A ground debugging system for a conical scanning single-photon lidar

Abstract

The application 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 system aims at solving the problem of low efficiency of coaxial adjustment and error correction of the conical scanning laser radar. The system comprises a base, a debugging installation platform, a positioning and orientation system, a radar data acquisition and control unit and a conical scanning single-photon laser radar. The debugging installation platform is used for debugging and correction on the ground, and the laser radar can efficiently simulate the movement of a carrier. The debugging steps of the laser radar after actual installation are simplified, and repeated steps in the use process are reduced. The radar data acquisition and control unit with the FPGA as the core is used to realize high time-precision control of the remaining parts, high-speed low-latency data acquisition and storage of the parts, and reduction of the introduced error in the debugging. The use of the area array GM-APD detector effectively reduces the data accumulation time of the laser radar using the GM-APD, and improves the frame rate of the laser radar based on the GM-APD.

Description

Technical Field

[0001] This invention belongs to the field of single-photon lidar technology, specifically relating to a ground-based debugging system for a conical scanning single-photon lidar. Background Technology

[0002] The array GM-APD single-photon lidar is a scintillation scanning lidar that uses an array GM-APD detector as the receiving element. It uses a high-repetition-rate, high-energy, narrow-pulse-width laser as the active light source, which 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 realize time-of-flight counting, which can simultaneously acquire distance information corresponding to echo signals from multiple points, making it more efficient than single-photon lidar that uses a single-point detector.

[0003] With industry development and application segmentation, LiDAR combining mechanical and other scanning modes has played a crucial role in applications such as terrain detection, target search, and autonomous driving. In the production and assembly of coaxial conical scanning LiDAR, the beam propagation axis and the receiving mirror optical axis cannot be perfectly aligned. The installation of beam deflection elements inevitably introduces deflection, and deviations in the half-cone angle and azimuth angle occur when using area array detectors, resulting in significant errors in the point cloud of this type of LiDAR. To ensure the accuracy of LiDAR detection using area array detectors and the convenience of debugging, a ground-based debugging system for conical scanning single-photon LiDAR is proposed. Summary of the Invention

[0004] To overcome the problem that existing single-photon lidar systems based on GM-APD detectors cannot simultaneously achieve both detection efficiency and detection accuracy, this invention provides a ground-based debugging system for conical scanning single-photon lidar, aiming to solve the problem of low efficiency in coaxial adjustment and error correction of conical scanning lidar.

[0005] The technical solution adopted in this invention is:

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

[0007] Base;

[0008] The debugging and installation platform provides an installation position for the conical scanning single-photon lidar, and achieves translation and rotation connection with the base through a rotation and translation device to simulate the radar following the carrier's movement;

[0009] The positioning and orientation system is fixedly installed on the debugging and installation platform. It is used to collect the attitude information of the debugging and installation platform and send data frames to the radar data acquisition and control unit and receive control through the serial port.

[0010] The radar data acquisition and control unit is fixedly installed on the debugging and installation platform. It 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 to acquire the data transmitted back by the positioning and orientation system and the conical scanning single-photon lidar.

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

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

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] 1. This invention utilizes a commissioning and installation platform for ground-based commissioning and calibration, enabling efficient simulation of lidar following the movement of a carrier. This significantly simplifies the commissioning process after the actual radar is installed, reducing repetitive steps during use.

[0015] 2. This invention uses an FPGA-based radar data acquisition and control unit to achieve high-time-precision control of the remaining parts, and to achieve high-speed, low-latency data acquisition and storage for each part, thereby reducing the errors introduced during debugging and improving debugging efficiency.

[0016] 3. By using an area array GM-APD detector, this invention effectively reduces the data accumulation time of lidar using GM-APD and improves the frame rate of lidar based on GM-APD.

[0017] 4. This invention uses a computer to process the data obtained from each part, optimizes the coaxiality of the beam, synchronizes the rotation angle and corrects the cone angle based on the data, thereby improving the efficiency of debugging.

[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 multiple adjustable mirrors and lenses to construct the optical axis adjustment path, ensuring that the laser propagation axis emitted by the laser is completely aligned with the receiving axis of the receiving telescope, thus guaranteeing accurate transmission and reception of the laser signal. A high-precision conical scanning system is added at the rear of the telescope, employing a high-precision hollow disc motor, metasurface beam deflection elements, and a high-precision grating encoder to achieve synchronous changes in the laser illumination direction and the receiving telescope's receiving direction. Attached Figure Description

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

[0020] Figure 2 This invention is an isometric Figure 1 ;

[0021] Figure 3 This invention is an isometric Figure 2 ;

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

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

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

[0025] Figure 7 This is a schematic diagram of the automatic adjustable eyeglass frame structure of the present invention;

[0026] The components include: 1. Base; 2. Rotation and translation device; 3. Debugging and installation platform; 4. Positioning and orientation system; 5. Area array GM-APD detector; 6. Sub-nanosecond laser; 7. Concave and convex lens pair; 8. Reflector 1; 9. Reflector 2; 10. Beam entry position into the coaxial system; 11. Grating reader; 12. Scanning motor; 13. Grating code disk; 14. Beam deflection element; 15. High-precision coaxial transceiver conical scanning system; 16. Radar data acquisition and control unit; 17. Reflector 3; 18. Reflector 4; 19. Total internal reflection lens; 20. Reflector 5; 21. Reflector 6; 22. Filter; 23. Concave and convex lens group; 24. Total internal reflection prism; 25. Fixture; 26. Lead screw; 27. Central prism; 28. Mirror frame; 29. ​​Limiter. Detailed Implementation

[0027] To better understand the purpose, structure, and function of this invention, the invention will be described in further detail below with reference to the accompanying drawings.

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

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

[0030] The debugging and installation platform 3 provides an installation position for the conical scanning single-photon lidar, and is connected to the base 1 by the rotation and translation device 2 to simulate the movement of the radar following the carrier, which facilitates debugging.

[0031] The rotation and translation device 2 is an integrated component of the upper slide rail and the lower hinge seat. The installation and debugging platform 3 is installed on the slide rail, and the hinge seat and the base 1 are hinged together by a shaft.

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

[0033] The positioning and orientation system 4 provides the altitude, longitude, and latitude of the current location to this debugging system, 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 20Hz. 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 a timestamp to the data in each frame.

[0034] The radar data acquisition and control unit 16 is fixedly installed on the debugging and installation platform 3. The radar data acquisition and control unit 16 sets the working parameters of the positioning and orientation system 4 (POS), sets the working parameters of the conical scanning single-photon lidar, and acquires the data transmitted back from the positioning and orientation system 4 and the conical scanning single-photon lidar.

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

[0036] A computer, connected to the radar data acquisition and control unit 16, is used to process information from the radar data acquisition and control unit 16 and the debugging and installation platform 3.

[0037] The computer acquires the real-time relative position of the laser spot in the field of view and adjusts the movable lens mount (automatic adjustment frame) in the high-precision coaxial transceiver conical scanning system to ensure coaxiality. It reads, downloads, and parses the data and system configuration information stored in the radar data acquisition and control unit 16 via the 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, and corrects the deviation after decoupling various factors, so as to realize the radar correction and calibration accuracy of the array GM-APD detector 5.

[0038] The computer that generates point clouds can quickly calibrate for scanning characteristics and installation errors. It receives output data from the radar data acquisition and control unit 16; performs coaxial beam adjustment; synchronizes the rotation angle of the metasurface elements and the rotation angle of the grating code disk 13; reduces computational complexity while ensuring accuracy by simplifying the modeling and optimization process; and corrects scanning cone angle errors and asymmetry errors in the scanning system.

[0039] Computers can perform the above functions using existing software, so I won't go into details here.

[0040] like Figure 1 , Figure 2 As shown, the conical scanning single-photon lidar includes an 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 under test and has errors due to lack of 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 transceiver beam axis.

[0041] A high-precision coaxial transceiver conical scanning system 15 is fixed to the front of the debugging and installation platform 3. This system uses multiple mirrors, prisms, filters 22, and concave and convex lenses to construct a coaxial optical path for transmission and reception, and to deflect the emitted laser beam, enabling the transmission of laser pulses and the reception of echo photons through the same telescope. The system includes a specially configured optical mirror 20 and a movable, automatically adjustable mirror mount, allowing for rapid adjustment of the beam direction.

[0042] The GM-APD array detector 5 communicates with the radar data acquisition and control unit 16 via the CameraLink interface to realize detector control and output of photon time-of-flight data measured by the detector.

[0043] The GM-APD detector 5 uses a domestically produced GD5551 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 via the BNC interface, and synchronously emits a narrow-pulse-width, high-repetition-rate sub-nanosecond laser with a wavelength of 1064nm.

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

[0046] like Figure 2 , Figure 3 , Figures 5-7As shown, the high-precision coaxial transceiver conical scanning system 15 includes a receiving telescope constructed using a concave-convex lens group 23, which is matched with a GM-APD detector 5 to achieve echo photon reception; the concave-convex lens group 23 is used to adjust the divergence angle of the laser pulse to match the field of view of the receiving telescope; a laser optical path is constructed using a reflector, a filter 22, and a prism group, and the transmission and reception optical paths are partially shared; a hollow disk scanning motor 12 and its controller are used, along with a beam deflection element 14: a metasurface diffraction element. The beam direction is changed by rotating the scanning motor 12 through the beam deflection element 14; a high-precision grating encoder includes a circular grating code disk 13 and a grating read head 11.

[0047] Specifically, it includes:

[0048] Reflector 1 (8), Reflector 2 (9), Reflector 3 (17), and Reflector 4 (18) are 1064nm single-sided coated reflectors used to sequentially deflect the output laser of sub-nanosecond laser 6. Using multiple reflectors facilitates adjustment of the laser beam propagation direction.

[0049] Total internal reflection lens 19 is used to change the direction of the laser beam passing through reflector four 18, so that it is incident at 45 degrees onto the central prism 27 of reflector five 20.

[0050] Reflector 5 20, a special prism, is mounted on an automatic adjustment frame; a small total internal reflection central prism 27 is machined at the center of the front, which is used to change the direction of the laser reflected by the total internal reflection lens 19 so that the laser is coaxial with the filter 22, and to minimize the obstruction of the light received by the lens.

[0051] Reflector 6, positioned between the first reflector 5 20 and the filter 22, is used to change the direction of the received light beam;

[0052] The filter 22, a 1064nm narrowband filter, reduces stray noise photons received by the receiving system consisting of the concave-convex lens group 23 and the total reflection prism 24;

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

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

[0055] The beam deflection element 14 can be any beam deflection element, such as a wedge prism, 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 and convex 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.

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

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

[0058] The grating reader 11 reads the grating etched on the grating code disk 13;

[0059] Concave-convex lens pair 7 is set between reflector 8 and reflector 9 to adjust the divergence angle of 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. The divergence angle of the beam is adjusted by the pair of concave and convex lenses 7 between the first mirror 8 and the second mirror 9 to match the focal length parameters of the receiving telescope. Then, the beam direction is adjusted by the first mirror 8 to the fourth mirror 18. After the beam is deflected by the central prism 27 of the fifth mirror 20, the laser propagation axis is made coaxial with the optical axis of the concave and convex lens group 23 of the receiving mirror. Then, the beam deflection element 14 makes the laser propagation direction have an angle MAA with the optical axis of the concave and 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.

[0061] When a laser beam hits an object, it is reflected. For general targets, this can be considered diffuse reflection. Photons will then propagate in the opposite direction along 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 reflector 5 20, the filter 22, the concave and convex lens group 23, and the total reflection prism 24, and finally reach the corresponding pixel of the area array GM-APD detector 5.

[0062] A filter 22 is installed in front of the concave-convex lens group 23 to filter out photons with wavelengths other than 1064nm, reducing stray light interference to the system. The grating code disk 13 rotates with the scanning motor 12. The light beam emitted by the fixedly mounted grating read head 11 illuminates the grating to obtain the light signal, and the grating read head 11 receives the light signal to obtain the encoder position. Thus, the rotation angle of the scanning motor 12 at a certain moment can be accurately obtained, that is, the position of the laser propagation axis in the scanning cone at a certain moment.

[0063] Figure 2 In the middle, 10 represents the position where the light beam enters the coaxial system, which is a circular hole.

[0064] like Figure 7As shown, the automatic adjusting frame includes a fixing frame 25, lead screws 26, a frame 28, and a limiter 29. The fixing frame 25 is a part of the fixing frame that is fixed in the optical path along with other lenses, and has precision threads tapped at the four corners. The frame 28 is the frame for the mirror 20, which can move within a small range, and has hemispherical washers machined at the four corners corresponding to the threads of the fixing frame 25. The mirror 20 is made of optical glass, with a small total internal reflection prism machined in the center, and the remaining parts are coated with an anti-reflection coating to improve transmittance. It is installed at the center of the frame 28. The four lead screws 26 are controlled by a computer to rotate, and the fixing frame 29 rotates with the lead screws 26. The distance between the four corners of the mirror frame 28 and the frame 28 will change; the limiter 29 is a limiter that can move within a certain range. The limiter 29 is on both the fixed frame 25 and the mirror frame 28. One end of the limiter 29 is fixedly connected to the mirror frame 28, and the other end is an arc surface that contacts the fixed frame 25 but is not connected. The angle of the mirror frame 28 relative to the fixed frame 25 is adjusted by the limiter 29 and the lead screw 26, thereby fine-tuning the angle of the mirror 20 mounted on the mirror frame 28, and fine-tuning the propagation direction of the laser incident from the bottom without changing the propagation direction of the light incident from the fixed frame 25 to the mirror 20.

[0065] Please refer to the computer-controlled automatic adjustment frame structure and its coaxial beam adjustment process. Figure 7 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 distribution of pixel values ​​within the image to identify obvious clusters of pixel values;

[0068] S3. Spatial distribution of pixel values ​​clustered in the image across thousands of frames;

[0069] S4. Estimate the spatial distribution center of the circle based on morphological methods, and determine the location of the center in a certain quadrant of the field of view and the absolute value of the distance between the center and the center of the field of view. If the absolute value of the distance is greater than the coaxial threshold, then 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 and the coaxial needs to be adjusted, the four lead screws 26 are controlled to rotate to adjust the position of the light spot according to the relative relationship between the center of the pixel value cluster and the center of the field of view, and the image is waited to stabilize.

[0071] S6. Repeat steps 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.

[0072] A method for synchronizing the rotation angle of the computer-controlled beam deflection element 14 with 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 and installation platform 3, the normal vector of the debugging and installation platform 3 is the Y-axis, and the X-axis is perpendicular to the beam direction and the plane where the Y-axis is located. Establish the XOY plane and cover the medium that absorbs 1064nm with the Y-axis.

[0074] S2. Scanning motor 12 rotates at low speed, the host computer acquires multiple frames of TOF images and counts the pixel value distribution in the images to find obvious pixel value clusters;

[0075] S3. Spatial distribution of pixel values ​​clustered in the image across thousands of frames;

[0076] S4. When the signal-free portion of the image appears as an approximate vertical stripe, the scanning motor 12 stops rotating;

[0077] S5. Determine whether the strip is located 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 with the minimum movement angle. The purpose of the intermittent rotation is to wait for the synthesized image to stabilize until the aforementioned dressing strip is located at the center of the field of view, and then stop the rotation.

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

[0079] The method for correcting scanning cone angle error and asymmetry error includes the following steps:

[0080] S1. Install the testing system indoors and set up multiple calibration boards for data comparison;

[0081] Conical scanning lidar achieves a conical scanning trajectory through a rotating reflector or laser emitter. Ideally, the cone angle φ0 of the laser beam should remain constant. However, in actual assembly, factors such as reflector tilt, eccentricity of the scanning motor 12's rotating shaft, or mechanical vibration may cause the cone angle to change periodically with the azimuth angle θ.

[0082] φ(θ)=φ0+δφ(θ)

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

[0084]

[0085] In the formula, a k ,b k Here, represents the Fourier coefficients, and n is the harmonic order, typically taken as n≤3. This error causes distortion of the scanned point cloud along the radial and height z-axis, significantly affecting the accuracy of 3D reconstruction, especially during long-distance measurements.

[0086] Indoors, place a high-reflectivity flat surface, such as a white wall or calibration board, to ensure the lidar scanning range covers the planar area. Acquire dense point cloud data through multiple scans, and extract the planar point set P. i =(r i ,θ i ,z i ), where z i Let z be the height coordinates. Ideally, a planar point cloud should satisfy the linear equation z = z. i =kr i However, cone angle asymmetry can disrupt this relationship. To correct for cone angle asymmetry, software is used to process the data.

[0087] Modeling and optimization of cone angle asymmetry error: Substitute the actual cone angle φ(θ) into the lidar coordinate equation:

[0088]

[0089] For a planar calibration plate, the theoretical height should meet the following requirements. Substituting the actual measured values, we construct a nonlinear least squares optimization problem:

[0090]

[0091] The Fourier coefficients α are solved iteratively using the Levberg-Marquardt algorithm or the Gauss-Newton method. k ,b k To reduce computational complexity, the main harmonic components, such as the fundamental frequency and the second harmonic, can be determined in advance through spectrum analysis, with n ≤ 2.

[0092] The cone angle is corrected using the aforementioned coefficients, and the corrected cone angle is calculated based on the current azimuth angle θ for point cloud regeneration.

[0093]

[0094] Based on the remapping of the point cloud coordinates using the corrected cone angle, the 3D coordinates of the point cloud are recalculated:

[0095] z corrected =rcosφ corrected (θ)

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

[0097] It enables rapid correction of cone angle errors and asymmetries using software in the later stages, without requiring hardware modifications.

[0098] In summary, by using the computer of the proposed ground debugging system for a conical scanning single-photon lidar, the coaxial beam offset and scanning mirror rotation angle can be debugged simultaneously at the hardware level, and the errors caused by the components themselves and their installation process can be significantly reduced at the software level by correcting the cone angle error and asymmetry, thus 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 at a frequency of 20Hz through an antenna, obtains the latitude, longitude and elevation information of the system and outputs it to the radar data acquisition and control unit 16;

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

[0102] like Figure 4 As shown, the radar data acquisition and control unit 16, as the core component for control and data acquisition of the radar system, realizes the control of the radar system and data acquisition; it 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 to organize and store the above-mentioned uploaded data locally.

[0104] The FPGA is equipped with an RS422 interface for communication with the positioning and orientation system 4, a USB interface for communication with the scanning motor 12, a BISS interface for communication with the grating encoder, an FMC interface for the CameraLink daughter card for communication with the area array GM-APD detector 5, an FMC daughter card for providing trigger signals, and an RJ45 interface for outputting stored data. Onboard NAND flash memory is used to store data transmitted back from each system.

[0105] FMC Daughter Card A: Based on the connection of FMC interface 1 of FPGA, it expands the Cmaera Link interface to connect to the area array GM-APD detector 5, realizes the control and data transmission of the area array GM-APD detector 5 by FPGA, configures the voltage, TEC temperature, gate 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: Based on the connection of FMC interface 2 of FPGA, it expands RS422 interface, BISS interface and SMA interface. The RS422 interface realizes the control and data transmission of the positioning and orientation system 4 by FPGA. The BISS interface realizes the uploading of position data of grating read head 11 to FPGA. The SMA interface realizes the output of synchronous trigger signal generated by FPGA to area array GM-APD detector 5 and high repetition rate sub-nanosecond laser 6.

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

[0108] DDR4: Connected to the FPGA, it is used to temporarily store data acquired 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 fixed format data frame;

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

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

[0111] The radar data acquisition and control unit 16 receives position and attitude information and timestamps, angular position data of the scanning system and photon flight time data measured by the GM-APD detector 5 sent to the radar data acquisition and control unit 16 by the positioning and orientation system 4, the high-precision coaxial transceiver conical scanning system 15, and the area array GM-APD detector 5; and stores the data from the above 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 a USB interface and a BISS interface. The USB interface is mainly used for communication with the motor controller, and the BISS interface is used for communication with the grating reader.

[0113] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A ground debugging system for a conical scanning single-photon lidar, characterized in that: The utility model relates to a kind of single-photon laser radar test platform, including Base (1); Debug installation platform (3) provides installation position for conical scanning single-photon laser radar, and is connected with base (1) by rotating translation device (2) to realize translation and rotation, to simulate radar to follow carrier movement; Positioning and orientation system (4) is fixedly installed in debug installation platform (3), for collecting debug installation platform (3) attitude information, data frame is sent to radar data acquisition and control unit (16) by serial port and accepts control; Radar data acquisition and control unit (16) is fixedly installed in debug installation platform (3), for setting the working parameter of positioning and orientation system (4) and setting the working parameter of conical scanning single-photon laser radar, and collecting positioning and orientation system (4) and conical scanning single-photon laser radar back data; Conical scanning single-photon laser radar is fixed in the front of debug installation platform (3), and follows debug installation platform (3) movement; Computer is connected to radar data acquisition and control unit (16), for processing the information of radar data acquisition and control unit (16) and debug installation platform (3), The high-precision coaxial transmitting and receiving conical scanning system (15) of the conical scanning single-photon laser radar includes: Mirror one (8), mirror two (9), mirror three (17), mirror four (18) are used for sequentially deflecting the laser output of sub-nanosecond laser (6), Total reflection lens (19) is used for changing the direction of laser beam through mirror four (18), so that it is incident to the center prism (27) of mirror five (20) at 45 degrees; Mirror five (20) is installed in automatic adjusting frame, and the front center is processed with center prism (27), which is used for changing the direction of laser reflected by total reflection lens (19) to make laser coaxial with optical filter (22); Mirror six (21) is arranged between the first mirror five (20) and optical filter (22), Optical filter (22) weakens stray noise photons received by receiving system composed of concave-convex lens group (23) and total reflection prism (24); Concave-convex lens group (23) adjusts the focal length of receiving system to 950mm, matches laser beam divergence angle and receiving system field of view angle; Total reflection prism (24) is used for reversing the propagation direction of the photons received by concave-convex lens group (23); Beam deflection element (14) makes the laser propagation direction have an angle MAA with the optical axis of concave-convex lens group (23), rotates with scanning motor (12), and can obtain a conical surface with a top angle of 2*MAA with the laser propagation axis as the generatrix; Scanning motor (12) drives beam deflection element (14) and grating code disc (13) to rotate around the optical axis of concave-convex lens group (23); Grating code disc (13) is fixed to the front end of scanning motor (12), and the outer side is etched with grating; Grating reader (11) reads the etched grating on grating code disc (13); Concave-convex lens pair (7) is arranged between mirror one (8) and mirror two (9), and adjusts the divergence angle of the laser output of sub-nanosecond laser (6) to 3.5mrad.

2. The ground debugging system of a conical scanning single-photon lidar according to claim 1, characterized in that: The conical scanning single-photon laser radar comprises a surface array GM-APD detector (5), a high-repetition sub-nanosecond laser (6) and a high-precision coaxial receiving and transmitting conical scanning system (15); The high-precision coaxial receiving and transmitting conical scanning system (15) is fixed at the front part of the debugging installation platform (3), The surface array GM-APD detector (5) communicates with the radar data acquisition and control unit (16) to realize detector control and detector measurement of photon flight time data output; The high-repetition sub-nanosecond laser (6) receives the control of the radar data acquisition and control unit (16) and synchronously emits sub-nanosecond laser with narrow pulse width and high repetition at a wavelength of 1064 nm.

3. The ground debugging system of a conical scanning single-photon lidar according to claim 1, characterized in that: The automatic adjusting mirror frame comprises a fixed frame (25), a lead screw (26), a mirror frame (28) and a stopper (29); the lead screw (26) is screw-mounted at four corners of the fixed frame (25), and hemispherical washers are processed at positions corresponding to the lead screw (26) at four corners of the mirror frame (28); a lens is processed with a small full-reflection center prism (27) at the center of the reflecting mirror five (20), the remaining part of the reflecting mirror five (20) is coated with an anti-reflection film to improve the transmittance, and the mirror frame (28) is installed at the center of the reflecting mirror five (20); the stopper (29) is arranged between the fixed frame (25) and the mirror frame (28).

4. The ground debugging system of a conical scanning single-photon lidar according to claim 3, characterized in that: The computer-controlled automatic adjusting mirror frame makes the laser coaxial with the optical filter (22), and comprises the following steps: S1. The host computer obtains multiple frames of TOF images when the rotating and translating device (2) is not working; S2. The pixel value distribution in the image is counted to find the obvious pixel value aggregation part; S3. The spatial distribution of the pixel value aggregation part in the image is accumulated in thousands of frames; S4. The center of the spatial distribution is estimated according to the morphological method, and the distance absolute value of the center of the spatial distribution from the center of the field of view is judged; when the distance absolute value is greater than the coaxial threshold, adjustment is needed, otherwise, the adjustment is completed, and the lead screw (26) is locked; S5. When the distance absolute value is greater than the coaxial threshold, the coaxial adjustment is needed, the relative relationship between the center of the pixel value aggregation part and the center of the field of view is controlled, the four lead screws (26) are controlled to rotate and adjust the position of the light spot, and the image is waited to be stable; S6. The above S1 to S5 are repeatedly performed until the distance between the center of the light spot and the center of the field of view is less than the coaxial threshold.

5. The ground debugging system of a conical scanning single-photon lidar according to claim 3, characterized in that: The synchronous method of the rotation angle of the computer-controlled beam deflection element (14) and the rotation angle of the grating code disc (13) comprises the following steps: S1. The debugging system is adjusted when the beam deflection element (14) is not installed; the debugging installation platform (3) is established with the light spot as the origin, the normal vector of the debugging installation platform (3) as the Y axis, the X axis perpendicular to the plane of the light beam direction and the Y axis, and the Y axis covered with a medium that absorbs 1064 nm; S2. The scanning motor (12) is rotated at a low speed, the host computer obtains multiple frames of TOF images and counts the pixel value distribution in the image to find the obvious pixel value aggregation part; S3. The spatial distribution of the pixel value aggregation part in the image is accumulated in thousands of frames; 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 located 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 with the minimum motion angle, and the purpose of intermittent rotation is to wait for the synthesized image to be stable until the aforementioned vertical strip is located at the center of the field of view, and the rotation is stopped; S6. Record the data of the grating code disc (13) at this time.

6. The ground debugging system of a conical scanning single-photon lidar according to claim 3, characterized in that: The method for correcting the scanning cone angle error and the asymmetry error, the flow includes: S1. Install the debugging system in the room, and set up multiple calibration boards for data comparison; S2. Arranging a high reflectivity plane in the room, ensuring that the lidar scanning range covers the plane area, obtaining dense point cloud data by multiple scans, and extracting the plane point set wherein is the height coordinate, Substitute the actual cone angle into the laser radar coordinate equation: For planar calibration board, the theoretical height should satisfy , the actual measurement value is substituted into, and a nonlinear least squares optimization problem is constructed: Solving the Fourier coefficients iteratively by the Levenberg-Marquardt algorithm or the Gauss-Newton method , , The cone angle is corrected by the foregoing coefficient, and the corrected cone angle is calculated according to the current azimuth angle The corrected cone angle is calculated for point cloud regeneration According to the corrected cone angle, remap the point cloud coordinates, and recalculate the three-dimensional coordinates of the point cloud: Finally, according to the coordinate information of multiple feature points in the point cloud, the error from the cone angle is corrected.

7. 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: through the antenna, receive GPS, Beidou satellite positioning data, obtain the longitude and latitude and elevation information of the system and output to the radar data acquisition and control unit (16); Dynamic offset angle measurement system: measure the real-time heading angle, pitch angle, roll angle, and output to the radar data acquisition and control unit (16).

8. 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 planar GM-APD detector (5), and store the parameters of the positioning and orientation system (4), the parameters of the scanning motor (12), and the parameters of the planar GM-APD detector (5) after sorting in local; FMC subcard A: based on the connection of FMC interface 1 of FPGA, expand the Cmaera Link interface for connecting to the planar GM-APD detector (5), realize the control and data transmission of FPGA to the planar GM-APD detector (5), and receive the TOF data of the planar GM-APD detector (5) through the Cmaera Link interface; FMC subcard B: based on the connection of FMC interface 2 of FPGA, expand RS422 interface, BISS interface, SMA interface, RS422 interface realizes the control and data transmission of FPGA to the positioning and orientation system (4), BISS interface realizes the position data upload of grating reader (11) to FPGA, SMA interface realizes the synchronization trigger signal output to planar GM-APD detector (5), high-repetition-rate sub-nanosecond laser (6) generated by FPGA; DDR4: connected with FPGA, used for temporarily storing the data obtained from planar GM-APD detector (5), positioning and orientation system (4), and high-precision coaxial transceiver conical scanning system (15), and re-packaging the data into fixed format data frames; USB and RJ45 interfaces, connected with FPGA, used for external communication, realizing motor controller control and internal data upload; NAND FLASH, connected with FPGA, used for storing the backhaul data frames and system status of the positioning and orientation system (4), grating reader (11), and planar GM-APD detector (5) after re-packaging.

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