downstream of the light source in the transmitted light path, at the following location: Between the light source and the one or more transmitter optics; Between any two transmitter optics; Between the one or more transmitter optics and the steering mechanism, wherein the steering mechanism receives the transmitted light from the first bandpass filter and scans the transmitted light into the field of view (FOV) along one or more directions; or Downstream of the steering mechanism in the transmitted light path.

6. The system of claim 4, wherein the second bandpass filter is disposed upstream of the detector in the receiving optical path, at the following location: Upstream of the deflection mechanism in the receiving optical path, wherein the deflection mechanism receives filtered return light and directs the filtered return light to the one or more receiver optics; Between the steering mechanism and the one or more receiver optics; Between any two receiver optics; or Between the one or more receiver optics and the detector.

7. The system according to claims 1 to 2, wherein the one or more bandpass filters of the synchronous filter structure include a single bandpass filter shared between the transmitted light path and the received light path.

8. The system of claim 7, wherein the single bandpass filter is disposed downstream of the light source in the transmitted light path and upstream of the detector in the received light path, at the following location: Between the one or more transmitter optics and the steering mechanism, and between the steering mechanism and the one or more receiver optics; Upstream of the steering mechanism in the transmitted light path; or Upstream of the steering mechanism in the receiving optical path.

9. The system according to any one of claims 1 to 2, wherein the transmitter optics comprises one or more of the following: a collimating lens, a filter, a beam shifting device, a fiber array, a movable or fixed mirror, a lens group, a prism, or a combination thereof.

10. The system according to any one of claims 1 to 2, wherein the receiver optics comprises one or more of the following: a collecting lens, a filter, an optical fiber array, a beam homogenizer, a movable or fixed mirror, a lens group, a prism, or a combination thereof.

11. The system according to any one of claims 1 to 2, the system further comprising a steering mechanism, the steering mechanism comprising one or more of the following: a rotatable multifaceted mirror, an oscillating mirror, an oscillating prism, or a combination thereof.

12. The system according to any one of claims 1 to 2, further comprising a control circuit configured to: The power level of the laser emitted by the light source is set to compensate for the power loss of the transmitted light caused by the synchronous filter structure.

13. The system of claim 12, wherein the power level of the laser emitted by the light source is set to an increased level compared to the power level of the laser emitted by the light source without using a synchronization filter structure.

14. The system of claim 13, wherein the increase in power level is inversely proportional to the power loss caused by the synchronous filter structure.

15. The system of claim 12, wherein the power level of the transmitted light, after compensation for the power loss, is within the range of an eye-safe laser power threshold.

16. A means of transport comprising a LiDAR system for reducing stray light using synchronous filtering, the system comprising: A light source that emits laser light having a first wavelength range; A transmitter comprising one or more transmitter optics disposed in a transmitted light path, the transmitter being configured to provide transmitted light based on the laser having the first wavelength range; A receiver, comprising a detector and one or more receiver optics disposed in a receiving optical path, the receiver being configured to receive return light including stray light and an optical signal formed based on the transmitted light; and A synchronization filter structure comprising one or more bandpass filters having substantially the same passband, wherein the synchronization filter structure is coupled to both the transmitter and the receiver, and the synchronization filter structure is configured to perform: The bandwidth of the laser is reduced from the first wavelength range to the second wavelength range, so that the transmitted light has the second wavelength range. Filtering out at least a portion of the stray light whose wavelength is outside the second wavelength range, and Most of the optical signal formed based on the transmitted light is transmitted to the detector.

17. A method for reducing stray light using synchronous filtering, the method comprising: A laser with a first wavelength range is emitted by a light source; The transmitter provides transmitted light based on the laser having the first wavelength range, the transmitter including one or more transmitter optics disposed in the transmitted light path; The receiver receives stray light and a return light, including optical signals formed based on the transmitted light, and the receiver includes a detector and one or more receiver optics disposed in the optical path. as well as The following operations are performed by a synchronization filter structure comprising one or more bandpass filters having substantially the same passband, wherein the synchronization filter structure is coupled to both the transmitter and the receiver: The bandwidth of the laser is reduced from the first wavelength range to the second wavelength range, so that the transmitted light has the second wavelength range. Filtering out at least a portion of the stray light whose wavelength is outside the second wavelength range, and Most of the optical signal formed based on the transmitted light is transmitted to the detector.

18. The method of claim 17, wherein the center wavelength of the first wavelength range is in the range of 700 nm to 20000 nm, and the bandwidth is at least + / - 5 nm.

19. The method according to any one of claims 17 to 18, wherein the center wavelength of the second wavelength range is in the range of 700 nm to 20000 nm and the bandwidth is + / - 2 nm.

20. The method according to any one of claims 17 to 18, the method further comprising: The power level of the laser emitted by the light source is set to compensate for the power loss of the transmitted light caused by the synchronous filter structure.

21. The method of claim 20, wherein the power level of the laser emitted by the light source is set to an increased level compared to the power level of the laser emitted by the light source without using a synchronization filter structure.

22. The method of claim 21, wherein the increase in power level is inversely proportional to the power loss caused by the synchronous filter structure.

23. The method of claim 20, wherein the power level of the transmitted light after the power loss has been compensated is within the human eye-safe laser power threshold range.

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