WO2020259327A1 - 一种激光雷达及激光雷达的探测方法 - Google Patents

一种激光雷达及激光雷达的探测方法 Download PDF

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Publication number
WO2020259327A1
WO2020259327A1 PCT/CN2020/095952 CN2020095952W WO2020259327A1 WO 2020259327 A1 WO2020259327 A1 WO 2020259327A1 CN 2020095952 W CN2020095952 W CN 2020095952W WO 2020259327 A1 WO2020259327 A1 WO 2020259327A1
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laser
laser beams
module
detection
lidar
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PCT/CN2020/095952
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English (en)
French (fr)
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王振伟
曾理
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华为技术有限公司
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Publication of WO2020259327A1 publication Critical patent/WO2020259327A1/zh
Priority to US17/557,381 priority Critical patent/US20220113417A1/en

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    • 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
    • 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
    • G01S7/481—Constructional features, e.g. arrangements of optical elements
    • G01S7/4814—Constructional features, e.g. arrangements of optical elements of transmitters alone
    • 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
    • G01S17/06—Systems determining position data of a target
    • G01S17/08—Systems determining position data of a target for measuring distance only
    • 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
    • G01S17/06—Systems determining position data of a target
    • G01S17/42—Simultaneous measurement of distance and other co-ordinates
    • 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
    • G01S17/89—Lidar systems specially adapted for specific applications for mapping or imaging
    • 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
    • G01S7/481—Constructional features, e.g. arrangements of optical elements
    • 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
    • G01S7/481—Constructional features, e.g. arrangements of optical elements
    • G01S7/4817—Constructional features, e.g. arrangements of optical elements relating to scanning
    • 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
    • G01S7/483—Details of pulse systems
    • G01S7/486—Receivers
    • G01S7/487—Extracting wanted echo signals, e.g. pulse detection
    • 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
    • G01S7/491—Details of non-pulse systems
    • G01S7/4911—Transmitters
    • 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
    • G01S7/491—Details of non-pulse systems
    • G01S7/4912—Receivers
    • G01S7/4913—Circuits for detection, sampling, integration or read-out
    • G01S7/4914—Circuits for detection, sampling, integration or read-out of detector arrays, e.g. charge-transfer gates
    • 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
    • G01S7/491—Details of non-pulse systems
    • G01S7/4912—Receivers
    • G01S7/4917—Receivers superposing optical signals in a photodetector, e.g. optical heterodyne detection
    • 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
    • G01S17/06—Systems determining position data of a target
    • G01S17/08—Systems determining position data of a target for measuring distance only
    • G01S17/32—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
    • G01S17/34—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
    • 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
    • G01S7/491—Details of non-pulse systems
    • G01S7/493—Extracting wanted echo signals

Definitions

  • This application relates to the field of laser detection technology, and in particular to a laser radar and a detection method of laser radar.
  • LiDAR light detection and ranging
  • LiDAR is a radar system that emits laser beams to detect the location and speed of a target.
  • the working principle of lidar is to transmit a detection signal (laser beam) to a target object (such as a vehicle, aircraft or missile), and then compare and process the received signal (echo signal) reflected from the target object with the transmitted signal , Can obtain the relevant information of the target object, such as target distance, azimuth, height, speed, posture, even shape and other parameters, so that the target object can be detected, tracked and identified.
  • lidars include pulse-based time-of-flight (TOF) ranging lidar and frequency modulated continuous wave (frequency modulated continuous waveform, FMCW) coherent ranging lidar.
  • TOF time-of-flight
  • FMCW frequency modulated continuous wave
  • the laser beam emitted by the FMCW radar is a frequency-modulated continuous laser.
  • the laser beam is divided into two, one of which is used as a local reference light, and the other is used as a probe light to be emitted towards the detection area. , Reflect the echo signal, the detector calculates the distance of the object through the echo signal and the intrinsic reference light.
  • the ranging resolution of FMCW lidar is c/2B, where c is the speed of light, and B is the modulation (frequency sweep) bandwidth.
  • a frequency modulation bandwidth above 10GHz is required.
  • the frequency modulation above 10GHz requires a frequency modulation time of much greater than the order of microseconds (usually on a time scale of sub-milliseconds) In this way, the scanning and ranging time of a target point generally takes more than 10 -4 seconds, that is, only about 10,000 points can be scanned per second. If the frame rate is considered to be 24 frames per second, then there are only about 400 points per frame. In this way, the density of the point cloud is also low, and the sharpness of the image is also low.
  • the present application provides a lidar and lidar detection method, which are used to increase the associated information of the target object obtained in one scan, so as to increase the density of the point cloud determined according to the associated information of the target object, thereby improving the clarity of the image .
  • this application provides a laser radar, which includes a laser, N first beam splitting modules, an included angle adjustment module, N detection modules, a scanning module, and a processing control module, where N is an integer greater than 1.
  • the laser is used to emit N laser beams and transmit the N laser beams to the N first beam splitting modules.
  • each first beam splitting module is used to divide the received laser beam into a first laser beam and a second laser beam to obtain the N th One laser beam and N second laser beams.
  • the included angle adjustment module is used to receive N second laser beams from N first beam splitting modules, and adjust the included angle between any two adjacent second laser beams among the N second laser beams to be greater than 0 degrees and not greater than the angular resolution of the lidar.
  • the scanning module is used to receive N second laser beams from the beam angle adjustment module, and respectively emit N second laser beams to the detection area at different detection angles.
  • each detection module is used to receive the first laser beam from the corresponding first beam splitting module, and to receive the corresponding echo signal, and to compare the received first laser beam Mix with the echo signal to obtain a beat signal, and determine the associated information of the target object in the detection area according to the beat signal, wherein the corresponding echo signal is from the corresponding first beam splitting module The signal reflected by the second laser beam in the detection area.
  • the processing control module is used to control the scanning module at different detection angles.
  • the N laser beams correspond to the N first beam splitting modules one-to-one, that is, one laser beam can be directed to one first beam splitting module.
  • the N first beam splitting modules correspond to the N detection modules in a one-to-one correspondence.
  • one detection module has a corresponding first beam splitting module.
  • the i-th detection module corresponds to the i-th first beam splitting module.
  • one echo signal corresponds to a second laser beam emitted into the detection area, that is, N second laser beams correspond to N echo signals, and N echo signals correspond to N second laser beams.
  • the i-th second laser beam corresponds to the i-th echo signal, where i is an integer greater than 0 and less than N.
  • the angle between any two adjacent second laser beams among the N second laser beams is adjusted to be greater than 0 degrees and not greater than the angular resolution of the lidar, that is, each second laser beam Interlace to scan the detection area.
  • the scanning module emits N second laser beams to the detection area for detection, which can reflect back N echo signals, one echo signal and one first laser beam can be
  • the associated information of a target object is determined, and N associated information can be determined according to the N echo signals and the corresponding N first laser beams. That is to say, through the lidar of the present application, more related information can be obtained in one detection process. Because the related information of the target object can be used to form an image, the point cloud density determined based on more related information is also higher. , The formed image definition is also higher.
  • the frequency modulation rate of the laser beam can be changed to avoid the crosstalk between the echo signals as much as possible.
  • Implementation mode one is to adopt modulator modulation.
  • the lidar further includes a modulator.
  • the modulator is used to modulate the N laser beams from the laser according to a first preset condition, where the first preset condition is that two laser beams with an included angle smaller than the preset angle adopt different frequency modulation rates.
  • Implementation mode two is to use laser modulation.
  • the laser is also used to modulate N laser beams according to a first preset condition, where the first preset condition is that two laser beams with an included angle smaller than the preset angle use different frequency modulation rates.
  • the laser performs tuning of the wavelength (frequency) of the laser beam according to the first preset condition, where the laser radar may include N lasers.
  • the two laser beams after modulation can be Corresponding echo signals will not affect each other, that is, help reduce crosstalk between echo signals.
  • the N laser beams are modulated according to the first preset condition, and the obtained laser beams are all frequency modulated continuous wave FMCW.
  • the FMCW measures the associated information of the target object based on the principle of coherent detection, it is generally difficult for the interference light from the external environment to coherently generate the beat signal with the intrinsic light. Therefore, the laser beam being FMCW helps to improve the anti-jamming capability of the lidar.
  • the Doppler effect can also be used to measure the movement rate of the target object relative to the lidar, which helps expand the application scenarios of lidar.
  • the processing control module is also used to control the synchronization between the scanning module and the modulator.
  • the processing control module is also used to control the synchronization between the scanning module, the detection module and the modulator.
  • the processing control module is also used to control the synchronization between the scanning module and the laser.
  • the processing control module is also used to control the synchronization between the scanning module, the laser and the detection module.
  • the beam angle adjustment module includes N optical fibers and a collimator, and the N optical fibers correspond to the N second laser beams in a one-to-one correspondence.
  • each optical fiber is used to receive the second laser beam from the corresponding first beam splitting module, and transmit the received second laser beam to the collimator.
  • the collimator is used to receive N second laser beams from N optical fibers and collimate the N second laser beams to obtain that the angle between any two adjacent second laser beams is greater than 0 degrees and not N second laser beams larger than the angular resolution of the lidar.
  • the light exits of the N fibers may all be located on the object focal plane of the collimator.
  • the scanning module may be located on the image-side focal plane of the collimator.
  • the lidar In order to transmit the echo signal to the corresponding detection module, the lidar also includes N light splitting modules. For each splitting module in the N splitting modules, each splitting module is used to transmit the received echo signal to the corresponding detection module, where the N splitting modules correspond to the N echo signals one-to-one. It can be understood that one second laser beam corresponds to one echo signal, one echo signal corresponds to one optical splitting module, and one echo signal corresponds to one detection module.
  • the i-th echo signal corresponds to the i-th optical splitting module and the i-th detection module. After the i-th optical splitting module receives the i-th echo signal, the i-th echo signal can be transmitted to the i-th echo signal.
  • a detection module For each splitting module in the N splitting modules, each splitting module is used to transmit the received echo signal to the corresponding detection module, where the N splitting modules correspond to the N echo signals one-to-one. It can be understood that one second laser beam corresponds to one echo signal, one echo signal corresponds to one optical splitting module,
  • the laser beam can be transmitted in space or through optical fibers.
  • the optical splitting module may be an optical fiber circulator, and the optical fiber circulator is located between the first beam splitting module and the included angle adjusting module.
  • the laser and the N first beam splitting modules, the N first beam splitting modules and the N fiber circulators, and the N fiber circulators and the included angle adjustment module are all connected by optical fibers.
  • this application provides a laser radar, which includes a laser, N first beam splitting modules, N detection modules, an optical phased array (OPA), and a processing control module.
  • the laser is used to emit N laser beams and transmit the N laser beams to the N first beam splitting modules.
  • each first beam splitting module is used to divide the received laser beam into a first laser beam and a second laser beam.
  • OPA is used to receive N second laser beams from N first beam splitting modules, and adjust the angle between any two adjacent second laser beams in the N second laser beams to be greater than 0 degrees and not It is greater than the angular resolution of the lidar, and the angle between any two adjacent second laser beams is emitted to the detection area at different detection angles is greater than 0 degrees and not greater than the N second of the angular resolution of the lidar Laser beam.
  • each detection module is used to receive the first laser beam from the corresponding first beam splitting module and the corresponding echo signal from the detection area, and The first laser beam and the echo signal are mixed to obtain a beat frequency signal, and the associated information of the target object in the detection area is determined according to the beat frequency signal.
  • the processing control module is used to control the OPA at different detection angles.
  • the N laser beams correspond to the N first beam splitting modules one-to-one, that is, one laser beam can be directed to one first beam splitting module.
  • the N first beam splitting modules correspond to the N detection modules one-to-one.
  • one detection module has a corresponding first beam splitting module.
  • the i-th detection module corresponds to the i-th first beam splitting module.
  • one echo signal corresponds to a second laser beam emitted into the detection area, that is, N second laser beams correspond to N echo signals, and N echo signals correspond to N second laser beams.
  • the i-th second laser beam corresponds to the i-th echo signal, where i is any integer from 1 to N.
  • the angle between any two adjacent second laser beams among the N second laser beams is adjusted to be greater than 0 degrees and not greater than the angular resolution of the lidar, that is, each second laser beam Staggered from each other, OPA emits N second laser beams to the detection area for detection at each detection angle, which can reflect back N echo signals, one echo signal and one first laser beam can determine the target object Associated information, N associated information can be determined based on N echo signals and corresponding N first laser beams. That is to say, through the lidar of the present application, more related information can be obtained in one detection process, that is, more scanning points can be obtained in one scanning process. Since the related information of the target object can be used to form an image, it is based on more information. The density of the point cloud determined by the associated information is also higher, and the resulting image definition is also higher.
  • OPA can phase-modulate the wavefronts of N second laser beams to obtain that the angle between any two adjacent second laser beams is greater than 0 degrees and not greater than the laser The angular resolution of the radar N second laser beam.
  • the present application provides a detection method of lidar, which can be applied to lidar, and the method includes dividing each of the N laser beams into a first laser beam and a second laser beam.
  • the angular resolution of the radar, and the adjusted N second laser beams are respectively emitted to the detection area at different detection angles; N echo signals from the detection area are received, and the N echo signals are transmitted into the detection area
  • the N second laser beams corresponding to each of the N echo signals are one-to-one; for each echo signal of the N echo signals, the echo signal is mixed with the corresponding first laser beam to obtain the beat frequency signal, and according to the beat frequency
  • the signal determines the associated information of the target object in the detection area.
  • the N laser beams are modulated according to a first preset condition; wherein, the first preset condition is: two laser beams with an included angle less than the preset angle adopt different frequency modulation rates.
  • the N laser beams are modulated according to the first preset condition, and the obtained laser beams are all frequency modulated continuous wave FMCW.
  • this application provides a lidar, which includes a module/unit that executes any of the above-mentioned third aspects or any possible implementation of the third aspect.
  • These modules/units can be realized by hardware, or by hardware executing corresponding software.
  • the present application provides a computer storage medium that stores program instructions that, when the program instructions run on the lidar, cause the lidar to execute the third aspect or any possible implementation of the third aspect above The method in the way.
  • this application provides a computer program product that, when the computer program product runs on a lidar, causes the lidar to execute the above-mentioned third aspect or any possible implementation method of the third aspect.
  • Fig. 1 is a schematic diagram of detection of a lidar provided by this application
  • FIG. 2 is a schematic diagram of the structure of a lidar provided by this application.
  • 3a is a schematic diagram of a light splitting principle diagram of a second beam splitting module provided by this application.
  • FIG. 3b is a schematic diagram of a light splitting principle diagram of another second beam splitting module provided by this application.
  • Figure 3c is a schematic diagram of the relationship between a laser and a laser beam provided by this application.
  • 3d is a schematic diagram of the relationship between another laser and laser beam provided by this application.
  • FIG. 4a is a schematic diagram of mixing processing of a second laser beam and echo signal provided by this application.
  • 4b is a schematic diagram of another second laser beam and echo signal mixing processing provided by this application.
  • 4c is a schematic diagram of another second laser beam and echo signal mixing processing provided by this application.
  • FIG. 5 is a schematic diagram of another relationship between a laser and a laser beam provided by this application.
  • FIG. 6 is a schematic structural diagram of an included angle adjustment module provided by this application.
  • Fig. 7a is a schematic structural diagram of a scanner provided by this application.
  • Figure 7b is a schematic diagram of a two-dimensional multi-beam scanning track provided by this application.
  • Figure 7c is a schematic structural diagram of another scanner provided by this application.
  • Figure 7d is a schematic diagram of another two-dimensional multi-beam scanning track provided by this application.
  • Fig. 8a is a schematic structural diagram of a lidar provided by this application.
  • FIG. 8b is a schematic structural diagram of another lidar provided by this application.
  • FIG. 8c is a schematic structural diagram of another lidar provided by this application.
  • FIG. 9 is a schematic flowchart of a method for detecting a lidar provided by this application.
  • Lidar usually works by emitting high-frequency electromagnetic waves and receiving electromagnetic energy scattered by the target. By comparing and analyzing the received echo signal and detection signal, it can extract target-related information, such as target location information.
  • Fig. 1 is a schematic diagram of a laser radar detection provided by this application. Lidar includes lasers and detectors. The laser emits a laser beam in a certain direction. If there is a target within a certain distance along the emitting direction of the laser beam, the laser beam can be reflected on the surface of the target. Figure 1 takes the target A in the emitting direction of the laser beam 1 as an example.
  • the laser beam 1 emitted by the laser is reflected on the surface of the target A, and the reflected signal is returned to the lidar detector as an echo signal ,
  • the detector can determine the associated information of target A based on the echo signal and local signal, such as the location information of target A.
  • Lidar can be used as a vehicle-mounted lidar (such as a scanning vehicle-mounted FMCW lidar), an airborne lidar, and other scenarios that require high accuracy.
  • lidar can also be installed on mobile platforms, such as satellites. In this case, the lidar needs the assistance of other devices in the mobile platform to determine its current position and steering information, so as to ensure the availability of measurement data.
  • the mobile platform may also include a global positioning system (GPS) device and an inertial measurement unit (IMU) device.
  • GPS global positioning system
  • IMU inertial measurement unit
  • the lidar can combine the measurement data of the GPS device and the IMU device to obtain the location of the target object. , Speed and other characteristic quantities.
  • the radar can provide geographic location information of the mobile platform through the GPS device in the mobile platform, and record the posture and steering information of the mobile platform through the IMU device.
  • the GPS device After determining the distance to the target object according to the echo signal, at least one of the geographic location information provided by the GPS device or the attitude and steering information provided by the IMU device can be used to convert the measurement point of the target object from the relative coordinate system
  • the geographic location information of the target object is obtained, so that the lidar can be applied to a moving platform. It is understandable that the lidar in this application can also be applied to autonomous driving scenarios, or can also be applied to connected car scenarios, and so on.
  • FIG. 2 exemplarily shows a schematic structural diagram of a laser radar provided by the present application.
  • the lidar includes a laser, N first beam splitting modules, an included angle adjustment module, N detection modules, a scanning module, and a processing control module.
  • the laser is used to emit N laser beams and transmit the N laser beams to the N first beam splitting modules.
  • each first beam splitting module is used to divide the received laser beam into a first laser beam and a second laser beam to obtain the N th One laser beam and N second laser beams.
  • the k-th first beam-splitting module among the N first beam-splitting modules is used to divide the received laser beam into the k-th first laser beam and the k-th second laser beam, and k is taken as Pass 1 to N.
  • the first laser beam is a local signal, which can also be called intrinsic light
  • the second laser beam is a detection signal, which can also be called detection light.
  • the included angle adjustment module is used to receive N second laser beams from N first beam splitting modules and adjust the included angle between any two adjacent second laser beams among the N second laser beams to Greater than 0 degrees and not greater than the angular resolution of the lidar.
  • the scanning module is used to receive N second laser beams from the beam angle adjustment module, and respectively emit N second laser beams to the detection area at different detection angles.
  • each detection module is used to receive the first laser beam from the corresponding first beam splitting module and the corresponding echo signal from the detection area, and The first laser beam and the echo signal are mixed to obtain a beat frequency signal, and the associated information of the target object in the detection area is determined according to the beat frequency signal.
  • the k-th detection module of the N detection modules is used to receive the k-th first laser beam from the k-th first beam splitting module and the k-th echo signal from the detection area , The k-th first laser beam and the k-th echo signal are mixed to obtain a beat signal, and the associated information of the target object in the detection area is determined according to the beat signal, and k is taken from 1 to N.
  • the processing control module is used to control the scanning module at different detection angles. It should be understood that the processing control module can control the scanning module to step at a certain detection angle, or it can be continuously rotated to a certain detection angle, and the scanning module can be at different detection angles. At each detection angle, it is directed to the detection area. Launch N second laser beams.
  • the N laser beams correspond to the N first beam splitting modules one to one
  • the N first beam splitting modules correspond to the N detection modules one to one
  • N is an integer greater than 1. It can also be understood that one laser beam can be transmitted to one first beam splitting module, and one first beam splitting module can correspond to one detection module.
  • the angular resolution of the lidar which can also be referred to as the scanning resolution of the lidar, refers to the preset angle between adjacent laser beams directed toward the detection area, or refers to the detection area The desired angle between adjacent laser beams.
  • the angle between any two adjacent second laser beams among the N second laser beams is adjusted to be greater than 0 degrees and not greater than the angular resolution of the lidar, that is, each second laser beam
  • the beams are interlaced to scan the detection area.
  • the scanning module emits N second laser beams to the detection area for detection at each detection angle, which can reflect back N echo signals, one echo signal and one first laser beam
  • the associated information of a target object can be determined, and N associated information can be determined based on the N echo signals and the corresponding N first laser beams. That is to say, through the lidar of the present application, more related information can be obtained in one detection process. Because the related information of the target object can be used to form an image, the point cloud density determined based on more related information is also higher. , The formed image definition is also higher. It should be understood that there can be one or more target objects.
  • N laser beams can be output by N lasers, or after a laser beam is output by one laser, N laser beams can be obtained by beam splitting through the beam splitting module; or K laser beams can be output by K lasers.
  • the laser beam is then split by one or more of the K laser beams through the beam splitting module to obtain N laser beams, where K is an integer less than N.
  • the laser radar may include one laser, or N lasers, or K lasers. The following are divided into three situations to explain separately.
  • Case 1 Lidar includes a laser.
  • the lidar also includes a second beam splitting module, the second beam splitting module is located between the laser and the first beam splitting module, the second beam splitting module is used to divide a laser beam emitted by the laser into N Laser beam. As shown in FIG. 3a, the second beam splitting module divides one laser beam emitted by the laser into three laser beams for example.
  • the second beam splitting module may be a diffractive optical element (DOE), and the DOE may evenly divide a laser beam from the laser into N laser beams, one of the N laser beams.
  • the transmission direction may be different or the same. It can be understood that the number of laser beams divided by the DOE and the interval between the laser beams can be determined by the physical structure of the DOE. That is, the physical structure of the DOE can be determined according to the interval between the N laser beams.
  • the first beam splitting module and the second beam splitting module can be the same.
  • the first beam splitting module is a DOE
  • the second beam splitting module may be a polarizing beam splitter (polarizing beam splitter, PBS) array.
  • PBS polarizing beam splitter
  • FIG. 3b it is a light splitting principle diagram of another second beam splitting module provided in this application.
  • Fig. 3b takes the example of dividing a laser beam emitted by the laser into three laser beams.
  • the laser injects a laser beam into the PBS array.
  • the PBS can divide the incident laser beam into two vertical linearly polarized lights, namely P-polarized light and S-polarized light.
  • the P-polarized light passes through completely and serves as the incident laser beam of the next PBS.
  • the S-polarized light is reflected to the corresponding first beam splitting module at an angle of 45 degrees, and the exit direction of the S-polarized light is at a 90-degree angle with the P-polarized light.
  • N laser beams can be reflected from N PBSs.
  • the first beam splitting module may be a PBS in the PBS array.
  • Case 2 Lidar includes N lasers.
  • Fig. 3c takes three lasers as an example. It should be understood that the N laser beams emitted by the N lasers may have a certain angle between them, or they may be parallel.
  • the lidar includes K lasers.
  • the first beam splitting module further includes a second beam splitting module.
  • the second beam splitting module please refer to the introduction of the above scenario 1, which will not be repeated here.
  • the laser when the lidar is used as a vehicle-mounted radar, the laser can emit a laser with a wavelength of 905 nm or a laser beam with a wavelength of 1550 nm.
  • the laser may be a semiconductor laser or a fiber laser.
  • the target object After the second laser beam is projected onto the target object by the scanning module, the target object will reflect the echo signal.
  • the detection module After the echo signal is transmitted to the detection module, the detection module performs mixing processing on the echo signal and the first laser beam.
  • the detection module can convert the echo signal and the beat signal of the first laser beam into an analog signal or a digital signal through photoelectric conversion.
  • the echo signal of one second laser beam may be injected into the corresponding detection of another second laser beam.
  • Module which in turn causes crosstalk between the two echo signals.
  • the two laser beams are laser beam A and laser beam B.
  • the laser beam A can be divided into the first laser beam A and the second laser beam A by the first beam splitting module.
  • the echo signal of the second laser beam A is the return signal.
  • the laser beam B can be divided into a first laser beam B and a second laser beam B by the first beam splitting module.
  • the echo signal of the second laser beam B is the echo signal B.
  • the echo signal A may be incident on the detection module corresponding to the second laser beam B, and the echo signal B may also be incident on the second laser beam.
  • the detection module corresponding to beam A the detection module may perform mixing processing on the echo signal A and the first laser beam B, and perform mixing processing on the echo signal B and the first laser beam A, thereby resulting in the echo signal A And the crosstalk between echo signal B.
  • the formation of a beat signal between the first laser beam and the echo signal generally requires: in the modulation period, the frequency modulation rate of the first laser beam and the frequency modulation rate of the echo signal are consistent within the frequency modulation duration (for example, ,the same). Based on this, the frequency modulation rate of the N laser beams can be changed to avoid crosstalk between echo signals as much as possible.
  • the N laser beams can be modulated according to the first preset condition to reduce the crosstalk between echo signals.
  • the first preset condition is that two laser beams with an included angle smaller than the preset angle adopt different frequency modulation rates.
  • the preset angle may be a critical angle at which echo signals corresponding to two laser beams generate crosstalk. It should be noted that the preset angle is related to the receiving angle (also referred to as the field of view) of the detection module.
  • the frequency modulation rate of the FM bandwidth, Kr i B i / t to frequency modulation.
  • the frequency modulation duration t refers to the frequency modulation duration starting from the initial frequency at the starting time of the frequency modulation.
  • the modulation mode of the laser beam may be a sawtooth wave modulation mode or a triangular wave modulation mode, which is not limited in this application.
  • the FM duration is either the up FM duration or the down FM duration.
  • the frequency modulation bandwidth B i refers to the difference between the frequency from the initial frequency to the maximum frequency within an upward frequency modulation period.
  • the frequency modulation duration t T.
  • the N laser beams are modulated according to the first preset condition.
  • This application can provide the following two possible implementation manners.
  • one laser beam corresponds to one frequency modulation rate, that is, N laser beams correspond to N frequency modulation rates one to one, and the N frequency modulation rates are different from each other.
  • the p-th laser beam may be modulated by the m-th frequency modulation rate
  • the q-th laser beam may be modulated by the n-th frequency modulation rate
  • the m-th frequency modulation rate and the n-th frequency modulation rate Different, the p-th laser beam is also different from the q-th laser beam.
  • the m-th frequency modulation rate is one of the N frequency modulation rates
  • the n-th frequency modulation rate is the m-th frequency modulation rate divided by the N frequency modulation rates.
  • the one outside the frequency modulation rate, the p-th laser beam and the q-th laser beam are different two of the N laser beams.
  • the three types of first laser beams and echo signals provided in this application are mixed with the echo signal.
  • the laser beam A can be divided into the first laser beam A and the second laser beam A by the first beam splitting module, and the echo signal A is the echo signal of the second laser beam A
  • the laser beam B can be divided into a first laser beam B and a second laser beam B by the first beam splitting module, and the echo signal B is the echo signal of the second laser beam B.
  • the modulation periods of the laser beam A and the laser beam B are both T, and the modulation modes are both triangular wave modulation.
  • the laser beam A is modulated by the frequency modulation rate Kr 1 and the frequency modulation bandwidth B 1.
  • the frequency modulation rate of the first laser beam is consistent with the frequency modulation rate of the echo signal within the frequency modulation time period, that is, the frequency modulation rate of the first laser beam A
  • the frequency modulation rate and the frequency modulation rate of the corresponding echo signal A are the same within the frequency modulation duration t.
  • the time when the echo signal A reaches the detection module is delayed by ⁇ 1 compared with the time when the first laser beam A reaches the detection module. Therefore,
  • the frequency f 1 Kr 1 * ⁇ 1 of the beat signal obtained after the echo signal A and the first laser beam A are mixed.
  • the frequency modulation rate Kr 1 may be the first frequency modulation rate among the N frequency modulation rates.
  • the laser beam B is modulated by the frequency modulation rate Kr 2 and the frequency modulation bandwidth B 2.
  • the frequency modulation rate of the first laser beam and the frequency modulation rate of the echo signal are the same within the frequency modulation duration, that is, the frequency modulation rate of the first laser beam B
  • the frequency modulation rate and the frequency modulation rate of the corresponding echo signal B are the same within the frequency modulation time length t.
  • the time when the echo signal B reaches the detection module is delayed by ⁇ 2 compared with the time when the first laser beam B reaches the detection module. Therefore,
  • the frequency modulation rate difference between the first laser beam A and the echo signal B is relatively large, (that is, the first laser beam A and the echo signal B are not coherent signals), so mixing processing cannot be performed. No beat signal can be obtained. It can also be understood that even if the echo signal B is injected into the detection module corresponding to the first laser beam A, it will not affect the formation of a beat signal between the first laser beam A and the echo signal A. Therefore, the echo signal B will not interfere with The echo signal A affects. In this way, the problem of crosstalk between echo signals can be avoided.
  • the detection light (second laser beam) or echo signal of vehicle-mounted FMCW lidar of other vehicles may cause damage to the detection module of the vehicle. interference.
  • N laser beams correspond to M frequency modulation rates, and the M frequency modulation rates are different from each other, where M is an integer less than N.
  • the angle between the laser beams is relatively large (for example, greater than the preset angle), the crosstalk between the echo signals corresponding to the second laser beam after the splitting of the laser beams is relatively small .
  • the three laser beams are laser beam a, laser beam b, and laser beam c respectively.
  • the angle between laser beam a and laser beam b is The angle between laser beam b and laser beam c is not greater than the preset angle, and the angle between laser beam a and laser beam c is greater than the preset angle, then laser beam a and laser beam c can be
  • the laser beam b can be modulated by one frequency modulation rate (Kr 4 ), and the laser beam b can be modulated by another frequency modulation rate (Kr 5 ).
  • the crosstalk between the echo signals corresponding to laser beam a and laser beam c is relatively small, even if the same frequency modulation rate is used for laser beam a and laser beam c for modulation, the crosstalk between each other is still small.
  • the angle between the laser beam a and the laser beam b is relatively small, the crosstalk between the echo signals corresponding to the laser beam a and the laser beam b will be relatively large, but it can also be modulated by different frequency modulation rates.
  • Reduce the crosstalk between the echo signals corresponding to the laser beam a and the laser beam b (the principle can be referred to the introduction of Fig. 4a, Fig. 4b and Fig. 4c).
  • different frequency modulation rates between the laser beam b and the laser beam c can also be used to reduce the crosstalk between the echo signals corresponding to the laser beam b and the laser beam c.
  • the modulation of the laser beam can be modulated by a modulator or laser.
  • the modulator may be an external modulator.
  • the modulation by a modulator can generally be frequency modulation by an acousto-optic modulator or an electro-optic modulator.
  • a wavelength tunable laser can be used to modulate N laser beams by a laser.
  • Acousto-optic modulator usually refers to an acousto-optic device that controls the intensity of the laser beam.
  • Acousto-optic modulation is an external modulation technology.
  • Electro-optical modulator refers to a modulator made by the electro-optical effect of certain electro-optical crystals, such as lithium niobate crystal (LiNb03), gallium arsenide crystal (GaAs) and lithium tantalate crystal (LiTa03).
  • the electro-optical effect means that when a voltage is applied to the electro-optical crystal, the refractive index of the electro-optical crystal will change, resulting in a change in the characteristics of the light wave passing through the crystal, realizing the modulation of the phase, amplitude, intensity, frequency and polarization state of the optical signal .
  • the wavelength tunable laser can change the wavelength as required.
  • One of the ways to change the wavelength is to change the injection current to change the refractive index of the luminescent material, thereby changing and controlling the output wavelength of the laser within a certain range. There are roughly three principles for achieving laser wavelength tuning.
  • the first is to change the wavelength of the laser by changing the wavelength corresponding to the low-loss region of the resonator by some elements (such as gratings).
  • the second is to move the energy level of the laser transition by changing some external parameters (such as magnetic field, temperature, etc.).
  • the third is to use nonlinear effects to achieve wavelength conversion and tuning (such as nonlinear optics, stimulated Raman scattering, etc.).
  • the lidar also includes N modulators, N modulators correspond to N laser beams, and N modulators correspond to N laser beams.
  • the frequency modulation rate corresponds to one-to-one, that is, each modulator uses a frequency modulation rate to modulate the incident laser beam, where the N frequency modulation rates are different from each other.
  • the lidar may also include M modulators.
  • the emitted laser beams modulated by the same modulator can be divided into two or more than two.
  • Each modulator in the M frequency modulation rates passes One frequency modulation rate modulates the incident laser beam, M modulators correspond to M frequency modulation rates one-to-one, and M different frequency modulation rates are different from each other.
  • the laser included in the laser radar may be any of the above-mentioned case 1, case 2 or case 3.
  • the lidar includes N lasers, and N lasers correspond to N different frequency modulation rates. That is, the laser can achieve N by changing the wavelength (or frequency). Each laser uses N different frequency modulation rates.
  • the lidar includes M lasers, and the M lasers correspond to M different frequency modulation rates.
  • the frequency modulation rate used can be the same, and in order to minimize the second laser beam split between the two laser beams
  • the angle between the two laser beams in the laser beams emitted by the same laser should be relatively large, for example, greater than the preset angle.
  • laser beam A and laser beam C can be emitted by one laser
  • laser beam B can be emitted by another laser
  • laser beam A and laser beam C The angle between the two is relatively large, so the crosstalk between the echo signals corresponding to the laser beam A and the laser beam C is relatively small.
  • the angle between the laser beam B and the laser beam A can be small or large, and the angle between the laser beam B and the laser beam C can be small or large. If the angle between the laser beam B and the laser beam A is small and/or the angle between the laser beam B and the laser beam C is small, the two lasers can use different frequency modulation rates to modulate the laser beams, specifically , These two lasers are realized by wavelength tuning.
  • the two lasers can use the same frequency modulation rate to modulate the laser beam, or Use different frequency modulation rates to modulate the laser beam.
  • M lasers need to emit N laser beams
  • the lidar also needs to include a second beam splitting module, which can be arranged between the laser and the first beam splitting module, and the second beam splitting module
  • the laser beams emitted by one or more of the M lasers can be split to realize that the M lasers emit N laser beams.
  • the second beam splitting module refer to the introduction of the second beam splitting module in the above scenario 1, which will not be repeated here.
  • the echo signals corresponding to the different second laser beams can only be mixed with the respective first laser beams to obtain the beat signal, which can effectively avoid the echo signal.
  • the detection module includes a signal receiving unit and a data acquisition unit.
  • the signal receiving unit may be a detector, such as any one of a PIN-type photodiode (also known as a PIN junction diode), an avalanche photodiode (APD), a PIN-type photodiode array, an APD array, or a PIN-type photodiode.
  • a balanced detection formed by a combination of photodiodes a balanced detection formed by a combination of APD, or a balanced detection formed by a combination of PIN photodiode arrays, or a balanced detection formed by a combination of APD arrays.
  • the signal receiving unit may be a detector
  • the data acquisition unit may be an analog-to-digital converter or an analog-to-digital converter (ADC).
  • the angle between the second laser beams needs to be adjusted to ensure that any of the N second laser beams
  • the angle between two adjacent second laser beams is greater than 0 degree and not greater than the angular resolution of the laser radar.
  • the angle between the N second laser beams can be adjusted by the combination of the fiber array and the collimator, or by the optical phased array (OPA), or by reflection
  • OPA optical phased array
  • the combination of mirrors is adjusted, so I won’t list them all here.
  • the structure of the combination of the optical fiber array and the collimator and the OPA are introduced in detail as follows.
  • the beam angle adjustment module includes N optical fibers and a collimator, and the N optical fibers correspond to the N second laser beams one-to-one, that is, one second laser beam can be coupled into one optical fiber.
  • each optical fiber is used to receive the second laser beam from the corresponding first beam splitting module, and transmit the received second laser beam to the collimator.
  • the kth optical fiber among the N optical fibers is used to receive the kth second laser beam from the kth first beam splitting module, and transmit the kth second laser beam to the collimator , K is taken from 1 to N.
  • the collimator is used to receive N second laser beams from N optical fibers, and to collimate the N second laser beams, so that the angle between any two adjacent second laser beams is greater than 0 N second laser beams that are not greater than the angular resolution of the lidar.
  • the collimator may be a collimating lens.
  • N optical fibers form an optical fiber array, and the intervals between the optical fibers may be equal or unequal.
  • the distance between the optical fibers and the focal length of the collimator can be controlled to realize that the angle between any two adjacent second laser beams among the N second laser beams emitted from the optical fiber and the collimator is greater than 0 degrees And not greater than the angular resolution of lidar. That is to say, the angle between any two adjacent second beams in the N second laser beams can be greater than 0 degrees and not greater than The angular resolution of the lidar.
  • the angle ⁇ between two adjacent second laser beams can be determined by the following formula (1).
  • the angle ⁇ between any adjacent second laser beams in the N second laser beams is equal.
  • the angle ⁇ between the adjacent second laser beams in the N second laser beams is also not equal.
  • the scanning module can be set on the collimator lens The image side is on the focal plane.
  • the scanning module may be a scanner, such as a reflective scanner.
  • Reflective scanners include but are not limited to mechanical rotating mirrors and MEMS micro galvanometers.
  • the reflective scanner changes the scanning direction of the scanner by mechanical rotation.
  • the scanning module is a reflective scanner, the reflective surface of the reflective scanner can be set on the image-side focal plane of the collimating lens.
  • the spots of the N second laser beams can be overlapped on the reflective surface of the scanner, and since the reflective surface of the scanner does not change the angle between the second laser beams, when the reflective scanner surrounds each other perpendicularly
  • the N second laser beams can be projected into the detection area by the scanner, and the angle between any two adjacent second laser beams is greater than 0 degrees and not greater than the lidar The angular resolution.
  • the scanner may be in a continuous operation mode or a stepping operation mode.
  • the included angle adjustment module is used to transmit the N second laser beams to the scanning module, and project them to the detection area through the scanning module.
  • Lidar can scan the detection area by changing the detection angle of the scanning module.
  • the lidar can preset multiple detection angles, and the scanning module can emit N second laser beams to the detection area at each detection angle of the multiple detection angles, so as to obtain the relevant information of the target object in the detection area, such as Distance; and then the scanned image (also called image) is obtained by analyzing the associated information of the target object.
  • FIG. 7a a schematic structural diagram of a scanner provided for the application.
  • the scanner can change the detection angle in two-dimensional directions (horizontal and vertical directions), and changing the detection angle can also be understood as making the scanner under different detection angles.
  • Figure 7a takes three second laser beams as an example. Under a detection angle, three second laser beams are projected to the detection area through the scanner to obtain three scanning points.
  • Figure 7a shows different filling patterns with different filling patterns. Scan point.
  • the detection angle is continuously changed, and the three second laser beams are continuously projected to the detection area, and a schematic diagram of the two-dimensional multi-beam scanning trajectory as shown in FIG. 7b can be obtained.
  • the scanning trajectory may be obtained by controlling the scanner to scan according to a preset scanning mode by the processing control module.
  • the processing control module controls the scanner to rotate the scanner in a two-dimensional direction, so that the scanner is scanned at different detection angles to obtain the scanning track.
  • the processing control module can control the scanning module to rotate horizontally and then vertically, or vertically and then horizontally, or vertically and horizontally together, or alternately rotating horizontally and vertically.
  • FIG. 7c a schematic structural diagram of another scanner provided for the application.
  • the scanner can change the detection angle in a one-dimensional direction (horizontal direction), so that the scanner is at different detection angles.
  • Fig. 7c takes three second laser beams as an example. Under a detection angle, three second laser beams are projected to the detection area through the scanner, and three scanning points are obtained.
  • Fig. 7c shows different filling patterns with different filling patterns. Scan point.
  • the scanner reflects the three incoming second laser beams to the detection area, the scanning points of each second laser beam present a one-dimensional distribution, and multiple second laser beams perform one-dimensional scanning to form a picture
  • the two-dimensional multi-beam scanning track shown in 7d Through the one-dimensional scanner, the volume of the lidar can be simplified, and the complexity of the control of the processing control module can be simplified.
  • the rotation axis of the one-dimensional scanner can be positioned on the N second laser beams when the scanner is assembled and adjusted. In the plane of incidence.
  • the one-dimensional scanner is only responsible for scanning the N second laser beams along one dimension (horizontal dimension shown in Figure 7c).
  • the angular resolution can be controlled by the processing control module.
  • the angular resolution in the vertical dimension is It is the angle between two adjacent second laser beams, and it can also be understood that the angular resolution in the vertical dimension can be determined by the angle adjustment module.
  • the functions of the aforementioned included angle adjustment module and scanning module can also be implemented through OPA.
  • the working principle of OPA is: by adjusting the phase relationship between the light waves radiated from each phase control unit (such as an optical phase shifter) so that they are in phase with each other in the set direction, resulting in mutually reinforcing interference.
  • the result of the interference is A high-intensity beam is generated in this direction, but the light waves emitted from the phase control units in other directions do not meet the condition of being in phase with each other, and the results of interference cancel each other out, so the radiation intensity is close to zero.
  • the phase control units that make up the phased array can scan the direction of a high-intensity laser beam or multiple high-intensity laser beams according to a designed program.
  • OPA can receive N second laser beams from N first beam splitting modules, and adjust the angle between any two adjacent second laser beams in the N second laser beams to be greater than 0 degrees and not greater than the angular resolution of the lidar, and the angle between any two adjacent second laser beams is emitted to the detection area at different detection angles is greater than 0 degrees and not greater than the angular resolution of the lidar N second laser beams.
  • the N second laser beams are injected into the OPA, and the phase adjustment of the wavefronts of the N second laser beams is performed by the OPA, so that any two adjacent ones of the N second laser beams
  • the angle between the second laser beams is adjusted to be greater than 0 degrees and not greater than the angular resolution of the lidar, and the N second laser beams scan the same field of view. It can also be understood that the N second laser beams scan the same field of view in a non-overlapping manner.
  • OPA performs two-dimensional scanning to obtain the scanning trajectory shown in FIG. 7b; performing one-dimensional scanning to obtain the scanning trajectory shown in FIG. 7d.
  • the lidar further includes N optical splitting modules, where the N optical splitting modules correspond to the N echo signals in a one-to-one correspondence. For each optical splitting module of the N optical splitting modules, each optical splitting module uses To transmit the received echo signal to the corresponding detection module. Or, it can also be understood that the k-th optical splitting module among the N optical splitting modules is used to transmit the k-th echo signal to the k-th detection module, and k is taken from 1 to N.
  • the light splitting module can be a perforated reflector, or it can be a PBS, or it can be a fiber circulator.
  • the beam splitting module is a perforated reflector
  • the hole of the perforated reflector can transmit the second laser beam to the included angle adjustment module
  • the reflector surface of the perforated reflector can reflect the echo signal to the corresponding detection module.
  • the light splitting module is a PBS
  • the second laser beam is transmitted from the PBS to the included angle adjustment module, and the echo signal is reflected to the corresponding detection module.
  • the optical splitting module is an optical fiber circulator
  • the second laser beam can be emitted from one port to the included angle adjustment module, and the echo signal can be emitted from the other port to the corresponding detector.
  • the k-th optical splitting module is used to transmit the k-th echo signal to the k-th detection module, and the k-th optical splitting mode does not affect the original optical path of the k-th second laser beam, and k is taken Pass 1 to N.
  • the kth echo signal is transmitted to the detector via the optical splitting module, the kth echo signal is collinear with the corresponding kth second laser beam, which is also called coaxial.
  • the processing control module when the N laser beams are modulated by the laser radar through the modulator, the processing control module is also used to control the synchronization between the scanner and the modulator.
  • the processing control module is also used to control the synchronization between the scanner and the laser. That is, the processing control module can control the scanning module to be at different detection angles, and can also be used to control the synchronization between the scanning module and the modulator; or, to control the synchronization between the scanning module and the laser.
  • the processing control module can also control the synchronization between the scanning module, the modulator and the detection module.
  • the processing control module is also used to control the synchronization between the scanning module, the laser and the detection module.
  • the synchronization between the laser and the scanning module is aimed at the synchronization between the frequency modulation of the laser and the scanning module; the synchronization between the laser, the detection module, and the scanning module mainly refers to the laser The frequency modulation, detection module, and scanning module are synchronized.
  • the processing control module may first control the scanning module to project N second laser beams to the detection area at a detection angle, and at the same time trigger the modulator (or laser) to perform frequency modulation on the N laser beams within a frequency modulation cycle. Modulation (see the above introduction for the detailed process). After the frequency modulation period ends, the modulator (or laser) stops modulation. The N second laser beams after frequency modulation are emitted by the scanning module to reach the detection area. After encountering the target object, the echo signals are reflected respectively, and they are respectively transmitted to the corresponding detection module through the corresponding optical splitting module.
  • the processing control module triggers the detection module
  • the data acquisition unit collects the echo signal and the beat signal after mixing the first laser beam, and then the processing control module obtains the associated information of the target object according to the beat signal, and processes the associated information of the target object to obtain an image. After that, the processing control module controls the scanning module to be at the next detection angle, and repeats the above process.
  • the signal receiving unit in the detection module can always receive the corresponding first laser beam and echo signal.
  • the processing control module may include a processing unit and a control unit.
  • the processing unit may be a general-purpose processor, a field programmable gate array (FPGA), and a signal data processing (digital signal processing, DSP) circuit, application specific integrated circuit (ASIC), or other programmable logic devices.
  • the control unit includes the drive of the scanner, the drive of the modulator, the frequency modulation drive of the laser, the drive of the detector, etc. These drives can be integrated or separate.
  • the FPGA can send control signals to each drive of the control unit, so that the drive of the scanner controls the scanning module, the drive of the modulator controls the modulator, and the drive of the detector controls the detection module to realize the scanning module, detection module and modulation Synchronization between the scanners; or, the drive of the scanner controls the scanning module, the frequency modulation of the laser drives the frequency modulation of the laser, and the drive controls the detection module of the detector to realize the frequency modulation between the scanning module, the detection module and the laser. Synchronize.
  • the FPGA can send a control signal to the drive of the scanning module, and the drive of the scanning module can control the scanner at a certain detection angle according to the control signal.
  • the laser beam in the lidar can be transmitted in space or through optical fibers.
  • FIG. 8a it is a schematic diagram of another Lidar structure provided in this application.
  • the beam of the lidar is transmitted in space.
  • the lidar includes a laser, N first beam splitting modules, included angle adjustment modules, N detectors, scanners, processing control modules, and N light splitting modules. Among them, there is a one-to-one correspondence between N first beam splitting modules, N detectors, and N optical splitting modules.
  • the included angle adjustment module is a combined structure of an optical fiber array and a collimator, which can be referred to the introduction of Figure 6 above, and will not be repeated here.
  • the spectroscopic module can be a perforated mirror or PBS.
  • the scanner is a reflective type, which can be referred to the introduction of Fig. 7a or Fig. 7c, which will not be repeated here.
  • N first beam splitting modules, N detectors, and processing control modules please refer to the introduction of the above corresponding content respectively, which will not be repeated here.
  • Fig. 8b it is a schematic diagram of another Lidar structure provided by this application.
  • the beam of the lidar is transmitted in space.
  • the lidar includes a laser, N first beam splitting modules, N detectors, OPA, processing control module, and N light splitting modules. Among them, there is a one-to-one correspondence between N first beam splitting modules, N detectors, and N optical splitting modules.
  • the difference from Fig. 8a is that the functions of the included angle adjustment module and the scanner are implemented by OPA, and the detailed introduction of OPA can be found in the above content, which will not be repeated here.
  • FIG. 8c another schematic diagram of the structure of a lidar is provided for this application.
  • the beam of the lidar is transmitted in the optical fiber.
  • the lidar includes a laser, N first beam splitting modules, included angle adjustment modules, N detectors, scanners, processing control modules, and N light splitting modules. Among them, there is a one-to-one correspondence between N first beam splitting modules, N detectors, and N optical splitting modules.
  • the splitting module is a fiber circulator, between the laser and the N first splitting modules, N first splitting modules and N optical fibers
  • the circulators, N optical fiber circulators and the included angle adjustment module can all be connected by optical fibers. The remaining parts can be referred to the introduction of Fig. 8a above, and will not be repeated here.
  • the lidar adopts a fiber-optic architecture, because after the laser emits a laser beam, the laser beam can enter the first beam splitting module, the fiber circulator, and the included angle adjustment module sequentially along the fiber channel, and then enter the scanning In this way, the optical path debugging process of the lidar can be simplified, and the installation process can be relatively simple.
  • the N laser beams are modulated according to the first preset condition, and the obtained laser beams may all be frequency modulated continuous wave FMCW.
  • FMCW measures the associated information of the target object based on the principle of coherent detection.
  • the frequency difference between the interference light of the external environment and the intrinsic light is relatively large. Therefore, it is difficult for the interference light of the external environment to coherently generate a beat signal with the intrinsic light. Therefore, the laser beam being FMCW helps to improve the anti-jamming capability of the lidar.
  • the Doppler effect can also be used to measure the movement rate of the target object relative to the lidar, thereby helping to expand the application scenarios of the lidar.
  • the detection method of lidar provided by this application can be referred to the introduction of FIG. 9 below.
  • the lidar detection method can be applied to the lidar of any of the above embodiments. As shown in Figure 9, the method includes the following steps:
  • Step 901 Divide each of the N laser beams into a first laser beam and a second laser beam to obtain N first laser beams and N second laser beams.
  • N is an integer greater than 1
  • the N laser beams can be the N laser beams emitted by the laser in the lidar.
  • the first beam splitting module may divide the laser beam into the first laser beam and the second laser beam.
  • the specific process please refer to the introduction of the first beam splitting module in the foregoing embodiment, which will not be repeated here.
  • one first laser beam corresponds to one second laser beam, that is, the N first laser beams and the N second laser beams have a one-to-one correspondence.
  • Step 902 Adjust the included angle between any two adjacent second laser beams among the N second laser beams to be greater than 0 degrees and not greater than the angular resolution of the lidar, and respectively detect at different detection angles The area emits adjusted N second laser beams.
  • the angular resolution of the lidar which can also be called the scanning resolution of the lidar, refers to the preset angle between the adjacent laser beams directed to the detection area, or refers to the adjacent The desired angle between the laser beams.
  • the adjustment of the included angle between the N second laser beams can be adjusted by the structure of the combination of the optical fiber array and the collimator, or by the OPA method, or by the combination of mirrors, I won't list them all here.
  • the structure of the combination of the optical fiber array and the collimator and the implementation of the OPA adjusting the included angle between the adjacent second laser beams, please refer to the introduction of the above-mentioned included angle adjusting module, which is not repeated here.
  • the processing control module may control the detection module to respectively emit adjusted N second laser beams to the detection area at different detection angles, and control the scanning module to scan in the detection area.
  • the specific process can be parameterized as described above The introduction to the detection module, scanning module and processing control module will not be repeated here.
  • Step 903 Receive N echo signals from the detection area.
  • a second laser beam corresponds to one echo signal.
  • N second laser beams are directed to the detection area and can reflect back N echo signals.
  • the N echo signals correspond to the N second laser beams emitted into the detection area one to one.
  • Step 904 For each of the N echo signals, the echo signal is mixed with the corresponding first laser beam to obtain N beat frequency signals, and the detection area is determined according to the beat frequency signals. Related information of the target object.
  • the i-th laser beam can be any laser beam of the N laser beams, and the i-th laser beam can be divided into the i-th first laser beam and the i-th laser beam.
  • the i-th second laser beam After the i-th second laser beam is directed to the detection area, it can reflect back the i-th echo signal, and the i-th first laser beam and the i-th echo signal can be mixed. Get the beat signal.
  • step 904 From step 901 to step 904, it can be seen that the angle between any two adjacent second laser beams among the N second laser beams is adjusted to be greater than 0 degrees and not greater than the angular resolution of the lidar, that is Each second laser beam is interlaced to scan the detection area.
  • the scanning module emits N second laser beams to the detection area for detection at each detection angle, which can reflect back N echo signals, one echo signal and one
  • the first laser beam can determine the associated information of a target object, and the N associated information can be determined according to the N echo signals and the corresponding N first laser beams. That is to say, through the lidar of the present application, more related information can be obtained in one detection process. Because the related information of the target object can be used to form an image, the point cloud density determined based on more related information is also higher. , The formed image definition is also higher.
  • the echo signal of one second laser beam may be injected into the corresponding detection of another second laser beam.
  • Module which in turn causes crosstalk between the two echo signals.
  • the present application may modulate N laser beams.
  • N laser beams may be modulated according to a first preset condition.
  • the two laser beams whose angles are smaller than the preset angle adopt different frequency modulation rates.
  • the specific modulation process please refer to the introduction of the first implementation and the second implementation in the detection module, which will not be repeated here.
  • the N laser beams are modulated according to the first preset condition, and the obtained laser beams are all frequency modulated continuous wave FMCW.
  • the Doppler effect can be used to measure the rate of movement of the target object relative to the lidar, thereby helping to expand the application scenarios of the lidar.

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Abstract

一种激光雷达及激光雷达的探测方法，激光雷达可应用于自动驾驶、网联车等领域，其中激光雷达包括：激光器用于发射N个激光束，并将N个激光束传输至N个第一分束模块。第一分束模块用于将接收到的激光束分为第一激光束和第二激光束。夹角调整模块用于接收N个第二激光束，并将N个第二激光束中任意相邻的两个第二回波信号之间的夹角调整为大于0度且不大于角分辨率。扫描模块用于接收N个第二激光束，并在不同探测角度下发射N个第二激光束。探测模块用于接收第一激光束和对应的回波信号，并进行混频处理得到拍频信号，根据拍频信号确定目标物体的关联信息。如此，可得到较多的关联信息，从而可提高形成图像的点云密度，从而提高图像的清晰度。

Description

一种激光雷达及激光雷达的探测方法
相关申请的交叉引用
本申请要求在2019年06月26日提交中国专利局、申请号为201910561295.2、申请名称为“一种激光雷达及激光雷达的探测方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及激光探测技术领域，尤其涉及一种激光雷达及激光雷达的探测方法。
背景技术
激光雷达(light detection and ranging，LiDAR)为发射激光束探测目标的位置、速度等特征量的雷达系统。激光雷达的工作原理是向目标物体(例如车辆、飞机或导弹)发射探测信号(激光束)，然后将接收到的从目标物体反射回来的信号(回波信号)与发射信号进行比较和处理后，可获得目标物体的有关信息，如目标距离、方位、高度、速度、姿态、甚至形状等参数，从而可对目标物体进行探测、跟踪和识别。
目前，常用的车载激光雷达包括基于脉冲飞行时间(time-of-flight，TOF)测距激光雷达和调频连续波(frequency modulated continuous waveform，FMCW)相干测距激光雷达。其中，由于FMCW激光雷达采用的是相干探测技术，外界环境的干扰光难以和本地参考光(local reference)相干混频产生拍频信号，因此FMCW雷达的抗干扰性能相对比较好。FMCW雷达发射的激光束为频率调制的连续激光，将激光束一分为二，其中一束作为本地参考光，另一束作为探测光向探测区域发射，探测光遇到探测区域的目标物体后，反射回波信号，探测器通过回波信号和本征参考光来计算物体的距离。
然而，FMCW激光雷达的测距分辨率为c/2B，c为光速，B为调制(扫频)带宽。为了达到厘米级别距离分辨率，则需要10GHz以上的调频带宽，对于车载FMCW激光雷达，频率调制到10GHz以上的带宽需要远大于微秒量级的调频时间(一般在亚毫秒以上的时间尺度)，这样，对一个目标点的扫描测距时间一般需要10 -4秒以上，即一秒只能扫描1万点左右，如果考虑帧频为24帧/秒，则每帧画面只有400个点左右，这样点云密度也较低，图像的清晰度也较低。
发明内容
本申请提供一种激光雷达及激光雷达的探测方法，用于增加一次扫描得到的目标物体的关联信息，从而可提高根据目标物体的关联信息确定出的点云密度，进而可提高图像的清晰度。
第一方面，本申请提供一种激光雷达，该激光雷达包括激光器、N个第一分束模块、夹角调整模块、N个探测模块、扫描模块和处理控制模块，N为大于1的整数。其中，激光器用于发射N个激光束，并将N个激光束传输至N个第一分束模块。针对N个第一分束模块中的每个第一分束模块，每个第一分束模块均用于将接收到的激光束分为第一激光 束和第二激光束，得到N个第一激光束和N个第二激光束。夹角调整模块用于接收来自N个第一分束模块的N个第二激光束，并将N个第二激光束中任意相邻的两个第二激光束之间的夹角调整为大于0度且不大于激光雷达的角分辨率。扫描模块用于接收来自光束夹角调整模块的N个第二激光束，并在不同探测角度下分别向探测区域发射N个第二激光束。针对N个探测模块中的每个探测模块，每个探测模块用于接收来自对应的第一分束模块的第一激光束，以及接收对应的回波信号，并对接收到的第一激光束和回波信号进行混频，得到拍频信号，并根据拍频信号确定探测区域中的目标物体的关联信息，其中，所述对应的回波信号为来自对应的第一分束模块的所述第二激光束在所述探测区域内反射回来的信号。处理控制模块用于控制扫描模块处于不同探测角度。
需要说明的是，N个激光束与N个第一分束模块一一对应，即一个激光束可射向一个第一分束模块。N个第一分束模块与所述N个探测模块一一对应，也可以理解为，一个探测模块有一个与其对应的第一分束模块。例如，第i个探测模块对应第i个第一分束模块。另外，一个回波信号与被发射到探测区域内的一个第二激光束对应，也就是，N个第二激光束对应N个回波信号，且N个回波信号与N个第二激光束一一对应，例如，第i个第二激光束对应第i个回波信号，其中i为大于0小于N的整数。
基于该方案，N个第二激光束中的任意相邻的两个第二激光束之间的夹角调整为大于0度且不大于所述激光雷达的角分辨率，即各个第二激光束相互交错对探测区域进行扫描，扫描模块在每个探测角度下，向探测区域发射N个第二激光束进行探测，可反射回N个回波信号，一个回波信号和一个第一激光束可确定出一个目标物体的关联信息，可根据N个回波信号和对应的N个第一激光束，确定出N个关联信息。也就是说，通过本申请的激光雷达，一次探测过程中获取到的关联信息较多，由于目标物体的关联信息可用于形成图像，从而根据较多的关联信息确定出的点云密度也较高，形成的图像清晰度也较高。
为了尽可能减少回波信号之间的串扰问题，可通过改变激光束的频率调制速率，以实现尽可能避免回波信号之间的串扰问题。本申请提供如下两种可能的实现方式。
实现方式一，采用调制器调制。
在该实现方式一中，激光雷达还包括调制器。调制器用于根据第一预设条件对来自激光器的N个激光束进行调制，其中，第一预设条件为夹角小于预设角度的两个激光束采用不同的频率调制速率。
实现方式二，采用激光器调制。
在该实现方式二中，激光器还用于根据第一预设条件调制N个激光束，其中，第一预设条件为夹角小于预设角度的两个激光束采用不同的频率调制速率。具体可以是，激光器根据第一预设条件进行激光束的波长(频率)的调谐，其中，激光雷达包括的激光器可以是N个。
基于上述两种实现方式，由于夹角小于预设角度的两个激光束对应的回波信号之间的串扰可能比较大，通过采用不同的频率调制速率，可使得调制后的两个激光束的对应的回波信号之间不会相互影响，即有助于减小回波信号之间的串扰。
在一种可能的实现方式中，根据第一预设条件对N个激光束进行调制，得到的激光束均为调频连续波FMCW。如此，由于FMCW测量目标物体的关联信息是基于相干探测原理，通常，外界环境干扰光难以与本征光相干产生拍频信号。因此，激光束为FMCW有助于提高激光雷达的抗干扰能力。进一步，激光束为FMCW时，还可以利用多普勒效应 测量出目标物体相对于激光雷达的运动速率，从而有助于扩展激光雷达的应用场景。
基于上述实现方式一，即在采用调制器对N个激光束进行调制的情况下，处理控制模块还用于控制扫描模块和调制器之间进行同步。
进一步，即在采用调制器对N个激光束进行调制的情况下，处理控制模块还用于控制扫描模块、探测模块和调制器之间进行同步。
基于上述实现方式二，即在采用激光器调制N个激光束的情况下，处理控制模块还用于控制扫描模块和激光器之间进行同步。
进一步，在采用激光器调制N个激光束的情况下，处理控制模块还用于控制扫描模块、激光器和探测模块之间进行同步。
在一种可能的实现方式中，光束夹角调整模块包括N个光纤和准直器，N个光纤与N个第二激光束一一对应。针对N个光纤中的每个光纤，每个光纤均用于接收来自对应的第一分束模块的第二激光束，并将接收到的该第二激光束传输至准直器。准直器用于接收来自N个光纤的N个第二激光束，并对N个第二激光束进行准直，得到任意相邻的两个第二激光束之间的夹角大于0度且不大于激光雷达的角分辨率的N个第二激光束。
其中，N个光纤的出光口可均位于准直器的物方焦平面上。
可选地，扫描模块可位于准直器的像方焦平面上。
为实现将回波信号传输至对应的探测模块，激光雷达还包括N个分光模块。针对N个分光模块中每个分光模块，每个分光模块用于将接收到的回波信号传输至对应的探测模块，其中，N个分光模块与N个回波信号一一对应。可以理解为，一个第二激光束对应一个回波信号，一个回波信号对应一个分光模块，一个回波信号也对应一个探测模块。例如，第i个回波信号对应第i个分光模块，对应第i个探测模块，当第i个分光模块接收到第i个回波信号后，可将该第i个回波信号传输第i个探测模块。
本申请中，激光束可以在空间中传输，也可以通过光纤传输。当激光束通过光纤传输时，分光模块可为光纤环形器，光纤环形器位于第一分束模块与夹角调整模块之间。激光器与N个第一分束模块之间、N个第一分束模块与N个光纤环形器之间、N个光纤环形器与夹角调整模块之间均通过光纤连接。
第二方面，本申请提供一种激光雷达，该激光雷达包括激光器、N个第一分束模块、N个探测模块、光学相控阵(optical phased array，OPA)和处理控制模块。其中，激光器用于发射N个激光束，并将N个激光束传输至N个第一分束模块。针对N个第一分束模块中的每个第一分束模块，每个第一分束模块均用于将接收到的激光束分为第一激光束和第二激光束。OPA用于接收来自N个第一分束模块的N个第二激光束，将N个第二激光束中任意相邻的两个第二激光束之间的夹角调整为大于0度且不大于激光雷达的角分辨率，并在不同探测角度下分别向探测区域发射任意相邻的两个第二激光束之间夹角大于0度且不大于激光雷达的角分辨率的N个第二激光束。针对N个探测模块中的每个探测模块，每个探测模块均用于接收来自对应的第一分束模块的第一激光束，以及接收来自探测区域的对应的回波信号，并对接收到的第一激光束和回波信号进行混频，得到拍频信号，并根据拍频信号确定探测区域中的目标物体的关联信息。处理控制模块用于控制OPA处于不同探测角度。
需要说明的是，N个激光束与N个第一分束模块一一对应，即一个激光束可射向一个第一分束模块。N个第一分束模块与所述N个探测模块一一对应，也可以理解为，一个探 测模块有一个与其对应的第一分束模块。例如，第i个探测模块对应第i个第一分束模块。另外，一个回波信号与被发射到探测区域内的一个第二激光束对应，也就是，N个第二激光束对应N个回波信号，且N个回波信号与N个第二激光束一一对应，例如，第i个第二激光束对应第i个回波信号，其中i为1至N中的任一整数。
基于该方案，N个第二激光束中的任意相邻的两个第二激光束之间的夹角调整为大于0度且不大于所述激光雷达的角分辨率，即各个第二激光束相互错开，OPA在每个探测角度下，向探测区域发射N个第二激光束进行探测，可反射回N个回波信号，一个回波信号和一个第一激光束可确定出一个目标物体的关联信息，可根据N个回波信号和对应的N个第一激光束，确定出N个关联信息。也就是说，通过本申请的激光雷达，一次探测过程中获取到的关联信息较多，即一次扫描过程得到的扫描点较多，由于目标物体的关联信息可用于形成图像，从而根据较多的关联信息确定出的点云密度也较高，形成的图像清晰度也较高。
在一种可能的实现方式中，OPA可通过对N个第二激光束的波阵面进行相位调制，得到任意相邻的两个第二激光束之间的夹角大于0度且不大于激光雷达的角分辨率的N个第二激光束。
第三方面，本申请提供一种激光雷达的探测方法，该激光雷达的探测方法可应用于激光雷达，该方法包括将N个激光束中的每个激光束分为第一激光束和第二激光束，得到N个第一激光束和N个第二激光束；将N个第二激光束中任意相邻的两个第二激光束之间的夹角调整为大于0度且不大于激光雷达的角分辨率，并在不同探测角度下分别向探测区域发射调整后的N个第二激光束；接收来自探测区域的N个回波信号，N个回波信号与被发射到探测区域内的N个第二激光束一一对应；针对N个回波信号中的每个回波信号，将回波信号与对应的第一激光束进行混频处理，得到拍频信号，并根据拍频信号确定探测区域中的目标物体的关联信息。
在一种可能的实现方式中，根据第一预设条件对N个激光束进行调制；其中，第一预设条件为：夹角小于预设角度的两个激光束采用不同的频率调制速率。
在一种可能的实现方式中，根据第一预设条件对N个激光束进行调制，得到的激光束均为调频连续波FMCW。
第四方面，本申请提供了一种激光雷达，该激光雷达包括执行上述任第三方面或第三方面任意可能实现方式的方法的模块/单元。这些模块/单元可以通过硬件实现，也可以通过硬件执行相应的软件实现。
第五方面，本申请提供了一种计算机存储介质，该计算机存储介质存储有程序指令，当程序指令在激光雷达上运行时，使得激光雷达执行上述第三方面或第三方面的任意可能的实现方式中的方法。
第八方面，本申请提供了一种计算机程序产品，当计算机程序产品在激光雷达上运行时，使得激光雷达执行上述第三方面或第三方面的任意可能的实现方式中的方法。
附图说明
图1为本申请提供的一种激光雷达的探测示意图；
图2为本申请提供的一种激光雷达的结构示意图；
图3a为本申请提供的一种第二分束模块的分光原理图示意图；
图3b为本申请提供的另一种第二分束模块的分光原理图示意图；
图3c为本申请提供的一种激光器与激光束的关系示意图；
图3d为本申请提供的另一种激光器与激光束的关系示意图；
图4a为本申请提供的一种第二激光束与回波信号进行混频处理的示意图；
图4b为本申请提供的另一种第二激光束与回波信号进行混频处理的示意图；
图4c为本申请提供的又一种第二激光束与回波信号进行混频处理的示意图；
图5为本申请提供的又一种激光器与激光束的关系示意图；
图6为本申请提供的一种夹角调整模块的结构示意图；
图7a为本申请提供的一种扫描器的结构示意图；
图7b为本申请提供的一种二维多光束扫描轨迹示意图；
图7c为本申请提供的另一种扫描器的结构示意图；
图7d为本申请提供的另一种二维多光束扫描轨迹示意图；
图8a为本申请提供的一种激光雷达的结构示意图；
图8b为本申请提供的另一种激光雷达的结构示意图；
图8c为本申请提供的又一种激光雷达的结构示意图；
图9为本申请提供的一种激光雷达的探测方法的方法流程示意图。
具体实施方式
激光雷达通常是通过发射高频电磁波并接收目标散射的电磁能量来工作的，通过比较分析接收到的回波信号与探测信号，可以提取与目标相关的信息，例如目标的位置信息。图1为本申请提供的一种激光雷达的探测示意图。激光雷达包括激光器和探测器。激光器以一定方向发射激光束，若在沿激光束的发射方向的一定距离内存在目标，则激光束可以在该目标的表面发生反射。图1以激光束1的发射方向存在目标A为例，激光器发射的激光束1在到达目标A后，在目标A的表面发生反射，被反射的信号作为回波信号返回至激光雷达的探测器，探测器根据回波信号和本地信号可确定出目标A的关联信息，例如目标A的位置信息等。
激光雷达可被用作车载激光雷达(例如扫描式车载FMCW激光雷达)、机载激光雷达等对精确度要求较高的场景。此外，激光雷达还可以安装于移动平台，如卫星。在此情况下，激光雷达需要移动平台中的其它装置的协助以确定自身当前的位置和转向信息，这样可保证测量数据的可用性。例如，移动平台中还可以包括全球定位系统(global positioning system，GPS)装置和惯性测量单元(inertial measurement unit，IMU)装置，激光雷达可以结合GPS装置和IMU装置的测量数据进而得到目标物体的位置、速度等特征量。例如，雷达可以通过移动平台中的GPS装置提供移动平台的地理位置信息，通过IMU装置记录移动平台的姿态和转向信息。在根据回波信号确定与目标物体之间的距离后，可以通过GPS装置提供的地理位置信息或IMU装置提供的姿态和转向信息中的至少一种，将目标物体的测量点由相对坐标系转换为绝对坐标系上的位置点，得到目标物体的地理位置信息，从而使激光雷达可以应用于移动的平台中。可以理解的是，本申请中激光雷达还可应用于自动驾驶场景中、或者也可应用于网联车场景中，等等。
基于上述内容，图2示例性示出了本申请提供的一种激光雷达的结构示意图。如图2 所示，该激光雷达包括激光器、N个第一分束模块、夹角调整模块、N个探测模块、扫描模块和处理控制模块，图2中以N＝3示例性说明。激光器，用于发射N个激光束，并将N个激光束传输至N个第一分束模块。针对N个第一分束模块中的每个第一分束模块，每个第一分束模块均用于将接收到的激光束分为第一激光束和第二激光束，得到N个第一激光束和N个第二激光束。也可以理解为，N个第一分束模块中的第k个第一分束模块用于将接收到的激光束分为第k个第一激光束和第k个第二激光束，k取遍1至N。其中，第一激光束为本地信号，也可称为本征光，第二激光束为探测信号，也可称为探测光。夹角调整模块，用于接收来自N个第一分束模块的N个第二激光束，并将N个第二激光束中任意相邻的两个第二激光束之间的夹角调整为大于0度且不大于激光雷达的角分辨率。扫描模块，用于接收来自光束夹角调整模块的N个第二激光束，并在不同探测角度下分别向探测区域发射N个第二激光束。针对N个探测模块中的每个探测模块，每个探测模块均用于接收来自对应的第一分束模块的第一激光束，以及接收来自探测区域的对应的回波信号，并对接收到的第一激光束和回波信号进行混频，得到拍频信号，并根据拍频信号确定探测区域中的目标物体的关联信息。或者也可以理解为，N个探测模块中的第k个探测模块用于接收来自第k个第一分束模块的第k个第一激光束，以及接收来自探测区域的第k个回波信号，对第k个第一激光束和第k个回波信号进行混频，得到拍频信号，并根据拍频信号确定探测区域中的目标物体的关联信息，k取遍1至N。处理控制模块，用于控制扫描模块处于不同探测角度。应理解，处理控制模块可以控制扫描模块步进处于某一个探测角度，或者也可以是连续转动到某一探测角度，扫描模块可以处于不同的探测角度，在每个探测角度下，均向探测区域发射N个第二激光束。
其中，N个激光束与N个第一分束模块一一对应，N个第一分束模块与N个探测模块一一对应，N为大于1的整数。也可以理解为，一个激光束可传输至一个第一分束模块，一个第一分束模块可对应一个探测模块。
需要说明的是，激光雷达的角分辨率，也可称为激光雷达的扫描分辨率，是指射向探测区域的相邻激光束之间的预设夹角，或者，是指射向探测区域的相邻激光束之间的期望夹角。
基于上述激光雷达，N个第二激光束中的任意相邻的两个第二激光束之间的夹角调整为大于0度且不大于所述激光雷达的角分辨率，即各个第二激光束相互交错对探测区域进行扫描，扫描模块在每个探测角度下，向探测区域发射N个第二激光束进行探测，可反射回N个回波信号，一个回波信号和一个第一激光束可确定出一个目标物体的关联信息，可根据N个回波信号和对应的N个第一激光束，确定出N个关联信息。也就是说，通过本申请的激光雷达，一次探测过程中获取到的关联信息较多，由于目标物体的关联信息可用于形成图像，从而根据较多的关联信息确定出的点云密度也较高，形成的图像清晰度也较高。应理解，目标物体可以是一个也可以是多个。
下面对图2所示的各个功能模块和结构分别进行介绍说明，以给出示例性的具体实现方案。
一、激光器
本申请中，N个激光束可以是由N个激光器输出，也可以由一个激光器输出一个激光束之后，通过分束模块进行分束得到N个激光束；或者也可以由K个激光器输出K个激 光束，之后通过分束模块对K个激光束中的一个或多个激光束进行分束，得到N个激光束，K为小于N的整数。也就是说，激光雷达可以包括一个激光器，或者也可以包括N个激光器，或者也可以包括K个激光器。以下分三种情形分别说明。
情形一，激光雷达包括一个激光器。
在该情形一下，激光雷达还包括第二分束模块，第二分束模块位于激光器与第一分束模块之间，该第二分束模块用于将激光器出射的一个激光束分为N个激光束。如图3a所示，以第二分束模块将激光器出射的一个激光束分为3个激光束示例性地说明。
在一种可能的实现方式中，第二分束模块可以为衍射光学器件(diffractive optical elements，DOE)，DOE可以将来自激光器的一个激光束均匀地分为N个激光束，N个激光束之间的传输方向可能不同，也可能相同。可以理解的是，DOE将激光束分出的数目和激光束之间的间隔可由DOE的物理结构来决定。也就是说，DOE的物理结构可根据N个激光束之间的间隔来确定。在该实现方式中，第一分束模块和第二分束模块可以相同，当第一分束模块为DOE时，N＝2，也就是说，DOE作为第一分束模块时，DOE可将接收到的一个激光束分为第一激光束和第二激光束，即DOE将接收到的激光束一分为二。
在另一种可能的实现方式中，第二分束模块可以为偏振分光棱镜(polarizing beam splitter，PBS)阵列。如图3b所示，为本申请提供的另一种第二分束模块的分光原理图。图3b以将激光器射出的一个激光束分为3个激光束为例说明。激光器向PBS阵列射入一个激光束，PBS可以把入射的激光束分成两个垂直的线偏振光，即P偏振光和S偏振光，其中P偏振光完全通过，作为下一个PBS的入射激光束，而S偏振光以45度角被反射至对应的第一分束模块，且S偏振光的出射方向与P偏振光成90度角。应理解，从N个PBS可反射出N个激光束。在该实现方式中，第一分束模块可为PBS阵列中的一个PBS。
情形二，激光雷达包括N个激光器。
在该情形二下，如图3c所示，一个激光器出射一个激光束，N个激光器出射N个激光束，图3c以三个激光器为例说明。应理解，N个激光器出射的N个激光束的之间可以呈一定的夹角，也可以是平行的。
情形三，激光雷达包括K个激光器。
在该情形三下，如图3d所示，以K＝2，N＝3为例说明。即两个激光器，发射3个激光束为例，其中一个激光器与第一分束模块之间还包括一个第二分束模块。该第二分束模块可参见上述情形一的介绍，此处不再赘述。
应理解，上述情形一、情形二和情形三中，在激光雷达作为车载雷达的情况下，激光器可以发射905nm波长的激光、或者也可发射1550nm波长的激光束。可选地，激光器可以为半导体激光器、也可以是光纤激光器。
二、探测模块
第二激光束被扫描模块投射到目标物体上后，目标物体会反射回波信号。回波信号传输至探测模块后，探测模块会对回波信号和第一激光束进行混频处理。示例性地，探测模块可通过光电转化将回波信号和第一激光束的拍频信号转化为模拟信号或数字信号的形式。
由于N个第二激光束中任意相邻的两个第二激光束之间的夹角比较小，因此，一个第二激光束的回波信号有可能射入另一个第二激光束对应的探测模块，进而造成两个回波信 号之间的串扰。例如两个激光束分别为激光束A和激光束B，激光束A经第一分束模块可分为第一激光束A和第二激光束A，第二激光束A的回波信号为回波信号A；激光束B经第一分束模块可分为第一激光束B和第二激光束B，第二激光束B的回波信号为回波信号B。由于第二激光束A和第二激光束B之间的夹角较小，因此，回波信号A可能射入第二激光束B对应的探测模块，回波信号B也可能射入第二激光束A对应的探测模块，如此，探测模块可能对回波信号A和第一激光束B进行混频处理，对回波信号B和第一激光束A进行混频处理，从而造成回波信号A和回波信号B之间的串扰问题。
又因为在探测模块中，第一激光束与回波信号之间形成拍频信号一般需要：在调制周期内，第一激光束的调频速率与回波信号的调频速率在调频时长内一致(例如，相同)。基于此，可通过改变对N个激光束的频率调制速率，来实现尽可能避免回波信号之间的串扰问题。本申请中，可以根据第一预设条件对N个激光束进行调制，以减小回波信号之间的串扰问题。其中，第一预设条件为夹角小于预设角度的两个激光束采用不同的频率调制速率。示例性地，预设角度可以为两个激光束对应的回波信号产生串扰的临界角度。需要说明的是，该预设角度与探测模块的接收角度(亦称为视场角)相关。
需要说明的是，频率调制速率Kr i＝调频带宽B i/调频时长t。其中，调频时长t是指从调频起始时刻的初始频率开始，经过第一时长，激光束的频率达到最大值，经过的这第一时长即为调频时长。
激光束的调制方式可以是锯齿波调制方式，也可以是三角波调制方式，本申请对此不做限定。当调制方式为三角波调制方式时，调频时长为上调频时长或下调频时长，上调频时长和下调频时长相等，调频时长t＝T/2(如图4a所示)，T表示调频周期，具体是指：从调频起始时刻的初始频率开始，经过第二时长，激光束的频率回到初始频率，经过的这第二时长即为调频周期。调频带宽B i是指：在一个上调频时长内，频率从初始频率到最大频率之差。当调制方式为锯齿波调制方式时，调频时长t＝T。
根据第一预设条件对N个激光束进行调制，本申请可提供如下两种可能的实现方式。
实现方式一，一个激光束对应一个频率调制速率，即N个激光束与N个频率调制速率一一对应、且这N个频率调制速率互不相同。
示例性地，可通过第m个频率调制速率对第p个激光束进行调制，通过第n个频率调制速率对第q个激光束进行调制，第m个频率调制速率与第n个频率调制速率不同，第p个激光束与第q个激光束也不同，其中，第m个频率调制速为N个频率调制速率中的一个，第n个频率调制速率为N个频率调制速率中除第m个频率调制速外的一个，第p个激光束和第q个激光束为N个激光束中不同的两个。通过不同频率调制速率调制后的激光束，可避免第二激光束对应的回波信号相互之间的串扰问题。下面针对该有益效果，本申请结合具体示例进行详细说明。
如图4a、图4b和图4c所示，为本申请提供的三种第一激光束与回波信号进行混频处理的示意图。以激光束A和激光束B为例说明，激光束A经第一分束模块可分为第一激光束A和第二激光束A，回波信号A为第二激光束A的回波信号，激光束B经第一分束模块可分为第一激光束B和第二激光束B，回波信号B为第二激光束B的回波信号。图4a、图4b和图4c中激光束A和激光束B的调制周期均为T、调制方式均为三角波调制。
如图4a所示，激光束A通过频率调制速率Kr 1、调频带宽B 1进行调制，第一激光束的调频速率与回波信号的调频速率在调频时长内一致，即第一激光束A的频率调制速率与对应的回波信号A的频率调制速率在调频时长t内是相同的，回波信号A到达探测模块的时间与第一激光束A到达探测模块时间相比延迟τ 1，因此，回波信号A和第一激光束A混频处理后得到的拍频信号的频率f 1＝Kr 1*τ 1。其中，频率调制速率Kr 1可为N个频率调制速率中的第1个频率调制速率。
如图4b所示，激光束B通过频率调制速率Kr 2、调频带宽B 2进行调制，第一激光束的调频速率与回波信号的调频速率在调频时长内一致，即第一激光束B的频率调制速率与对应的回波信号B的频率调制速率在调频时长t内是相同的，回波信号B到达探测模块的时间与第一激光束B到达探测模块时间相比延迟τ 2，因此，回波信号B和第一激光束B混频处理后得到的拍频信号的频率f 1＝Kr 2*τ 2，其中，频率调制速率Kr 2可为N个频率调制速率中的第2个频率调制速率。
如图4c所示，第一激光束A与回波信号B之间的频率调制速率相差较大，(即第一激光束A与回波信号B不是相干信号)，因此不能进行混频处理，也得到不到拍频信号。也可以理解为，即便回波信号B射入第一激光束A对应的探测模块，也不会影响第一激光束A与回波信号A形成拍频信号，因此，回波信号B不会对回波信号A造成影响。如此，可实现了避免回波信号之间的串扰问题。
进一步，在激光雷达大规模应用的场景中，例如车载FMCW激光雷达的应用场景中，由于其他车辆的车载FMCW激光雷达的探测光(第二激光束)或回波信号有可能对本车探测模块造成干扰。为了尽可能避免这种情况下的串扰问题，对N个激光束可以分别随机选择频率调制速率Kr i(i＝1、2、3…)进行调制，且不同的激光束对应的频率调制速率不同。如此，也可以进一步增强FMCW激光雷达的抗干扰能力。
实现方式二，N个激光束与M个频率调制速率对应、且M个频率调制速率互不相同，其中M为小于N的整数。
也可以理解为，N个激光束中可存在两个或两个以上的激光束采用一个频率调制速率，为了尽可能避免回波信号之间的串扰问题，对应一个频率调制速率的两个或两个以上的激光束之间需满足：激光束之间的夹角比较大(例如大于预设角度)，则激光束分束后的第二激光束对应的回波信号相互之间的串扰比较小。
为了便于说明，以N＝3，M＝2为例说明，三个激光束分别为激光束a、激光束b和激光束c为说明，其中，激光束a和激光束b之间的夹角不大于预设角度，激光束b和激光束c之间的夹角不大于预设角度，激光束a和激光束c之间的夹角大于预设角度，则激光束a和激光束c可以通过一个频率调制速率(Kr 4)进行调制，激光束b可通过另一个频率调制速率(Kr 5)进行调制。由于激光束a和激光束c之间夹角比较大，因此，激光束a和激光束c对应的回波信号之间串扰本身比较小，即便用相同的频率调制速率对激光束a和激光束c进行调制，相互之间的串扰仍是较小的。而且，虽然激光束a与激光束b之间的夹角比较小，激光束a和激光束b对应的回波信号之间的串扰会比较大，但是通过不同的频率调制速率调制后，也可减小激光束a与激光束b对应的回波信号之间的串扰(原理可参见上述图4a、图4b和图4c的介绍)。同样地，激光束b和激光束c之间也可通过不同的频率调制速率来减小激光束b和激光束c对应的回波信号相互之间的串扰问题。
基于上述实现方式一和实现方式二，对激光束进行调制可以是调制器进行调制，也可以是激光器调制。可选地，调制器可为外调制器。需要说明的是，通过调制器调制一般可由声光调制器或者电光调制器进行频率调制。通过激光器对N个激光束调制一般可使用波长可调谐激光器。其中，(1)声光调制器通常是指控制激光束强度变化的声光器件。声光调制是一种外调制技术，调制信号是以电信号(调幅)形式作用于电声换能器上，再转化为以电信号形式变化的超声场，当光波通过声光介质时，由于声光作用，使光载波受到调制而成为“携带”信息的强度调制波。(2)电光调制器是指利用某些电光晶体，如铌酸锂晶体(LiNb03)、砷化稼晶体(GaAs)和钽酸锂晶体(LiTa03)的电光效应制成的调制器。电光效应即当把电压加到电光晶体上时，电光晶体的折射率将发生变化，结果引起通过该晶体的光波特性的变化，实现对光信号的相位、幅度、强度、频率以及偏振状态的调制。(3)波长可调谐激光器可以根据需要进行波长的改变，改变波长的方法之一是通过改变注入电流，使发光材料的折射率发生改变，从而在一定范围内改变和控制激光器的输出波长。实现激光波长调谐的原理大致有三种。第一种是通过某些元件(如光栅)改变谐振腔低损耗区所对应的波长来改变激光的波长。第二种是通过改变某些外界参数(如磁场、温度等)使激光跃迁的能级移动。第三种是利用非线性效应实现波长的变换和调谐(如非线性光学、受激喇曼散射等)。
在采用调制器对N个激光束进行调制的情况下，基于上述实现方式一，激光雷达还包括N个调制器，N个调制器与N个激光束一一对应，N个调制器与N个频率调制速率一一对应，即每个调制器采用一个频率调制速率对射入的激光束进行调制，其中，N个频率调制速率互不相同。基于上述实现方式二，激光雷达还可包括M个调制器，经同一个调制器调制后的出射的激光束可分为两个或两个以上，M个频率调制速率中的每个调制器通过一个频率调制速率对射入的激光束进行调制，M个调制器与M个频率调制速率一一对应，且M个不同的频率调制速率互不相同。
需要说明的是，在采用调制器对N个激光束进行调制的情况下，激光雷达包括的激光器可以是上述情形一、情形二或情形三中的任一种。
在采用激光器调制N个激光束的情况下，基于上述实现方式一，激光雷达包括N个激光器，N个激光器对应N个不同的频率调制速率，即激光器可通过改变波长(或频率)，实现N个激光器采用N个不同的频率调制速率。基于上述实现方式二，激光雷达包括M个激光器，M个激光器对应M个不同的频率调制速率。需要说明的是，经过同一个激光器发射的两个或两个以上的激光束中，采用的频率调制速率可以是相同的，而且为了尽可能减小这两个激光束分束后的第二激光束对应的回波信号之间的串扰，同一个激光器发射的激光束中两个激光束之间得夹角要比较大，例如，大于预设角度。
如图5所示，以N＝2，M＝3为例说明，即激光束A与激光束C可以由一个激光器发射，激光束B由另一种激光器发射，激光束A与激光束C之间的夹角较大，因此，激光束A与激光束C对应的回波信号相互之间的串扰比较小。激光束B与激光束A之间的夹角可以较小、也可以较大，激光束B与激光束C之间的夹角可以较小、也可以较大。如果激光束B与激光束A之间的夹角较小和/或激光束B与激光束C之间的夹角较小，则两个激光器可以采用不同的频率调制速率调制激光束，具体地，这两个激光器通过波长调谐实现。若激光束B与激光束A之间的夹角较大、且激光束B与激光束C之间的夹角也较大，则两个激光器可以采用相同的频率调制速率调制激光束，也可以采用不同的频率调制速率 调制激光束。
需要说明的是，M个激光器要发射N个激光束，激光雷达还需包括第二分束模块，该第二分束模块可以设置于激光器与第一分束模块之间，第二分束模块可以将M个激光器中的某一个或某多个射出的激光束进行分束，以实现M个激光器发射N个激光束。该第二分束模块可参见上述情形一中第二分束模块的介绍，此处不再赘述。
通过上述实现方式一或实现方式二，不同第二激光束对应的回波信号，只能与各自的对应的第一激光束进行混频处理，得到拍频信号，从而可有效避免回波信号之间的串扰。
在一种可能的实现方式中，探测模块包括信号接收单元和数据采集单元。其中，信号接收单元可以是探测器，例如PIN型光电二极管(亦称为PIN结二极管)、雪崩光电二极管(avalanche photodiode，APD)、PIN型光电二极管阵列、APD阵列中任一种，或者PIN型光电二极管组合形成的平衡探测、APD组合形成的平衡探测、或者PIN型光电二极管阵列组合形成的平衡探测、或者APD阵列组合形成的平衡探测。示例性地，信号接收单元可以是探测器，数据采集单元可以是模/数转换器或者模数转换器(analog-to-digital converter，ADC)。
三、夹角调整模块
本申请中，为了得到目标物体的较多的关联信息，N个第二激光束进入扫描模块之前，需要对第二激光束之间的夹角进行调整，以保证N个第二激光束中任意相邻的两个第二激光束之间的夹角为大于0度且不大于激光雷达的角分辨率。对N个第二激光束之间夹角的调整可以通过光纤阵列与准直器组合的结构进行调整，也可以通过光学相控阵(optical phased array，OPA)的方式进行调整，也可以通过反射镜的组合进行调整，此处不再一一列举。如下分别对光纤阵列与准直器组合的结构、以及OPA进行详细介绍。
如图6所示，为本申请提供的一种夹角调整模块的结构示意图。该光束夹角调整模块包括N个光纤和准直器，N个光纤与N个第二激光束一一对应，即一个第二激光束可耦合进一个光纤。针对N个光纤中的每个光纤，每个光纤均用于接收来自对应的第一分束模块的第二激光束，并将接收到的第二激光束传输至准直器。或者也可以理解为，N个光纤中的第k个光纤用于接收来自第k个第一分束模块的第k个第二激光束，并将第k个第二激光束传输至准直器，k取遍1至N。准直器，用于接收来自N个光纤的N个第二激光束，并对N个第二激光束进行准直，得到任意相邻的两个第二激光束之间的夹角为大于0度且不大于激光雷达的角分辨率的N个第二激光束。在一种可能的实现方式中，准直器可以是准直透镜。
进一步，N个光纤的出光口均位于准直器的物方焦平面上(如图6所示)。其中，N个光纤形成光纤阵列，光纤之间的间隔可以是相等的，也可以是不相等的。可以通过控制光纤之间的间隔和准直器的焦距，来实现从光纤和准直器出射的N个第二激光束中任意相邻的两个第二激光束之间的夹角大于0度且不大于激光雷达的角分辨率。也就是说，可通过选择合适的光纤间隔d和准直器的焦距f，来满足N个第二激光束中任意相邻两个相邻第二光束之间的夹角大于0度且不大于激光雷达的角分辨率。
示例性地，两个相邻第二激光束之间的夹角θ可通过如下公式(1)确定。
θ＝arctan(d/f)    公式(1)
当激光雷达的角分辨率θ＝0.1°时，可选择光纤之间的间隔d＝35um，准直器的焦距 f＝2cm来实现。也可以理解为，在一种可能的实现中，N个第二激光束中任意相邻两个相邻第二光束之间的夹角等于激光雷达的角分辨率。
可以理解的是，当光纤之间的间隔是相等时，N个第二激光束中任意相邻第二激光束之间的夹角θ是相等的。当光纤之间的间隔是不相等时，N个第二激光束中相邻第二激光束之间的夹角θ也是不相等的。
四、扫描模块
基于上述图6所示的夹角调整模块，由于从准直器出射的N个第二激光束的光斑在准直器的像方焦平面上重合，因此，可以将扫描模块设置于准直透镜的像方焦平面上。
在一种可能实现方式中，扫描模块可以为扫描器，例如反射式扫描器。反射式扫描器包括但不限于机械旋转镜和MEMS微振镜。反射式扫描器是通过机械转动来改变扫描器的扫描方向。当扫描模块为反射式扫描器时，可将反射式扫描器的反射面设置于准直透镜的像方焦平面上。这样，N个第二激光束的光斑可在扫描器的反射面上重合，且由于扫描器的反射面不会改变第二激光束之间的夹角，因此，当反射式扫描器围绕相互垂直两个转轴进行旋转扫描时，N个第二激光束可被扫描器投射到探测区域中、且仍满足任意相邻的两个第二激光束之间的夹角大于0度且不大于激光雷达的角分辨率。可选地，扫描器可以是连续运转模式，也可以是步进运转模式。
夹角调整模块用于将N个第二激光束传输至扫描模块，经扫描模块投射至探测区域。激光雷达可通过改变扫描模块的探测角度完成对探测区域的扫描。例如，激光雷达可预设多个探测角度，扫描模块可以在多个探测角度的每个探测角度下向探测区发射N个第二激光束，进而可得到探测区域内目标物体的关联信息，例如距离；进而根据目标物体的关联信息分析得到扫描图像(也称为图像)。
如图7a所示，为申请提供的一种扫描器的结构示意图。该扫描器可以在二维方向(水平方向和垂直方向)上变换探测角度，变换探测角度也可理解为使得扫描器处于不同的探测角度下。图7a以三个第二激光束为例说明，在一个探测角度下，三个第二激光束经过扫描器被投射到探测区，得到三个扫描点，图7a以不同的填充图案表示不同的扫描点。不断的变化探测角度，三个第二激光束被不断的投射到探测区域，可得到如图7b所示的二维多光束扫描轨迹示意图。该扫描轨迹可以是处理控制模块控制扫描器按照预设的扫描方式进行扫描得到的。也可以理解为，是处理控制模块控制扫描器在二维方向上旋转扫描器，使扫描器处于不同探测角度下扫描得到的扫描轨迹。例如，处理控制模块可控制扫描模块先水平方向旋转后垂直方向旋转，或者先垂直方向旋转后水平方向旋转，或者垂直方向和水平方向一起旋转，或者水平方向和垂直方向交替旋转等。
如图7c所示，为申请提供的另一种扫描器的结构示意图。该扫描器可以在一维方向(水平方向)上变换探测角度，使得扫描器处于不同的探测角度下。图7c以三个第二激光束为例说明，在一个探测角度下，三个第二激光束经过扫描器被投射到探测区，得到三个扫描点，图7c以不同的填充图案表示不同的扫描点。经过多次扫描后，可得到如图7d所示的二维多光束扫描轨迹示意图。也可以理解为，扫描器将射入的三个第二激光束反射至探测区域，每个第二激光束的扫描点呈现一维分布，多个第二激光束做一维扫描，拼成图7d所示的二维多光束扫描轨迹。通过一维扫描器，可简化激光雷达的体积，以及简化处理控制模块控制的复杂度。
需要说明的是，当扫描器为一维方向(水平方向)上旋转的扫描器时，在进行该类扫描器的装调时，可以将一维扫描器的旋转轴位于N个第二激光束所在的入射平面内。一维扫描器只负责将N个第二激光束沿一个维度(图7c所示为水平维度)扫描，在水平维度上可通过处理控制模块控制角分辨率，在垂直维度上的角分辨率即为相邻两个第二激光束之间的夹角，也可以理解为垂直维度上的角分辨率可由夹角调整模块来确定。
在一种可能的实现方式中，上述夹角调整模块和扫描模块的功能也可通过OPA来实现。OPA工作原理为：通过调节从各个相控单元(如光学移相器)辐射出的光波之间的相位关系，使其在设定方向上彼此同相，产生相互加强的干涉，干涉的结果是在该方向上产生一束高强度光束，而在其他方向上从各相控单元射出的光波都不满足彼此同相的条件，干涉的结果彼此相抵消，因此，辐射强度接近于零。组成相控阵的各相控单元在处理控制模块的控制下，可使一个高强度激光束或多个高强度激光束的指向按设计的程序实现扫描。
在本申请中，OPA可接收来自N个第一分束模块的N个第二激光束，将N个第二激光束中任意相邻的两个第二激光束之间的夹角调整为大于0度且不大于激光雷达的角分辨率，并在不同探测角度下分别向探测区域发射任意相邻的两个第二激光束之间夹角大于0度且不大于激光雷达的角分辨率的N个第二激光束。
一种可能的实现方式中，N个第二激光束射入OPA中，经过OPA对N个第二激光束的波阵面进行相位调整，使得N个第二激光束中任意相邻的两个第二激光束之间的夹角调整为大于0度且不大于激光雷达的角分辨率，且N个第二激光束均对同一视场扫描。也可以理解为，N个第二激光束以相互不重叠的方式对同一视场进行扫描。其中，OPA进行二维扫描，得到如上述图7b所示的扫描轨迹；进行一维扫描，得到如上述图7d所示的扫描轨迹。
五、分光模块
N个第二激光束中的第i个第二激光束射向探测区域中的目标物体后，反射回第i个回波信号，需要将第i个回波信号传输至第i个探测模块，i为1至N中的任一整数。在一种可能的实现方式中，激光雷达还包括N个分光模块，其中，N个分光模块与N个回波信号一一对应，针对N个分光模块中每个分光模块，每个分光模块用于将接收到的回波信号传输至对应的探测模块。或者也可以理解为，N个分光模块中第k个分光模块用于将第k个回波信号传输至第k个探测模块，k取遍1至N。
其中，分光模块可以是打孔反射镜，或者也可以是PBS、或者也可以是光纤环形器。当分光模块为打孔反射镜，打孔反射镜的孔可使第二激光束透传至夹角调整模块，打孔反射镜的反射镜面可将回波信号反射至对应的探测模块。当分光模块为PBS时，第二激光束从PBS透射至夹角调整模块，将回波信号反射至对应的探测模块。当分光模块为光纤环形器时，可将第二激光束从一个端口射向夹角调整模块，将回波信号从另一个端口射向对应的探测器。也可以理解为，第k个分光模块用于将第k个回波信号传输至第k个探测模块，且第k个分光模对第k个第二激光束的原光路不产生影响，k取遍1至N。
需要说明的是，第k个回波信号经分光模块传输至探测器之前，第k个回波信号与对应的第k个第二激光束共线，也称为共轴。
六、处理控制模块
在一种可能的实现中，当激光雷达中对N个激光束进行调制是通过调制器时，处理控制模块还用于控制扫描器和调制器之间进行同步。当激光雷达中对N个激光束的进行调制是通过激光器改变波长实现时，处理控制模块还用于控制扫描器和激光器之间进行同步。即处理控制模块可以控制扫描模块处于不同探测角度，还可用于控制扫描模块和调制器之间进行同步；或者，控制扫描模块和激光器之间进行同步。
进一步，当激光雷达中对N个激光束进行调制是通过调制器时，处理控制模块还可控制扫描模块、调制器和探测模块之间进行同步。当激光雷达中对N个激光束的进行调制是通过激光器调波长调谐时，处理控制模块还用于控制扫描模块、激光器和探测模块之间进行同步。
需要说明的是，本申请中，对于激光器与扫描模块之间进行同步，针对的是激光器的频率调制与扫描模块之间进行同步；激光器、探测模块、扫描模块之间进行同步，主要是指激光器的频率调制、探测模块、扫描模块之间进行同步。
示例性地，处理控制模块可先控制扫描模块在一个探测角度下，向探测区域投射N个第二激光束，同时触发调制器(或者激光器)在一个调频周期内对N个激光束进行频率的调制(详细过程可参见上述介绍)，调频周期结束后调制器(或者激光器)停止调制。调频后的N个第二激光束经扫描模块出射到达探测区域，遇到目标物体后分别反射回波信号，经各自对应的分光模块分别传输至对应的探测模块，处理控制模块触发探测模块中的数据采集单元采集回波信号和第一激光束混频后的拍频信号，之后处理控制模块根据拍频信号得到目标物体的关联信息，对目标物体的关联信息进行处理，得到图像。之后处理控制模块控制扫描模块处于下一个探测角度，并重复上述过程。
需要说明的是，在处理控制模块控制探测模块与调制器同步、或者与激光器的频率调制同步的过程中，探测模块中的信号接收单元可以一直接收对应的第一激光束和回波信号。
在一种可能的实现方式中，处理控制模块可以包括处理单元和控制单元，处理单元可以是通用处理器、现场可编程门阵列(field programmable gate array，FPGA)、信号数据处理(digital signal processing，DSP)电路、专门应用的集成电路(application specific integrated circuit，ASIC)、或者其他可编程逻辑器件。控制单元包括扫描器的驱动、调制器的驱动、激光器的频率调制驱动、探测器的驱动等，这些驱动可以是集成在一起，也可以是分开的。
可选地，FPGA可向控制单元的各个驱动发送控制信号，使扫描器的驱动控制扫描模块、调制器的驱动控制调制器、探测器的驱动控制探测模块，以实现扫描模块、探测模块和调制器之间进行同步；或者，使扫描器的驱动控制扫描模块、激光器的频率调制驱动控制激光器的频率调制、探测器的驱动控制探测模块，以实现扫描模块、探测模块和激光器的频率调制之间进行同步。以扫描器为例，FPGA可以向扫描模块的驱动发送控制信号，扫描模块的驱动可根据该控制信号控制扫描器处于某一个探测角度。
本申请中，激光雷达中的激光束可以在空间传输，也可以通过光纤传输。如图8a所示，为本申请提供的另一种激光雷达结构示意图。该激光雷达的光束是在空间中传输。该激光雷达包括激光器、N个第一分束模块、夹角调整模块、N个探测器、扫描器、处理控制模块，N个分光模块。其中，N个第一分束模块、N个探测器和N个分光模块三者之间一一对应。夹角调整模块为光纤阵列与准直器的组合结构，可参见上述图6的介绍，此处不再 赘述。分光模块可以为打孔反射镜或者PBS。扫描器为反射式器，可参见上述图7a或图7c的介绍，此处不再赘述。激光器、N个第一分束模块、N个探测器和处理控制模块分别参见上述相应内容的介绍，此处不再赘述。
如图8b所示，为本申请提供的另一种激光雷达结构示意图。该激光雷达的光束是在空间中传输。该激光雷达包括激光器、N个第一分束模块、N个探测器、OPA、处理控制模块，N个分光模块。其中，N个第一分束模块、N个探测器和N个分光模块三者之间一一对应。与图8a的区别是，夹角调整模块和扫描器的功能由OPA实现，OPA的详细介绍可参见上述内容，此处不再赘述。
如图8c所示，为本申请提供又一种激光雷达结构示意图。该激光雷达的光束是在光纤中传输。该激光雷达包括激光器、N个第一分束模块、夹角调整模块、N个探测器、扫描器、处理控制模块，N个分光模块。其中，N个第一分束模块、N个探测器和N个分光模块三者之间一一对应。图8c所示的激光雷达与图8a所示的激光雷达结构的区别为：分光模块为光纤环形器，激光器与N个第一分束模块之间、N个第一分束模块与N个光纤环形器之间、N个光纤环形器与夹角调整模块之间均可通过光纤连接。其余部分可参见上述图8a的介绍，此处不再赘述。
基于上述图8c所示的激光雷达，该激光雷达采用光纤架构，因为激光器射出激光束后，激光束可沿光纤通道依次进入第一分束模块、光纤环形器、夹角调整模块，然后进入扫描器，如此，可以简化激光雷达的光路调试过程，可使得安装过程比较简单。
上述任一实施例中的根据第一预设条件对N个激光束进行调制，得到的激光束可均为调频连续波FMCW。FMCW测量目标物体的关联信息是基于相干探测原理。一般情况下，外界环境干扰光与本征光之间的频率相差比较大，因此，外界环境干扰光难以与本征光相干产生拍频信号。因此，激光束为FMCW有助于提高激光雷达的抗干扰能力。
进一步，激光束为FMCW时，还可以利用多普勒效应测量出目标物体相对于激光雷达的运动速率，从而有助于扩展激光雷达的应用场景。
基于上述内容和相同的构思，本申请提供的一种激光雷达的探测方法，可参见下述图9的介绍。该激光雷达的探测方法可应用于上述任一实施例的激光雷达。如图9所示，该方法包括以下步骤：
步骤901，将N个激光束中的每个激光束分为第一激光束和第二激光束，得到N个第一激光束和N个第二激光束。
此处，N为大于1的整数，N个激光束可为激光雷达中的激光器发射的N个激光束，关于激光器发射N个激光束的详细过程可参见上述激光器部分的描述，此处不再赘述。另外，可以是第一分束模块将激光束分为第一激光束和第二激光束，具体的过程可参见上述实施例中对第一分束模块的介绍，此处不再赘述。
其中，一个第一激光束对应一个第二激光束，即N个第一激光束和N个第二激光束一一对应。
步骤902，将N个第二激光束中任意相邻的两个第二激光束之间的夹角调整为大于0度且不大于激光雷达的角分辨率，并在不同探测角度下分别向探测区域发射调整后的N个第二激光束。
其中，激光雷达的角分辨率，也可称为激光雷达的扫描分辨率，是指射向探测区域的相邻激光束之间的预设夹角，或者，是指射向探测区域的相邻激光束之间的期望夹角。
本申请中，对N个第二激光束之间夹角的调整可以通过光纤阵列与准直器组合的结构进行调整，也可以通过OPA的方式进行调整，也可以通过反射镜的组合进行调整，此处不再一一列举。关于光纤阵列与准直器组合的结构、以及OPA调整相邻第二激光束之间的夹角的实现方式可参见上述夹角调整模块的介绍，此处不再赘述。
该步骤902中，可以是处理控制模块控制探测模块在不同的探测角度下分别向探测区域发射调整后的N个第二激光束，并控制扫描模块在探测区域内进行扫描，具体过程可参数上述对探测模块、扫描模块和处理控制模块的介绍，此处不再赘述。
步骤903，接收来自探测区域的N个回波信号。
当第二激光束射向探测区域后，经目标物体反射回回波信号，一个第二激光束对应一个回波信号，N个第二激光束射向探测区域，可反射回N个回波信号，N个回波信号与被发射到探测区域内的N个第二激光束一一对应。
步骤904，针对N个回波信号中的每个回波信号，将回波信号与对应的第一激光束进行混频处理，得到N个拍频信号，并根据拍频信号确定探测区域中的目标物体的关联信息。
此处，以第i个激光束为例，其中，第i个激光束可为N个激光束的任意一激光束，可将第i个激光束分为第i个第一激光束和第i个第二激光束，第i个第二激光束射向探测区域后，可反射回第i个回波信号，可将第i个第一激光束和第i个回波信号进行混频处理，得到拍频信号。
从上述步骤901至步骤904可以看出，N个第二激光束中的任意相邻的两个第二激光束之间的夹角调整为大于0度且不大于激光雷达的角分辨率，即各个第二激光束相互交错对探测区域进行扫描，扫描模块在每个探测角度下，向探测区域发射N个第二激光束进行探测，可反射回N个回波信号，一个回波信号和一个第一激光束可确定出一个目标物体的关联信息，可根据N个回波信号和对应的N个第一激光束，确定出N个关联信息。也就是说，通过本申请的激光雷达，一次探测过程中获取到的关联信息较多，由于目标物体的关联信息可用于形成图像，从而根据较多的关联信息确定出的点云密度也较高，形成的图像清晰度也较高。
由于N个第二激光束中任意相邻的两个第二激光束之间的夹角比较小，因此，一个第二激光束的回波信号有可能射入另一个第二激光束对应的探测模块，进而造成两个回波信号之间的串扰问题。为了尽可能避免回波信号之间的串扰问题，本申请可对N个激光束进行调制，示例性地，可根据第一预设条件对N个激光束进行调制，第一预设条件为夹角小于预设角度的两个激光束采用不同的频率调制速率。具体的调制过程可参见上述探测模块中的实现方式一和实现方式二的介绍，此处不再赘述。
进一步地，可选地，根据第一预设条件对N个激光束进行调制，得到的激光束均为调频连续波FMCW。如此，可利用多普勒效应测量出目标物体相对于激光雷达的运动速率，从而有助于扩展激光雷达的应用场景。
尽管结合具体特征及其实施例对本申请进行了描述，显而易见的，在不脱离本申请的精神和范围的情况下，可对其进行各种修改和组合。相应地，本说明书和附图仅仅是所附权利要求所界定的方案进行示例性说明，且视为已覆盖本申请范围内的任意和所有修改、变化、组合或等同物。
显然，本领域的技术人员可以对本申请进行各种改动和变型而不脱离本发明的精神和范围。这样，倘若本申请实施例的这些修改和变型属于本申请权利要求及其等同技术的范围之内，则本申请也意图包含这些改动和变型在内。

Claims (16)

  1. 一种激光雷达，其特征在于，包括：激光器、N个第一分束模块、夹角调整模块、N个探测模块、扫描模块和处理控制模块，所述N个第一分束模块与所述N个探测模块一一对应；
    所述激光器，用于发射N个激光束，并将所述N个激光束传输至所述N个第一分束模块，所述N个激光束与所述N个第一分束模块一一对应，所述N为大于1的整数；
    针对所述N个第一分束模块中的每个第一分束模块，所述第一分束模块用于将接收到的激光束分为第一激光束和第二激光束，得到N个第一激光束和N个第二激光束；
    所述夹角调整模块，用于接收来自所述N个第一分束模块的N个第二激光束，并将所述N个第二激光束中任意相邻的两个第二激光束之间的夹角调整为大于0度且不大于所述激光雷达的角分辨率；
    所述扫描模块，用于接收来自所述光束夹角调整模块的N个第二激光束，并在不同探测角度下分别向探测区域发射所述N个第二激光束；
    针对所述N个探测模块中的每个探测模块，所述探测模块用于接收来自对应的第一分束模块的所述第一激光束，以及接收对应的回波信号，并对接收到的所述第一激光束和所述回波信号进行混频，得到拍频信号，并根据所述拍频信号确定所述探测区域中的目标物体的关联信息，其中，所述对应的回波信号为来自对应的第一分束模块的所述第二激光束在所述探测区域内反射回来的信号；
    所述处理控制模块，用于控制所述扫描模块处于不同探测角度。
  2. 如权利要求1所述的激光雷达，其特征在于，所述激光雷达还包括调制器；
    所述调制器，用于根据第一预设条件对来自所述激光器的N个激光束进行调制；
    所述第一预设条件为：夹角小于预设角度的两个激光束采用不同的频率调制速率。
  3. 如权利要求1所述的激光雷达，其特征在于，所述激光器还用于：
    根据第一预设条件调制所述N个激光束；
    所述第一预设条件为：夹角小于预设角度的两个激光束采用不同的频率调制速率。
  4. 如权利要求1至3任一项所述的激光雷达，其特征在于，所述光束夹角调整模块包括N个光纤和准直器，所述N个光纤与所述N个第二激光束一一对应；
    针对所述N个光纤中的每个光纤，所述光纤用于接收来自对应的所述第一分束模块的所述第二激光束，并将接收到的所述第二激光束传输至所述准直器；
    所述准直器，用于接收来自所述N个光纤的N个第二激光束，并对所述N个第二激光束进行准直，得到任意相邻的两个第二激光束之间的夹角大于0度且不大于所述激光雷达的角分辨率的所述N个第二激光束。
  5. 如权利要求4所述的激光雷达，其特征在于，所述N个光纤的出光口均位于所述准直器的物方焦平面上。
  6. 如权利要求4或5所述的激光雷达，其特征在于，所述扫描模块位于所述准直器的像方焦平面上。
  7. 如权利要求1至6任一项所述的激光雷达，其特征在于，所述激光雷达还包括N个分光模块，所述N个分光模块与所述N个回波信号一一对应，所述N个分光模块与所述N个探测模块一一对应；
    针对所述N个分光模块中每个分光模块，所述分光模块用于将接收到的所述回波信号传输至对应的探测模块。
  8. 如权利要求7所述的激光雷达，其特征在于，所述分光模块为光纤环形器，所述光纤环形器位于所述第一分束模块与所述夹角调整模块之间；
    所述激光器与所述N个第一分束模块之间、所述N个第一分束模块与所述N个光纤环形器之间、所述N个光纤环形器与所述夹角调整模块之间均通过光纤连接。
  9. 如权利要求2至8任一项所述的激光雷达，其特征在于，根据所述第一预设条件对所述N个激光束进行调制，得到的激光束均为调频连续波FMCW。
  10. 如权利要求2所述的激光雷达，其特征在于，所述处理控制模块还用于控制所述扫描模块和所述调制器之间进行同步。
  11. 如权利要求3所述的激光雷达，其特征在于，所述处理控制模块还用于控制所述扫描模块和所述激光器之间进行同步。
  12. 一种激光雷达的探测方法，其特征在于，包括：
    将N个激光束中的每个激光束分为第一激光束和第二激光束，得到N个第一激光束和N个第二激光束，其中，所述N为大于1的整数；
    将所述N个第二激光束中任意相邻的两个第二激光束之间的夹角调整为大于0度且不大于所述激光雷达的角分辨率，并在不同探测角度下分别向探测区域发射调整后的所述N个第二激光束；
    接收来自所述探测区域的N个回波信号，所述N个回波信号与被发射到所述探测区域内的所述N个第二激光束一一对应；
    针对所述N个回波信号中的每个回波信号，将所述回波信号与对应的第一激光束进行混频处理，得到拍频信号，并根据所述拍频信号确定所述探测区域中的目标物体的关联信息。
  13. 如权利要求12所述的方法，其特征在于，所述方法还包括：
    根据第一预设条件对所述N个激光束进行调制；
    其中，所述第一预设条件为：夹角小于预设角度的两个激光束采用不同的频率调制速率。
  14. 如权利要求13所述的方法，其特征在于，所述根据所述第一预设条件对所述N个激光束进行调制，得到的激光束均为调频连续波FMCW。
  15. 一种计算机可读存储介质，其特征在于，所述计算机可读存储介质中存储有计算机程序或指令，当所述计算机程序或指令被激光雷达执行时，实现如权利要求12至14中任一项所述的方法。
  16. 一种计算机程序产品，其特征在于，所述计算机程序产品包括计算机程序或指令，当所述计算机程序或指令被激光雷达执行时，实现如权利要求12至14中任一项所述的方法。
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