Ground debugging system of conical scanning single-photon laser radar

Abstract

The invention discloses a ground debugging system of a conical scanning single-photon laser radar, and belongs to the technical field of single-photon laser radars. The objective of the invention is to solve the problem of low efficiency of coaxial adjustment and error correction of a conical scanning laser radar. Comprising a base, a debugging and mounting platform, a positioning and orienting system, a radar data acquisition and control unit and a conical scanning single-photon laser radar, debugging and correction are carried out on the ground through the debugging and mounting platform, and the motion of the laser radar following a carrier can be efficiently simulated. Debugging steps after actual installation of the radar are simplified, and repeated steps in the using process are reduced; according to the invention, through the radar data acquisition and control unit with the FPGA as the core, high-time-precision control of other parts is realized, high-speed and low-time-delay data acquisition and storage of each part are realized, and introduced errors of debugging are reduced; according to the invention, by using the area array GM-APD detector, the data accumulation time of the laser radar using the GM-APD is effectively reduced, and the frame rate of the laser radar based on the GM-APD is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of single-photon lidar, and particularly relates to a ground debugging system for a conical scanning single-photon lidar. Background Art

[0002] An array GM-APD single photon lidar is a flash scanning lidar that uses an array GM-APD detector as the receiving element. With a high-repetition-rate, high-energy, and narrow-pulse-width laser as the active light source, it has the advantages of long measurement distance, high measurement point density, and strong anti-interference ability. Secondly, the array GM-APD single photon lidar uses a Geiger-mode avalanche photodiode array to achieve time-of-flight counting, and can simultaneously obtain the distance information corresponding to the echo signals of multiple points, with a higher measurement efficiency compared to single-photon lidars using single-point detectors.

[0003] With the development of the industry and the subdivision of application fields, lidars combined with mechanical scanning modes have played an important role in application fields such as terrain detection, target search, and autonomous driving. In the production and assembly of coaxial conical scanning lidars, the optical axis of the light beam propagation and the optical axis of the receiving mirror cannot be completely aligned. There must be deflections in the installation of the light beam deflection element, and there are deviations in the half-cone angle and direction angle when using an array detector, resulting in obvious errors in the point cloud of this type of lidar. To ensure the accuracy of the detection and the convenience of debugging of lidars using array detectors, a ground debugging system for a conical scanning single-photon lidar is proposed. Summary of the Invention

[0004] To overcome the problem that it is difficult to simultaneously meet the two requirements of detection efficiency and detection accuracy in existing single-photon lidar systems based on GM-APD detectors, the present invention provides a ground debugging system for a conical scanning single-photon lidar, aiming to solve the problem of low efficiency in coaxial adjustment and error correction of conical scanning lidars.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A ground debugging system for a conical scanning single-photon lidar, comprising

[0007] A base;

[0008] A debugging installation platform, which provides an installation position for the conical scanning single-photon lidar and is translationally and rotationally connected to the base through a rotation and translation device to simulate the movement of the lidar following the carrier;

[0009] A positioning and orientation system, fixedly installed on the debugging installation platform, used to collect the attitude information of the debugging installation platform, and send data frames to the lidar data acquisition and control unit through a serial port and receive control;

[0010] The radar data acquisition and control unit is fixedly installed on the debugging and installation platform, and is used to set the working parameters of the positioning and orientation system and the working parameters of the conical scanning single-photon lidar, and collect the return data of the positioning and orientation system and the conical scanning single-photon lidar;

[0011] The conical scanning single-photon lidar is fixed at the front of the debugging and installation platform and moves with the debugging and installation platform.

[0012] The computer is connected to the radar data acquisition and control unit and is used to process the information of the radar data acquisition and control unit and the debugging and installation platform.

[0013] The present invention has the following beneficial effects compared with the prior art:

[0014] 1. The present invention can efficiently simulate the movement of the lidar following the carrier through debugging and calibration on the ground by the debugging and installation platform. It significantly simplifies the debugging steps after the radar is actually installed on the machine and reduces the repeated steps during use;

[0015] 2. The present invention realizes high-time-precision control of the rest of the parts through the radar data acquisition and control unit with FPGA as the core, and realizes high-speed and low-latency data acquisition and storage of each part, reducing the introduced error in debugging and improving the debugging efficiency;

[0016] 3. The present invention effectively reduces the data accumulation time of the lidar using GM-APD by using a planar array GM-APD detector, and improves the frame rate of the lidar based on GM-APD;

[0017] 4. The present invention processes the data obtained from each part by using a computer, optimizes the beam coaxiality, synchronous rotation angle and correction cone angle according to the data, and improves the debugging efficiency.

[0018] 5. The high-precision coaxial transceiver conical scanning system combines a high-precision conical scanning system and a coaxial transceiver optical system. The coaxial transceiver optical system uses an optical axis adjustment optical path constructed by multiple adjustable reflectors and lenses, with the goal that the laser propagation axis emitted by the laser and the receiving axis of the receiving telescope are completely coincident, to ensure the accurate transmission and reception of laser signals; and a high-precision conical scanning system is added at the rear end of the telescope, and the synchronous change of the laser irradiation direction and the receiving direction of the receiving telescope is realized by using a high-precision hollow disk motor, a metasurface beam deflection element, and a high-precision grating encoder. Description of the Drawings

[0019] Figure 1 is a schematic block diagram of the structure of the present invention;

[0020] Figure 2 is an axonometric drawing of the present inventionFigure 1 ;

[0021] Figure 3 is the isometric view of the present invention Figure 2 ;

[0022] Figure 4 is the schematic diagram of the radar data acquisition and control unit of the present invention;

[0023] Figure 5 is the schematic diagram of the high-precision coaxial transceiver conical scanning system of the present invention Figure 1 ;

[0024] Figure 6 is the schematic diagram of the high-precision coaxial transceiver conical scanning system of the present invention Figure 2 ;

[0025] Figure 7 is the schematic diagram of the automatic adjustment mirror frame structure of the present invention;

[0026] Wherein: 1. Base; 2. Rotary translation device; 3. Debugging and installation platform; 4. Positioning and orientation system; 5. Area array GM-APD detector; 6. Sub-nanosecond laser; 7. Concave-convex lens pair; 8. Mirror 1; 9. Mirror 2; 10. Position where the light beam enters the coaxial system; 11. Grating head; 12. Scanning motor; 13. Grating code disk; 14. Light beam deflection element; 15. High-precision coaxial transceiver conical scanning system; 16. Radar data acquisition and control unit; 17. Mirror 3; 18. Mirror 4; 19. Total reflection lens; 20. Mirror 5; 21. Mirror 6; 22. Filter; 23. Concave-convex lens group; 24. Total reflection prism; 25. Fixed bracket; 26. Lead screw; 27. Central prism; 28. Mirror frame; 29. Limiter. Specific embodiments

[0027] In order to better understand the purpose, structure and function of the present invention, the following further detailed description of the present invention will be made with reference to the accompanying drawings.

[0028] As Figure 1 , Figure 2 shown, the present invention provides a ground debugging system for a conical scanning single-photon lidar, including

[0029] Base 1, which bears all the equipment of this debugging system;

[0030] Debugging and installation platform 3, which provides an installation position for the conical scanning single-photon lidar and is translationally and rotationally connected to the base 1 through the rotary translation device 2 to simulate the movement of the lidar following the carrier for easy debugging.

[0031] The rotation and translation device 2 is an integrated component with a slide rail at the upper end and a hinge seat at the lower end. An adjustment and installation platform 3 is installed on the slide rail, and the hinge seat is hinged to the base 1 through a shaft.

[0032] The positioning and orientation system 4 is fixedly installed on the adjustment and installation platform 3 and is used to collect the attitude information of the adjustment and installation platform 3. The output data frame of the positioning and orientation system 4 contains longitude and latitude, altitude, attitude angle information, and a timestamp, and sends the data frame to the radar data acquisition and control unit 16 through a serial port and receives control.

[0033] The positioning and orientation system 4 provides the altitude, longitude, and latitude of the location where this debugging system is located, as well as the heading angle, roll angle, and pitch angle of the system's own angular offset measuring instrument. In this debugging system, the positioning and orientation system 4 operates at 20 Hz. After the system initialization is completed, it continuously sends the aforementioned position and attitude information to the FPGA of the radar data acquisition and control unit 16, and attaches the timestamp of this frame of data to each frame.

[0034] The radar data acquisition and control unit 16 is fixedly installed on the adjustment and installation platform 3. The working parameters of the positioning and orientation system 4 (POS) are set through the radar data acquisition and control unit 16, the working parameters of the conical scanning single-photon lidar are set through the radar data acquisition and control unit 16, and the data returned by the positioning and orientation system 4 and the conical scanning single-photon lidar are collected.

[0035] The conical scanning single-photon lidar is fixed to the front of the adjustment and installation platform 3 and moves with the adjustment and installation platform 3.

[0036] The computer is connected to the radar data acquisition and control unit 16 and is used to process the information of the radar data acquisition and control unit 16 and the adjustment and installation platform 3.

[0037] The computer obtains the relative position of the real-time laser spot in the field of view and adjusts the movable lens seat (automatic adjustment mirror frame) in the high-precision coaxial transceiver conical scanning system to ensure coaxiality. It reads, downloads, and analyzes the data and system configuration information stored in the radar data acquisition and control unit 16 through a local area network, and runs the existing high-speed denoising algorithm on the TOF data; it is used to analyze the deviation between the radar point cloud and the existing true value, decouple each factor and correct it, and realize the radar calibration and accuracy calibration of the area array GM-APD detector 5.

[0038] The computer that realizes point cloud generation can quickly calibrate for scanning characteristics and installation errors. It receives the output data from the radar data acquisition and control unit 16; performs coaxial beam adjustment; synchronizes the rotation angle of the metasurface element and the rotation angle of the grating code disk 13; reduces the computational complexity while ensuring accuracy through simplified modeling and optimized processes; corrects the scanning cone angle error and asymmetry error in the scanning system.

[0039] The computer can achieve the above functions through existing software, which will not be elaborated here.

[0040] As Figure 1 、 Figure 2 shown, the conical scanning single-photon lidar includes a planar array GM-APD detector 5, a high-repetition-rate sub-nanosecond laser 6, and a high-precision coaxial transceiver conical scanning system 15. It is a system to be debugged, and there are errors without debugging and calibration. Among them, the high-precision coaxial transceiver conical scanning system 15 has errors on the rotation axis and errors in the offset of the transmitting and receiving beam axes.

[0041] The high-precision coaxial transceiver conical scanning system 15 is fixed to the front of the debugging and installation platform 3. The high-precision coaxial transceiver conical scanning system 15 uses multiple reflectors, prisms, filters 22, and convex and concave lenses to construct a coaxial transceiver optical path and deflect the emitted laser beam, so as to emit laser pulses and receive echo signal photons through the same telescope. There is a special configuration optical lens, reflector five 20, and a movable mirror base with an automatic adjustment mirror frame in this system, which can achieve rapid adjustment of the beam direction.

[0042] The planar array GM-APD detector 5 communicates with the radar data acquisition and control unit 16 through a CameraLink interface to achieve detector control and output of the detector-measured photon flight time data;

[0043] The planar array GM-APD detector 5 uses a domestic GD5551 type 64*64 InGaAs Geiger avalanche focal plane camera;

[0044] The high-repetition-rate sub-nanosecond laser 6 is controlled by the radar data acquisition and control unit 16 through a BNC interface, and synchronously emits sub-nanosecond lasers with a narrow pulse width and a high repetition rate at a wavelength of 1064 nm.

[0045] The high-repetition-rate sub-nanosecond laser 6 includes a DC power supply, a sub-nanosecond laser, and its controller. The DC power supply supplies power to the laser and the laser controller. The laser controller receives the trigger signal from the radar data acquisition and control unit 16 and turns on the sub-nanosecond laser output;

[0046] As Figure 2 、 Figure 3 、 Figures 5 to 7As shown, the high-precision coaxial transceiver conical scanning system 15 includes a receiving telescope formed by using a concave-convex lens group 23, and matches a surface array GM-APD detector 5 to receive echo photons; uses the concave-convex lens group 23 to adjust the divergence angle of the laser pulse to match the field of view angle of the receiving telescope; uses a reflector, a filter 22, and a prism group to construct a laser optical path, and realizes the sharing of part of the optical paths for transmission and reception; uses a hollow disk-shaped scanning motor 12 and its controller, and a beam deflection element 14: a metasurface diffraction element. The direction of the beam passing through the beam deflection element 14 is changed by rotating the scanning motor 12; a high-precision grating encoder, including a circular grating code disk 13 and a grating read head 11.

[0047] Specifically, it includes:

[0048] The first reflector 8, the second reflector 9, the third reflector 17, and the fourth reflector 18 are 1064nm single-sided coated reflectors, which are used to deflect the laser output by the sub-nanosecond laser 6 in sequence. Using multiple reflectors facilitates adjusting the propagation direction of the laser beam;

[0049] The total reflection lens 19 is used to change the direction of the laser beam passing through the fourth reflector 18 so that it is incident on the central prism 27 of the fifth reflector 20 at an angle of 45 degrees;

[0050] The fifth reflector 20 is a special prism installed on an automatic adjustment mirror mount; a small total reflection central prism 27 is machined at the center of the front surface, which is used to change the direction of the laser reflected by the total reflection lens 19 so that the laser is coaxial with the filter 22, while minimizing the blocking of the light received by the lens;

[0051] The sixth reflector 6 is arranged between the first fifth reflector 20 and the filter 22 and is used to change the direction of the received beam;

[0052] The filter 22 is a 1064nm narrow-band filter, which weakens the stray noise photons received by the receiving system composed of the concave-convex lens group 23 and the total reflection prism 24;

[0053] The concave-convex lens group 23 adjusts the focal length of the receiving system to 950mm to match the laser beam divergence angle and the field of view angle of the receiving system;

[0054] The total reflection prism 24 is used to reverse the propagation direction of the photons received by the concave-convex lens group 23;

[0055] The beam deflection element 14 uses any beam deflection element, such as a wedge prism, etc., to add a fixed angle of deflection to the outgoing beam relative to the propagation direction of the incident light. The beam deflection element 14 makes the laser propagation direction have an angle MAA with the optical axis of the concave-convex lens group 23. As the scanning motor 12 rotates, a conical surface with a vertex angle of 2*MAA can be obtained with the laser propagation axis as the generatrix;

[0056] The scanning motor 12 is a hollow disc motor that drives the beam deflection element 14 and the grating code disc 13 to rotate around the optical axis of the convex-concave lens group 23;

[0057] The grating code disc 13 has a grating etched on its outer side and is fixed to the front end of the scanning motor 12;

[0058] The grating read head 11 reads the grating etched on the grating code disc 13;

[0059] The convex-concave lens pair 7 is arranged between the first mirror 8 and the second mirror 9, and adjusts the divergence angle of the laser output by the sub-nanosecond laser 6 to 3.5 mrad;

[0060] As shown by the green line in the figure, the laser beam is emitted from the sub-nanosecond laser 6 and passes through the convex-concave lens pair 7 between the first mirror 8 and the second mirror 9 to adjust the divergence angle of the beam to match the focal length parameter of the receiving telescope; then, it passes through the first mirror 8 to the fourth mirror 18 to adjust the beam direction, and after being deflected by the central prism 27 of the fifth mirror 20, the laser propagation axis is made coaxial with the optical axis of the convex-concave lens group 23 of the receiving mirror. Then, through the beam deflection element 14, there is an angle MAA between the laser propagation direction and the optical axis of the convex-concave lens group 23. As the scanning motor 12 rotates, with the laser propagation axis as the generatrix, a conical surface with a vertex angle of 2*MAA can be obtained;

[0061] After the laser irradiates the object and is reflected, for a general target, it can be considered as diffuse reflection, and then there will be photons propagating in the reverse direction of the laser propagation axis as shown by the yellow line in the figure. After entering the beam deflection element 14, they pass through the central prism 27 of the fifth mirror 20, pass through the filter 22, the convex-concave lens group 23, and the total reflection prism 24, and reach the pixels at the corresponding positions of the area array GM-APD detector 5.

[0062] The filter 22 is installed in front of the convex-concave lens group 23 to filter out photons with wavelengths other than 1064 nm and reduce the interference of stray light on the system. The grating code disc 13 rotates with the scanning motor 12. The beam emitted by the fixedly installed grating read head 11 irradiates the grating to obtain an optical signal, and the grating read head 11 receives this optical signal to obtain the encoder position; thus, the rotation angle of the scanning motor 12 at a certain moment, that is, the position of the laser propagation axis in the scanning conical surface at a certain moment, can be accurately obtained.

[0063] Figure 2 10 in it is the position where the beam enters the coaxial system and is a circular hole.

[0064] Such as Figure 7As shown in the figure, the automatic adjustment mirror frame includes a fixed frame 25, a lead screw 26, a mirror frame 28, and a stopper 29; the fixed frame 25 is the part of the fixed frame fixed in the optical path together with other lenses, and precision threads are tapped at the four corners; the mirror frame 28 is the mirror frame of the fifth mirror 20 that can move within a small range, and hemispherical washers are processed at the four corners corresponding to the threads of the fixed frame 25; the fifth mirror 20 is made of optical glass, and a small total reflection prism is processed in the center. The rest of the part is coated with an antireflection film to improve the transmittance, and it is installed at the center of the mirror frame 28; four lead screws 26 are rotated by a computer. As the lead screw 26 rotates, the distance between the four corners of the fixed frame 25 and the mirror frame 28 will change; the stopper 29 is a stopper that can move within a certain range. The stopper 29 is provided on both the fixed frame 25 and the mirror frame 28. One end of the stopper 29 is fixedly connected to the mirror frame 28, and the other end is an arc surface that contacts but is not connected to the fixed frame 25. The angle of the mirror frame 28 relative to the fixed frame 25 is adjusted jointly by the stopper 29 and the lead screw 26, and then the angle of the fifth mirror 20 lens installed on the mirror frame 28 is finely adjusted, and the propagation direction of the laser incident from the bottom is finely adjusted with almost no change in the light propagation direction incident on the fifth mirror 20 from the direction of the fixed frame 25.

[0065] For the computer-controlled automatic adjustment mirror frame structure and the coaxial beam adjustment process therein, please refer to Figure 7 , and the adjustment process includes:

[0066] S1. The host computer obtains multiple frames of TOF images when the rotation and translation device 2 is not working;

[0067] S2. Statistically analyze the pixel value distribution in the image and find the obvious pixel value aggregation part;

[0068] S3. Accumulate the spatial distribution of the values in the pixel value aggregation part in thousands of frames in the image;

[0069] S4. Estimate the center of the circle of the spatial distribution according to the morphological method, and judge which quadrant of the field of view the center of the circle is located in and the absolute value of the distance between the center of the circle and the center of the field of view. When the absolute value of the distance is greater than the coaxial threshold value, adjustment is required, otherwise the adjustment is completed and the lead screw 26 is locked;

[0070] S5. When the absolute value of the distance is greater than the coaxial threshold value and coaxial adjustment is required, according to the relative relationship between the center of the pixel value aggregation part and the center of the field of view, control the rotation of the four lead screws 26 to adjust the position of the light spot and wait for the image to stabilize;

[0071] S6. Repeat the above S1 to S5 until the distance between the center of the light spot and the center of the field of view is less than the coaxial threshold value.

[0072] The method for synchronizing the rotation angle of the beam deflection element 14 controlled by the computer and the rotation angle of the grating code disk 13 includes the following steps:

[0073] S1. Adjust the debugging system when the beam deflection element 14 is not installed. With the light spot as the origin at the front edge of the debugging installation platform 3, the normal vector of the debugging installation platform 3 as the Y-axis, and the X-axis perpendicular to the plane where the beam direction and the Y-axis are located, establish the XOY plane, and cover the medium that absorbs 1064 nm with the Y-axis;

[0074] S2. The scanning motor 12 rotates at a low speed, and the host computer acquires multiple frames of TOF images and statistically analyzes the pixel value distribution in the images to find obvious pixel value aggregation parts;

[0075] S3. Accumulate the spatial distribution in the image of the values in the pixel value aggregation part in thousands of frames;

[0076] S4. When the signal-free part in the image presents an approximate vertical strip, the scanning motor 12 stops rotating;

[0077] S5. Judge whether the strip is on the left or right side of the field of view at this time and the absolute value of the distance from the center of the field of view; control the scanning motor 12 to rotate intermittently in the corresponding direction at the minimum movement angle. The purpose of intermittent rotation is to wait for the composite image to stabilize until the aforementioned dressing strip is located at the center of the field of view, and then stop rotating;

[0078] S6. Record the data of the grating code disk 13 at this time.

[0079] A method for correcting the scanning cone angle error and the asymmetry error, the process includes:

[0080] S1. Install the test system indoors and set multiple calibration plates for comparing data;

[0081] The conical scanning lidar realizes a conical scanning trajectory through a rotating mirror or a laser emitter. Ideally, the cone angle φ0 of the laser beam should be kept constant. However, in actual assembly, due to factors such as the tilt of the mirror, the eccentricity of the rotation axis of the scanning motor 12, or mechanical vibration, the cone angle may change periodically with the azimuth angle θ, that is:

[0082] φ(θ) = φ0 + δφ(θ)

[0083] Among them, δφ(θ) is the cone angle deviation function, which can usually be decomposed into the form of a Fourier series:

[0084]

[0085] In the formula, a k , b k are the Fourier coefficients, and n is the harmonic order, usually taking n ≤ 3. This error will cause distortion of the scanned point cloud in the radial direction and the height direction z-axis, especially significantly affecting the 3D reconstruction accuracy in long-distance measurement.

[0086] Arrange a high-reflectivity plane such as a white wall or a calibration board indoors to ensure that the scanning range of the lidar covers the plane area. Obtain dense point cloud data through multiple scans and extract the plane point set P i =(r i ,θ i ,z i ), where z i is the height coordinate. Ideally, the plane point cloud should satisfy the linear equation z i =kr i , but the cone angle asymmetry will destroy this relationship. To correct the cone angle asymmetry, use software to process the data.

[0087] Modeling and optimizing the cone angle asymmetry error, substitute the actual cone angle φ(θ) into the lidar coordinate equation:

[0088]

[0089] For the plane calibration board, the theoretical height should satisfy Substitute the actual measured values to construct a non-linear least squares optimization problem:

[0090]

[0091] Iteratively solve for the Fourier coefficients a k ,b k using the Levenberg-Marquardt algorithm or the Gauss-Newton method. To reduce the computational complexity, the main harmonic components such as the fundamental frequency and the second harmonic can be determined in advance through spectral analysis, restricting n≤2.

[0092] Perform cone angle correction using the aforementioned coefficients, calculate the corrected cone angle according to the current azimuth angle θ for point cloud regeneration

[0093]

[0094] Remap the point cloud coordinates according to the corrected cone angle and recalculate the three-dimensional coordinates of the point cloud:

[0095] z corrected =rcosφ corrected (θ)

[0096] Finally, correct the error from the cone angle based on the coordinate information of multiple feature points in the point cloud.

[0097] Implement fast correction of cone angle error and asymmetry using software later without modifying the hardware.

[0098] In summary, by using the computer of the proposed ground debugging system for a conical scanning single-photon lidar, the beam offset in the coaxial direction, the rotation angle of the scanning mirror can be debugged at the hardware level, and the cone angle error and asymmetry can be corrected at the software level, significantly reducing the errors caused by the components themselves and their installation processes, and significantly improving the debugging efficiency of the conical scanning lidar.

[0099] The positioning and orientation system 4 includes a GPS system and a dynamic offset angle measurement system;

[0100] GPS system: Receives GPS and Beidou satellite positioning data through an antenna at a frequency of 20 Hz, obtains the longitude, latitude, and elevation information of the system, and outputs it to the radar data acquisition and control unit 16;

[0101] Dynamic offset angle measurement system: Measures the real-time heading angle, pitch angle, and roll angle at a frequency of 20 Hz through a built-in IMU and outputs them to the radar data acquisition and control unit 16.

[0102] As Figure 4 shown, the radar data acquisition and control unit 16, as the control and data acquisition core component of the radar system, realizes the control of the radar system and data acquisition; mainly includes

[0103] FPGA: The control core of the radar data acquisition and control unit 16, used to configure the parameters of the positioning and orientation system 4 (POS), the scanning motor 12, and the area array GM-APD detector 5, and store the uploaded data of the above parts after sorting locally;

[0104] The FPGA is equipped with an RS422 interface for communicating with the positioning and orientation system 4, a USB interface for communicating with the scanning motor 12, a BISS interface for communicating with the grating encoder, a CameraLink daughter card for communicating with the area array GM-APD detector 5 using an FMC interface, an FMC daughter card for providing a trigger signal, and an RJ45 interface for outputting the stored data. The on-board NANDFLASH is used to store the data transmitted back by each system.

[0105] FMC daughter card A: Based on the connection of the FMC interface 1 of the FPGA, it expands the Cmaera Link interface for connecting to the area array GM-APD detector 5, realizes the control and data transmission of the FPGA to the area array GM-APD detector 5, configures the voltage, TEC temperature, gating delay, detection gate width, and trigger frequency of the area array GM-APD detector 5, and receives the TOF data of the area array GM-APD detector 5 through the Cmaera Link interface.

[0106] FMC daughter card B: Connects to the FMC interface 2 based on FPGA, expands the RS422 interface, BISS interface, and SMA interface. The RS422 interface enables the FPGA to control the positioning and orientation system 4 and transfer data. The BISS interface uploads the position data of the grating read head 11 to the FPGA. The SMA interface outputs the synchronous trigger signal generated by the FPGA to the area array GM-APD detector 5 and the high-repetition-rate sub-nanosecond laser 6;

[0107] FMC daughter card A and FMC daughter card B stably provide synchronous trigger signals with fixed time delays for the positioning and orientation system 4, high-precision coaxial transceiver conical scanning system 15, area array GM-APD detector 5, and high-repetition-rate sub-nanosecond laser 6;

[0108] DDR4: Connects to the FPGA, is used to temporarily store the data obtained from the area array GM-APD detector 5, positioning and orientation system 4, and high-precision coaxial transceiver conical scanning system 15, and repackages it into data frames with a fixed format;

[0109] USB and RJ45 interfaces, connect to the FPGA, are used for external communication, and enable motor controller control and internal data upload;

[0110] NAND FLASH, connects to the FPGA, is used to store the repackaged return data frames and system status of the positioning and orientation system 4, grating read head 11, and area array GM-APD detector 5.

[0111] The radar data acquisition and control unit 16 receives the position and attitude information, timestamps, angular position data of the scanning system, and the photon flight time data measured by the area array GM-APD detector 5 sent by the positioning and orientation system 4, high-precision coaxial transceiver conical scanning system 15, and area array GM-APD detector 5 to the radar data acquisition and control unit 16; and stores the data from these three data sources in the NAND-flash of the radar data acquisition and control unit 16.

[0112] The high-precision coaxial transceiver conical scanning system 15 communicates with the radar data acquisition and control unit 16 using the USB interface and BISS interface. The USB interface is mainly used for motor controller communication, and the BISS interface is used for grating read head communication.

[0113] It will be understood that the present invention is described by way of some embodiments, and those skilled in the art will know that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the present invention. Additionally, under the teaching of the present invention, these features and embodiments can be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the scope protected by the present invention.

Claims

1. A ground debugging system for a conical scanning single-photon lidar, characterized in that: including a base (1); a debugging and installation platform (3), which provides an installation position for the conical scanning single-photon lidar and is translationally and rotationally connected to the base (1) through a rotation and translation device (2) to simulate the movement of the lidar following the carrier; a positioning and orientation system (4), fixedly installed on the debugging and installation platform (3), used to collect the attitude information of the debugging and installation platform (3), and send data frames to the radar data acquisition and control unit (16) through a serial port and receive control; a radar data acquisition and control unit (16), fixedly installed on the debugging and installation platform (3), used to set the working parameters of the positioning and orientation system (4) and the working parameters of the conical scanning single-photon lidar, and collect the return data of the positioning and orientation system (4) and the conical scanning single-photon lidar; a conical scanning single-photon lidar, fixed to the front of the debugging and installation platform (3) and moving with the debugging and installation platform (3); a computer, connected to the radar data acquisition and control unit (16), used to process the information of the radar data acquisition and control unit (16) and the debugging and installation platform (3).

2. The ground debugging system of a conical scanning single-photon lidar according to claim 1, characterized in that: The conical scanning single-photon lidar includes a planar array GM-APD detector (5), a high-repetition-rate sub-nanosecond laser (6), and a high-precision coaxial transceiver conical scanning system (15); a high-precision coaxial transceiver conical scanning system (15), fixed to the front of the debugging and installation platform (3), a planar array GM-APD detector (5), communicating with the radar data acquisition and control unit (16) to realize detector control and output of detector-measured photon flight time data; a high-repetition-rate sub-nanosecond laser (6), controlled by the radar data acquisition and control unit (16) to synchronously emit sub-nanosecond laser with a narrow pulse width and a high repetition rate at a wavelength of 1064 nm.

3. The ground debugging system of a conical scanning single-photon lidar according to claim 2, characterized in that: The high-precision coaxial transceiver conical scanning system (15) includes: a first mirror (8), a second mirror (9), a third mirror (17), and a fourth mirror (18), used to deflect the laser output by the sub-nanosecond laser (6) in sequence, a total reflection lens (19), used to change the direction of the laser beam passing through the fourth mirror (18) so that it is incident on the central prism (27) of the fifth mirror (20) at an angle of 45 degrees; a fifth mirror (20), installed on an automatic adjustment mirror mount; a central prism (27) is machined in the center of the front surface, used to change the direction of the laser reflected by the total reflection lens (19) so that the laser is coaxial with the filter (22); a sixth mirror (21), arranged between the first fifth mirror (20) and the filter (22), a filter (22), weakening the stray noise photons received by the receiving system composed of a concave-convex lens group (23) and a total reflection prism (24); a concave-convex lens group (23), adjusting the focal length of the receiving system to 950 mm to match the laser beam divergence angle and the receiving system field of view angle; a total reflection prism (24), used to reverse the propagation direction of the photons received by the concave-convex lens group (23); The beam deflection element (14) makes the laser propagation direction form an angle MAA with the optical axis of the convex-concave lens group (23). As it rotates with the scanning motor (12), a conical surface with an apex angle of 2*MAA can be obtained with the laser propagation axis as the generatrix. The scanning motor (12) drives the beam deflection element (14) and the grating code disk (13) to rotate around the optical axis of the convex-concave lens group (23). The grating code disk (13) has a grating etched on the outside and is fixed to the front end of the scanning motor (12). The grating read head (11) reads the grating etched on the grating code disk (13). The convex-concave lens pair (7) is arranged between the first mirror (8) and the second mirror (9) to adjust the divergence angle of the laser output by the sub-nanosecond laser (6) to 3.5 mrad.

4. The ground debugging system of a conical scanning single-photon lidar according to claim 3, characterized in that: The automatic adjustment mirror frame includes a fixed frame (25), a lead screw (26), a mirror frame (28), and a stopper (29); the lead screws (26) are threadedly installed at the four corners of the fixed frame (25), and hemispherical washers are machined at the four corners of the mirror frame (28) corresponding to the lead screws (26). The fifth mirror (20) is a lens with a small total reflection center prism (27) machined at the center, and the rest of the fifth mirror (20) is coated with an antireflection film to improve the transmittance. It is installed at the center of the mirror frame (28), and a stopper (29) is arranged between the fixed frame (25) and the mirror frame (28).

5. The ground debugging system of a conical scanning single-photon lidar according to claim 4, characterized in that: The computer controls the automatic adjustment mirror frame to make the laser coaxial with the filter (22), including the following steps; S1. The upper computer obtains multiple frames of TOF images when the rotation and translation device (2) is not working. S2. Statistically analyze the pixel value distribution in the image and find the obvious pixel value aggregation part. S3. Accumulate the spatial distribution of the values in the pixel value aggregation part in thousands of frames in the image. S4. Estimate the center of the spatial distribution according to the morphological method, and judge which quadrant of the field of view the center is located in and the absolute value of the distance between the center and the center of the field of view. When the absolute value of the distance is greater than the coaxial threshold, adjustment is required, otherwise the adjustment is completed and the lead screw (26) is locked. S5. When the absolute value of the distance is greater than the coaxial threshold and coaxial adjustment is required, according to the relative relationship between the center of the pixel value aggregation part and the center of the field of view, control the four lead screws (26) to rotate to adjust the spot position and wait for the image to stabilize. S6. Repeat the above S1 to S5 until the distance between the spot center and the field of view center is less than the coaxial threshold.

6. The ground debugging system of a conical scanning single-photon lidar according to claim 4, characterized in that: The method for synchronizing the rotation angle of the computer-controlled beam deflection element (14) and the rotation angle of the grating code disk (13) includes the following steps: S1. Adjust the debugging system when the beam deflection element (14) is not installed. With the spot as the origin at the front edge of the debugging installation platform (3), the normal vector of the debugging installation platform (3) as the Y-axis, and the X-axis perpendicular to the plane where the beam direction and the Y-axis are located, establish the XOY plane, and cover the Y-axis with a medium that absorbs 1064 nm. S2. The scanning motor (12) rotates at a low speed, and the upper computer obtains multiple frames of TOF images and statistically analyzes the pixel value distribution in the images to find the obvious pixel value aggregation part. S3. Accumulate the spatial distribution of the values in the pixel value aggregation part in thousands of frames in the images. S4. When the signal-free part in the image presents an approximate vertical strip, the scanning motor (12) stops rotating. S5. Determine whether the strip is on the left or right side of the current field of view and the absolute value of the distance from the center of the field of view; control the scanning motor (12) to rotate intermittently in the corresponding direction at the minimum movement angle. The purpose of intermittent rotation is to wait for the synthetic image to stabilize until the aforementioned dressing strip is at the center of the field of view, and then stop rotating; S6. Record the data of the grating code disk (13) at this time.

7. The ground debugging system of a conical scanning single-photon lidar according to claim 4, characterized in that: A method for correcting the scanning cone angle error and the asymmetry error, the process includes: S1. Install the test system indoors and set multiple calibration plates for comparing data; S2. Arrange a high-reflectivity plane indoors to ensure that the lidar scanning range covers the plane area. Obtain dense point cloud data through multiple scans and extract the plane point set P i =(r i , θ i , z i ), where z i is the height coordinate Substitute the actual cone angle φ(θ) into the lidar coordinate equation: For the planar calibration board, the theoretical height should satisfy Substitute the actual measured values to construct a non-linear least squares optimization problem: Iteratively solve for the Fourier coefficients a k , b k , Perform cone angle correction through the aforementioned coefficients, and calculate the corrected cone angle according to the current azimuth angle θ for point cloud regeneration Remap the point cloud coordinates according to the corrected cone angle, and recalculate the three-dimensional coordinates of the point cloud: z corrected = r cos φ corrected (θ) Finally, correct the error from the cone angle according to the coordinate information of multiple feature points in the point cloud.

8. The ground debugging system of a conical scanning single photon lidar according to claim 1, characterized in that: The positioning and orientation system (4) includes a GPS system and a dynamic offset angle measurement system; GPS system: Receive GPS and Beidou satellite positioning data through the antenna, obtain the longitude, latitude and elevation information of the system where it is located, and output it to the radar data acquisition and control unit (16); Dynamic offset angle measurement system: Measure the real-time heading angle, pitch angle, and roll angle, and output them to the radar data acquisition and control unit (16).

9. The ground debugging system of a conical scanning single-photon lidar according to claim 1, characterized in that: The radar data acquisition and control unit (16) includes FPGA: Used to configure the parameters of the positioning and orientation system (4), the parameters of the scanning motor (12), and the parameters of the area array GM-APD detector (5), and store the uploaded data of the above parts locally after sorting; FMC daughter card A: Based on the connection of the FMC interface 1 of the FPGA, expand the Cmaera Link interface to connect to the area array GM-APD detector (5), realize the control and data transmission of the area array GM-APD detector (5) by the FPGA, and receive the TOF data of the area array GM-APD detector (5) through the Cmaera Link interface; FMC daughter card B: Based on the connection of the FMC interface 2 of the FPGA, expand the RS422 interface, BISS interface, and SMA interface. The RS422 interface realizes the control and data transmission of the positioning and orientation system (4) by the FPGA. The BISS interface realizes the uploading of the position data of the grating reader head (11) to the FPGA. The SMA interface realizes the output of the synchronous trigger signal generated by the FPGA to the area array GM-APD detector (5) and the high-repetition-rate sub-nanosecond laser (6); DDR4: Connected to the FPGA, used to temporarily store the data obtained from the area array GM-APD detector (5), the positioning and orientation system (4), and the high-precision coaxial transceiver conical scanning system (15), and repackage it into a data frame with a fixed format; USB and RJ45 interfaces, connected to the FPGA, used for external communication, realizing motor controller control and internal data uploading; NAND FLASH, connected to the FPGA, used to store the re-encapsulated return data frames and system status of the positioning and orientation system (4), the grating reader head (11), and the area array GM-APD detector (5).

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