WO2022021237A1 - 一种激光雷达和智能车辆 - Google Patents

一种激光雷达和智能车辆 Download PDF

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Publication number
WO2022021237A1
WO2022021237A1 PCT/CN2020/105930 CN2020105930W WO2022021237A1 WO 2022021237 A1 WO2022021237 A1 WO 2022021237A1 CN 2020105930 W CN2020105930 W CN 2020105930W WO 2022021237 A1 WO2022021237 A1 WO 2022021237A1
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Prior art keywords
signal
wave plate
laser
polarization state
beat
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PCT/CN2020/105930
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English (en)
French (fr)
Inventor
李孟麟
刘彤辉
姜彤
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华为技术有限公司
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Application filed by 华为技术有限公司 filed Critical 华为技术有限公司
Priority to EP20947111.9A priority Critical patent/EP4187283A4/en
Priority to CN202080004707.3A priority patent/CN112639529B/zh
Priority to CN202210292408.5A priority patent/CN114814882A/zh
Priority to PCT/CN2020/105930 priority patent/WO2022021237A1/zh
Publication of WO2022021237A1 publication Critical patent/WO2022021237A1/zh
Priority to US18/161,665 priority patent/US20230176215A1/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
    • G01S17/02—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
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W30/00—Purposes of road vehicle drive control systems not related to the control of a particular sub-unit, e.g. of systems using conjoint control of vehicle sub-units
    • B60W30/08—Active safety systems predicting or avoiding probable or impending collision or attempting to minimise its consequences
    • B60W30/095—Predicting travel path or likelihood of collision
    • 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
    • G01S17/50—Systems of measurement based on relative movement of target
    • G01S17/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
    • 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
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/88—Lidar systems specially adapted for specific applications
    • G01S17/93—Lidar systems specially adapted for specific applications for anti-collision purposes
    • G01S17/931—Lidar systems specially adapted for specific applications for anti-collision purposes of land vehicles
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/481—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
    • G01S7/4811—Constructional features, e.g. arrangements of optical elements common to transmitter and receiver
    • 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
    • G01S7/4912—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
    • 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
    • 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
    • G01S7/495—Counter-measures or counter-counter-measures using electronic or electro-optical means
    • 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
    • G01S7/499—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00 using polarisation effects
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W2420/00—Indexing codes relating to the type of sensors based on the principle of their operation
    • B60W2420/40—Photo, light or radio wave sensitive means, e.g. infrared sensors
    • B60W2420/408—Radar; Laser, e.g. lidar

Definitions

  • the present application relates to the field of radar detection, in particular to a lidar and an intelligent vehicle.
  • LiDAR is an optical remote sensing technology that obtains target-related information by detecting the scattered light characteristics of the target.
  • LiDAR has high measurement accuracy, fine temporal and spatial resolution, and can complete functions such as mapping, tracking, and imaging recognition. It has broad application prospects in the fields of intelligent transportation, autonomous driving, atmospheric environment monitoring, geographic mapping, and drones.
  • LiDAR can be mainly divided into three types according to the modulation method: Pulsed LiDAR, Amplitude Modulated Continuous Wave LiDAR (AMCW LiDAR) and Coherent LiDAR.
  • a linear frequency modulation laser signal is emitted, and the echo signal formed by the laser signal reflected by the target is received by the lidar.
  • the echo signal and the local oscillator signal will be coherent at the front end of the detector, and the generated frequency is the echo signal.
  • the beat frequency signal which is the difference between the instantaneous frequency of the wave signal and the local oscillator signal, can obtain the speed information and distance information of the target by analyzing the beat frequency signal.
  • the common laser radar transmits and receives signals through the optical fiber optical path. Due to the limitation of the size of the optical fiber, the energy of the received echo signal will be limited, resulting in low detection accuracy of the laser radar.
  • the embodiment of the present application discloses a laser radar optical system, which can transmit signals through a spatial optical path, expand the receiving aperture according to actual needs, and increase the received echo signals.
  • a first aspect of the embodiments of the present application discloses a laser radar, including: a laser, for generating a laser signal; a beam shaping module, for collimating the laser signal; and a beam splitting module, for The laser signal is subjected to beam splitting processing to obtain the detection signal and the local oscillator signal; the receiving module is used to receive the echo signal and transmit the echo information to the optical mixing module; wherein, the echo signal is the detection signal reflected back by the target object
  • the optical mixing module is used to optically mix the local oscillator signal and the echo signal to obtain the first beat signal and the second beat signal; the phase difference between the first beat signal and the second beat signal is 180 degrees; the differential receiving unit is used for differential reception of the first beat signal and the second beat signal; the first beat signal and the second beat signal are used to determine the target information of the target object.
  • the coherent detection optical path is realized by the beam shaping module, the beam splitting module, the receiving module and the optical mixing module, which can increase the aperture of the received echo signal, and can also weaken the optical crosstalk problem to the echo signal, so that the received echo signal can be received. more energy of the echo signal. Therefore, after mixing the local oscillator signal and the echo signal, more energy of the first beat frequency signal and the second beat frequency signal can be obtained, which improves the detection accuracy of the laser radar for the target object.
  • the beam splitting module includes a beam splitter and a first half-wave plate, the first half-wave plate is arranged between the beam shaping module and the beam splitter, and the first half-wave plate is arranged between the beam shaping module and the beam splitter. Used to adjust the polarization direction of the laser signal.
  • the target information of the target object includes at least one of distance or speed.
  • the receiving module includes a quarter wave plate, a quarter wave plate is arranged on the side where the beam splitter outputs the detection signal, and a quarter wave plate is arranged on the side where the optical mixing module inputs the echo signal.
  • One wave plate, and a quarter wave plate is used to convert the polarization state of the passing echo signal and probe signal.
  • the polarization state of the echo signal and the detection signal is changed by a quarter wave plate, so that the problem of frequency mixing efficiency can be improved.
  • the quarter-wave plate set on the side where the beam splitter outputs the detection signal is the same wave plate as the quarter-wave plate set on the side where the optical mixing module inputs the echo signal, or , the quarter-wave plate set on the side of the beam splitter outputting the detection signal, and the quarter-wave plate set on the side of the optical mixing module inputting the echo signal are two different wave plates.
  • the optical mixing module includes a beam combiner and a polarization beam splitter prism
  • the wave plate further includes a second half-wave plate
  • the polarization beam splitter prism includes a first polarization beam splitter prism
  • the second half-wave plate is arranged on the between the beam combiner and the first polarized beam splitter prism
  • the beam splitter, the beam combiner, the second half-wave plate and the first polarized beam splitter prism are arranged on the same axis
  • the beam combiner is used to combine the polarization state
  • the converted echo signal and local oscillator signal are combined into one optical path
  • the second half-wave plate is used to convert the combined echo signal and local oscillator signal on one optical path into the first 45 degree polarization respectively signal and the second 45-degree polarized signal
  • the first 45-degree polarized signal and the second 45-degree polarized signal are signals with orthogonal polarization directions
  • the 45-degree polarized light is subjected to frequency mixing processing to
  • the polarizing beam splitting prism includes a second polarizing beam splitting prism; the beam splitter and the second polarizing beam splitting prism are arranged on the same axis;
  • the echo signal converted by the polarization state is subjected to frequency mixing processing to obtain a first beat signal and a second beat signal with a phase difference of 180 degrees;
  • the echo signal and the local oscillator signal are signals with orthogonal polarization directions.
  • the polarization states of the detection signal and the local oscillator signal are linear polarization states.
  • the polarization state of the detection signal after polarization state conversion is a circular polarization state or an elliptical polarization state.
  • the polarization state of the echo signal is a circular polarization state or an elliptical polarization state; the polarization state of the echo signal after the polarization state conversion is performed is a linear polarization state.
  • a second aspect of the embodiments of the present application discloses an intelligent vehicle, including: a lidar and a processor, where the lidar is configured to perform the functions of the lidar in the first aspect, and the processor is configured to drive intelligently based on the lidar.
  • the intelligent driving of the intelligent vehicle based on the lidar can improve the accuracy of the driving route and increase the driving safety factor.
  • FIG. 1 is a functional block diagram of an intelligent vehicle provided by an embodiment of the present application.
  • FIG. 2 is a schematic diagram of the architecture of a laser radar based on an optical fiber optical path provided by an embodiment of the present application
  • FIG. 2A is a schematic diagram of the architecture of a lidar provided by an embodiment of the present application.
  • FIG. 2B is a schematic diagram of a beat frequency signal generated by a triangular wave provided by an embodiment of the present application
  • FIG. 3 is a schematic flowchart of a method for generating a beat signal provided by an embodiment of the present application
  • 3A is a schematic structural diagram of a lidar provided by an embodiment of the present application.
  • FIG. 3B is a schematic structural diagram of another laser radar provided by an embodiment of the present application.
  • 3C is a schematic structural diagram of another lidar provided by an embodiment of the present application.
  • FIG. 3D is a schematic structural diagram of another lidar provided by an embodiment of the present application.
  • FIG. 1 is a functional block diagram of an intelligent vehicle provided by an embodiment of the present application.
  • the intelligent vehicle 001 may be configured in a fully or partially autonomous driving mode.
  • the intelligent vehicle 001 can control itself while in an autonomous driving mode, and can determine the current state of the vehicle and its surrounding environment through human operation, determine the possible behavior of at least one other vehicle in the surrounding environment, and determine the other A confidence level corresponding to the likelihood that the vehicle will perform a possible action, the intelligent vehicle 001 is controlled based on the determined information.
  • the intelligent vehicle 001 may be placed to operate without human interaction.
  • Intelligent vehicle 001 may include various subsystems, such as travel system 102 , sensor system 104 , control system 106 , one or more peripherals 108 and power supply 110 , computer system 112 and user interface 116 .
  • intelligent vehicle 001 may include more or fewer subsystems, and each subsystem may include multiple elements. Additionally, each of the subsystems and elements of the intelligent vehicle 001 may be wired or wirelessly interconnected.
  • the travel system 102 may include components that provide powered motion for the intelligent vehicle 001 .
  • travel system 102 may include engine 118 , energy source 119 , transmission 120 , and wheels/tires 121 .
  • the engine 118 may be an internal combustion engine, an electric motor, an air compression engine, or other types of engine combinations, such as a hybrid engine consisting of a gas oil engine and an electric motor, a hybrid engine consisting of an internal combustion engine and an air compression engine.
  • Engine 118 converts energy source 119 into mechanical energy.
  • Examples of energy sources 119 include gasoline, diesel, other petroleum-based fuels, propane, other compressed gas-based fuels, ethanol, solar panels, batteries, and other sources of electricity. Energy source 119 may also provide energy to other systems of intelligent vehicle 001 .
  • Transmission 120 may transmit mechanical power from engine 118 to wheels 121 .
  • Transmission 120 may include a gearbox, a differential, and a driveshaft.
  • transmission 120 may also include other devices, such as clutches.
  • the drive shaft may include one or more axles that may be coupled to one or more wheels 121 .
  • Sensor system 104 may include several sensors that sense information about the environment surrounding intelligent vehicle 001 .
  • the sensor system 104 may include a positioning system 122 (the positioning system may be a GPS system, a Beidou system or other positioning systems), an inertial measurement unit (IMU) 124, a lidar 126, a laser rangefinder 128 and camera 130 .
  • the sensor system 104 may also include sensors that monitor the internal systems of the smart vehicle 001 (eg, an in-vehicle air quality monitor, a fuel gauge, an oil temperature gauge, etc.). Sensor data from one or more of these sensors can be used to detect objects and their corresponding characteristics (position, shape, orientation, velocity, etc.). This detection and identification is a critical function for the safe operation of the autonomous intelligent vehicle 001.
  • the positioning system 122 may be used to estimate the geographic location of the intelligent vehicle 001 .
  • the IMU 124 is used to sense position and orientation changes of the intelligent vehicle 001 based on inertial acceleration.
  • IMU 124 may be a combination of an accelerometer and a gyroscope.
  • the IMU 124 can be used to measure the curvature of the smart vehicle 001 .
  • the lidar 126 may utilize radio signals to sense objects within the surrounding environment of the intelligent vehicle 001 .
  • a radar system is used to transmit detection signals to detect characteristic quantities such as position, velocity, etc. of a target object. Its working principle is to transmit a detection signal (laser beam) to the target object, and then coherent the received signal (echo signal) reflected from the target object with the local oscillator signal, and the generated frequency is the instantaneous echo signal and local oscillator signal.
  • the phase difference between the first beat signal and the second beat signal is 180 degrees.
  • the differential receiving unit amplifies the first beat frequency signal and the second beat frequency signal differentially and outputs them to the processor, and the processor processes to obtain the speed, distance and other information of the target object.
  • the laser rangefinder 128 may utilize laser light to sense objects in the environment in which the intelligent vehicle 001 is located.
  • the laser rangefinder 128 may include one or more laser sources, laser scanners, and one or more detectors, among other system components.
  • Camera 130 may be used to capture multiple images of the surrounding environment of intelligent vehicle 001 .
  • Camera 130 may be a still camera or a video camera.
  • Control system 106 controls the operation of the intelligent vehicle 001 and its components.
  • Control system 106 may include various elements including steering system 132 , throttle 134 , braking unit 136 , sensor fusion algorithms 138 , computer vision system 140 , route control system 142 , and obstacle avoidance system 144 .
  • Steering system 132 is operable to adjust the heading of intelligent vehicle 001 .
  • it may be a steering wheel system.
  • the throttle 134 is used to control the operating speed of the engine 118 and thus the speed of the intelligent vehicle 001 .
  • the braking unit 136 is used to control the deceleration of the intelligent vehicle 001 .
  • the braking unit 136 may use friction to slow the wheels 121 .
  • the braking unit 136 may convert the kinetic energy of the wheels 121 into electrical current.
  • the braking unit 136 may also take other forms to slow down the wheels 121 to control the speed of the smart vehicle 001 .
  • Computer vision system 140 is operable to process and analyze images captured by camera 130 in order to identify objects and/or features in the environment surrounding intelligent vehicle 001 .
  • the objects and/or features may include traffic signals, road boundaries and obstacles.
  • Computer vision system 140 may use object recognition algorithms, Structure from Motion (SFM) algorithms, video tracking, and other computer vision techniques.
  • SFM Structure from Motion
  • the computer vision system 140 may be used to map the environment, track objects, estimate the speed of objects, and the like.
  • the route control system 142 is used to determine the travel route of the intelligent vehicle 001 .
  • route control system 142 may combine data from sensors 138, GPS 122, and one or more predetermined maps to determine a driving route for intelligent vehicle 001.
  • Obstacle avoidance system 144 is used to identify, evaluate and avoid or otherwise overcome potential obstacles in the environment of intelligent vehicle 001 .
  • control system 106 may additionally or alternatively include components other than those shown and described. Alternatively, some of the components shown above may be reduced.
  • the intelligent vehicle 001 interacts with external sensors, other vehicles, other computer systems, or the user through peripheral devices 108 .
  • Peripherals 108 may include a wireless communication system 146 , an onboard computer 148 , a microphone 150 and/or a speaker 152 .
  • peripherals 108 provide a means for a user of intelligent vehicle 001 to interact with user interface 116 .
  • the onboard computer 148 may provide information to the user of the smart vehicle 001 .
  • User interface 116 may also operate on-board computer 148 to receive user input.
  • the onboard computer 148 can be operated via a touch screen.
  • peripherals 108 may provide a means for intelligent vehicle 001 to communicate with other devices located within the vehicle.
  • microphone 150 may receive audio (eg, voice commands or other audio input) from a user of intelligent vehicle 001 .
  • speaker 152 may output audio to the user of smart vehicle 001 .
  • Wireless communication system 146 may wirelessly communicate with one or more devices, either directly or via a communication network.
  • wireless communication system 146 may use 3G cellular communications, such as CDMA, EVDO, GSM/GPRS, or 4G cellular communications, such as LTE. Or 5G cellular communications.
  • the wireless communication system 146 may communicate with a wireless local area network (WLAN) using WiFi.
  • WLAN wireless local area network
  • the wireless communication system 146 may communicate directly with the device using an infrared link, Bluetooth, or ZigBee.
  • Other wireless protocols, such as various vehicle communication systems, for example, wireless communication system 146 may include one or more dedicated short range communications (DSRC) devices, which may include a combination of vehicle and/or roadside stations. public and/or private data communications between them.
  • DSRC dedicated short range communications
  • Power supply 110 may provide power to various components of intelligent vehicle 001 .
  • the power source 110 may be a rechargeable lithium-ion or lead-acid battery.
  • One or more battery packs of such batteries may be configured as a power source to provide power to various components of the intelligent vehicle 002 .
  • power source 110 and energy source 119 may be implemented together, such as in some all-electric vehicles.
  • Computer system 112 may include at least one processor 113 that executes instructions 115 stored in a non-transitory computer-readable medium such as data storage device 114 .
  • Computer system 112 may also be multiple computing devices that control individual components or subsystems of intelligent vehicle 001 in a distributed fashion.
  • the processor 113 may be any conventional processor, such as a commercially available CPU. Alternatively, the processor may be a dedicated device such as an ASIC or other hardware-based processor.
  • FIG. 1 functionally illustrates a processor, memory, and other elements of the computer in the same block, one of ordinary skill in the art will understand that the processor, computer, or memory may actually include storage that may or may not be Multiple processors, computers, or memories within the same physical enclosure.
  • the memory may be a hard drive or other storage medium located within an enclosure other than a computer.
  • reference to a processor or computer will be understood to include reference to a collection of processors or computers or memories that may or may not operate in parallel.
  • some components such as the steering and deceleration components may each have their own processor that only performs computations related to component-specific functions .
  • a processor may be located remotely from the vehicle and in wireless communication with the vehicle. In other aspects, some of the processes described herein are performed on a processor disposed within the vehicle while others are performed by a remote processor, including taking steps necessary to perform a single maneuver.
  • memory 114 may include instructions 115 (eg, program logic) executable by processor 113 to perform various functions of intelligent vehicle 001 , including those described above.
  • Memory 124 may also contain additional instructions including sending data, receiving data from, interacting with and/or controlling one or more of travel system 102 , sensing system 104 , control system 106 and peripherals 108 instruction.
  • the memory 114 may store data such as road maps, route information, the position, direction, speed of the vehicle, and the speed, position of objects around the vehicle (eg, other vehicles), and other such data, among other information. . Such information may be used by intelligent vehicle 001 and computer system 112 during operation of intelligent vehicle 001 in autonomous, semi-autonomous, and/or manual modes.
  • User interface 116 for providing information to or receiving information from a user of intelligent vehicle 001 .
  • user interface 116 may include one or more input/output devices within the set of peripheral devices 108 , such as wireless communication system 146 , onboard computer 148 , microphone 150 and speaker 152 .
  • Computer system 112 may control functions of intelligent vehicle 001 based on input received from various subsystems (eg, travel system 102 , sensor system 104 , and control system 106 ) and from user interface 116 .
  • computer system 112 may utilize input from control system 106 in order to control steering unit 132 to avoid obstacles detected by sensor system 104 and obstacle avoidance system 244 .
  • computer system 112 is operable to provide control over many aspects of intelligent vehicle 001 and its subsystems.
  • one or more of these components described above may be installed or associated with the intelligent vehicle 001 separately.
  • data storage device 114 may exist partially or completely separate from intelligent vehicle 001 .
  • the above-described components may be communicatively coupled together in a wired and/or wireless manner.
  • FIG. 1 should not be construed as a limitation on the embodiments of the present application.
  • the above-mentioned intelligent vehicles 001 can be cars, trucks, motorcycles, buses, boats, airplanes, helicopters, lawn mowers, recreational vehicles, playground vehicles, construction equipment, trams, golf carts, trains, and trolleys, etc.,
  • the embodiments of the present application are not particularly limited.
  • FIG. 1 is only an exemplary implementation in the embodiments of the present application, and the smart vehicles in the embodiments of the present application include but are not limited to the above structures.
  • the commonly used laser radar is shown in Figure 2 as a schematic diagram of the architecture of the laser radar based on the optical fiber path.
  • 1 fiber optic coupler The laser signal emitted by the laser is coupled into the optical path through the fiber.
  • the laser signal is divided into two parts: the detection signal and the local oscillator signal through a 1 ⁇ 2 fiber coupler.
  • the echo signal is coupled into the fiber through the lens, received by the fiber circulator, and then passes through the 2 ⁇ 1 fiber coupler with the local oscillator signal to generate the beat frequency signal, and then the beat frequency signal is received by the detector and processed by the differential amplifier circuit.
  • both the transmitted probe signal and the received echo signal need to pass through the fiber circulator, the existence of the fiber circulator may cause crosstalk to the received echo signal; and the echo signal needs to be coupled into the fiber through the lens, due to the limitation of the fiber size , the aperture of the lens cannot be too large, which will limit the energy of the received echo signal, resulting in low detection accuracy of the lidar.
  • FIG. 2A is a schematic diagram of the architecture of a laser radar provided by an embodiment of the present application.
  • the laser radar includes a laser 200 , a beam shaping module 201 , and a beam splitter.
  • a module 202 a receiving module 203 , an optical mixing module 204 , a differential receiving unit 205 , an analog-to-digital converter (Analog digital converte, ADC) 206 and a processor 207 .
  • ADC analog-to-digital converter
  • the lidar in the embodiments of the present application can be applied to various fields such as intelligent transportation, automatic driving, atmospheric environment monitoring, geographic mapping, and unmanned aerial vehicles, and can perform functions such as distance measurement, speed measurement, target tracking, and imaging recognition.
  • the laser 200 generates a laser signal
  • the laser signal generated by the laser can be a frequency modulated continuous wave (Frequency Modulated Continuous Wave, FMCW) signal
  • the modulation waveform of its laser frequency can be a sawtooth shape, a triangle wave, or other forms of waveforms.
  • the laser signal generated by the laser 200 is an FMCW signal
  • the laser 200 may be a frequency modulated laser (Tunable Laser, TL), such as a Distributed Feedback Laser (DFB), a Laser Diode (LD), a fiber laser and a vertical Cavity Surface Emitting Laser (Vertical Cavity Surface Emitting Laser, VCSEL), etc.
  • DFB Distributed Feedback Laser
  • LD Laser Diode
  • VCSEL Vertical Cavity Surface Emitting Laser
  • the laser signal may be called a laser pulse, a laser beam, a laser or other names, as long as the meanings are the same, they all belong to the protection scope of the embodiments of the present application.
  • the laser signal generated by the laser 200 is used to measure at least one of the speed or the distance of the target object 210 .
  • the beam shaping module 201 is used to perform collimation processing on the laser signal generated by the laser 200, and the laser signal after the collimation processing can meet the preset optical characteristics requirements such as the spot size, divergence angle and beam waist radius. It should be noted that the beam shaping module 201 may be a lens, that is, composed of one or more than two lenses.
  • the beam splitting module 202 is configured to perform beam splitting processing on the laser signal after the collimation processing, and the beam splitting processing obtains the detection signal and the local oscillator signal; wherein, the laser signal is subjected to the beam splitting processing to obtain the detection signal and the local oscillator signal.
  • the optical properties such as energy, polarization state, etc. are all the same, and are the same as the optical properties of the laser signal generated by the laser 200 .
  • the receiving module 203 includes a scanner 203A, which is also called a 2D scanner.
  • the receiving module 203 is used to convert the polarization state of the detection signal, and the scanner 203A transmits the detection signal at a certain angle; after the transmission signal is transmitted, it is reflected by the target object 210 to form an echo signal; at this time, the scanning
  • the receiver 203A is further configured to receive the echo signal, and the receiving module 203 is further configured to convert the polarization state of the received echo signal, and then converge the echo signal to the optical mixing module.
  • the module for transmitting and the module for receiving in the receiving module 203 may be relatively independent modules.
  • the receiving module 203 is generally composed of a telephoto optical system, and the telephoto optical system may include at least one of Kepler type, Galileo type, Newton type, Cassegrain type and other telescopic optical systems.
  • the optical mixing module 204 is configured to perform mixing processing on the echo signal received by the receiving module 203 and the local oscillator signal separated by the beam splitting module 202 to obtain a first beat frequency signal and a second beat frequency signal.
  • the optical mixing module has the properties of semi-transmission and semi-reflection, that is, the received signal is subjected to reflection processing and refraction processing to form two beams of signals. Wherein, the first beat frequency signal and the second beat frequency are used to determine at least one of the distance or the speed of the target object.
  • the beat signal obtained by performing mixing processing by the optical mixing module 204 includes a first beat signal and a second beat signal, and the phase difference between the first beat signal and the second beat signal is 180 degrees.
  • the beat frequency signal is a signal whose frequency is the difference between the local oscillator signal and the instantaneous frequency of the echo signal.
  • the beat signal may also be referred to as a beat signal, a beat signal, etc., and the embodiments of the present application do not impose any restrictions on the name of the beat signal.
  • the detector 211 and the detector 212 wherein the first beat frequency signal generated by the optical mixing module 204 is received through the photosensitive surface of the detector 211, and the second beat frequency signal received by the optical mixing module 204 is collected through the photosensitive surface of the detector 212. beat signal.
  • the differential receiving unit 205 is configured to perform differential reception on the first beat signal and the second beat signal received by the detector 211 and the detector 212 to obtain one beat signal.
  • the signal obtained by differential reception can greatly reduce the noise and improve the signal-to-noise ratio, thereby improving the measurement accuracy of the radar detection system.
  • the analog-to-digital converter ADC206 is used to sample the beat frequency signal, so that sampling is essentially a process of converting an analog signal into a digital signal.
  • the processor 207 may include a digital signal processor (Digital signal processor, DSP), a central processing unit (CPU), an accelerated processing unit (APU), a graphics processing unit (GPU), a microprocessor or a microcontroller, etc.
  • DSP Digital signal processor
  • CPU central processing unit
  • APU accelerated processing unit
  • GPU graphics processing unit
  • microprocessor or a microcontroller etc.
  • a device with computing capability is described in the accompanying drawing by taking a DSP as an example, the processor is used to process the sampled beat signal, thereby obtaining information such as the speed and distance of the target object 210 .
  • the target object 210 is also called a reflector, and the target object 210 can be any object in the scanning direction of the scanner, for example, it can be a person, a mountain, a vehicle, a tree, a bridge, etc.
  • FIG. 1 is a vehicle as the example is illustrated.
  • the operation of processing the sampled beat signal to obtain information such as the speed and distance of the target object 210 may be performed by one or more processors 207 , for example, by one or more DSPs , of course, it can also be completed by one or more processors 207 combined with other devices, for example, a DSP combined with one or more central processing units CPU to complete.
  • the processor 207 processes the beat signal, it can be specifically realized by calling a computer program stored in a computer-readable storage medium, and the computer-readable storage medium includes, but is not limited to, random access memory (RAM), read-only memory (ROM), erasable programmable read only memory (EPROM), or portable read-only memory (compact disc read-only memory, CD-ROM), which can It is configured in the processor 207 and may be independent of the processor 207 .
  • RAM random access memory
  • ROM read-only memory
  • EPROM erasable programmable read only memory
  • CD-ROM compact disc read-only memory
  • the laser 200 may be one or multiple.
  • the one laser 200 may be The laser signal with positive slope and the laser signal with negative slope are alternately emitted in the time domain; when there are two lasers 200 , one of them emits a laser signal with a positive slope, and the other emits a laser signal with a negative slope, and the two lasers 200 can be synchronized emit a laser signal.
  • the echo signal is mixed with the local oscillator signal after a period of flight time.
  • the time from the start to the return of the echo signal, the beat signal generated by the echo signal and the local oscillator signal is constant for a certain period of time after the flight time.
  • the beat frequency signal obtained after the differential reception of the two beat frequency signals is performed, and this period of time is the beat frequency time.
  • the beat frequency signal can accurately reflect the distance and speed information of the target object.
  • the beat frequency signal needs to include the beat frequency f 1 corresponding to the positive slope and the beat frequency f 2 corresponding to the negative slope.
  • FIG. 3 is a schematic flowchart of a method for generating a beat frequency signal provided by an embodiment of the present application. The process can be implemented based on the lidar shown in FIG. 2A, and the method includes but is not limited to the following steps:
  • Step S300 The beam shaping module performs collimation processing on the laser signal generated by the laser.
  • the spatial distribution of the spot energy of the laser signal generated by the laser 200 in the lidar optical system is generally non-uniform, with generally high middle and low edges, and a typical spatial distribution of the spot energy is a Gaussian distribution.
  • the beam of the laser signal has different beam waist positions and sizes in the fast axis direction and the slow axis direction, so that the laser signal forms a beam in the fast axis direction and an astigmatic beam in the slow axis direction, and the beam in the fast axis direction and the slow axis direction.
  • the beams have different divergence angles, the beam in the fast axis direction has a larger divergence angle, and the beam in the slow axis direction is smaller, so that the beam of the laser signal emitted from the laser 200 has asymmetry and the beam quality is not high .
  • it is necessary to pass the beam shaping module. 201 collimates the beam of the laser signal in the direction of the fast axis, and at the same time homogenizes the beam in the direction of the slow axis.
  • the beam shaping module 201 may be composed of one or more lenses.
  • the embodiment of the present application uses a beam shaping module composed of two lenses as an example for description. Actual requirements (such as spot size, divergence angle and beam waist radius and other specific requirements) should be used to select the corresponding lens.
  • Step S301 The beam splitting module performs beam splitting processing on the collimated laser signal to obtain a detection signal and a local oscillator signal.
  • the laser signal generated by the laser 200 in the lidar optical system is a frequency-modulated continuous-wave laser signal
  • the information carried by the frequency-modulated continuous-wave laser signal is mainly frequency information.
  • Coherence is performed to obtain a beat frequency signal, and at least one of the distance or the speed of the target object is obtained by calculating the beat frequency signal. Therefore, the beam splitting module 202 needs to perform beam splitting processing on the collimated laser signal to obtain the detection signal and the local oscillator signal.
  • the local oscillator signal and the detection signal are linearly polarized laser signals with the same polarization direction.
  • the beam splitting module 202 includes an optional first half-wave plate 2022 and a beam splitter 2021 .
  • the laser signal processed by the beam shaping module 201 is a linearly polarized laser signal, and the polarization direction of the linearly polarized laser signal is adjusted by the optional first half-wave plate 2022, and is aligned by the beam splitter 2021 in the beam splitting module 202.
  • the polarized laser signal is subjected to beam splitting processing to obtain a local oscillator signal and a detection signal.
  • the beam splitting module 202 includes a first half-wave plate 2022 and a beam splitter 2041.
  • the included angle of the linear polarization directions can adjust the angle of the laser signal passing through the first half-wave plate.
  • the first half-wave plate 2022 is used to adjust the linearly polarized laser signal to a signal with a polarization direction of 45 degrees. Therefore, after the beam splitter 2021 splits the signal The polarization directions of the obtained local oscillator signal and echo signal are also 45 degrees.
  • the beam splitter 2021 can be a polarized beam splitter, a non-polarized beam splitter prism, a semi-silvered prism, or a flat beam splitter lens.
  • the beam splitter 2021 shown in FIG. 3A is one provided by the embodiment of the present application. Example.
  • the laser signal is reflected and refracted by the beam splitter 2021 and split into two or more beams of signals. As shown in FIG. 3A , in this embodiment of the present application, the signal reflected by the beam splitter 2021 is used as the local oscillator signal, and the signal obtained by refraction by the beam splitter 2021 is used as the detection signal.
  • the laser signal emitted by the laser is a linearly polarized signal
  • the beam is shaped by the light shaping module and then processed by the beam splitting module; if the laser signal emitted by the laser is not a linearly polarized signal, it needs to be split in the Module 202 previously converts the laser signal to a linearly polarized signal.
  • the specific conversion method is to set a wave plate before the beam splitting module 202 (not shown in the embodiment of the present application), which may be to set a wave plate between the beam shaping module 201 and the beam splitting module 102, or set the wave plate between the laser 200 and the beam Wave plates are arranged between the shaping modules 201 .
  • the number and type of wave plates can be selected according to actual conditions, and the embodiments of the present application do not impose any limitations.
  • Step S302 the receiving module is configured to receive the echo signal and transmit the echo signal to the optical mixing module.
  • the polarization state of the detection signal emitted by the receiving module 203 to the target object is the circular polarization state or the elliptical polarization state state.
  • the polarization state of the laser signal generated by the laser 200 and emitted by the beam shaping module 201 is the linear polarization state, so the polarization state of the detection signal obtained by the beam splitting processing by the beam splitter 2021 is also the linear polarization state.
  • a quarter-wave plate (ie, a quarter-wave plate) is arranged on the side of the beam splitter 2021 where the detection signal is output, and the quarter-wave plate is used to convert the polarization state of the detection signal from a linear polarization state to a circular polarization state.
  • the receiving module 203 receives the echo signal obtained by the detection signal transmitted by the target object, and aggregates the echo signal into the optical mixing module 204 for mixing with the local oscillator signal.
  • a quarter wave plate needs to be set on the side of the input echo signal of the optical mixing module. The quarter wave plate is used to mix the echo signal.
  • the polarization state of the wave signal is converted from a circular polarization state to a linear polarization state.
  • the quarter-wave plate provided on the side where the beam splitter 2021 outputs the detection signal is the same wavelength plate as the quarter-wave plate provided on the side where the optical mixing module inputs the echo signal.
  • the receiving module 203 includes a polarization beam splitting prism 2031 , a quarter-wave plate 2032 , a primary mirror 2033 and a secondary mirror 2035 .
  • the receiving module further includes optical devices such as the secondary mirror 2034 . It should be noted that the receiving module is used to emit the detection signal and receive the echo signal.
  • the quarter wave plate 2032 is disposed at the refracting light surface of the polarizing beam splitter prism 2031 , and the laser 200 , the beam shaping module 201 , the beam splitting module 202 , the polarizing beam splitting prism 2031 and the quarter wave plate 2032 are disposed on the same axis.
  • the detection signal is transmitted through the polarization beam splitting prism 2031 to the quarter-wave plate 2032, and then converted into a detection signal whose polarization state is a circular polarization state or an elliptical polarization state, and is emitted to the target object through the scanner.
  • the reflected signal is reflected by the target object to obtain an echo signal
  • the echo signal is received by the scanner to the transmitter module 203, and then converted into an echo signal whose polarization state is linear polarization state after the quarter-wave plate 2032, and passes through the polarization beam splitter prism.
  • 2031 is refracted to an optical module composed of a primary mirror 2033, a secondary mirror 2034 and a secondary mirror 2035, and the above-mentioned optical module converges the echo signal to the optical mixing module 204 for optical mixing with the local oscillator signal.
  • FIG. 3D is a schematic structural diagram of another lidar optical system provided by an embodiment of the present application.
  • the receiving module 203 shown in FIG. 3B or FIG. 3D includes an apertured primary mirror 2036, a first quarter-wave plate 2037, a second quarter-wave plate 2038, a primary mirror 2033, a secondary mirror 2035, and other optical devices .
  • the receiving module further includes optical devices such as the secondary mirror 2034 .
  • the receiving module is used to emit the detection signal and receive the echo signal.
  • the fast axes of the first quarter-wave plate 2037 and the second quarter-wave plate 2038 shown in FIG. 3B and FIG. 3D are 45 degrees from the polarization direction of the detection signal obtained by the beam splitting process.
  • the first quarter-wave plate 2037 is disposed between the refracted light surface of the beam splitter 2021 and the incident surface of the apertured main mirror 2036.
  • the laser 200, the beam shaping module 201, the beam splitting module 202, and the apertured main reflection mirror 2036 and the first quarter wave plate 2037 are arranged on the same axis.
  • the second quarter wave plate 2038 is disposed between the light exit surface of the receiving module 103 and the light entrance surface of the optical mixing module 204 .
  • the detection signal is converted into a signal whose polarization state is a circular polarization state or an elliptical polarization state through the first quarter-wave plate 2037, and is emitted to the target object after passing through the apertured main mirror 2036 and the scanner.
  • the detection signal is reflected by the target object to obtain an echo signal, and the echo signal is received by the scanner to the receiving module 203, and is reflected by the apertured primary mirror 2036 to the optical mode composed of the primary mirror 2033, the secondary mirror 2034 and the secondary mirror 2035.
  • the above-mentioned optical module gathers the echo signal to the second quarter wave plate 2038, and the second quarter wave plate 2038 changes the polarization state of the echo signal from circular polarization state or elliptical polarization state. It is converted into a linear polarization state, and then output to the optical mixing module 204 for optical mixing with the local oscillator signal.
  • Step S303 The optical mixing module performs optical mixing on the local oscillator signal and the echo signal to obtain a first beat signal and a second beat signal.
  • the interference light beam formed by the local oscillator signal and the echo signal based on free space mixing is used to obtain the information in the beat frequency signal.
  • the optical mixing module 204 it is necessary to adjust the spot size of the local oscillator signal and the echo signal in the optical mixing module 204 to be basically consistent, and then perform mixing processing on the local oscillator signal and the echo signal whose polarization direction is converted to obtain the first beat frequency signal and The second beat frequency signal.
  • the optical mixing module has semi-transmissive and semi-reflective properties, it will transmit and reflect the passed signal, so the first beat frequency signal and the second beat frequency signal are obtained after processing the passed local oscillator signal and echo signal.
  • the echo signal and the local oscillator signal after the polarization direction conversion are linearly polarized signals with orthogonal polarization directions.
  • the optical mixing module 204 includes a beam shaping lens 2042 , a diaphragm 2043 , a beam combiner 2044 , a second half-wave plate 2045 , a first polarizing beam splitter prism 2046 and The first lens 2047 and the second lens 2048.
  • the beam splitter 2021 , the beam combiner 2044 , the second half-wave plate 2045 and the first polarizing beam splitter prism 2046 are arranged on the same axis.
  • the second half-wave plate 2045 is disposed between the beam combiner 2044 and the first polarization beam splitter prism 2046.
  • the beam combiner 2044 is used to combine the local oscillator signal and the echo signal.
  • the second half-wave The angle between the fast axis of the sheet 2045 and the polarization directions of the local oscillator signal and the echo signal is 45°.
  • the local oscillator signal is shaped into a signal consistent with the spot size of the echo signal after passing through the beam shaping lens 2042 and the diaphragm 2043.
  • the beam combiner mirror 2044 combines the polarization state-converted echo signal and the local oscillator signal into one optical path.
  • the echo signal and the local oscillator signal combined into one optical path are converted into the first 45 degree polarization signal and the second (45+90) degree polarization signal by the second half-wave plate 2045 respectively.
  • the first 45-degree polarization signal and the second 45-degree polarization signal are mixed at the first polarization beam splitter prism 2046 to obtain the first beat frequency signal and the second beat frequency signal with a phase difference of 180 degrees.
  • the optical mixing module 204 includes a beam shaping lens 2042 , a diaphragm 2043 , a second polarizing beam splitting prism 2040 , and a first lens 2047 and a second lens 2048 .
  • the local oscillator signal is shaped by the beam shaping lens 2042 and the diaphragm 2043 into a signal consistent with the spot size of the echo signal, and the polarization direction of the local oscillator signal is 45 degrees.
  • the polarization direction of the echo signal after polarization state conversion is (45+90) degrees, and the echo signal and the local oscillator signal are linearly polarized light with orthogonal polarization directions.
  • the local oscillator signal and the echo signal are mixed to obtain a first beat signal and a second beat signal with a phase difference of 180 degrees.
  • the first beat frequency signal and the second beat frequency signal obtained by the optical mixing module 204 are collected on the photosensitive surfaces of the detector 211 and the detector 212 through the first lens 2047 and the second lens 2048 respectively, and then received by the differential receiving unit 205
  • the first beat frequency signal and the second beat frequency signal received on the detector 211 and the detector 212 are differentially amplified to obtain one beat frequency signal, and the one beat frequency signal obtained by differential amplification is sent to the detector by the differential receiving unit 205.
  • the signals received on 211 and detector 212 are differentially amplified and then output.
  • the differentially amplified output signal can greatly reduce noise and improve the signal-to-noise ratio, thereby improving the measurement accuracy.
  • the polarization states of the first 45-degree polarization signal and the second 45-degree polarization signal are linear polarization states.
  • the wave plates mentioned in the embodiments of this application include a quarter wave plate, a first quarter wave plate, a second quarter wave plate, and a first half wave plate
  • the plate and the second half-wave plate can be coated or bonded to a certain light-emitting surface or a certain light-incident surface of the optical lens adjacent to the above-mentioned wave plate to realize their functions.
  • the function of the quarter-wave plate 2032 can be realized by coating or bonding the wave plate on the refracting and exiting surface of the polarizing beam splitter prism 2031;
  • the half-wave plate 2045 can be coated on the refracting and incident surface of the first polarizing beam splitter prism or the wave plate can be bonded to realize the function of the second half-wave plate 2045 .
  • a spatial optical path composed of optical modules such as a wave plate, a beam splitter, and a polarizing beam splitting prism is used to realize the coherent detection and receiving optical path, and the aperture of the received echo signal is increased, so that more The energy of the echo signal increases the accuracy of the radar detection system to detect the target object; the signal is received and detected by the optical module such as the polarization beam splitter prism or the apertured main reflector in the transmitting and receiving module, which can avoid the docking caused by optical crosstalk. Interference of the echo signal; converting the polarization state of the probe signal and the echo signal can improve the optical mixing efficiency.
  • the term “when” may be interpreted to mean “if” or “after” or “in response to determining" or “in response to detecting" depending on the context.
  • the phrases “in determining" or “if detecting (the stated condition or event)” can be interpreted to mean “if determining" or “in response to determining" or “on detecting (the stated condition or event)” or “in response to the detection of (the stated condition or event)”.
  • the above-mentioned embodiments it may be implemented in whole or in part by software, hardware, firmware or any combination thereof.
  • software it can be implemented in whole or in part in the form of a computer program product.
  • the computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of the present application are generated.
  • the computer may be a general purpose computer, special purpose computer, computer network, or other programmable device.
  • the computer instructions may be stored in or transmitted from one computer readable storage medium to another computer readable storage medium, for example, the computer instructions may be downloaded from a website site, computer, server or data center Transmission to another website site, computer, server, or data center by wire (eg, coaxial cable, optical fiber, digital subscriber line) or wireless (eg, infrared, wireless, microwave, etc.).
  • the computer-readable storage medium may be any available medium that can be accessed by a computer or a data storage device such as a server, data center, etc. that includes an integration of one or more available media.
  • the usable media may be magnetic media (eg, floppy disks, hard disks, magnetic tapes), optical media (eg, DVDs), or semiconductor media (eg, solid state drives), and the like.
  • the process can be completed by instructing the relevant hardware by a computer program, and the program can be stored in a computer-readable storage medium.
  • the program When the program is executed , which may include the processes of the foregoing method embodiments.
  • the aforementioned storage medium includes: ROM or random storage memory RAM, magnetic disk or optical disk and other mediums that can store program codes.

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Abstract

一种激光雷达和智能车辆，具体可以应用于智能车辆领域，其中，该激光雷达包括：激光器产生激光信号；光束整形模块对激光信号进行准直处理（步骤S300）；分束模块对激光信号进行分束处理，得到探测信号和本振信号（步骤S301）；接收模块接收回波信息并将回波信号传输至光学混频模块（步骤S302）；光学混频模块对本振信号和回波信息进行混频处理得到第一拍频信号和第二拍频信号（步骤S303）；差分接收单元对第一拍频信号和第二拍频信号进行差分接收；第一拍频信号和第二拍频信用于确定目标物体的距离或速度中的至少一项。该激光雷达可以通过空间光路来传输信号，根据实际需求扩大接收口径，增加接收到的回波信号。

Description

一种激光雷达和智能车辆 技术领域
本申请涉及雷达探测领域，尤其涉及一种激光雷达和智能车辆。
背景技术
激光雷达(LiDAR)是通过探测目标的散射光特性来获取目标相关信息的光学遥感技术。LiDAR具有高测量精度、精细的时间和空间分辨率，能完成测绘、跟踪和成像识别等功能，在智能交通、自动驾驶、大气环境监测、地理测绘、无人机等领域具有广阔的应用前景。LiDAR按照调制方式可以主要分为三种：脉冲激光雷达(Pulsed LiDAR)，调幅连续波激光雷达(AMCW LiDAR)和相干激光雷达(Coherent LiDAR)。
对于相干激光雷达来说，发射的是线性调频激光信号，激光信号经目标反射后形成的回波信号被激光雷达接收，回波信号与本振信号将在探测器前端产生相干，生成频率为回波信号与本振信号瞬时频率之差的拍频信号，通过对拍频信号的分析可以得到目标的速度信息和距离信息。
常见的激光雷达通过光纤光路发射信号和接收信号，由于光纤尺寸的限制，会限制接收到的回波信号的能量，从而导致激光雷达探测的精度不高。
发明内容
本申请实施例公开了一种激光雷达光学系统，可以通过空间光路来传输信号，根据实际需求扩大接收口径，增加接收到的回波信号。
本申请实施例第一方面公开了一种激光雷达，包括：激光器，用于产生激光信号；光束整形模块，用于对激光信号进行准直处理；分束模块，用于对进行准直处理后的激光信号进行分束处理，得到探测信号和本振信号；接收模块，用于接收回波信号并将回波信息传输至光学混频模块；其中，回波信号为探测信号经目标物体反射回的信号；光学混频模块，用于对本振信号和回波信号进行光学混频得到第一拍频信号和第二拍频信号；第一拍频信号和第二拍频信号之间的相位差为180度；差分接收单元，用于对第一拍频信号和第二拍频信号进行差分接收；第一拍频信号和第二拍频信号用于确定目标物体的目标信息。
上述方法中，通过光束整形模块、分束模块、接收模块和光学混频模块实现相干探测光路，可以增加接收回波信号的口径，还可以削弱对回波信号的光学串扰问题，从而可以接收到更多的回波信号的能量。因此，将本振信号和回波信号进行混频后可以得到更多的第一拍频信号和第二拍频信号的能量，提高了激光雷达对目标物体的探测精度。
可选地，分束模块包括分束镜和第一二分之一波片，第一二分之一波片设置于光束整形模块和分束镜之间，并且第一二分之一波片用于调整激光信号的偏振方向。
可选地，目标物体的目标信息包括距离或速度中的至少一项。
可选地，接收模块包括四分之一波片，在分束镜输出探测信号的一侧设置有四分之一波片，在光学混频模块输入回波信号的一侧设置有四分之一波片，并且四分之一波片用于对经过的回波信号和探测信号进行偏振态转换。
上述方法中，通过四分之一波片来改变回波信号和探测信号的偏振态，从而可以改善混频效率的问题。
可选地，在分束镜输出探测信号的一侧设置的四分之一波片，与光学混频模块输入回波信号的一侧设置的四分之一波片为同一个波片，或者，在分束镜输出探测信号的一侧设置的四分之一波片，与光学混频模块输入回波信号的一侧设置的四分之一波片为两个不同的波片。
可选地，光学混频模块包括合束镜和偏振分光棱镜，波片还包括第二二分之一波片，偏振分光棱镜包括第一偏振分光棱镜；第二二分之一波片设置于合束镜和第一偏振分光棱镜之间；分束镜、合束镜、第二二分之一波片和第一偏振分光棱镜设置于同一轴线上；合束镜，用于将进行偏振态转换的回波信号和本振信号合束到一个光路上；第二二分之一波片，用于将合束到一个光路上的回波信号和本振信号分别转换成第一45度偏振信号和第二45度偏振信号；其中，第一45度偏振信号和第二45度偏振信号为偏振方向正交的信号；第一偏振分光棱镜，用于对第一45度偏振光和第二45度偏振光进行混频处理得到相位差180度的第一拍频信号和第二拍频信号。
可选地，偏振分光棱镜包括第二偏振分光棱镜；分束镜和第二偏振分光棱镜设置于同一轴线上；第二偏振分光棱镜，用于对分别在两个光路上的本振信号和进行偏振态转换的回波信号进行混频处理得到相位差180度的第一拍频信号和第二拍频信号；回波信号和本振信号是偏振方向正交的信号。
可选地，所述探测信号和本振信号的偏振态为线偏振态。
可选地，进行偏振态转化后的探测信号的偏振态为圆偏振态或椭圆偏振态。
可选地，回波信号的偏振态为圆偏振态或椭圆偏振态；进行偏振态转化后的回波信号的偏振态为线偏振态。
本申请实施例第二方面公开了一种智能车辆，包括：激光雷达以及处理器，激光雷达用于执行第一方面的激光雷达的功能，处理器用于基于激光雷达来智能驾驶。
上述方法中，智能车辆基于激光雷达来智能驾驶可以提高驾驶路线的精确度，增加驾驶安全系数。
附图说明
图1是本申请实施例提供的一种智能车辆的功能框图；
图2是本申请实施例提供的一种基于光纤光路的激光雷达的架构示意图；
图2A是本申请实施例提供的一种激光雷达的架构示意图；
图2B是本申请实施例提供的一种三角波产生的拍频信号的示意图
图3是本申请实施例提供的一种拍频信号生成方法的流程示意图；
图3A是本申请实施例提供的一种激光雷达的结构示意图；
图3B是本申请实施例提供的另一种激光雷达的结构示意图；
图3C是本申请实施例提供的另一种激光雷达的结构示意图；
图3D是本申请实施例提供的另一种激光雷达的结构示意图。
具体实施方式
下面结合本申请实施例中的附图对本申请实施例进行描述。
本申请实施例提供了一种智能车辆001，请参见图1，图1是本申请实施例提供的一种智能车辆的功能框图。在一个实施例中，可以将智能车辆001配置为完全或部分地自动驾驶模式。例如，智能车辆001可以在处于自动驾驶模式中的同时控制自身，并且可通过人为操作来确定车辆及其周边环境的当前状态，确定周边环境中的至少一个其他车辆的可能行为，并确定该其他车辆执行可能行为的可能性相对应的置信水平，基于所确定的信息来控制智能车辆001。在智能车辆001处于自动驾驶模式中时，可以将智能车辆001置为在没有和人交互的情况下操作。
智能车辆001可包括各种子系统，例如行进系统102、传感器系统104、控制系统106、一个或多个外围设备108以及电源110、计算机系统112和用户接口116。可选地，智能车辆001可包括更多或更少的子系统，并且每个子系统可包括多个元件。另外，智能车辆001的每个子系统和元件可以通过有线或者无线互连。
行进系统102可包括为智能车辆001提供动力运动的组件。在一个实施例中，行进系统102可包括引擎118、能量源119、传动装置120和车轮/轮胎121。引擎118可以是内燃引擎、电动机、空气压缩引擎或其他类型的引擎组合，例如气油发动机和电动机组成的混动引擎，内燃引擎和空气压缩引擎组成的混动引擎。引擎118将能量源119转换成机械能量。
能量源119的示例包括汽油、柴油、其他基于石油的燃料、丙烷、其他基于压缩气体的燃料、乙醇、太阳能电池板、电池和其他电力来源。能量源119也可以为智能车辆001的其他系统提供能量。
传动装置120可以将来自引擎118的机械动力传送到车轮121。传动装置120可包括变速箱、差速器和驱动轴。在一个实施例中，传动装置120还可以包括其他器件，比如离合器。其中，驱动轴可包括可耦合到一个或多个车轮121的一个或多个轴。
传感器系统104可包括感测关于智能车辆001周边的环境的信息的若干个传感器。例如，传感器系统104可包括定位系统122(定位系统可以是GPS系统，也可以是北斗系统或者其他定位系统)、惯性测量单元(inertial measurement unit，IMU)124、激光雷达126、激光测距仪128以及相机130。传感器系统104还可包括被监视智能车辆001的内部系统的传感器(例如，车内空气质量监测器、燃油量表、机油温度表等)。来自这些传感器中的一个或多个的传感器数据可用于检测对象及其相应特性(位置、形状、方向、速度等)。这种检测和识别是自主智能车辆001的安全操作的关键功能。
定位系统122可用于估计智能车辆001的地理位置。IMU 124用于基于惯性加速度来感测智能车辆001的位置和朝向变化。在一个实施例中，IMU 124可以是加速度计和陀螺仪的组合。例如：IMU124可以用于测量智能车辆001的曲率。
激光雷达126可利用无线电信号来感测智能车辆001的周边环境内的物体。在一些实施例中，用于发射探测信号来探测目标物体的位置、速度等特征量的雷达系统。其工作原理是向目标物体发射探测信号(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)与本振信号产生相干，生成频率为回波信号和本振信号瞬时频率之差的第一拍频 信号和第二拍频信号。其中，第一拍频信号和第二拍频信号的相位差为180度。然后由差分接收单元对第一拍频信号和第二拍频信号进行差分放大后输出给处理器，由处理器进行处理得到目标物体的速度、距离等信息。
激光测距仪128可利用激光来感测智能车辆001所位于的环境中的物体。在一些实施例中，激光测距仪128可包括一个或多个激光源、激光扫描器以及一个或多个检测器，以及其他系统组件。
相机130可用于捕捉智能车辆001的周边环境的多个图像。相机130可以是静态相机或视频相机。
控制系统106为控制智能车辆001及其组件的操作。控制系统106可包括各种元件，其中包括转向系统132、油门134、制动单元136、传感器融合算法138、计算机视觉系统140、路线控制系统142以及障碍物避免系统144。
转向系统132可操作来调整智能车辆001的前进方向。例如在一个实施例中可以为方向盘系统。
油门134用于控制引擎118的操作速度并进而控制智能车辆001的速度。
制动单元136用于控制智能车辆001减速。制动单元136可使用摩擦力来减慢车轮121。在其他实施例中，制动单元136可将车轮121的动能转换为电流。制动单元136也可采取其他形式来减慢车轮121转速从而控制智能车辆001的速度。
计算机视觉系统140可以操作来处理和分析由相机130捕捉的图像以便识别智能车辆001周边环境中的物体和/或特征。所述物体和/或特征可包括交通信号、道路边界和障碍物。计算机视觉系统140可使用物体识别算法、运动中恢复结构(Structure from Motion，SFM)算法、视频跟踪和其他计算机视觉技术。在一些实施例中，计算机视觉系统140可以用于为环境绘制地图、跟踪物体、估计物体的速度等等。
路线控制系统142用于确定智能车辆001的行驶路线。在一些实施例中，路线控制系统142可结合来自传感器138、GPS 122和一个或多个预定地图的数据以为智能车辆001确定行驶路线。
障碍物避免系统144用于识别、评估和避免或者以其他方式越过智能车辆001的环境中的潜在障碍物。
当然，在一个实例中，控制系统106可以增加或替换地包括除了所示出和描述的那些以外的组件。或者也可以减少一部分上述示出的组件。
智能车辆001通过外围设备108与外部传感器、其他车辆、其他计算机系统或用户之间进行交互。外围设备108可包括无线通信系统146、车载电脑148、麦克风150和/或扬声器152。
在一些实施例中，外围设备108提供智能车辆001的用户与用户接口116交互的手段。例如，车载电脑148可向智能车辆001的用户提供信息。用户接口116还可操作车载电脑148来接收用户的输入。车载电脑148可以通过触摸屏进行操作。在其他情况中，外围设备108可提供用于智能车辆001与位于车内的其它设备通信的手段。例如，麦克风150可从智能车辆001的用户接收音频(例如，语音命令或其他音频输入)。类似地，扬声器152可向智能车辆001的用户输出音频。
无线通信系统146可以直接地或者经由通信网络来与一个或多个设备无线通信。例如，无线通信系统146可使用3G蜂窝通信，例如CDMA、EVD0、GSM/GPRS，或者4G蜂窝通信，例如LTE。或者5G蜂窝通信。无线通信系统146可利用WiFi与无线局域网(wireless local area network，WLAN)通信。在一些实施例中，无线通信系统146可利用红外链路、蓝牙或ZigBee与设备直接通信。其他无线协议，例如：各种车辆通信系统，例如，无线通信系统146可包括一个或多个专用短程通信(dedicated short range communications，DSRC)设备，这些设备可包括车辆和/或路边台站之间的公共和/或私有数据通信。
电源110可向智能车辆001的各种组件提供电力。在一个实施例中，电源110可以为可再充电锂离子或铅酸电池。这种电池的一个或多个电池组可被配置为电源为智能车辆002的各种组件提供电力。在一些实施例中，电源110和能量源119可一起实现，例如一些全电动车中那样。
智能车辆001的部分或所有功能受计算机系统112控制。计算机系统112可包括至少一个处理器113，处理器113执行存储在例如数据存储装置114这样的非暂态计算机可读介质中的指令115。计算机系统112还可以是采用分布式方式控制智能车辆001的个体组件或子系统的多个计算设备。
处理器113可以是任何常规的处理器，诸如商业可获得的CPU。替选地，该处理器可以是诸如ASIC或其它基于硬件的处理器的专用设备。尽管图1功能性地图示了处理器、存储器、和在相同块中的计算机的其它元件，但是本领域的普通技术人员应该理解该处理器、计算机、或存储器实际上可以包括可以或者可以不存储在相同的物理外壳内的多个处理器、计算机、或存储器。例如，存储器可以是硬盘驱动器或位于不同于计算机的外壳内的其它存储介质。因此，对处理器或计算机的引用将被理解为包括对可以或者可以不并行操作的处理器或计算机或存储器的集合的引用。不同于使用单一的处理器来执行此处所描述的步骤，诸如转向组件和减速组件的一些组件每个都可以具有其自己的处理器，所述处理器只执行与特定于组件的功能相关的计算。
在此处所描述的各个方面中，处理器可以位于远离该车辆并且与该车辆进行无线通信。在其它方面中，此处所描述的过程中的一些在布置于车辆内的处理器上执行而其它则由远程处理器执行，包括采取执行单一操纵的必要步骤。
在一些实施例中，存储器114可包含指令115(例如，程序逻辑)，指令115可被处理器113执行来执行智能车辆001的各种功能，包括以上描述的那些功能。存储器124也可包含额外的指令，包括像行进系统102、传感系统104、控制系统106和外围设备108中的一个或多个发送数据、从其接收数据、与其交互和/或对其进行控制的指令。
除了指令115以外，存储器114还可存储数据，例如道路地图、路线信息，车辆的位置、方向、速度以及车辆周围目标物体(比如说其他车辆)的速度、位置等其它这样的数据，以及其他信息。这种信息可在智能车辆001在自主、半自主和/或手动模式中操作期间被智能车辆001和计算机系统112使用。
用户接口116，用于向智能车辆001的用户提供信息或从其接收信息。可选地，用户接口116可包括在外围设备108的集合内的一个或多个输入/输出设备，例如无线通信系统146、车载电脑148、麦克风150和扬声器152。
计算机系统112可基于从各种子系统(例如，行进系统102、传感器系统104和控制系统106)以及从用户接口116接收的输入来控制智能车辆001的功能。例如，计算机系统112可利用来自控制系统106的输入以便控制转向单元132来避免由传感器系统104和障碍物避免系统244检测到的障碍物。在一些实施例中，计算机系统112可操作来对智能车辆001及其子系统的许多方面提供控制。
可选地，上述这些组件中的一个或多个可与智能车辆001分开安装或关联。例如，数据存储装置114可以部分或完全地与智能车辆001分开存在。上述组件可以按有线和/或无线方式来通信地耦合在一起。
可选地，上述组件只是一个示例，实际应用中，上述各个模块中的组件有可能根据实际需要增添或者删除，图1不应理解为对本申请实施例的限制。
上述智能车辆001可以为轿车、卡车、摩托车、公共汽车、船、飞机、直升飞机、割草机、娱乐车、游乐场车辆、施工设备、电车、高尔夫球车、火车、和手推车等，本申请实施例不做特别的限定。
可以理解的是，图1中的智能车辆功能图只是本申请实施例中的一种示例性的实施方式，本申请实施例中的智能车辆包括但不仅限于以上结构。
目前，常用的激光雷达如图2所示的基于光纤光路的激光雷达的架构示意图，从图2可以看出基于光纤光路的激光雷达包括激光器、1×2光纤耦合器、光纤环形器和2×1光纤耦合器。激光器发出的激光信号经过光纤耦合进入光路，经过1×2光纤耦合器将激光信号分为探测信号和本振信号两部分，探测信号经光纤环形器后出射至目标物体，经目标物体反射后形成的回波信号经透镜耦合进光纤，经光纤环形器接收后再与本振信号经过2×1光纤耦合器产生拍频信号，然后拍频信号被探测器接收后由差分放大电路进行处理。
因为发射探测信号和接收回波信号都需要经过光纤环形器，光纤环形器的存在可能会对接收到的回波信号造成串扰现象；并且回波信号需要经过透镜耦合进入光纤，由于光纤尺寸的限制，透镜的口径不能过大，会限制接收到的回波信号的能量，从而导致激光雷达探测的精度不高。
为解决上述问题，本申请提出了一种激光雷达，请参见图2A，图2A是本申请实施例提供的一种激光雷达的架构示意图，该激光雷达包括激光器200、光束整形模块201、分束模块202、接收模块203、光学混频模块204、差分接收单元205、模拟数字转换器(Analog digital converte，ADC)206和处理器207。
本申请实施例中的激光雷达能够应用于智能交通、自动驾驶、大气环境监测、地理测绘、无人机等各种领域，能够完成距离测量、速度测量、目标跟踪、成像识别等功能。
激光器200产生激光信号，激光器产生的激光信号可以是调频连续波(Frequency Modulated Continuous Wave，FMCW)信号，其激光频率的调制波形可以是锯齿形，也可以是三角波，或者其他形式的波形。当激光器200生成的激光信号是FMCW信号时，激光器200可以是调频激光器(Tunable Laser，TL)，如分布反馈激光器(Distributed Feedback Laser，DFB)、激光二极管(Laser diode，LD)、光纤激光器和垂直腔面发射激光器(Vertical Cavity Surface Emitting Laser，VCSEL)等。可以理解的是，激光信号可以称为激光脉冲、激光束、 激光或者其他名称，只要含义相同，均属于本申请实施例的保护范围。在本申请实施例中，激光器200生成的激光信号用于对目标物体210的速度或距离中的至少一种进行测量。
光束整形模块201，用于对激光器200产生的激光信号进行准直处理，进行准直处理后的激光信号可以满足预设的光斑尺寸、发散角和束腰半径，等光学特性要求。需要说明的是，光束整形模块201可以为透镜，即由一个或者两个以上透镜组成。
分束模块202，用于对进行准直处理后的激光信号进行分束处理，分束处理得到探测信号和本振信号；其中，将激光信号进行分束处理得到的探测信号和本振信号的能量、偏振态，等光学特性都是一致的，都与由激光器200产生的激光信号的光学特性相同。
接收模块203，包括扫描器203A，扫描器203A也称2D扫描器。接收模块203用于对探测信号的偏振态进行转换，并由扫描器203A将探测信号按照一定的角度发射出去；发射信号发射出去之后，被目标物体210反射回来形成回波信号；这时，扫描器203A还用于接收该回波信号，接收模块203还用于对接收到的回波信号的偏振态进行转换，然后将该回波信号汇聚到光学混频模块处。接收模块203中用于发射的模块和用于接收的模块可以是相对独立的模块。接收模块203一般由一个望远光学系统组成，其望远光学系统可以包括开普勒型、伽利略型、牛顿型、卡塞格林型等望远光学系统中的至少一种。
光学混频模块204，用于对接收模块203接收到的回波信号和通过分束模块202分出的本振信号进行混频处理得到第一拍频信号和第二拍频信号。光学混频模块具有半透半反的性质，也即对接收到的信号进行反射处理和折射处理形成两束信号。其中，第一拍频信号和第二拍频用于确定目标物体的距离或速度中的至少一项。通过光学混频模块204进行混频处理得到的拍频信号包括第一拍频信号和第二拍频信号，第一拍频信号和第二拍频信号之间的相位差为180度。需要说明的是，拍频信号是频率为本振信号和回波信号瞬时频率之差的信号。拍频信号也可称为拍波信号、差频信号等，本申请实施例对拍频信号的名称不做任何限制。
探测器211和探测器212，其中，通过探测器211的光敏面来接收光学混频模块204产生的第一拍频信号，通过探测器212的光敏面来采集光学混频模块204接收的第二拍频信号。
差分接收单元205，用于对探测器211和探测器212上接收到的第一拍频信号和第二拍频信号进行差分接收得到一路拍频信号。差分接收得到的信号可以大幅地降低噪声，提高信噪比，从而提高雷达探测系统的测量精度。
模拟数字转换器ADC206，用于对拍频信号进行采样，这样采样实质是将模拟信号转换为数字信号的过程。
处理器207，该处理器可以包括数字信号处理器(Digital signal processor，DSP)、中央处理器(CPU)、加速处理器(APU)、图像处理单元(GPU)、微处理器或微控制器等具有计算能力的器件，附图以DSP为例来介绍，该处理器用于对采样得到的拍频信号进行处理，从而得到目标物体210的速度、距离等信息。
本申请实施例中，目标物体210也称反射物，目标物体210可以是扫描器扫描方向上的任何物体，例如，可以是人、山、车辆、树木、桥梁等等，图1是以车辆为例进行了示意。
本申请实施例中，对采样得到的拍频信号进行处理，从而得到目标物体210的速度、距离等信息的操作，可以由一个或多个处理器207，例如，由一个或多个DSP来完成，当然也可以由一个或多个处理器207结合其他器件来完成，例如，一个DSP结合一个或多个中央处理器CPU来共同完成。处理器207对拍频信号进行处理时，可以具体通过调用计算机可读存储介质存储的计算机程序来实现，该计算机可读存储介质包括但不限于是随机存储记忆体(random access memory，RAM)、只读存储器(read-only memory，ROM)、可擦除可编程只读存储器(erasable programmable read only memory，EPROM)、或便携式只读存储器(compact disc read-only memory，CD-ROM)，其可以配置在处理器207中，也可以独立于处理器207。
本申请实施例中，上述提及的某些器件可以是单份，也可以是多份，例如，激光器200可以是一个，也可以是多个，当为一个激光器200时，这一个激光器200可以在时域上交替发射正斜率的激光信号和负斜率的激光信号；当存在两个激光器200时，其中一个发射正斜率的激光信号，另一个发射负斜率的激光信号，两个激光器200可以同步发射激光信号。
如图2B所示，以该激光信号频率的调制波形为三角波线性调频为例，回波信号经过一段飞行时间之后与本振信号混频，这段飞行时间就是激光信号分出的探测信号从出射开始至回波信号返回的时间，回波信号经过飞行时间后与本振信号生成的拍频信号在一定时间内是恒定的，其中，拍频信号为差分接收单元对第一拍频信号和第二拍频信号进行差分接收后得到的拍频信号，这段时间即为拍频时间。拍频信号能准确反映目标物体的距离和速度信息，拍频信号需要包括对应于正斜率的拍频f 1和对应于负斜率的拍频f 2，与目标物体的速度相关的频谱f 速度可以表示为f 速度＝(f 1-f 2)/2，与目标物体的距离相关的频率f 距离可以表示为f 距离＝(f 1+f 2)/2。得到和f 速度和f 距离后就可以计算得到目标物体(与激光雷达)的距离和目标物体的移动速度。
请参见图3，图3是本申请实施例提供的一种拍频信号生成方法的流程示意图，该流程可以基于图2A所示的激光雷达来实现，该方法包括但不限于如下步骤：
步骤S300：光束整形模块对激光器生成的激光信号进行准直处理。
具体地，激光雷达光学系统中的激光器200产生的激光信号的光斑能量在空间的分布一般不均匀，普遍都是中间高边缘低，典型的光斑能量在空间的分布为高斯分布。激光信号的光束在快轴方向和慢轴方向上具有不同的束腰位置和大小，从而激光信号形成快轴方向的光束和慢轴方向的像散光束，快轴方向的光束和慢轴方向的光束具有不同的发散角，快轴方向上的光束的发散角较大，慢轴方向上的光束发散角较小，以至于从激光器200发出的激光信号的光束具有不对称性，光束质量不高。为了保证本申请实施例中的激光雷达光学系统在使用过程中能够具有较高的精准度以实现灵敏的信息采集，并且要使得激光信号的光斑能量分布均匀且光束质量高，需要通过光束整形模块201对激光信号在快轴方向上的光束进行准直，且同时对慢轴方向上的光束进行均化。
请参见图3A所示的光束整形模块201，光束整形模块201可以由一个或者多个透镜组成，本申请实施例以由两个透镜组成的光束整形模块为例进行说明，在实际应用中可根据 实际需求(比如光斑尺寸、发散角和束腰半径等具体要求)来选择相应的透镜。
步骤S301：分束模块对进行准直处理后的激光信号进行分束处理，得到探测信号和本振信号。
具体地，在本申请实施例中，激光雷达光学系统中的激光器200生成的激光信号是调频连续波激光信号，调频连续波激光信号携带的信息主要为频率信息，通过本振信号和回波信号进行相干得到拍频信号，通过拍频信号计算得到目标物体的距离或速度中的至少一项。因此，需要通过分束模块202对进行准直处理后的激光信号进行分束处理，得到探测信号和本振信号。其中，本振信号和探测信号为偏振方向相同的线偏振激光信号。
可选地，如图3A和图3B所示，分束模块202包括可选的第一二分之一波片2022和分束镜2021。光束整形模块201处理后的激光信号为线偏振激光信号，由可选的第一二分之一波片2022调整线偏振激光信号的偏振方向，经分束模块202中的分束镜2021对线偏振激光信号进行分束处理得到本振信号和探测信号。
可选地，如图3C和图3D所示，分束模块202包括第一二分之一波片2022和分束镜2041，通过调整第一二分之一波片2022的快轴与激光信号的线偏振方向的夹角可以调整经过第一二分之一波片的激光信号的角度。在申请实施例所提供的图3C和图3D中，第一二分之一波片2022用于将线偏振激光信号调整为偏振方向为45度的信号，因此经过分束镜2021分束处理后得到的本振信号和回波信号的偏振方向也是45度。
分束镜2021可以是偏振分光镜，或者是非偏振分光棱镜，也可以是半镀银棱镜，还可以是平板型分光镜片，如图3A所示的分束镜2021是本申请实施例提供的一个示例。激光信号经过分束镜2021的反射和折射，分束为两束或更多束信号。如图3A所示，在本申请实施例中，将由分束镜2021反射得到的信号为本振信号，将由分束镜2021折射得到的信号为探测信号。
需要说明的是，若激光器发出的激光信号为线偏振信号，则经过光整形模块进行光束整形后由分束模块进行分束处理；若激光器发出的激光信号不是线偏振信号时，需要在分束模块202之前将激光信号转换成线偏振信号。具体转换方式是在分束模块202之前设置波片(本申请实施例中没有具体图示出)，可以是在光束整形模块201和分束模块102之间设置波片，或者在激光器200和光束整形模块201之间设置波片。波片的数量和类别可根据实际情况进行选择，本申请实施例不做任何限制。
步骤S302：接收模块用于接收回波信号并将回波信号传输至光学混频模块。
具体地，在本申请实施例中，因为圆偏振态或者椭圆偏振态的探测信号具有更好的稳定性，所以由接收模块203出射至目标物体的探测信号的偏振态为圆偏振态或者椭圆偏振态。而经激光器200生成的激光信号经过光束整形模块201发射的激光信号的偏振态为线偏振态，所以由分束镜2021分束处理得到的探测信号的偏振态也为线偏振态，因此需要在分束镜2021输出探测信号的一侧设置四分之一波片(即1/4波片)，四分之一波片用于将探测信号的偏振态从线偏振态转换成圆偏振态。接收模块203接收探测信号经目标物体发射得到的回波信号，并将回波信号汇聚到光学混频模块204中与本振信号进行混频。为了提高混频效率，在回波信号与本振信号进行混频之前，需要在光学混频模块输入回波信号的一侧设置四分之一波片，四分之一波片用于将回波信号的偏振态从圆偏振态转换成线偏 振态。
可选地，分束镜2021输出探测信号的一侧设置的四分之一波片，与光学混频模块输入回波信号的一侧设置的四分之一波片为同一波片。如图3A或者图3C所示，接收模块203包括偏振分光棱镜2031、四分之一波片2032、主镜2033、次镜2035。可选地，接收模块还包括次反射镜2034等光学器件。需要说明的是，接收模块用于出射探测信号并接收回波信号。四分之一波片2032设置于偏振分光棱镜2031的折射出光面处，激光器200、光束整形模块201、分束模块202、偏振分光棱镜2031和四分之一波片2032设置于同一轴线上。探测信号经过偏振分光棱镜2031透射到四分之一波片2032后转化成偏振态为圆偏振态或者椭圆偏振态的探测信号，并经扫描器出射至目标物体上。反射信号经目标物体反射后得到回波信号，回波信号经扫描器接收至发射模块203，四分之一波片2032后转化成偏振态为线偏振态的回波信号，并通过偏振分光棱镜2031折射到由主镜2033、次反射镜2034和次镜2035组成的光学模组上，由上述光学模组将回波信号汇聚到光学混频模块204处与本振信号进行光学混频。
可选地，分束镜2021输出探测信号的一侧设置的四分之一波片，与光学混频模块输入回波信号的一侧设置的四分之一波片为两个不同的波片。如图3B或者图3D所示，图3D是本申请实施例提供的另一种激光雷达光学系统的架构示意图。图3B或者图3D所示的接收模块203包括开孔主反射镜2036、第一四分之一波片2037、第二四分之一波片2038、主镜2033、次镜2035，等光学器件。可选地，接收模块还包括次反射镜2034等光学器件。需要说明的是，接收模块用于出射探测信号并接收回波信号。图3B和图3D所示的第一四分之一波片2037、第二四分之一波片2038的快轴与分束处理得到的探测信号的偏振方向成45度。第一四分之一波片2037设置于分束镜2021的折射出光面和开孔主反射镜2036的入射面之间，激光器200、光束整形模块201、分束模块202、开孔主反射镜2036和第一四分之一波片2037设置于同一轴线上。第二四分之一波片2038设置于接收模块103的出光面和光学混频模块204的入光面之间。探测信号经过第一四分之一波片2037转化成偏振态为圆偏振态或者椭圆偏振态的信号，经过开孔主反射镜2036和扫描器后出射至目标物体上。探测信号经目标物体反射后得到回波信号，回波信号经扫描器接收至接收模块203，由开孔主反射镜2036反射到由主镜2033、次反射镜2034和次镜2035组成的光学模组上，由上述光学模组将回波信号汇聚到第二四分之一波片2038处，由第二四分之一波片2038将回波信号的偏振态由圆偏振态或者椭圆偏振态转换成线偏振态，然后再出射至光学混频模块204处与本振信号进行光学混频。
步骤S303：光学混频模块对本振信号和回波信号进行光学混频得到第一拍频信号和第二拍频信号。
具体地，本申请实施例是利用本振信号与回波信号基于自由空间混频形成的干涉光光束来获取拍频信号中的信息，为了保证本振信号和回波信号充分的发生混频，需要在光学混频模块204中将本振信号和回波信号的光斑尺寸调整到基本保持一致，然后再对本振信号和进行偏振方向转换的回波信号进行混频处理得到第一拍频信号和第二拍频信号。因为光学混频模块具有半透半反性质，会对经过的信号进行透射处理和反射处理，所以对经过的本振信号和回波信号进行处理后得到第一拍频信号和第二拍频信号。其中，经过偏振方 向转换的回波信号与本振信号是偏振方向正交的线偏振信号。
可选地，如图3A或者图3B所示，光学混频模块204包括光束整形透镜2042、光阑2043、合束镜2044、第二二分之一波片2045、第一偏振分光棱镜2046和第一透镜2047、第二透镜2048。其中，分束镜2021、合束镜2044、第二二分之一波片2045和第一偏振分光棱镜2046设置于同一轴线上。第二二分之一波片2045设置于合束镜2044和第一偏振分光棱镜2046之间，合束镜2044用于对本振信号与回波信号进行合束处理，第二二分之一波片2045的快轴与本振信号、回波信号的偏振方向的夹角为45°。本振信号通过光束整形透镜2042和光阑2043后整形成与回波信号的光斑尺寸一致的信号，由合束镜2044将进行偏振态转换的回波信号和本振信号合束到一个光路上后，由第二二分之一波片2045将合束到一个光路上的回波信号和本振信号分别转换成第一45度偏振信号和第二(45+90)度偏振信号。第一45度偏振信号和第二45度偏振信号在第一偏振分光棱镜2046处进行混频得到相位差为180度的第一拍频信号和第二拍频信号。
可选地，如图3C和图3D所示，光学混频模块204包括光束整形透镜2042、光阑2043、第二偏振分光棱镜2040和第一透镜2047、第二透镜2048。本振信号由光束整形透镜2042和光阑2043整形成与回波信号的光斑尺寸一致的信号，本振信号的偏振方向为45度。经过偏振态转化后的回波信号的偏振方向为(45+90)度，回波信号和本振信号为偏振方向正交的线偏振光，由第二偏振分光棱镜2040对分别在两路上的本振信号和回波信号进行混频处理得到相位差180度的第一拍频信号和第二拍频信号。
通过光学混频模块204得到的第一拍频信号和第二拍频信号分别通过第一透镜2047和第二透镜2048汇聚到探测器211和探测器212的光敏面上，然后由差分接收单元205对探测器211和探测器212上接收到的第一拍频信号和第二拍频信号进行差分放大得到一路拍频信号，经过差分放大得到的一路拍频信号，由差分接收单元205对探测器211和探测器212上接收的信号经差分放大后输出。经差分放大输出的信号可以大幅地降低噪声，提高信噪比，从而实现提高测量的精度。需要说明的是，第一45度偏振信号和第二45度偏振信号的偏振态为线偏振态。
需要说明的是，在本申请实施例中提及的波片，包括四分之一波片、第一四分之一波片、第二四分之一波片、第一二分之一波片以及第二二分之一波片可在与上述波片相邻的光学透镜的某一出光面或者某一入光面镀膜或者粘合波片来实现其功能。举例来说，对于图3A所示的四分之一波片2032可以在偏振分光棱镜2031的折射出光面处镀膜或者粘合波片来实现四分之一波片2032的功能；同理，第二二分之一波片2045可以在第一偏振分光棱镜的折射入光面处镀膜或者粘合波片来实现第二二分之一波片2045的功能。
在图3所示的方法中，由波片、分束镜和偏振分光棱镜等光学模块组成的空间光路来实现相干探测接收光路，增加了接收回波信号的口径，从而可以接收到更多的回波信号的能量，增加雷达探测系统对目标物体探测的精度；通过发射接收模组中的偏振分光棱镜或者开孔主反射镜等光学模块来接收和探测信号，可以避免光学串扰带来的对接收回波信号的干扰；对探测信号和回波信号的偏振态进行转换可以提高光学混频效率。
上述实施例中所用，根据上下文，术语“当…时”可以被解释为意思是“如果…”或“在…后”或“响应于确定…”或“响应于检测到…”。类似地，根据上下文，短语“在确定…时”或“如 果检测到(所陈述的条件或事件)”可以被解释为意思是“如果确定…”或“响应于确定…”或“在检测到(所陈述的条件或事件)时”或“响应于检测到(所陈述的条件或事件)”。
在上述实施例中，可以全部或部分地通过软件、硬件、固件或者其任意组合来实现。当使用软件实现时，可以全部或部分地以计算机程序产品的形式实现。所述计算机程序产品包括一个或多个计算机指令。在计算机上加载和执行所述计算机程序指令时，全部或部分地产生按照本申请实施例所述的流程或功能。所述计算机可以是通用计算机、专用计算机、计算机网络、或者其他可编程装置。所述计算机指令可以存储在计算机可读存储介质中，或者从一个计算机可读存储介质向另一个计算机可读存储介质传输，例如，所述计算机指令可以从一个网站站点、计算机、服务器或数据中心通过有线(例如同轴电缆、光纤、数字用户线)或无线(例如红外、无线、微波等)方式向另一个网站站点、计算机、服务器或数据中心进行传输。所述计算机可读存储介质可以是计算机能够存取的任何可用介质或者是包含一个或多个可用介质集成的服务器、数据中心等数据存储设备。所述可用介质可以是磁性介质，(例如，软盘、硬盘、磁带)、光介质(例如DVD)、或者半导体介质(例如固态硬盘)等。
本领域普通技术人员可以理解实现上述实施例方法中的全部或部分流程，该流程可以由计算机程序来指令相关的硬件完成，该程序可存储于计算机可读取存储介质中，该程序在执行时，可包括如上述各方法实施例的流程。而前述的存储介质包括：ROM或随机存储记忆体RAM、磁碟或者光盘等各种可存储程序代码的介质。

Claims (11)

  1. 一种激光雷达，其特征在于，包括：
    激光器，用于产生激光信号；
    光束整形模块，用于对所述激光信号进行准直处理；
    分束模块，用于对进行准直处理后的所述激光信号进行分束处理，得到探测信号和本振信号；
    接收模块，用于接收回波信号并将所述回波信号传输至光学混频模块，其中，所述回波信号为所述探测信号照射目标物体后形成的反射信号；
    所述光学混频模块，用于对所述本振信号和所述回波信号进行光学混频得到第一拍频信号和第二拍频信号，其中，所述第一拍频信号和所述第二拍频信号之间的相位差为180度；
    差分接收单元，用于对所述第一拍频信号和所述第二拍频信号进行差分接收；所述第一拍频信号和所述第二拍频信号用于确定所述目标物体的目标信息。
  2. 根据权利要求1所述的雷达，其特征在于，所述分束模块包括分束镜和第一二分之一波片，所述第一二分之一波片设置于所述光束整形模块和所述分束镜之间，所述第一二分之一波片用于调整所述激光信号的偏振方向。
  3. 根据权利要求1所述的雷达，其特征在于，所述接收模块包括四分之一波片，在所述分束模块输出所述探测信号的一侧设置有四分之一波片，在所述光学混频模块输入所述回波信号的一侧设置有四分之一波片，所述四分之一波片用于对经过的所述回波信号和所述探测信号进行偏振态转换。
  4. 根据权利要求3所述的雷达，其特征在于，
    所述分束模块输出所述探测信号的一侧设置的四分之一波片，与所述光学混频模块输入所述回波信号的一侧设置的四分之一波片为同一个波片，或者，
    所述分束模块输出所述探测信号的一侧设置的四分之一波片，与所述光学混频模块输入所述回波信号的一侧设置的四分之一波片为两个不同的波片。
  5. 根据权利要求4所述的雷达，其特征在于，所述光学混频模块包括合束镜、第一偏振分光棱镜和第二二分之一波片；所述第二二分之一波片设置于所述合束镜和所述第一偏振分光棱镜之间；所述分束镜、所述合束镜、所述第二二分之一波片和所述第一偏振分光棱镜设置于同一轴线上；
    所述合束镜，用于将进行偏振态转换的所述回波信号和所述本振信号合束到一个光路上；
    所述第二二分之一波片，用于将合束到一个光路上的所述回波信号和所述本振信号分别转换成第一45度偏振信号和第二45度偏振信号；其中，所述第一45度偏振信号和所述 第二45度偏振信号为偏振方向正交的信号；
    所述第一偏振分光棱镜，用于对所述第一45度偏振光和所述第二45度偏振光进行混频处理得到所述第一拍频信号和所述第二拍频信号。
  6. 根据权利要求4所述的雷达，其特征在于，所述光学混频模块包括第二偏振分光棱镜；所述分束镜和所述第二偏振分光棱镜设置于同一轴线上；
    所述第二偏振分光棱镜，用于对分别在两个光路上的所述本振信号和进行偏振态转换的所述回波信号进行混频处理，得到所述第一拍频信号和所述第二拍频信号。
  7. 根据权利要求1-6任一项所述的雷达，其特征在于，所述探测信号和所述本振信号的偏振态为线偏振态。
  8. 根据权利要求7所述的雷达，其特征在于，进行偏振态转化后的所述探测信号的偏振态为圆偏振态或椭圆偏振态。
  9. 根据权利要求7所述的雷达，其特征在于，所述回波信号的偏振态为圆偏振态或椭圆偏振态，进行偏振态转化后的所述回波信号的偏振态为线偏振态。
  10. 根据权利要求1-9任一项所述的雷达，其特征在于，所述目标信息包括距离或速度中的至少一项。
  11. 一种智能车辆，其特征在于，包括：激光雷达以及处理器，所述激光雷达用于执行权利要求1-10任一项所述的激光雷达的功能，所述处理器用于基于所述激光雷达智能驾驶。
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