WO2023185757A1 - 激光雷达系统及其校准方法 - Google Patents

激光雷达系统及其校准方法 Download PDF

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Publication number
WO2023185757A1
WO2023185757A1 PCT/CN2023/084144 CN2023084144W WO2023185757A1 WO 2023185757 A1 WO2023185757 A1 WO 2023185757A1 CN 2023084144 W CN2023084144 W CN 2023084144W WO 2023185757 A1 WO2023185757 A1 WO 2023185757A1
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WIPO (PCT)
Prior art keywords
lidar system
light
calibration
stray light
period
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PCT/CN2023/084144
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English (en)
French (fr)
Inventor
解华彪
刘佳尧
夏冰冰
石拓
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北京一径科技有限公司
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Publication of WO2023185757A1 publication Critical patent/WO2023185757A1/zh

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/88—Lidar systems specially adapted for specific applications
    • G01S17/93—Lidar systems specially adapted for specific applications for anti-collision purposes
    • G01S17/931—Lidar systems specially adapted for specific applications for anti-collision purposes of land vehicles
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/497—Means for monitoring or calibrating

Definitions

  • the present disclosure relates to lidar systems, and more particularly to methods for calibrating lidar systems, lidar systems, vehicles, electronic devices, media, and program products that perform the methods.
  • LiDAR systems also known as laser detection and ranging (LiDAR or LADAR) systems, measure the position, speed and other information of a target object by emitting a laser beam to the target object and receiving the beam reflected from the target object.
  • LiDAR laser detection and ranging
  • LADAR laser detection and ranging
  • Ambient light such as lights or beams from other lidar systems.
  • the lidar system When the lidar system is used in high-speed, long-distance (e.g., hundreds of meters) scenarios (e.g., equipped with vehicles with advanced driver assistance systems (ADAS) or autonomous driving functions), the reflection from the target object to the optical receiver The light itself may have very little power.
  • ADAS advanced driver assistance systems
  • SNR signal-to-noise ratio
  • the present disclosure provides a method for calibrating a lidar system, as well as lidar systems, vehicles, electronic devices, and corresponding media and program products that perform the method, It can improve the measurement of stray light during the calibration process and achieve better calibration results.
  • LiDAR systems include fiber lasers.
  • the method includes instructing, by one or more processors, the fiber laser to emit one or more calibration beams during a light emission region of the calibration period.
  • the method also includes instructing, by the one or more processors, the lidar system to detect stray light signals during a light detection zone following the light emission zone of the calibration period. Stray light signals can include ambient light noise or pulsed light from other lidar systems.
  • the method also includes adjusting, by the one or more processors, a configuration of the lidar system during subsequent operating periods based on the detected stray light signals.
  • the light detection zone and the light emission zone are separated by a silent zone.
  • the length of the quiet zone is related to the time it takes for the emitted calibration beam or beams to reflect back from the outside to the lidar system.
  • the method also includes instructing, by the one or more processors, the lidar system not to detect stray light signals during the quiet zone of the calibration period.
  • the calibration period is set within a retrace period of the lidar system during which the scanner of the lidar system returns from the scanning end point to the scanning starting point.
  • the lidar system is a non-coaxial optical transceiver system.
  • the calibration period is arranged within at least part of a scanning period of the lidar system during which the scanner of the lidar system travels from a scanning start point to a scanning end point.
  • instructing the lidar system to detect stray light signals includes dividing at least a portion of the plurality of receiving units of the lidar system into a plurality of receiving unit subgroups, and a light detection area during the calibration period During this period, the lidar system uses multiple receiving unit subgroups in sequence to detect stray light signals.
  • instructing the lidar system to detect the stray light signal includes determining amplified spontaneous emission (ASE) from emitting the one or more calibration beams to the fiber laser based on the emitted one or more calibration beams.
  • ASE amplified spontaneous emission
  • the pump source of the fiber laser is turned on.
  • adjusting the configuration of the lidar system during subsequent operating periods based on the detected stray light signal includes: adjusting the laser based on determining that the stray light signal includes ambient light noise and determining the interfered receiving unit.
  • the radar system is The configuration during the subsequent working period includes at least one of the following: adjusting the transmit power of the laser corresponding to the echo signal of the scanning beam reflected from the interfered receiving unit, adjusting the sensitivity of the interfered receiving unit and its associated receiving circuit, and adjusting the affected receiving unit. The gain of the interfering receiving unit and its associated receiving circuitry.
  • adjusting the configuration of the lidar system during subsequent operating periods based on the detected stray light signal includes determining based on the detected stray light signal that the stray light signal includes pulses from other lidar systems. light and the receiving unit determined to be interfered with, and based on the determination that stray light signals include pulsed light from other lidar systems and the receiving unit determined to be interfered with, adjust the configuration of the lidar system during the subsequent operating period, including: enabling the lidar system Operate at crosstalk-resistant operating parameters during subsequent operating periods.
  • the lidar system includes a light source, scanner, light receiver and controller.
  • the light source is configured to emit light.
  • Light sources include fiber lasers.
  • the scanner is configured to direct the light to scan the target object.
  • the light receiver is configured to detect light reflected by the target object.
  • the controller is communicatively coupled with the light source, scanner, and light receiver. The controller is configured to perform the method for calibrating the lidar system as previously described.
  • the vehicle includes a lidar system and vehicle controller.
  • LiDAR systems include fiber lasers.
  • the vehicle controller is communicatively coupled with the lidar system.
  • the vehicle controller is configured to perform the method for calibrating the lidar system as previously described.
  • Electronic devices include processors and memories.
  • the memory is communicatively coupled to the processor and stores computer readable instructions.
  • the computer-readable instructions when executed by the processor, cause the electronic device to perform the method for calibrating the lidar system as described above.
  • Another aspect of the present disclosure relates to a computer-readable storage medium storing computer-readable instructions that, when executed by a processor of an electronic device, cause the electronic device to perform the calibration of a lidar system as described above. Methods.
  • Another aspect of the present disclosure relates to a computer program product comprising computer readable instructions that, when executed by a processor of an electronic device, implement the method for calibrating a lidar system as previously described.
  • Figure 1 shows a schematic diagram of the composition of a lidar system according to an embodiment of the present disclosure
  • Figure 2a shows an example of laser luminous point distribution when the lidar system performs field of view scanning according to an embodiment of the present disclosure
  • Figure 2b shows an example of a receiving field of view of a lidar system according to an embodiment of the present disclosure
  • Figure 2c shows a structural example of an optical receiver of a lidar system according to an embodiment of the present disclosure
  • Figure 2d shows an example of the correspondence relationship between the laser light emitting point and the receiving field of view of the lidar system according to an embodiment of the present disclosure
  • Figure 3 shows a schematic diagram of the lidar system having stray light in the receiving field of view
  • FIG. 4 shows an exemplary operating mode of a lidar system according to an embodiment of the present disclosure when the lidar system emits light normally during the operating period, and its amplified spontaneous emission (ASE) light noise situation;
  • ASE amplified spontaneous emission
  • Figure 5 shows the working mode of the lidar system when it does not emit light during the calibration period and its ASE light noise situation
  • Figure 6 shows an exemplary operating mode and its ASE optical noise situation when the lidar system emits a calibration beam during the calibration period according to an embodiment of the present disclosure
  • Figure 7 shows a schematic diagram of the working mode of the lidar system during the calibration period and its ASE optical noise situation according to an embodiment of the present disclosure
  • FIG. 8 illustrates a flowchart of a method for calibrating a lidar system according to an embodiment of the present disclosure
  • Figures 9a and 9b respectively show a schematic diagram of the scanning line and a schematic diagram of the laser luminous point cloud when the lidar system performs row-column raster scanning;
  • Figure 10 illustrates different time configurations of calibration periods for a lidar system according to an embodiment of the present disclosure
  • Figure 11 shows a schematic diagram of the composition of a vehicle integrated with a lidar system according to an embodiment of the present disclosure
  • FIG. 12 shows a configuration block diagram of an electronic device according to an embodiment of the present disclosure.
  • the general working principle of fiber lasers is as follows: the pump source provides pumping light, which enters the optical fiber as the gain medium and causes the gain medium to achieve particle number inversion.
  • the resonant cavity provides forward light feedback for the excited photons. When the resonant cavity When the internal gain is higher than the loss, a laser signal is output.
  • the pump source can be a semiconductor laser.
  • the calibration period of the lidar system is usually relatively short.
  • the laser needs to be turned off quickly and turned back on after a short time interval.
  • the pump source it usually takes a long time for the pump source to switch on and off, and it is difficult to turn off and then on again within a short time interval.
  • the fiber laser will be in a situation where the pump source is turned on and the enable signal that triggers the laser to emit light is turned off. That is, the pump source of the fiber laser is turned on but does not emit light.
  • ASE optical noise is a broadband light source that affects measurements of stray light from other objects during calibration. That is to say, the inventors of the present disclosure realized that for fiber lasers, it is not preferable to turn off laser emission during the calibration period because no light may be emitted but it may not achieve better stray light measurement results.
  • the present disclosure proposes a method for calibrating a lidar system including instructing the lidar system to emit a calibration beam during the calibration period.
  • the emission of the calibration beam consumes the inversion particles in the fiber gain medium, which can suppress the growth of ASE optical noise for a period of time.
  • a period of time after the calibration beam is emitted can be used to detect stray light signals, and based on the monitored stray light
  • the signal adjusts the configuration of the lidar system during subsequent periods of normal illumination operation.
  • This calibration method is particularly suitable for lidar systems including fiber lasers.
  • FIG. 1 illustrates an exemplary lidar system 100 to which the technology of the present disclosure may be applied.
  • LiDAR system 100 may include a light source 102, a scanner 104, a light receiver 106, and a controller 108.
  • Light source 102 emits a transmission beam for scanning target object 120 .
  • the light source 102 may be a laser, such as a solid state laser (such as a vertical cavity surface emitting laser (VCSEL) or an external cavity semiconductor laser (ECDL)), a laser diode, a fiber laser.
  • VCSEL vertical cavity surface emitting laser
  • ECDL external cavity semiconductor laser
  • Light source 102 may also include LEDs.
  • the light source 102 can emit different forms of light beams, including pulsed light, continuous light (CW), and quasi-continuous light.
  • the operating wavelength of the light source may be 650nm to 1150nm, 800nm to 1000nm, 850nm to 950nm or 1300nm to 1600nm.
  • the light source 102 may further include an optical component optically coupled to the light source 102 for collimating or focusing the light beam emitted by the light source 102 .
  • light source 102 includes at least one fiber laser. Each emitted beam emitted by the light source 102 may be a continuous stream of light lasting a certain period of time, or may be one or more light pulses.
  • the scanner 104 is used to deflect the direction of the emitted beam from the light source 102 to scan the target object 120 to achieve a wider emission field of view or scanning field of view.
  • Scanner 104 may be any number of optical mirrors driven by any number of drivers.
  • the scanner 104 may include a planar mirror, a prism, a mechanical galvanometer, a polarizing grating, an optical phased array (OPA), or a microelectromechanical system (MEMS) galvanometer.
  • OPA optical phased array
  • MEMS microelectromechanical system
  • the mirror surface rotates or translates in one or two dimensions under electrostatic/piezoelectric/electromagnetic driving.
  • the scanner 104 guides the light beam from the light source to various positions within the field of view to achieve scanning of the target object 120 within the field of view.
  • the optical receiver may include a receiving unit and associated receiving circuitry. Each receiving circuit can be used to process the output electrical signal of the corresponding receiving unit.
  • the receiving unit includes various forms of photodetectors or one-dimensional or two-dimensional arrays of photodetectors. Correspondingly, the receiving circuit may be one circuit or an array of multiple circuits. Photodetectors measure the power, phase, or time characteristics of reflected light and produce a corresponding current output.
  • the photodetector can be an avalanche diode (APD), a single photon avalanche diode (SPAD), a PN type photodiode or a PIN type photodiode.
  • APD avalanche diode
  • SPAD single photon avalanche diode
  • PN type photodiode or a PIN type photodiode.
  • Controller 108 is communicatively coupled with one or more of light source 102 , scanner 104 , and light receiver 106 .
  • the controller 108 can control whether and when the light source 102 emits a light beam.
  • the controller 108 can control the scanner 104 to scan the beam to a specific location.
  • the controller 108 can process and analyze the electrical signals output by the light receiver to ultimately determine the position, speed and other characteristics of the target object 120 .
  • the controller 108 may include an integrated circuit (IC), an application specific integrated circuit (ASIC), a microchip, a microcontroller, a central processing unit, a graphics processing unit (GPU), a digital signal processor (DSP), a field programmable gate array ( FPGA) or other circuits suitable for executing instructions or implementing logical operations.
  • IC integrated circuit
  • ASIC application specific integrated circuit
  • microchip microchip
  • microcontroller a central processing unit
  • GPU graphics processing unit
  • DSP digital signal processor
  • FPGA field programmable gate array
  • controller 108 Instructions executed by controller 108 may be preloaded into integrated or separate memory (not shown).
  • the memory may store configuration data or commands for the light source 102, scanner 104, or light receiver 106.
  • the memory may also store the electrical signal output from the light receiver 106 or the analysis results based on the output electrical signal. For example, the memory can store information about stray light signals detected during a calibration period for use in subsequent work periods.
  • Memory may include random access memory (RAM), read-only memory (ROM), hard disk, optical disk, magnetic disk, flash memory or other volatile or non-volatile memory, etc.
  • Controller 108 may include single or multiple processing circuits. In the case of multiple processing circuits, each processing circuit may have the same or different structures, and interact or cooperate with each other through electrical, magnetic, optical, acoustic, mechanical, etc. means.
  • lidar system 100 may also include transmit lens 110 .
  • the emission lens 110 may be used to expand the beam emitted by the light source 102 and turned by the scanner 104 .
  • the emission lens 110 may include diffractive optical elements (DOEs) for shaping, splitting, or diffusing the light beam.
  • DOEs diffractive optical elements
  • the emission lens 110 may exist alone or may be integrated into other components (such as the scanner 104 or the light source 102).
  • the position of the emission lens 110 in the emission light path from the light source 102 to the target object 120 is not limited to that shown in FIG. 1 , but can be changed to other positions.
  • the emission lens 110 can be arranged between the light source 102 and the scanner 104, so that the light beam emitted by the light source 102 is first expanded by the emission lens 110 and then deflected by the scanner 104.
  • lidar system 100 may also include receiving lens 112 .
  • the receiving lens 112 is located in front of the light receiver 106 on the receiving path of the emitted light from the target object 120 to the light receiver 106 .
  • the receiving lens 112 may comprise an imaging system lens such that the focus of the reflected beam is in front of, behind or just above the detection surface of the photodetector or photodetector array.
  • the receiving lens 112 may be integrated into the light receiver 106 instead of existing as a separate component.
  • lidar system 100 may also include a housing 114 for enclosing one or more of the aforementioned components therein for protection.
  • the housing 114 is made of an opaque material, and a transparent area or window 116 may be provided on the housing 114 to allow the emitted light beam or the reflected light beam to pass through.
  • the housing 114 itself is a transparent material, thereby allowing the emitted or reflected light beam to pass through from any location.
  • lidar system 100 may include a coaxial optical transceiver system.
  • a coaxial optical transceiver system means that the transmission path from the light source 102 to the target object 120 and the reception path from the target object 120 to the light receiver 106 at least partially overlap.
  • the reflected beam may be reversed through the scanner 104 and then reach the light receiver 106 .
  • the exit angle of the emitted beam changes with the deflection of the scanner 104, but the reception angle of the light that can be received by the optical receiver 106 also changes synchronously with the deflection of the scanner 104, that is, the receiving field of view Always maintain a scanning range comparable to that of the emitted beam.
  • lidar system 100 may include a non-coaxial optical transceiver system.
  • a non-coaxial optical transceiver system means that the transmission path from the light source 102 to the target object 120 does not overlap with the reception path from the target object 120 to the optical receiver 106 .
  • the reflected beam does not pass through the scanner 104 to reach the light receiver 106 .
  • the total receiving field of view of the optical receiver 106 is fixed and does not change with the deflection of the scanner 104.
  • LiDAR system 100 can control scanner 104 to direct the emitted beam according to a predetermined scanning pattern.
  • the scanner 104 presents a closed scanning pattern in space when scanning, and scans repeatedly periodically.
  • Common scanning patterns include row and column raster patterns, Lissajous patterns, spiral patterns, etc.
  • Figure 2a shows an example of a laser point cloud image when the lidar system scans according to a row-column raster scanning pattern.
  • Each pixel 204 in the point cloud represents a position in the emission field of view 202 (or scanning field of view) where the scanner directs the emitted beam.
  • the collection of all pixels 204 constitutes the emission field of view 202 of the lidar system.
  • the emission field of view 202 may have various shapes, and is not limited to the rectangular shape shown in FIG. 2a.
  • Each pixel 204 may be associated with one or more emitted beams or one or more measurements.
  • Figure 2b shows an example of the receiving field of view distribution of a lidar system including a non-coaxial optical transceiver system.
  • the light receiver 106 of the lidar system is composed of multiple receiving sub-modules, each receiving sub-module including one or more receiving units and their corresponding receiving circuits.
  • Each receiving sub-module can receive reflected light within a relatively small range.
  • each rectangle 208 in Figure 2b represents the range of reflected light that a corresponding receiving sub-module of the lidar system can receive, which is also called the receiving field of view of the corresponding receiving sub-module.
  • the collection of the receiving fields of view of all receiving sub-modules constitutes the total receiving field of view 206 of the optical receiver.
  • Figure 2c shows a schematic diagram of the composition of an optical receiver for providing the receiving field of view lidar system of Figure 2b.
  • the optical receiver includes a One or more receiving units 210 and corresponding one or more receiving circuits 214.
  • the receiving units 210 are connected to corresponding receiving circuits 214 via electrical connections 212 .
  • the receiving field of view 208 in Figure 2b corresponds to the receiving sub-module composed of the receiving unit 216 and the corresponding receiving circuit 218 in Figure 2c.
  • Figure 2d shows an example of the correspondence between the laser emission and the receiving field of view during normal operation of the lidar system having the scanning laser point cloud of Figure 2a and the receiving field of view of Figure 2b.
  • the emitted beam is directed to different positions in the emitting field of view, and the controller instructs the receiving sub-module in the optical receiver whose receiving field of view corresponds to that position to open to receive the reflected beam.
  • the controller instructs the receiving sub-module in the optical receiver whose receiving field of view corresponds to that position to open to receive the reflected beam.
  • pixel 218 may correspond to pixel 204 in Figure 2a and receive field of view 220 may correspond to receive field of view 208 in Figure 2b.
  • the receiving sub-module corresponding to the receiving field of view 220 needs to be turned on, that is, the receiving sub-module including the receiving unit 216 and the receiving circuit 218 in Figure 2c can be turned on.
  • the receiving sub-modules in the optical receiver other than the receiving sub-module corresponding to the receiving field of view 220 may be turned off or dormant.
  • the transmitting field of view, the receiving field of view and the corresponding receiving sub-module distribution shown in Figures 2a to 2d are only schematic.
  • the lidar system according to the present disclosure may have different scanning patterns, transmitting fields of view, receiving field of view distribution, shapes, numbers and distributions of receiving sub-modules, and the corresponding relationship between the transmitting field of view 2 and the receiving field of view.
  • the source of stray light can be ambient light noise, including but not limited to: strong sunlight, street lights, lights from other vehicles, or continuous light from other lidar systems.
  • the source of stray light can also be pulsed light from other lidar systems.
  • Figure 3 shows an example of a lidar system receiving stray light in the field of view.
  • the receiving field of view 300 and the rectangular area 302 may correspond to the receiving field of view 206 and the rectangular area 208 in Figure 2b.
  • Sunlight 304 and pulsed light 306 from other lidar systems are detected in the receiving field of view 300 .
  • the receiving sub-module corresponding to the rectangular area 302 is not affected by the sunlight 304 and the pulse light 306, the receiving sub-module corresponding to the rectangular area overlapping the position of the sunlight 304 or the pulse light 306 will be interfered, resulting in reduced measurement accuracy. Therefore, it is necessary to measure the stray light in the receiving field of view and adjust the configuration of the lidar system 100 or the corresponding receiving sub-module based on the measurement results to reduce or eliminate the interference effect from the stray light. This process is called calibration of the lidar system.
  • FIG. 4 illustrates an exemplary operating mode of a lidar system when emitting light normally, according to an embodiment of the present disclosure.
  • Normal illumination means that the lidar system emits a beam to scan the target object and measures the reflected beam (or echo signal). During each working period, the lidar system emits a scanning beam, selects the corresponding receiving sub-module and detects the echo signal. After detecting the echo signal, the lidar system can calculate the distance of the target object based on the flight time, the object reflectivity based on the intensity and distance of the echo signal, and the deflection position/deflection angle of the scanner when the scanning beam is emitted. The spatial position of the target object, thereby obtaining the three-dimensional measurement result of the target object.
  • the length or period of the working period can be constant or variable.
  • the length of the duty cycle, or the emission interval of the scanning beam is constant and is denoted as time T1.
  • T1 is typically a few hundred nanoseconds to a few microseconds.
  • the scanning beam emitted during each working period can be continuous light that lasts for a certain period of time, or it can be one or more light pulses.
  • the scanning beams emitted in different working periods can be the same or different.
  • the lidar system can emit a scanning beam according to a predetermined scanning pattern period by period, and start the corresponding receiving sub-module at the point cloud position covering the scanning beam in the receiving field of view to receive and detect the echo signal.
  • the ASE optical noise can be suppressed within a certain length of time. After exceeding this time length, the ASE optical noise gradually increases until the scanning beam of the next working period is emitted, and the ASE optical noise is suppressed again.
  • the length of the working period can be set relatively short, which is enough to complete the reception and detection of the corresponding receiving sub-module. Therefore, the ASE optical noise has not yet accumulated to a large value.
  • the corresponding receiving sub-module can be configured to start reception and detection relatively soon after the scanning beam is emitted. At this time, the ASE optical noise has not yet begun to accumulate or the accumulated amount is still small. Therefore, the reception and detection of echo signals during the working period are basically not affected by ASE optical noise or are less affected.
  • Figure 5 illustrates an exemplary operating mode of lidar system 100 when no light is emitted during the calibration period.
  • the lidar system Before starting the calibration period, the lidar system may be operated in a working period, as described in conjunction with Figure 4. In the later part of the working period, ASE optical noise gradually increases. Unlike the work period, at the beginning of the calibration period, the lidar system does not emit light and therefore cannot consume the inversion particle population that causes ASE optical noise. and, For fiber lasers, although the enable control signal can be quickly turned off to prevent it from emitting light, its pump source is likely to be unable to be turned off quickly with the beginning of the calibration period, resulting in a continuous increase in the number of inversion particles and ASE optical noise. Accumulate further and reach a stable maximum value after a period of time.
  • the time for ASE optical noise to appear and reach a stable maximum is typically several hundred microseconds.
  • one or more receiving sub-modules are still configured to receive and detect stray light sequentially or simultaneously, then when the ASE optical noise increases to a certain optical noise threshold, the ASE optical noise will not interfere with the stray light measurement results. Ignoring it will reduce the measurement accuracy. Therefore, the inventors of the present disclosure recognized that for fiber lasers, not emitting light during the calibration period may not be optimal given the ASE optical noise.
  • embodiments of the present disclosure propose to emit one or more calibration beams during the calibration period to suppress ASE optical noise, and use the time period in which the ASE optical noise is suppressed to measure stray light.
  • a calibration period includes a light emission area and a light detection area in chronological order.
  • the light emission region may be the time period during which a fiber laser used in a lidar system emits one or more calibration beams.
  • the light detection zone may be a time period during which a light receiver of a lidar system detects stray light signals.
  • the light emitting area and the light detecting area can be located anywhere during the calibration period, just keep the light emitting area in front of the light detecting area.
  • the light-emitting area may or may not be adjacent to the light-detecting area.
  • Tmax can be the time length limit of the light detection area.
  • the optical noise threshold can be predetermined based on the design of the lidar system and the specific application scenarios (such as transmit beam power, receiver sensitivity, ranging range, etc.).
  • the lidar system may determine Tmax based on one or more emitted calibration beams (e.g., based on their intensity, time interval, number, etc.).
  • the lidar system is controlled to terminate the light detection area, that is, to stop detecting stray light signals. This can ensure that the detection of stray light signals is hardly or rarely affected by ASE optical noise, improves the accuracy of calibration measurements, and improves the calibration effect.
  • FIG. 6 shows a specific example of the lidar system operating according to the calibration period configuration of FIG. 7 according to an embodiment of the present disclosure.
  • the fiber laser of the lidar system emits n calibration beams in the light emission area of the calibration period (corresponding to the light emission area of Figure 7), where n is an integer greater than or equal to one.
  • n calibration beams are distributed at fixed time intervals. The time interval between two consecutive calibration beams is T3.
  • Each calibration beam can be a continuous stream of light lasting a certain time, or it can be one or more light pulses.
  • Each calibration beam can be the same or different. As n becomes larger and T3 becomes smaller, the ASE optical noise suppression time after the calibration beam is emitted becomes longer, but it will no longer improve further after a certain level.
  • n and T3 can be selected based on the specific conditions of the fiber pulse laser and system.
  • T3 is less than the time interval during which the lidar system emits a scanning beam during normal lighting conditions (i.e., time T1 in FIG. 4 ).
  • the light receiver of the lidar system After emitting the calibration beam, the light receiver of the lidar system performs measurement of the stray light signal in the light detection area (corresponding to the light detection area in Figure 7).
  • the time length of the light detection area can be from the completion of emission of the calibration beam to the end of the current calibration period, which is recorded as T2.
  • T2 can be smaller than Tmax. In some embodiments, T2 may be greater than T1.
  • the lidar system may use all receiving sub-modules for calibration measurements, or may only use at least a part of the multiple receiving sub-modules for calibration measurements.
  • the lidar system can use all required receiving sub-modules at once to perform calibration measurements. This is feasible when the parallel data processing capabilities of the optical receiver of the lidar system are strong. In this way, the calibration measurement can be completed quickly in a short time, the time period during which the required ASE optical noise is suppressed can be shorter, and accordingly, the number of required calibration beams can be smaller and the intervals can be larger. In some cases, even only one light pulse may be needed as the calibration beam. At this time, the calibration beam and the scanning beam during the normal lighting operation can be the same. The only difference between the calibration period and the working period lies in the objects and methods used by the optical receiver to receive and detect.
  • the optical receiver detects the echo of the scanning beam, and usually only turns on the corresponding receiving sub-module according to the direction of the scanning beam.
  • the optical receiver detects stray light signals instead of the echo of the calibration beam, and all receiving sub-modules can be turned on at one time for detection.
  • the receiving sub-module required by the lidar system can be divided into multiple receiving sub-module sub-groups, and the light detection area is divided into multiple detection time periods, and multiple detection time periods are used in turn.
  • a subgroup of receiving submodules is used to detect stray light signals.
  • the division of multiple receiving sub-modules into multiple receiving sub-module sub-groups may depend on the parallel data processing capabilities of the optical receiver of the lidar system. More specifically, the number of receiving sub-modules in each receiving sub-module sub-group can be based on the parallel data of the optical receiver Processing capacity is determined.
  • each receiving sub-module subgroup may include only one receiving sub-module.
  • each receiving sub-module subgroup may have one or more rows, one or more columns, or other division methods according to the array of receiving units.
  • the number of multiple detection time periods set in the light detection area of a calibration period is also limited by the time length limit Tmax of the light detection area.
  • Tmax the time length limit value of the light detection area.
  • each receiving sub-module subgroup includes one row of the array of receiving units, and assuming that in order to detect stray light signals, four rows of the array of receiving units are needed, then a total of four detections need to be arranged Time period T0.
  • T0 Time period
  • two detection time periods T0 are allowed to be arranged according to Tmax. Therefore, two calibration periods can be used to complete a calibration measurement.
  • Two calibration periods may or may not be contiguous in time. The calibration beams emitted during different calibration periods can be the same or different.
  • the light emission and light detection regions of the calibration period may be separated by a silent zone.
  • the quiet zone is the period of time when the optical receiver does not detect stray light signals.
  • the length of the quiet zone is related to the time required for the emitted calibration beam or beams to be reflected from the outside back to the light receiver.
  • the silent zone is represented by T4.
  • T2 the light detection area
  • T5 the light detection area.
  • the light detection area not only avoids the interference of the echo of the calibration beam, but also avoids the possibility of ASE optical noise accumulating to exceed the optical noise threshold.
  • the stray light signal measured in such a light detection area has higher accuracy.
  • Figure 8 is a flow diagram of a method 800 for calibrating a lidar system.
  • Method 800 may be performed in lidar system 100 of FIG. 1 .
  • Method 800 begins at block 802, where one or more processors may instruct the fiber laser of lidar system 100 to emit one or more calibration beams during the light emission region of the calibration period.
  • the one or more processors may be implemented in the controller 108 of the lidar system 100 .
  • the calibration beam is the beam emitted during the calibration period.
  • the main function of the calibration beam is to suppress the ASE optical noise of the fiber laser.
  • the calibration beam may be the same as or different from the scanning beam during normal illumination in terms of pulse number, duration, time interval, intensity and other characteristics.
  • the one or more processors may instruct the lidar system 100 to detect stray light signals during the light detection region following the light emission region of the calibration period.
  • the stray light signal is different from the echo signal of the emitted calibration beam or beams. Stray light signals can include ambient light noise or pulsed light from other lidar systems.
  • the light receiver 106 of the lidar system 100 may receive a total signal including an echo signal of the calibration beam and a stray light signal during the light detection zone, and based on the echo signal of the calibration beam The known information extracts the stray light signal from the total signal.
  • the optical receiver 106 may avoid receiving the echo signal of the calibration beam and only receive stray light signals. For example, the silent zone may be set as shown in FIG. 6 .
  • one or more processors may adjust the configuration of lidar system 100 during subsequent operating periods based on the detected stray light signals.
  • the working period may be a time period during which the lidar system 100 emits a scanning beam to scan a target object and receives and detects an echo signal reflected back from the target object by the scanning beam.
  • the processor may determine the type of stray light based on characteristics of the detected stray light signal. For example, if the electrical signal corresponding to the detected stray light is a direct current signal, the processor may determine that the stray light signal includes ambient light noise. Ambient light noise includes but is not limited to: daylight, street lights, lights from other vehicles, and continuous light from other lidar systems.
  • the processor may determine that the stray light signal includes pulse light from other laser lidar systems.
  • the processor can also determine the interfered receiving sub-module, including the interfered receiving unit and its associated receiving circuit, based on the position of the detected stray light signal in the receiving field of view.
  • the processor can specifically adjust the configuration of the lidar system 100 during subsequent operating periods.
  • adjustment measures may include one or more of the following:
  • the transmit power of the corresponding laser can be increased or the sensitivity/gain of the relevant receiving sub-module can be increased, so that the signal-to-noise ratio of the received echo signal of the scanning beam relative to the ambient light noise is improved.
  • the transmit power of the corresponding laser can be reduced or the sensitivity/gain of the relevant receiving sub-module can be reduced, thereby saving system power consumption.
  • adjustment measures may include allowing the lidar system to operate with Anti-crosstalk operating parameter operation.
  • the anti-crosstalk operating parameters are mainly used to improve the ability of the optical receiver of the lidar system to distinguish the echo signal of its own scanning beam from the pulsed light from other lidar systems.
  • operating with anti-crosstalk operating parameters includes adjusting the pulse repetition frequency, operating wavelength or intensity distribution of the laser corresponding to the interfered receiving sub-module, so that it can be distinguished from the pulsed light of other lidar systems.
  • the lidar system controls the scanner to produce different deflections according to a preset scanning pattern. After reaching the scanning end point from the scanning starting point, it takes a period of time to return the scanner's deflection position to the scanning starting point for the next round of scanning. This process is called the retrace period. Correspondingly, the process of the scanner's deflection position from the scanning starting point to the scanning end point is called the scanning period.
  • the scanning period and the retrace period together constitute a frame in which the lidar system scans the emission field of view.
  • Figures 9a and 9b respectively show a schematic diagram of the scanning line and the corresponding schematic diagram of the laser luminous point cloud when the lidar system performs row-column raster scanning.
  • the number of deflection positions during the retrace period is small, and the number of corresponding point clouds is also small.
  • the dense curve 902 represents the scan period, while the sparse curve 904 represents the retrace period. Since the number of point clouds during the retrace period is small and the measurement data is difficult to utilize, the resources of the lidar system are actually idle during the retrace period.
  • FIG. 10 illustrates different time configurations of a calibration period (eg, the calibration period shown in FIG. 7 ) by a lidar system according to an embodiment of the present disclosure.
  • the calibration period according to embodiments of the present disclosure may be scheduled anywhere within the scan period or retrace period of a frame.
  • one or more calibration periods of the lidar system may be set within a scan period. In some cases, calibration periods can overlap with work periods. At this time, the scanning beam is used as the calibration beam.
  • the lidar system can receive and detect the echo signal of the scanning beam/calibration beam in a relatively short period of time after emitting the scanning beam/calibration beam, and measure the stray light signal in the time period after the working period/calibration period.
  • calibration periods may be interspersed with work periods. For example, the lidar system can arrange a working period and a calibration period for each pixel of the scanning pattern, emit a scanning beam during the working period to measure the target object, and emit a calibration beam during the calibration period to detect stray light signals. . This method can be applied to both coaxial optical transceiver systems and non-coaxial optical transceiver systems.
  • one or more calibration periods of the lidar system may be set within the retrace period. This can avoid idle resources of the lidar system during the retrace period.
  • This method can be applied to coaxial optical transceiver systems, but is especially suitable for non-coaxial optical transceiver systems.
  • the transmitting field of view changes continuously during the retrace period
  • the receiving field of view is independent of the deflection position of the scanner. Therefore, one or more receiving sub-modules can be traversed to measure the receiving field of view. A wider range of stray light signals within the field.
  • the calibration period can be scheduled anywhere during the retrace period.
  • the entire retrace period can be filled with the calibration period; if the number of receiving sub-modules is small, only part of the time period of the retrace period can be selected to schedule the calibration period.
  • one or more receiving sub-modules may be selected for each calibration period, depending on the parallel data processing capability of the receiving system or other design factors.
  • the length of the retrace period is shorter than the length of the scan period.
  • the opening time of each receiving sub-module can be shorter than the opening time of the receiving sub-module during the working period.
  • the calibration period can be performed on a fixed periodic basis, for example, once or multiple times per frame or per multiple frames, without any event triggering.
  • the working period according to embodiments of the present disclosure may be located within the scan period (as shown in Figure 10), but in some cases may also be located within the retrace period (not shown).
  • techniques for calibrating a lidar system according to embodiments of the present disclosure may be implemented in one or more processors within the lidar system, such as by a controller.
  • the techniques for calibrating the lidar system according to embodiments of the present disclosure may also be implemented in one or more processors of the vehicle device, for example, by the vehicle Controller implementation.
  • the technology of calibrating the lidar system according to embodiments of the present disclosure may be collaboratively implemented by the vehicle controller and the controller of the lidar system.
  • FIG. 11 shows a schematic diagram of a vehicle 1100 integrated with a lidar system according to an embodiment of the present disclosure.
  • Vehicle 1100 may include at least a lidar system 1102, a vehicle controller 1104, and a mobility system 1106.
  • LiDAR system 1102 may be implemented using LiDAR system 100 in FIG. 1 .
  • the light source 1112, the scanner 1114, the light receiver 1116 and the controller 1118 respectively correspond to the light source 102, the scanner 104, the light receiver 106 and the controller 108 of the lidar system 100.
  • vehicle controller 1104 may be communicatively coupled to light source 1112 , scanner 1114 and light receiver 1116 via controller 1118 .
  • the vehicle controller 1104 may also be directly communicatively coupled with the light source 1112, the scanner 1114, and the light receiver 1116.
  • lidar system 1102 may not include controller 1118 .
  • the technology of calibrating the lidar system according to the embodiment of the present disclosure can be implemented independently by the vehicle controller 1104, or can be implemented collaboratively partly by the vehicle controller 1104 and partly by the controller 1118.
  • maneuverable System 1106 may include a power subsystem, a braking subsystem, a steering subsystem, etc. Vehicle controller 1104 may adjust maneuvering system 1106 based on detection results from lidar system 1102 .
  • the technology for calibrating a lidar system may also be implemented in an electronic device in the form of computer-readable instructions.
  • FIG. 12 shows a configuration block diagram of an electronic device 1200 according to an embodiment of the present disclosure.
  • the electronic device 1200 may be used to perform a method of calibrating a lidar system according to embodiments of the present disclosure, such as method 800 .
  • Electronic device 1200 may be any type of general or special purpose computing device, such as a desktop computer, laptop computer, server, mainframe computer, cloud-based computer, tablet computer, wearable device, vehicle electronics, etc.
  • the electronic device 1200 includes an input/output (I/O) interface 1201 , a network interface 1202 , a memory 1204 and a processor 1203 .
  • I/O input/output
  • I/O interface 1201 is a collection of components that can receive input from and/or provide output to the user.
  • I/O interface 1201 may include, but is not limited to, buttons, keyboards, keypads, LCD displays, LED displays, or other similar display devices, including display devices with touch screen capabilities that enable interaction between the user and the electronic device.
  • Communication interface 1202 may include various adapters and circuitry implemented in software and/or hardware to enable communication with the lidar system using wired or wireless protocols.
  • the wired protocol is, for example, any one or more of a serial port protocol, a parallel port protocol, an Ethernet protocol, a USB protocol or other wired communication protocols.
  • the wireless protocol is, for example, any IEEE 802.11 Wi-Fi protocol, cellular network communication protocol, etc.
  • Memory 1204 includes a single memory or one or more memories or storage locations, including but not limited to random access memory (RAM), dynamic random access memory (DRAM), static random access memory (SRAM), read only memory (ROM) ), EPROM, EEPROM, flash memory, logic blocks of FPGA, hard disk, or any other layer of the memory hierarchy.
  • RAM random access memory
  • DRAM dynamic random access memory
  • SRAM static random access memory
  • ROM read only memory
  • EPROM electrically erasable programmable read only memory
  • EEPROM electrically erasable programmable read only memory
  • flash memory logic blocks of FPGA, hard disk, or any other layer of the memory hierarchy.
  • Memory 1204 may be used to store any type of instructions, software, or algorithms, including instructions 1205 for controlling the general functionality and operation of electronic device 1200 .
  • Processor 1203 controls the general operation of electronic device 1200.
  • the processor 1203 may include, but is not limited to, a CPU, a hardware microprocessor, a hardware processor, a multi-core processor, a single-core processor, a microcontroller, an application specific integrated circuit (ASIC), a DSP, or other similar processing device capable of executing Any type of instructions, algorithms, or software for controlling the operation and functionality of electronic device 1200 of the embodiments described in this disclosure.
  • Processor 1203 may be various implementations of digital circuitry, analog circuitry, or mixed-signal (a combination of analog and digital) circuitry that perform functions in a computing system.
  • Processor 1203 may include, for example, a portion or circuit such as an integrated circuit (IC), a separate processor core, an entire processor core, a separate processor, a programmable hardware device such as a field programmable gate array (FPGA), and/or Systems that include multiple processors.
  • IC integrated circuit
  • FPGA field programmable gate array
  • Internal bus 1206 may be used to establish communication between components of electronic device 1200 .
  • Electronic device 1200 is communicatively coupled to the lidar system to be calibrated to control operation of the lidar system.
  • a calibration method according to the present disclosure may be stored on the memory 1204 of the electronic device 1200 in the form of computer-readable instructions.
  • the processor 1203 implements the calibration method by reading stored computer-readable instructions.
  • electronic device 1200 is described using specific components, in alternative embodiments different components may be present in electronic device 1200 .
  • electronic device 1200 may include one or more additional processors, memory, network interfaces, and/or I/O interfaces. Additionally, one or more of the components may not be present in electronic device 1200 . Additionally, although separate components are shown in Figure 12, in some embodiments some or all of a given component may be integrated into one or more of the other components in electronic device 1200.
  • the present disclosure may be implemented as any combination of devices, systems, integrated circuits, and computer programs or program products on non-transitory computer-readable media.
  • Computer-executable instructions in the computer-readable storage medium or program product may be configured to perform operations corresponding to the above-described apparatus and method embodiments.
  • the embodiments of the computer-readable storage medium or program product will be clear to those skilled in the art, and therefore will not be described again.
  • Computer-readable storage media and program products for carrying or including the computer-executable instructions described above are also within the scope of the present disclosure.
  • Such storage media may include, but are not limited to, floppy disks, optical disks, magneto-optical disks, memory cards, memory sticks, and the like.
  • a plurality of functions included in one unit in the above embodiments may be implemented by separate devices.
  • above Multiple functions implemented by multiple units in the embodiment may be implemented by separate devices respectively.
  • one of the above functions may be implemented by multiple units. Such a configuration is included in the technical scope of the present disclosure.
  • the steps described in the flowchart include not only processing performed in time series in the stated order but also processing performed in parallel or individually and not necessarily in time series. Furthermore, even in steps processed in time series, the order can be changed appropriately.

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Abstract

一种校准激光雷达系统(100)的方法（800）、激光雷达系统(100)、车辆(1100)、电子设备(1200)及相应的介质和程序产品。方法（800）包括指示光纤激光器在校准期的光发射区期间发射一个或多个校准光束（802）；指示在光发射区之后的光检测区期间检测杂散光信号（804）；基于杂散光信号调整激光雷达系统(100)在后续工作期期间的配置（806）。

Description

激光雷达系统及其校准方法
优先权信息
本申请是以CN申请号为202210309936.7，申请日为2022年03月28日的申请为基础，并主张其优先权，该CN申请的公开内容在此作为整体引入本申请中。
技术领域
本公开涉及激光雷达系统，更具体而言涉及用于校准激光雷达系统的方法、执行该方法的激光雷达系统、车辆、电子设备、介质以及程序产品。
背景技术
激光雷达系统，又称为激光探测和测距(LiDAR或LADAR)系统，通过向目标对象发射激光光束并接收从目标对象反射的光束来测量目标对象的位置、速度等信息。在激光雷达系统通过光接收器检测的光中，除了期望的来自目标对象的反射光，还往往存在来自视场(FOV)中其它对象的杂散光，包括诸如强烈的太阳光、其它车辆的车灯光等环境光或者来自其它激光雷达系统的光束。在激光雷达系统应用于高速、远距离(例如几百米)的场景(例如，配备于带有高级驾驶辅助系统(ADAS)或者自动驾驶功能的车辆)时，从目标对象到达光接收器的反射光本身功率可能很小。在杂散光较强时，光接收器的输出信号信噪比(SNR)大大恶化，测量精度降低，给激光雷达系统的使用带来了困难。
因此，有必要对来自视场中其它对象的杂散光进行测量，以期调整或优化激光雷达系统对目标对象的测量结果。
发明内容
为了解决当前激光雷达系统的上述缺陷中的至少一些，本公开提供了一种用于校准激光雷达系统的方法、以及执行该方法的激光雷达系统、车辆、电子设备以及相应的介质和程序产品，能够改善校准过程中对杂散光的测量，实现更好的校准效果。
本公开的一个方面涉及一种用于校准激光雷达系统的方法。激光雷达系统包括光纤激光器。该方法包括由一个或多个处理器指示光纤激光器在校准期的光发射区期间发射一个或多个校准光束。该方法还包括由一个或多个处理器指示激光雷达系统在校准期的在光发射区之后的光检测区期间检测杂散光信号。杂散光信号可以包括环境光噪声或来自其它激光雷达系统的脉冲光。该方法还包括由一个或多个处理器基于所检测的杂散光信号调整激光雷达系统在后续工作期期间的配置。
在根据第一方面的一些实施例中，光检测区与光发射区由静默区隔开。静默区的长度与所发射的一个或多个校准光束从外部反射回激光雷达系统的时间相关联。该方法还包括在校准期的静默区期间，由一个或多个处理器指示激光雷达系统不检测杂散光信号。
在根据第一方面的一些实施例中，校准期被设置在激光雷达系统的回扫期内，在回扫期内激光雷达系统的扫描器从扫描终点返回到扫描起点。
在根据第一方面的一些实施例中，激光雷达系统为非同轴光学收发系统。
在根据第一方面的一些实施例中，校准期被设置在激光雷达系统的扫描期的至少一部分内，在扫描期激光雷达系统的扫描器从扫描起点行进到扫描终点。
在根据第一方面的一些实施例中，指示激光雷达系统检测杂散光信号包括：将激光雷达系统的多个接收单元的至少一部分划分成多个接收单元子组，以及在校准期的光检测区期间使激光雷达系统依次使用多个接收单元子组检测杂散光信号。
在根据第一方面的一些实施例中，指示激光雷达系统检测杂散光信号包括：基于所发射的一个或多个校准光束确定从发射一个或多个校准光束到光纤激光器的放大自发辐射(ASE)光噪声增大到达到光噪声阈值的第一时间；以及在第一时间到期时或之前，指示激光雷达系统停止检测杂散光信号。
在根据第一方面的一些实施例中，在校准期内，光纤激光器的泵浦源开启。
在根据第一方面的一些实施例中，基于所检测的杂散光信号调整激光雷达系统在后续工作期期间的配置包括：基于确定杂散光信号包括环境光噪声以及确定受干扰的接收单元，调整激光雷达系统在 后续工作期期间的配置，包括以下至少一个：调整扫描光束反射于受干扰的接收单元的回波信号对应的激光器的发射功率、调整受干扰的接收单元及其相关联接收电路的灵敏度以及调整受干扰的接收单元及其相关联接收电路的增益。
在根据第一方面的一些实施例中，基于所检测的杂散光信号调整激光雷达系统在后续工作期期间的配置包括：基于所检测的杂散光信号确定杂散光信号包括来自其它激光雷达系统的脉冲光以及确定受干扰的接收单元，以及基于确定杂散光信号包括来自其它激光雷达系统的脉冲光以及确定受干扰的接收单元，调整激光雷达系统在后续工作期期间的配置，包括：使激光雷达系统在后续工作期期间以抗串扰工作参数操作。
本公开的另一个方面涉及一种激光雷达系统。该激光雷达系统包括光源、扫描器、光接收器和控制器。光源被配置为发射光。光源包括光纤激光器。扫描器被配置为引导光以扫描目标对象。光接收器被配置为检测由目标对象反射的光。控制器与光源、扫描器和光接收器通信地耦接。控制器被配置为执行如前所述的用于校准激光雷达系统的方法。
本公开的另一个方面涉及一种车辆。车辆包括激光雷达系统和车辆控制器。激光雷达系统包括光纤激光器。车辆控制器与激光雷达系统通信地耦接。车辆控制器被配置为执行如前所述的用于校准激光雷达系统的方法。
本公开的另一个方面涉及一种电子设备。电子设备包括处理器和存储器。存储器通信耦接到处理器并且存储计算机可读指令。计算机可读指令在由处理器执行时，使得电子设备执行如前所述的用于校准激光雷达系统的方法。
本公开的另一个方面涉及一种存储有计算机可读指令的计算机可读存储介质，该指令在由电子设备的处理器执行时，使得该电子设备执行如前所述的用于校准激光雷达系统的方法。
本公开的另一个方面涉及一种计算机程序产品，包括计算机可读指令，该计算机可读指令在被电子设备的处理器执行时实现如前所述的用于校准激光雷达系统的方法。
附图说明
下面结合具体的实施例，并参照附图，对本公开的上述和其它目的和优点做进一步的描述。在附图中，相同的或对应的技术特征或部件将采用相同或对应的附图标记来表示。
图1示出根据本公开的实施例的激光雷达系统的组成示意图；
图2a示出根据本公开的实施例的激光雷达系统进行视场扫描时的激光发光点分布示例；
图2b示出根据本公开的实施例的激光雷达系统的接收视场示例；
图2c示出根据本公开的实施例的激光雷达系统的光接收器的结构示例；
图2d示出根据本公开的实施例的激光雷达系统的激光发光点和接收视场对应性关系示例；
图3示出激光雷达系统在接收视场中存在杂散光的示意图；
图4示出根据本公开的实施例的激光雷达系统在工作期正常发光时的示例性工作模式及其放大自发辐射(ASE)光噪声情况；
图5示出激光雷达系统在校准期不发光时的工作模式及其ASE光噪声情况；
图6示出根据本公开的实施例的激光雷达系统在校准期发射校准光束时的示例性工作模式及其ASE光噪声情况；
图7示出根据本公开的实施例的激光雷达系统在校准期的工作模式示意及其ASE光噪声情况；
图8示出根据本公开的实施例的用于校准激光雷达系统的方法的流程图；
图9a和图9b分别示出激光雷达系统进行行列光栅式扫描时的扫描线示意图和激光器发光点云示意图；
图10示出根据本公开的实施例的激光雷达系统对校准期的不同时间配置方式；
图11示出根据本公开的实施例的集成了激光雷达系统的车辆的组成示意图；
图12示出根据本公开的实施例的电子设备的配置框图。
具体实施方式
参考附图进行以下详细描述，并且提供以下详细描述以帮助全面理解本公开的各种示例实施例。 以下描述包括各种细节以帮助理解，但是这些细节仅被认为是示例，而不是为了限制本公开，本公开是由随附权利要求及其等同内容限定的。在以下描述中使用的词语和短语仅用于能够清楚一致地理解本公开。另外，为了清楚和简洁起见，可能省略了对公知的结构、功能和配置的描述。本领域普通技术人员将认识到，在不脱离本公开的范围的情况下，可以对本文描述的示例进行各种改变和修改。
如前所述，在对激光雷达系统进行校准时，需要测量来自视场中其它对象的杂散光。为了准确测量杂散光，一些已有的方法要求激光雷达系统在校准期间不发光。然而，本公开的发明人认识到，对于采用光纤激光器的激光雷达系统，这些方法可能带来问题。
光纤激光器的一般工作原理如下：泵浦源提供抽运光，抽运光进入作为增益介质的光纤后使得增益介质达到粒子数反转，谐振腔为激发的光子提供正向光反馈，当谐振腔内增益高于损耗时形成激光信号输出。泵浦源可以是半导体激光器。
为了不占用激光雷达系统的正常工作时间，激光雷达系统的校准期时长通常相对较短。从正常发光的工作期到校准期再返回到工作期的切换中，若让激光雷达系统在校准期不发光，则需要快速关闭激光器并在短的时间间隔后重新开启。而对于光纤激光器来说，其泵浦源实现开关的时间通常较长，在短的时间间隔内难以关闭后再重新开启。结果，光纤激光器将处于泵浦源开启而触发激光器发光的使能信号被关断的情形，即，光纤激光器的泵浦源开启但不发光。随着光纤激光器不发光的时间累积，光纤激光器会产生放大自发辐射(ASE)光噪声，并且ASE光噪声会越来越强。ASE光噪声是一个宽带光源，会影响校准期对来自其它对象的杂散光的测量。也就是说，本公开的发明人认识到，对于光纤激光器而言，在校准期关闭激光发射并非优选，因为不发光可能反而无法实现更好的杂散光测量效果。
基于此，本公开提出的一种校准激光雷达系统的方法包括指示激光雷达系统在校准期发射校准光束。校准光束的发射消耗了光纤增益介质中的反转粒子，能够在一段时间内抑制ASE光噪声的增长，进而可以利用校准光束发射后的一段时间来检测杂散光信号，并基于所监测的杂散光信号调整激光雷达系统在后续正常发光的工作期期间的配置。该校准方法尤其适用于包括光纤激光器的激光雷达系统。
图1示出了一种示例性的激光雷达系统100，其可以应用本公开的技术。激光雷达系统100可以包括光源102、扫描器104、光接收器106和控制器108。光源102发射用于对目标对象120进行扫描的发射光束。光源102可以是激光器，例如固态激光器(诸如垂直腔面发射激光器(VCSEL)或外腔半导体激光器(ECDL))、激光器二极管、光纤激光器。光源102也可以包括LED。光源102可以发射不同形式的光束，包括脉冲光、连续光(CW)和准连续光。光源的工作波长可以是650nm至1150nm、800nm至1000nm、850nm至950nm或者1300nm至1600nm。在一个或多个实施例中，光源102还可以包括与光源102光学耦接的光学组件，用于对光源102发出的光束进行准直或聚焦。在一个或多个实施例中，光源102包括至少一个光纤激光器。由光源102发出的每个发射光束可以是持续一定时间的连续光，也可以是一个或多个光脉冲。
扫描器104用于使来自光源102的发射光束的方向发生偏转，以对目标对象120进行扫描，实现更宽的发射视场或扫描视场。扫描器104可以是由任意数量的驱动器驱动的任意数量的光学镜子。例如，扫描器104可以包括平面反射镜、棱镜、机械振镜、偏振光栅、光学相控阵(OPA)、微电机系统(MEMS)振镜。对于MEMS振镜，反射镜面在静电/压电/电磁驱动下在一维或二维方向上发生旋转或平移。在驱动器的驱动下，扫描器104将来自光源的光束引导至视场内的各个位置，以实现对视场内目标对象120的扫描。
光束从目标对象120反射后，一部分反射光返回到激光雷达系统100，并由光接收器106接收。光接收器106接收并检测来自目标对象120的反射光的一部分并产生对应的电信号。光接收器可以包括接收单元和相关联的接收电路。每个接收电路可以用于处理相应的接收单元的输出电信号。接收单元包括各种形式的光电探测器或光电探测器一维或二维阵列，相应地，接收电路可以为一个电路或多个电路的阵列。光电探测器测量反射光的功率、相位或时间特性，并产生相应的电流输出。光电探测器可以是雪崩二极管(APD)、单光子雪崩二极管(SPAD)、PN型光电二极管或PIN型光电二极管。
控制器108与光源102、扫描器104和光接收器106中的一个或多个通信耦接。控制器108可以控制光源102是否以及何时发射光束。控制器108可以控制扫描器104将光束扫描至具体的位置。控制器108可以处理和分析由光接收器输出的电信号，以最终确定目标对象120的位置、速度等特征。控 制器108可以包括集成电路(IC)、专用集成电路(ASIC)、微芯片、微控制器、中央处理器、图形处理单元(GPU)、数字信号处理器(DSP)、现场可编程门阵列(FPGA)或者其它适合执行指令或实现逻辑操作的电路。由控制器108执行的指令可以被预加载到集成或单独的存储器(未示出)中。存储器可以存储用于光源102、扫描器104或光接收器106的配置数据或命令。存储器也可以存储从光接收器106输出的电信号或者基于输出电信号的分析结果。例如，存储器可以存储在校准期内检测的杂散光信号的相关信息以供后续工作期使用。存储器可以包括随机访问存储器(RAM)、只读存储器(ROM)、硬盘、光盘、磁盘、闪存存储器或其它易失性或非易失性存储器等。控制器108可以包括单个或多个处理电路。在多个处理电路的情况下，各处理电路可以具有相同或不同的构造，彼此间通过电、磁、光、声、机械等方式交互或者协同操作。
在一个或多个实施例中，激光雷达系统100还可以包括发射透镜110。发射透镜110可以用于对由光源102发射并由扫描器104转向的光束进行扩束。发射透镜110可以包括衍射光学元件(DOE)，用于对光束进行整形、分离或扩散。发射透镜110可以单独存在，也可以集成到其它部件(例如扫描器104或光源102)中。发射透镜110在从光源102到目标对象120的发射光路中的位置不限于图1中所示，而是可以变更到其它位置。例如，发射透镜110可以被布置在光源102和扫描器104之间，这样光源102发出的光束先经过发射透镜110扩束后再被扫描器104转向。
在一个或多个实施例中，激光雷达系统100还可以包括接收透镜112。接收透镜112在发射光从目标对象120到光接收器106的接收路径上位于光接收器106之前。接收透镜112可以包括成像系统透镜，以使得反射光束的焦点在光电探测器或光电探测器阵列的探测表面的前方或后方或者正好位于探测表面之上。在一些情况下，代替作为单独的部件存在，接收透镜112也可以被集成到光接收器106中。
在一个或多个实施例中，激光雷达系统100还可以包括外壳114，用于将前述部件中的一个或多个包封在其中以进行保护。在一些实施例中，外壳114为不透明材料，并且外壳114上可以开设透明区域或窗口116以允许发射光束或反射光束通过。在另一些实施例中，外壳114自身为透明材料，由此允许发射光束或反射光束从任意位置通过。
在一些实施例中，激光雷达系统100可以包括同轴光学收发系统。同轴光学收发系统是指从光源102到目标对象120的发射路径与从目标对象120到光接收器106的接收路径至少部分重叠。例如，与图1所示不同，反射光束可以反向经由扫描器104后到达光接收器106。对于同轴光学收发系统而言，不仅发射光束的出射角度随扫描器104偏转而变化，光接收器106可接收到的光的接收角度也随扫描器104偏转而同步变化，即，接收视场始终保持与发射光束的扫描范围相当。
在另一些实施例中，激光雷达系统100可以包括非同轴光学收发系统。非同轴光学收发系统是指从光源102到目标对象120的发射路径与从目标对象120到光接收器106的接收路径没有重叠部分。例如，如图1所示，反射光束并没有再经由扫描器104到达光接收器106。对于非同轴光学收发系统而言，尽管发射光束的出射角度随扫描器104偏转而变化，但光接收器106的总接收视场是固定的，并不随扫描器104的偏转而变化。
激光雷达系统100可以控制扫描器104按照预定的扫描图案引导发射光束。通常情况下，扫描器104扫描时在空间呈现一种闭合的扫描图案，并且周期性的重复扫描。常见的扫描图案包括行列光栅式、李萨如图形、螺旋图形等。图2a示出激光雷达系统按照行列光栅式扫描图案进行扫描时的激光点云图的一个示例。点云图中的每个像素点204表示扫描器将发射光束引导至发射视场202(或称扫描视场)中的位置。所有像素点204的合集构成了激光雷达系统的发射视场202。根据预定扫描图案的不同，发射视场202可以具有各种不同的形状，不限于图2a所示的矩形形状。每个像素点204可以与一个或多个发射光束或者一次或多次测量相关联。
图2b示出了包括非同轴光学收发系统的激光雷达系统的接收视场分布示例。在该示例中，激光雷达系统的光接收器106由多个接收子模块组成，每个接收子模块包括一个或多个接收单元及其相应的接收电路。每个接收子模块能够接收相对较小范围内的反射光。例如，图2b中每一个矩形208表示激光雷达系统的相应一个接收子模块能够接收的反射光的范围，也称为相应接收子模块的接收视场。所有接收子模块的接收视场的合集构成了光接收器的总接收视场206。
图2c示出了为了提供图2b的接收视场激光雷达系统的光接收器的组成示意图。光接收器包括一 个或多个接收单元210和相应的一个或多个接收电路214。接收单元210通过电气连接件212连接到相应的接收电路214。例如，图2b中的接收视场208对应于图2c中的接收单元216和相应的接收电路218组成的接收子模块。
图2d示出了具有图2a的扫描激光点云和图2b的接收视场的激光雷达系统在正常工作时激光发光和接收视场之间的对应关系的示例。在正常工作时，随着扫描器的偏转作用，发射光束被指向发射视场中的不同位置，控制器指示光接收器中接收视场与该位置相对应的接收子模块开启，以接收反射光束，完成测量。例如，像素218可以对应于图2a中的像素204，接收视场220可以对应于图2b中的接收视场208。当激光雷达系统产生指向像素点218处的发射光束时，需要使接收视场220对应的接收子模块开启，即可以开启图2c中的包括接收单元216和接收电路218的接收子模块。光接收器中除了与接收视场220对应的接收子模块之外的接收子模块可以被关闭或休眠。
应认识到，图2a至图2d所示出的发射视场、接收视场及对应的接收子模块分布仅仅是示意性的。根据本公开的激光雷达系统可以具有与之不同的扫描图案、发射视场、接收视场分布、接收子模块的形状、数量和分布以及发射视场2与接收视场的对应关系。
尽管将接收视场划分为多个与接收子模块对应的较小视场并且根据扫描点云的位置开启相应的较小视场能够在一定程度上降低噪声、提高信噪比，然而若在整个接收视场的范围内存在较强的固定或动态的杂散光，该杂散光依然会对视场与其重叠的相应接收子模块的测量产生干扰。杂散光的来源可以是环境光噪声，包括但不限于：较强的日光、路灯光、来自其它车辆的车灯光或者来自其它激光雷达系统的连续光。杂散光的来源还可以是来自其它激光雷达系统的脉冲光。图3示出了激光雷达系统接收视场中的杂散光的示例。接收视场300和矩形区域302可以对应于图2b中的接收视场206和矩形区域208。接收视场300中检测到日光304和来自其它激光雷达系统的脉冲光306。尽管矩形区域302对应的接收子模块没有受到日光304和脉冲光306的影响，但与日光304或脉冲光306的位置重叠的矩形区域所对应的接收子模块都会被干扰，致使测量精度降低。因此，有必要对接收视场中的杂散光进行测量，并根据测量结果调整激光雷达系统100或者相应接收子模块的配置，以减小或消除来自杂散光的干扰效应。这一过程称为激光雷达系统的校准。
下面结合图4-图5来说明对于包括光纤激光器的激光雷达系统而言在校准期不发光并不利于改善校准过程中的测量结果。
图4示出根据本公开的实施例的激光雷达系统在正常发光时的示例性工作模式。正常发光是指激光雷达系统发射光束以对目标对象进行扫描并测量反射光束(或称为回波信号)。在每个工作期内，激光雷达系统发射一扫描光束，选择相应的接收子模块并检测回波信号。在检测到回波信号后，激光雷达系统可以根据飞行时间计算目标对象的距离，根据回波信号的强度和距离计算物体反射率，同时根据在发射扫描光束时扫描器的偏转位置/偏转角度计算目标对象的空间位置，由此获得目标对象的三维测量结果。
工作期的长度或者周期可以恒定或变化。在图4的示例中，工作期的长度或者称为扫描光束的发光间隔是恒定的，被记为时间T1。取决于激光雷达系统的具体设计，T1通常为几百纳秒到几微秒。在每个工作期内发射的扫描光束可以是持续一定时间的连续光，也可以是一个或多个光脉冲。不同工作期内发射的扫描光束可以相同或者不同。如图2a至2d所述，激光雷达系统可以按照预定的扫描图案逐工作期发射扫描光束，并启动接收视场中覆盖扫描光束的点云位置的相应接收子模块来接收和检测回波信号。在每个工作期内，由于扫描光束的发射消耗了一定的反转粒子数，因此可以在一定时间长度内抑制ASE光噪声。超过该时间长度后，ASE光噪声逐渐增加，直到下一个工作期的扫描光束被发射后，ASE光噪声再次得到抑制。一般情况下，工作期的长度可以设定得相对较短，足够完成相应接收子模块的接收和检测即可，因此ASE光噪声尚未积累到较大的量值。
此外，为了及时检测到回波信号，可以配置相应接收子模块在扫描光束发射后较近的时间内即启动接收和检测，此时ASE光噪声尚未开始累积或者累积的量依然较小。因此，在工作期内对回波信号的接收和检测基本不会受到ASE光噪声的影响或者受到的影响较小。
图5示出激光雷达系统100在校准期不发光时的示例性工作模式。在开始校准期之前，激光雷达系统可以工作于工作期，如结合图4所描述的。在工作期的后期，ASE光噪声逐渐增加。与工作期不同，在校准期开始时，激光雷达系统不发光，因此不能消耗导致产生ASE光噪声的反转粒子数。而且， 对于光纤激光器，虽然能够通过快速关闭使能控制信号而使其不发光，但其泵浦源很可能无法随着校准期的开始而被快速关闭，从而导致反转粒子数持续增加，ASE光噪声进一步累积，并在一段时间后达到稳定最大值。取决于光纤激光器的内部设计，ASE光噪声从显现到达到稳定最大值的时间通常为几百微秒。在这个过程中，如果依然配置一个或多个接收子模块依次或者同时接收并探测杂散光，则当ASE光噪声增大到一定光噪声阈值时，ASE光噪声对杂散光测量结果的干扰将无法忽略不计，致使测量精度下降。因此，本公开的发明人认识到，对于光纤激光器而言，在考虑ASE光噪声的情况下，在校准期不发光可能并非最佳方案。
鉴于此，本公开的实施例提出在校准期内发射一个或多个校准光束以抑制ASE光噪声，并利用ASE光噪声被抑制的时间段测量杂散光。下面结合图6和图7介绍本公开的实施例的一些方面。
如图7所示，根据本公开的实施例的校准期按时间先后顺序包括光发射区和光检测区。光发射区可以是用于激光雷达系统的光纤激光器发射一个或多个校准光束的时间段。光检测区可以是用于激光雷达系统的光接收器检测杂散光信号的时间段。光发射区和光检测区可以位于校准期内的任何位置，只需保持光发射区在光检测区之前。光发射区可以与光检测区相邻接或不相邻接。在校准期光纤激光器的泵浦源处于开启状态，导致有可能累积ASE光噪声。然而，由于一个或多个校准光束的发射，ASE光噪声在一段时间内得到抑制，然后逐渐增大。将从发射完一个或多个校准光束开始到ASE光噪声逐渐增大到达到光噪声阈值的时间段的长度记为Tmax，则Tmax可以是光检测区的时间长度极限值。光噪声阈值可以根据激光雷达系统的设计以及所应用的具体场景(例如发射光束功率、接收器灵敏度、测距范围等)预先确定。激光雷达系统可以根据发射的一个或多个校准光束(例如根据其强度、时间间隔、数量等)确定Tmax。在达到Tmax时或之前，激光雷达系统被控制成终止光检测区，即停止检测杂散光信号。由此可以确保杂散光信号的检测几乎不或者很少受到ASE光噪声的影响，提高校准测量的准确性，改善校准效果。
图6示出了根据本公开的实施例的激光雷达系统按照图7的校准期配置进行工作的一种具体示例。如图6所示，激光雷达系统的光纤激光器在校准期的光发射区内发射n个校准光束(对应图7的光发射区)，n为大于等于一的整数。n个校准光束按固定时间间隔分布。连续两个校准光束之间的时间间隔为T3。每个校准光束可以是持续一定时间的连续光，也可以是一个或多个光脉冲。各个校准光束可以相同，也可以不同。随着n越大，T3越小，校准光束发射后的ASE光噪声抑制时间越长，但在一定程度后不再进一步改善。因此，可以依据光纤脉冲激光器和系统具体情况选择n和T3的最优值。在一些实施例中，T3小于在正常发光时激光雷达系统发射扫描光束的时间间隔(即图4中的时间T1)。
发射完校准光束后，激光雷达系统的光接收器在光检测区内执行对杂散光信号的测量(对应图7的光检测区)。光检测区的时间长度可以是从校准光束发射完开始到当前校准期结束，记为T2。T2可以小于Tmax。在一些实施例中，T2可以大于T1。在光接收器包括多个接收子模块的情况下，激光雷达系统可以使用所有接收子模块进行校准测量，也可以只需要使用多个接收子模块中的至少一部分进行校准测量。例如，在对激光雷达系统的杂散光信号具有先验知识的情况下，比如可能提前知道某个较强环境光光源的位置，则可以不用使用所有接收子模块来进行接收和检测，而是仅使用与杂散光信号相关联的接收子模块。
在一些实施例中，激光雷达系统可以同时一次性使用所有需要的接收子模块来进行校准测量。这在激光雷达系统的光接收器的并行数据处理能力较强时是可行的。这样，可以在短的时间内快速完成校准测量，所需的ASE光噪声被抑制的时间段可以较短，相应地，所需要的校准光束的数量可以更少，而间隔可以更大。在一些情况下，甚至可能仅需要一个光脉冲作为校准光束。此时，校准光束与正常发光工作期的扫描光束可以相同。校准期和工作期的区别仅在于光接收器进行接收检测的对象和方式不同。在工作期中，光接收器检测的是扫描光束的回波，且通常根据扫描光束的指向仅开启相应的接收子模块。而在校准期，光接收器检测的是杂散光信号，而非校准光束的回波，且可以一次性开启所有的接收子模块来进行检测。
在另一些实施例中，可以将激光雷达系统所需要用到的接收子模块划分成多个接收子模块子组，并且将光检测区划分成多个检测时间段，在各个检测时间段依次使用多个接收子模块子组来检测杂散光信号。将多个接收子模块划分成多个接收子模块子组可以取决于激光雷达系统的光接收器的并行数据处理能力。更具体而言，每个接收子模块子组中的接收子模块的数量可以根据光接收器的并行数据 处理能力确定。在一些情况下，每个接收子模块子组可以仅包括一个接收子模块。在另一些情况下，每个接收子模块子组可以按照接收单元的阵列取一行或多行、一列或多列或者采用其它划分方式。
另一方面，在一个校准期的光检测区设置的多个检测时间段的数量还受限于光检测区的时间长度极限值Tmax。当接收子模块子组的数量较多以至于用来依次使用接收子模块子组进行接收检测的光检测区的多个检测时间段之和超过了光检测区的时间长度极限值Tmax，可以设置两个或更多个校准期，将多个接收子模块子组的接收检测分布在这两个或更多个校准期之内。例如，在图6的示例中，每个接收子模块子组包括接收单元的阵列的一行，而且假设为了检测杂散光信号，需要用到接收单元的阵列的四行，那么一共需要安排四个检测时间段T0。而在一个校准期内根据Tmax最多只允许安排两个检测时间段T0。因此，可以使用两个校准期来完成一次校准测量。两个校准期可以在时间上邻接或者不邻接。在不同校准期内发射的校准光束可以相同，也可以不同。
在一些实施例中，校准期的光发射区和光检测区可以由静默区隔开。静默区是光接收器不检测杂散光信号的时间段。静默区的长度与所发射的一个或多个校准光束从外部反射回到光接收器所需的时间相关联。例如，在图6中，静默区由T4表示。取代将T2作为光检测区，此时仅将T5作为光检测区。这样，光检测区既避开了校准光束的回波的干扰，也避开了ASE光噪声累积至超过光噪声阈值的可能性。在这样的光检测区测得的杂散光信号具有更高的准确性。
图8是用于校准激光雷达系统的方法800的流程图。方法800可以在图1的激光雷达系统100中执行。方法800开始于框802，其中一个或多个处理器可以指示激光雷达系统100的光纤激光器在校准期的光发射区期间发射一个或多个校准光束。该一个或多个处理器可以激光雷达系统100的控制器108中实现。校准光束是指在校准期内发射的光束。校准光束的主要作用是抑制光纤激光器的ASE光噪声。校准光束可以与正常发光的工作期的扫描光束在脉冲数量、持续时间、时间间隔、强度等特性方面相同或不同。
在框804处，一个或多个处理器可以指示激光雷达系统100在校准期的光发射区之后的光检测区期间检测杂散光信号。杂散光信号不同于所发射的一个或多个校准光束的回波信号。杂散光信号可以包括环境光噪声或者来自其它激光雷达系统的脉冲光。在一些示例性实施方式中，激光雷达系统100的光接收器106可以在光检测区期间接收包括校准光束的回波信号和杂散光信号在内的总信号，并基于对校准光束的回波信号的已知信息从总信号中提取出杂散光信号。在另一些示例性实施方式，光接收器106可以避免接收校准光束的回波信号，而仅接收杂散光信号，例如可以按照图6的方式设置静默区。
对光发射区和光检测区的具体配置和实现方式已经结合图6和图7进行了详细介绍，在此不做赘述。
在框806处，一个或多个处理器可以基于所检测的杂散光信号调整激光雷达系统100在后续工作期期间的配置。工作期可以是激光雷达系统100发射扫描光束以对目标对象进行扫描以及接收和检测扫描光束自目标对象反射回的回波信号的时间段。处理器可以根据检测的杂散光信号的特性确定杂散光的类型。例如，若检测到的杂散光对应的电信号为直流信号，则处理器可以确定杂散光信号包括环境光噪声。环境光噪声包括但不限于：日光、路灯光、来自其它车辆的车灯光以及来自其它激光雷达系统的连续光。又例如，如检测到的杂散光对应的电信号为脉冲信号，则处理器可以确定杂散光信号包括来自其它激光激光雷达系统的脉冲光。此外，处理器还可以根据检测的杂散光信号在接收视场中的位置确定受干扰的接收子模块，包括受干扰的接收单元及其相关联接收电路。
在确定杂散光的类型和受干扰的接收子模块后，处理器可以针对性地调整激光雷达系统100在后续工作期期间的配置。对于环境光噪声，调整措施可以包括以下中的一种或多种：
●调整扫描光束反射于受干扰的接收子模块的回波信号对应的激光器的发射功率；
●调整受干扰的接收子模块的灵敏度；以及
●调整受干扰的接收子模块的增益。
例如，当环境光噪声较大时，可以增大相应激光器的发射功率或提高相关接收子模块的灵敏度/增益，使得接收到的扫描光束的回波信号相对于环境光噪声的信噪比提高。而当环境光噪声较小时，则可以减小相应激光器的发射功率或降低相关接收子模块的灵敏度/增益，由此能够节省系统消耗功率。
而对于来自其它激光雷达系统的脉冲光，调整措施可以包括使激光雷达系统在后续工作期期间以 抗串扰工作参数操作。抗串扰工作参数主要用于改善激光雷达系统的光接收器鉴别其自身扫描光束的回波信号与来自其它激光雷达系统的脉冲光的能力。具体来说，以抗串扰工作参数操作包括调整与受干扰的接收子模块对应的激光器的脉冲重复频率、工作波长或强度分布等，由此能够与其他激光雷达系统的脉冲光区分开。
激光雷达系统按照预设扫描图案控制扫描器产生不同的偏转。当从扫描起点到达扫描终点后，需要一段时间来使扫描器的偏转位置回到扫描起点以便进行下一轮扫描，这段过程称为回扫期。相应地，扫描器的偏转位置从扫描起点到扫描终点的过程称为扫描期。扫描期和回扫期共同构成了激光雷达系统对发射视场进行一次扫描的一帧。图9a和9b分别示出激光雷达系统进行行列光栅式扫描时的扫描线示意图和对应的激光器发光点云示意图。通常，为了让扫描器快速回到扫描起点，回扫期的偏转位置数量较少，对应的点云数量也较少。如图9a中，密集曲线902表示扫描期，而稀疏曲线904表示回扫期。由于回扫期的点云数量较少，测量数据难以得到利用，因此在回扫期内激光雷达系统的资源实际上处于闲置状态。
图10示出根据本公开的实施例的激光雷达系统对校准期(例如图7中所示的校准期)的不同时间配置方式。根据本公开的实施例的校准期可以安排在一帧的扫描期或回扫期内的任何位置。
在一些示例性实施方式中，激光雷达系统的一个或多个校准期可以设置在扫描期内。在一些情况下，校准期可以与工作期重叠复用。此时，扫描光束被用作校准光束。激光雷达系统在发射扫描光束/校准光束后可以在较近的一段时间内接收并检测扫描光束/校准光束的回波信号，并在工作期/校准期内之后的时间段测量杂散光信号。在另一些情况下，校准期可以与工作期交织穿插出现。例如，激光雷达系统可以对扫描图案的每个像素点分别进行安排工作期和校准期，在工作期内发射扫描光束进行目标对象的测量，而在校准期内发射校准光束进行杂散光信号的检测。这种方式既可适用于同轴光学收发系统，也可适用于非同轴光学收发系统。
在另一些示例性实施方式中，激光雷达系统的一个或多个校准期可以设置在回扫期内。这样可以避免激光雷达系统在回扫期的资源闲置。这种方式可以适用于同轴光学收发系统，但尤其适用于非同轴光学收发系统。对于非同轴光学收发系统而言，在回扫期内虽然发射视场不断变化，但接收视场是与扫描器的偏转位置无关的，因而可以遍历一个或多个接收子模块，测量接收视场内更大范围的杂散光信号。校准期可以安排在回扫期的任意位置。若需要遍历的接收子模块的数量较多，可以将整个回扫期都填充上校准期；若接收子模块的数量较少，可以只选择回扫期的部分时间段安排校准期。如前所述，每个校准期选择的接收子模块可以是一个或多个，根据接收系统的并行数据处理能力或其它设计因素而定。通常来说，回扫期的时间长度短于扫描期的时间长度。为了遍历所有需要的接收子模块，每个接收子模块的开启时间相较工作期内接收子模块的开启时间可以更短。
在一些实施例中，校准期可以按照固定周期执行，例如每帧或者每多个帧设置一次或多次，而无需任何事件触发。
根据本公开的实施例的工作期可以位于扫描期内(如图10所示)，但在一些情况下也可以位于回扫期内(未示出)。
在一些实施例中，根据本公开的实施例的校准激光雷达系统的技术可以在激光雷达系统内部的一个或多个处理器实现，例如由控制器实现。在另一些实施例中，当激光雷达系统被安装在车辆装置中时，根据本公开的实施例的校准激光雷达系统的技术也可以在车辆装置的一个或多个处理器中实现，例如由车辆控制器实现。或者，根据本公开的实施例的校准激光雷达系统的技术可以由车辆控制器和激光雷达系统的控制器协同实现。
图11示出根据本公开的实施例的集成了激光雷达系统的车辆1100的组成示意图。车辆1100至少可以包括激光雷达系统1102、车辆控制器1104和机动系统1106。激光雷达系统1102可以使用图1中的激光雷达系统100实现。相应地，光源1112、扫描器1114、光接收器1116和控制器1118分别与激光雷达系统100的光源102、扫描器104、光接收器106和控制器108对应。不同之处在于，车辆控制器1104可以通过控制器1118与光源1112、扫描器1114和光接收器1116通信耦接。在另一些实施例中，车辆控制器1104也可以直接与光源1112、扫描器1114和光接收器1116通信耦接。在一些实施例中，激光雷达系统1102可以不包括控制器1118。根据本公开的实施例的校准激光雷达系统的技术可以由车辆控制器1104独立实现，也可以部分由车辆控制器1104、部分由控制器1118来协同实现。机动 系统1106可以包括动力子系统、制动子系统和转向子系统等。车辆控制器1104可以根据激光雷达系统1102的探测结果调整机动系统1106。
此外，根据本公开的实施例的校准激光雷达系统的技术也可以以计算机可读指令的形式在电子设备中被实现。
图12示出了根据本公开的实施例的电子设备1200的配置框图。电子设备1200可以用于执行根据本公开的实施例的校准激光雷达系统的方法，例如方法800。电子设备1200可为任何类型的通用或专用计算设备，诸如台式计算机、膝上型计算机、服务器、大型计算机、基于云的计算机、平板计算机、可穿戴设备、车辆电子装置等。如图12所示，电子设备1200包括输入输出(Input/Output,I/O)接口1201、网络接口1202、存储器1204和处理器1203。
I/O接口1201是可以从用户接收输入和/或向用户提供输出的组件的集合。I/O接口1201可以包括但不限于按钮、键盘、小键盘、LCD显示器、LED显示器或其它类似的显示设备，包括具有触摸屏能力使得能够进行用户和电子设备之间的交互的显示设备。
通信接口1202可以包括各种适配器以及以软件和/或硬件实现的电路系统，以便能够使用有线或无线协议与激光雷达系统通信。有线协议例如是串口协议、并口协议、以太网协议、USB协议或其它有线通信协议中的任何一种或多种。无线协议例如是任何IEEE 802.11Wi-Fi协议、蜂窝网络通信协议等。
存储器1204包括单个存储器或一个或多个存储器或存储位置，包括但不限于随机存取存储器(RAM)、动态随机存取存储器(DRAM)、静态随机存取存储器(SRAM)、只读存储器(ROM)、EPROM、EEPROM、闪存、FPGA的逻辑块、硬盘或存储器层次结构的任何其他各层。存储器1204可以用于存储任何类型的指令、软件或算法，包括用于控制电子设备1200的一般功能和操作的指令1205。
处理器1203控制电子设备1200的一般操作。处理器1203可以包括但不限于CPU、硬件微处理器、硬件处理器、多核处理器、单核处理器、微控制器、专用集成电路(ASIC)、DSP或其他类似的处理设备，能够执行根据本公开中描述的实施例的用于控制电子设备1200的操作和功能的任何类型的指令、算法或软件。处理器1203可以是在计算系统中执行功能的数字电路系统、模拟电路系统或混合信号(模拟和数字的组合)电路系统的各种实现。处理器1203可以包括例如诸如集成电路(IC)、单独处理器核心的部分或电路、整个处理器核心、单独的处理器、诸如现场可编程门阵列(FPGA)的可编程硬件设备、和/或包括多个处理器的系统。
可以使用内部总线1206来建立电子设备1200的组件之间的通信。
电子设备1200通信耦接到待校准的激光雷达系统，以控制激光雷达系统的操作。例如，可以将根据本公开的校准方法以计算机可读指令的形式存储在电子设备1200的存储器1204上。处理器1203通过读取所存储的计算机可读指令来实施校准方法。
尽管使用特定组件来描述电子设备1200，但是在替选实施例中，电子设备1200中可以存在不同的组件。例如，电子设备1200可以包括一个或多个附加处理器、存储器、网络接口和/或I/O接口。另外，电子设备1200中可能不存在组件的一个或多个。另外，尽管在图12中示出单独的组件，但是在一些实施例中，给定组件的一些或全部可以集成到电子设备1200中的其他组件中的一个或多个中。
本公开可以被实现为装置、系统、集成电路和非瞬时性计算机可读介质上的计算机程序或程序产品的任何组合。
应当理解，根据本公开实施例的计算机可读存储介质或程序产品中的计算机可执行指令可以被配置为执行与上述设备和方法实施例相应的操作。当参考上述设备和方法实施例时，计算机可读存储介质或程序产品的实施例对于本领域技术人员而言是明晰的，因此不再重复描述。用于承载或包括上述计算机可执行指令的计算机可读存储介质和程序产品也落在本公开的范围内。这样的存储介质可以包括但不限于软盘、光盘、磁光盘、存储卡、存储棒等等。
另外，应当理解，上述系列处理和设备也可以通过软件和/或固件实现。在通过软件和/或固件实现的情况下，在相关设备的存储介质存储构成相应软件的相应程序，当所述程序被执行时，能够执行各种功能。
例如，在以上实施例中包括在一个单元中的多个功能可以由分开的装置来实现。替选地，在以上 实施例中由多个单元实现的多个功能可分别由分开的装置来实现。另外，以上功能之一可由多个单元来实现。这样的配置包括在本公开的技术范围内。
在本公开中，流程图中所描述的步骤不仅包括以所述顺序按时间序列执行的处理，而且包括并行地或单独地而不是必须按时间序列执行的处理。此外，甚至在按时间序列处理的步骤中，也可以适当地改变该顺序。
本公开实施例的术语“包括”、“包含”或者其任何其他变体意在涵盖非排他性的包含，从而使得包括一系列要素的过程、方法、物品或者设备不仅包括那些要素，而且还包括没有明确列出的其他要素，或者是还包括为这种过程、方法、物品或者设备所固有的要素。在没有更多限制的情况下，由语句“包括一个……”限定的要素，并不排除在包括所述要素的过程、方法、物品或者设备中还存在另外的相同要素。
本公开中的术语“或”表示包括性的“或”，而非排除性的“或”。提及的“第一”组件不必然要求提供“第二”组件。此外，除非明确指示，否则“第一”或“第二”组件不表示将提及的组件限制于特定顺序。术语“基于”意指“至少部分基于”。

Claims (29)

  1. 一种用于校准激光雷达系统的方法，其中，所述激光雷达系统包括光纤激光器，所述方法包括：
    由一个或多个处理器指示所述光纤激光器在校准期的光发射区期间发射一个或多个校准光束；
    由所述一个或多个处理器指示所述激光雷达系统在所述校准期的在所述光发射区之后的光检测区期间检测杂散光信号，所述杂散光信号包括环境光噪声或来自其它激光雷达系统的脉冲光；以及
    由所述一个或多个处理器基于所检测的所述杂散光信号调整所述激光雷达系统在后续工作期期间的配置。
  2. 根据权利要求1所述的方法，其中，所述光检测区与所述光发射区由静默区隔开，所述静默区的长度与所发射的一个或多个所述校准光束从外部反射回所述激光雷达系统的时间相关联，所述方法还包括：
    在所述校准期的所述静默区期间，由所述一个或多个处理器指示所述激光雷达系统不检测所述杂散光信号。
  3. 根据权利要求1所述的方法，其中，所述校准期被设置在所述激光雷达系统的回扫期内，在所述回扫期内所述激光雷达系统的扫描器从扫描终点返回到扫描起点。
  4. 根据权利要求3所述的方法，其中，所述激光雷达系统为非同轴光学收发系统。
  5. 根据权利要求1所述的方法，其中，所述校准期被设置在所述激光雷达系统的扫描期的至少一部分内，在所述扫描期内所述激光雷达系统的扫描器从扫描起点行进到扫描终点。
  6. 根据权利要求1所述的方法，其中，所述指示所述激光雷达系统检测杂散光信号包括：
    将所述激光雷达系统的多个接收单元的至少一部分划分成多个接收单元子组；以及
    在所述光检测区期间使所述激光雷达系统依次使用多个所述接收单元子组检测所述杂散光信号。
  7. 根据权利要求1所述的方法，其中，所述指示所述激光雷达系统检测杂散光信号包括：
    基于所发射的一个或多个所述校准光束确定一个或多个所述校准光束到所述光纤激光器产生的放大自发辐射(ASE)光噪声增大到达到光噪声阈值的第一时间；以及
    在所述第一时间到期时或之前，指示所述激光雷达系统停止检测所述杂散光信号。
  8. 根据权利要求1所述的方法，其中，在所述校准期内，所述光纤激光器的泵浦源开启。
  9. 根据权利要求1所述的方法，其中基于所检测的杂散光信号调整激光雷达系统在后续工作期期间的配置包括：
    基于所检测的杂散光信号确定所述杂散光信号包括环境光噪声以及确定受干扰的接收单元；以及
    基于确定所述杂散光信号包括环境光噪声以及确定受干扰的接收单元，调整激光雷达系统在后续工作期期间的配置，包括以下至少一个：
    调整扫描光束反射于受干扰的接收单元的回波信号对应的激光器的发射功率；
    调整受干扰的接收单元及其相关联接收电路的灵敏度；以及
    调整受干扰的接收单元及其相关联接收电路的增益。
  10. 根据权利要求1所述的方法，其中基于所检测的杂散光信号调整激光雷达系统在后续工作期期间的配置包括：
    基于所检测的杂散光信号确定所述杂散光信号包括来自其它激光雷达系统的脉冲光以及确定受干扰的接收单元；以及
    基于确定所述杂散光信号包括来自其它激光雷达系统的脉冲光以及确定受干扰的接收单元，调整激光雷达系统在后续工作期期间的配置，包括：使激光雷达系统在后续工作期期间以抗串扰工作参数操作。
  11. 一种激光雷达系统，其中，包括：
    光源，被配置为发射光，所述光源包括光纤激光器；
    扫描器，被配置为引导所述光以扫描目标对象；
    光接收器，被配置为检测由所述目标对象反射的光；以及
    控制器，所述控制器与所述光源、所述扫描器和所述光接收器通信地耦接，所述控制器被配置为校准所述激光雷达系统，包括：
    指示所述光纤激光器在校准期的光发射区期间发射一个或多个校准光束；
    指示所述光接收器在所述校准期的在所述光发射区之后的光检测区期间检测杂散光信号，所述杂散光信号包括环境光噪声或来自其它激光雷达系统的脉冲光；以及
    基于所检测的所述杂散光信号调整所述激光雷达系统在后续工作期期间的配置。
  12. 根据权利要求11所述的激光雷达系统，其中，所述光检测区与所述光发射区由静默区隔开，所述静默区的长度与所发射的一个或多个所述校准光束从外部反射回所述激光雷达系统的时间相关联，所述控制器还被配置为：
    在所述校准期的所述静默区期间，指示所述激光雷达系统不检测所述杂散光信号。
  13. 根据权利要求11所述的激光雷达系统，其中，所述校准期被设置在所述激光雷达系统的回扫期内，在所述回扫期内所述激光雷达系统的扫描器从扫描终点返回到扫描起点。
  14. 根据权利要求13所述的激光雷达系统，其中，所述激光雷达系统为非同轴光学收发系统。
  15. 根据权利要求11所述的激光雷达系统，其中，所述校准期被设置在所述激光雷达系统的扫描期的至少一部分内，在所述扫描期内所述激光雷达系统的扫描器从扫描起点行进到扫描终点。
  16. 一种车辆，其中，包括：
    激光雷达系统，包括光纤激光器；以及
    车辆控制器，与所述激光雷达系统通信地耦接，所述车辆控制器被配置为执行根据权利要求1-10中任一项所述的用于校准激光雷达系统的方法。
  17. 根据权利要求16所述的车辆，其中，所述激光雷达系统还包括：
    光源，被配置为发射光，所述光源包括所述光纤激光器；
    扫描器，被配置为引导所述光以扫描目标对象；
    光接收器，被配置为检测由所述目标对象反射的光；以及
    控制器，所述控制器与所述光源、所述扫描器、所述光接收器及所述车辆控制器通信地耦接，所述控制器和/或所述车辆控制器用于：
    指示所述光纤激光器在校准期的光发射区期间发射一个或多个校准光束；
    指示所述光接收器在所述校准期的在所述光发射区之后的光检测区期间检测杂散光信号，所述杂散光信号包括环境光噪声或来自其它激光雷达系统的脉冲光；以及
    基于所检测的所述杂散光信号调整所述激光雷达系统在后续工作期期间的配置。
  18. 根据权利要求17所述的车辆，其中，所述光检测区与所述光发射区由静默区隔开，所述静默区的长度与所发射的一个或多个所述校准光束从外部反射回所述激光雷达系统的时间相关联，所述控制器和/或所述车辆控制器还用于在所述校准期的所述静默区期间，指示所述激光雷达系统不检测所述杂散光信号。
  19. 根据权利要求17所述的车辆，其中，所述校准期被设置在所述激光雷达系统的回扫期内，在所述回扫期内所述激光雷达系统的扫描器从扫描终点返回到扫描起点。
  20. 根据权利要求19所述的车辆，其中，所述激光雷达系统为非同轴光学收发系统。
  21. 根据权利要求17所述的车辆，其中，所述校准期被设置在所述激光雷达系统的扫描期的至少一部分内，在所述扫描期内所述激光雷达系统的扫描器从扫描起点行进到扫描终点。
  22. 根据权利要求17所述的车辆，其中，所述控制器和/或所述车辆控制器还用于将所述激光雷达系统的多个接收单元的至少一部分划分成多个接收单元子组；以及在所述光检测区期间使所述激光雷达系统依次使用多个所述接收单元子组检测所述杂散光信号。
  23. 根据权利要求17所述的车辆，其中，所述控制器和/或所述车辆控制器还用于基于所发射的一个或多个所述校准光束确定一个或多个所述校准光束到所述光纤激光器产生的放大自发辐射(ASE)光噪声增大到达到光噪声阈值的第一时间；以及在所述第一时间到期时或之前，指示所述激光雷达系统停止检测所述杂散光信号。
  24. 根据权利要求17所述的车辆，其中，在所述校准期内，所述光纤激光器的泵浦源开启。
  25. 根据权利要求17所述的车辆，其中，所述控制器和/或所述车辆控制器用于基于所检测的杂散光信号确定所述杂散光信号包括环境光噪声以及确定受干扰的接收单元；
    在基于确定所述杂散光信号包括所述环境光噪声以及确定受干扰的接收单元的情况下，所述控制 器和/或所述车辆控制器还用于执行调整扫描光束反射于受干扰的接收单元的回波信号对应的激光器的发射功率；调整受干扰的接收单元及其相关联接收电路的灵敏度；以及调整受干扰的接收单元及其相关联接收电路的增益中的至少一个。
  26. 根据权利要求17所述的车辆，其中，所述控制器和/或所述车辆控制器用于基于所检测的杂散光信号确定所述杂散光信号包括来自其它激光雷达系统的脉冲光以及确定受干扰的接收单元；
    在基于确定所述杂散光信号包括来自所述脉冲光以及确定受干扰的接收单元的情况下，所述控制器和/或所述车辆控制器还用于使所述激光雷达系统在后续工作期期间以抗串扰工作参数操作。
  27. 一种电子设备，其中，包括：
    处理器；以及
    存储器，通信耦接到所述处理器并且存储计算机可读指令，所述计算机可读指令在由所述处理器执行时，使得所述电子设备执行根据权利要求1-10中任一项所述的用于校准激光雷达系统的方法。
  28. 一种存储有计算机可读指令的计算机可读存储介质，所述计算机可读指令在由电子设备的处理器执行时，使得电子设备执行如权利要求1-10中任一项所述的方法。
  29. 一种包括计算机可读指令的计算机程序产品，所述计算机可读指令在由电子设备的处理器执行时，使得电子设备执行如权利要求中1-10任一项所述的方法。
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