Scanning type single-photon laser radar imaging system and imaging method

Abstract

The invention discloses a scanning type single-photon laser radar imaging system and an imaging method, and solves the technical problems of fuzzy depth estimation and insufficient background noise suppression capability caused by asynchronization of scanning galvanometer motion and pixel acquisition in the prior art. The imaging system comprises a signal acquisition unit, a time-to-digital converter, a signal delay generator, a galvanometer control unit and a main control unit, the signal acquisition unit is of a transceiving integrated structure, and the signal delay generator is respectively connected with the laser, the detector and the time-to-digital converter and is used for sending a synchronous signal to provide time sequence control; the main control unit is connected with the galvanometer control unit and is used for sending a deflection instruction to the galvanometer control unit; the galvanometer control unit is respectively connected with the galvanometer and the time-to-digital converter, and is used for controlling the deflection angle of the galvanometer, acquiring the deflection time information of the galvanometer and transmitting the deflection time information to the main control unit through the time-to-digital converter; and the main control unit processes the received electric signal and time information and realizes imaging.

Description

Technical Field

[0001] The present invention relates to a single-photon laser radar system, and in particular to a scanning single-photon laser radar imaging system and an imaging method. Background Art

[0002] A scanning single-photon lidar system is an ultra-sensitive detection system based on the time-of-flight (ToF) principle. It emits laser pulses and captures reflected signals at the single-photon level, combining this with precise scanning to achieve high-resolution three-dimensional imaging. The core advantage of a scanning single-photon lidar system lies in its ability to overcome the signal-to-noise ratio limitations of traditional lidar systems, enabling it to accurately extract target depth information even in extremely low light or complex background noise conditions (such as strong sunlight and atmospheric scattering).

[0003] Existing scanning single-photon LiDAR systems suffer from asynchrony between the scanning mirror's motion and pixel acquisition during dynamic scanning, leading to blurred depth estimation. This significantly reduces imaging clarity, particularly on complex surfaces and at interfaces with sudden depth changes. Furthermore, background noise and optical coupling efficiency are key factors affecting system performance.

[0004] Based on this, Chinese invention patent publication number CN119326402A discloses an imaging scanning drive device and method. This device improves scanning stability and accuracy by optimizing the drive circuit and control algorithm of the scanning galvanometer. However, this device still does not solve the problem of depth estimation ambiguity caused by the asynchronous movement of the scanning galvanometer and pixel acquisition, and there is still room for improvement in background noise suppression and optical coupling efficiency.

[0005] Chinese invention patent publication number CN119126502A discloses a method, system, and related equipment for adjusting pixel rows during laser scanning imaging. This solution improves image resolution and clarity by adjusting the position and size of pixel rows in real time. However, this solution primarily focuses on pixel row adjustment and still does not address the synchronization of scanning mirror motion and pixel acquisition, nor does it consider background noise suppression.

[0006] Chinese invention patent publication number CN116400379A discloses a single-photon lidar 3D imaging system and method. This imaging system improves detection sensitivity and imaging accuracy by optimizing optical design and signal processing algorithms. However, this imaging system still has shortcomings in the synchronous control of scanning mirror motion and pixel acquisition. In particular, the problem of depth estimation ambiguity in dynamic scanning scenarios has not been effectively resolved. Summary of the Invention

[0007] The purpose of the present invention is to solve the problem of depth estimation ambiguity caused by the asynchronous movement of the scanning galvanometer and pixel acquisition, as well as the technical problem of insufficient background noise suppression capability in the prior art, and to provide a scanning single-photon lidar imaging system and imaging method.

[0008] To achieve the above objectives, the technical solutions provided by the present invention are:

[0009] A scanning single-photon lidar imaging system with the following features:

[0010] The device comprises a signal acquisition unit, a time-to-digital converter, a signal delay generator, a galvanometer control unit, and a main control unit; the signal acquisition unit comprises a laser, a beam expander, a first reflector, a second reflector, a galvanometer, a bandpass filter, a coupling lens, and a detector, which are sequentially arranged along the output optical path of the laser;

[0011] The beam expander is arranged close to the laser to limit the divergence angle of the outgoing light; a 45° positioning hole is provided on the first reflector, and the central axis of the positioning hole coincides with the optical axis of the outgoing light; the first reflector and the second reflector are arranged in parallel, and the reflecting surfaces of the two are opposite to each other; the galvanometer is a two-dimensional scanning galvanometer; the bandpass filter is located on the reflected light path of the first reflector to filter out background noise; the coupling lens is located at the light output end of the bandpass filter and is connected to the detector through a multimode optical fiber; the outgoing light of the laser passes through the beam expander, the positioning hole of the first reflector, the second reflector, and the galvanometer in sequence to reach the surface of the target object, forming an echo light with target information, and the echo light passes through the galvanometer, the second reflector, the first reflector, the bandpass filter, the coupling lens, and the multimode optical fiber in sequence to be received by the detector; the detector, the time-to-digital converter and the main control unit are connected in sequence, and the detector is used to convert the echo light into an electrical signal, and transmit it to the main control unit through the time-to-digital converter;

[0012] The signal delay generator is connected to the laser, the detector and the time-to-digital converter respectively, and is used to send out synchronization signals to provide timing control;

[0013] The main control unit is connected to the galvanometer control unit and is used to send deflection instructions to the galvanometer control unit; the galvanometer control unit is respectively connected to the galvanometer and the time-to-digital converter, and is used to control the deflection angle of the galvanometer, while obtaining the time information of the galvanometer deflection state and transmitting it to the main control unit via the time-to-digital converter; the main control unit is used to process the received electrical signals and time information and realize imaging.

[0014] Furthermore, the galvanometer control unit includes an FPGA, a digital-to-analog converter and an analog-to-digital converter respectively connected to the FPGA, and a galvanometer driver board;

[0015] The FPGA is connected to the main control unit and is used to receive the deflection instruction sent by the main control unit, and convert the deflection instruction into a control signal and send it to the digital-to-analog converter;

[0016] The digital-to-analog converter is connected to a galvanometer drive board, which is provided with an X-axis control pin and a Y-axis control pin electrically connected to the galvanometer respectively; the digital-to-analog converter is used to convert the control signal into a corresponding voltage signal, and drive the galvanometer deflection through the X-axis control pin or the Y-axis control pin;

[0017] The analog-to-digital converter is connected to the galvanometer driver board and is used to obtain the actual deflection information of the galvanometer and feed it back to the FPGA;

[0018] The FPGA is connected to the time-to-digital converter and is used to calculate the received actual deflection information and obtain the time information of the galvanometer deflection state, and then transmit it to the time-to-digital converter.

[0019] Furthermore, it also includes a beam reduction component located between the bandpass filter and the coupling lens;

[0020] The shrinking assembly includes a first lens and a second lens arranged in sequence; the first lens is a convex lens with one side being flat and the other side being convex, which is arranged close to the bandpass filter, and the convex side faces the bandpass filter; the second lens is a concave lens with one side being flat and the other side being concave, and the concave side is arranged facing the coupling lens.

[0021] Furthermore, the diameters of the first lens and the second lens are the same, both ranging from 10 to 50.4 mm; the focal length of the first lens is 60 mm; and the focal length of the second lens is -30 mm.

[0022] Furthermore, the diameter of the first lens and the second lens is 25.4 mm.

[0023] Furthermore, the laser is a narrow pulse width pulse laser with a central wavelength of 532 nm.

[0024] Furthermore, the central wavelength of the bandpass filter is 532 nm and the bandwidth is 1 nm;

[0025] The detector adopts a silicon-based single-photon avalanche detector.

[0026] Furthermore, the main control unit is a PC controller.

[0027] At the same time, the present invention also provides a scanning single-photon laser radar imaging method, which is special in that it includes the following steps:

[0028] Step 1: Assemble the above-mentioned scanning single-photon lidar imaging system;

[0029] Step 2: Generate a synchronization signal through a signal delay generator and send it to the laser, detector, and time-to-digital converter respectively, so that the detector and time-to-digital converter are in working state, and the laser emits outgoing light at the same time;

[0030] At the same time, according to the deflection angle requirement of the galvanometer, the main control unit sends a deflection instruction to the galvanometer control unit;

[0031] Step 3: The outgoing light passes through the beam expander, the positioning hole of the first reflector, the second reflector, and the galvanometer in sequence, and reaches the surface of the target object, forming an echo light with target information. The echo light passes through the galvanometer, the second reflector, the first reflector, the bandpass filter, the coupling lens, and the multimode optical fiber, and is received by the detector. The detector converts the received echo light into an electrical signal and transmits it to the time-to-digital converter. The time-to-digital converter records the electrical signal in a time-resolved mode and transmits it to the main control unit.

[0032] At the same time, the galvanometer control unit controls the galvanometer to deflect, obtains the time information of the galvanometer deflection state, and transmits it to the main control unit through the time-to-digital converter;

[0033] Step 4: The main control unit uses a pixel-by-pixel depth reconstruction algorithm to calculate based on the electrical signal transmitted in step 3 and the time information of the galvanometer deflection state, and outputs a three-dimensional image of the target object, thereby realizing scanning single-photon lidar imaging.

[0034] Furthermore, in step 3, the galvanometer control unit controls the galvanometer to deflect, obtains time information of the galvanometer deflection state, and transmits it to the main control unit via a time-to-digital converter, specifically:

[0035] 3.1、FPGA receives the deflection command sent by the main control unit and converts it into a control signal and sends it to the digital-to-analog converter;

[0036] 3.2. The digital-to-analog converter converts the control signal into a corresponding voltage signal, and drives the galvanometer to deflect through the X-axis control pin or Y-axis control pin on the galvanometer driver board;

[0037] 3.3. The analog-to-digital converter obtains the actual deflection state information of the galvanometer in real time through the galvanometer driver board and feeds it back to the FPGA;

[0038] 3.4. The time information of the galvanometer deflection state is calculated by FPGA and transmitted to the main control unit through the time-to-digital converter.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1. The present invention introduces a time-to-digital converter, a signal delay generator, a galvanometer control unit, and a main control unit into an optical system primarily based on a signal acquisition unit. By collaboratively optimizing the optical architecture and electronic control, the present invention achieves synchronous control of the galvanometer scanning and data acquisition timing, systematically resolving the depth estimation ambiguity problem in traditional single-photon lidar systems and significantly improving ranging accuracy and three-dimensional imaging clarity in dynamic scanning scenarios.

[0041] 2. The galvanometer control unit of the present invention performs real-time synchronous control based on FPGA. The control signal generated by FPGA drives the galvanometer to deflect through the digital-to-analog converter and the galvanometer driver board, and obtains the position feedback of the galvanometer through the analog-to-digital converter to ensure that the galvanometer collects data at a stable point. This method reduces depth estimation errors, especially at surface junctions, and significantly improves edge clarity and spatial resolution.

[0042] 3. The present invention incorporates a beam reduction assembly, comprising a first lens and a second lens, between the bandpass filter and the coupling lens to match the core diameter and numerical aperture requirements of the multimode fiber. This design enables efficient coupling of the echo light into the detector, thereby improving photon collection efficiency. Furthermore, the bandpass filter effectively filters out background noise, further enhancing the signal-to-noise ratio.

[0043] 4. This invention uses FPGA to achieve real-time synchronization control, which not only improves the accuracy of data acquisition but also enables efficient real-time data processing. Simultaneously, the synchronization signal and timestamp generated by the FPGA ensure the precise establishment of the data acquisition window, reducing time jitter and system latency. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a schematic structural diagram of an embodiment of a scanning single-photon laser radar imaging system of the present invention;

[0045] Figure 2 This is a circuit operation timing diagram of the FPGA in an embodiment of a scanning single-photon laser radar imaging system of the present invention.

[0046] The following are the descriptions of the reference numerals:

[0047] 1-Laser, 2-Beam expander, 3-First reflector, 4-Second reflector, 5-Galvanometer, 6-Bandpass filter, 7-First lens, 8-Second lens, 9-Coupling lens, 10-Multimode optical fiber, 11-Detector, 12-Time-to-digital converter, 13-Signal delay generator, 14-Main control unit, 15-Digital-to-analog converter, 16-Analog-to-digital converter, 17-Galvanometer driver board. DETAILED DESCRIPTION

[0048] In order to make the objects, advantages and features of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and specific examples. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0049] like Figure 1 As shown, this embodiment provides a scanning single-photon lidar imaging system, including a signal acquisition unit, a time-to-digital converter 12 (TDC), a signal delay generator 13, a galvanometer control unit and a main control unit 14; the signal acquisition unit includes a laser 1, a beam expander 2, a first reflector 3, a second reflector 4, a galvanometer 5, a bandpass filter 6, a coupling lens 9 and a detector 11, which are arranged in sequence along the output light path of the laser 1.

[0050] Laser 1 is used to emit outgoing light. It can be a narrow-pulse pulse laser with a central wavelength of 532nm. Lasers of this wavelength are stable and reliable, and have better underwater penetration than lasers of other wavelengths. A beam expander 2 is positioned near laser 1 to limit the divergence angle of the outgoing light. A 45° positioning hole is provided on the first reflector 3. This 45° positioning hole separates the transmitting and receiving optical paths, and the central axis of the positioning hole coincides with the optical axis of the outgoing light. The first reflector 3 and the second reflector 4 are arranged parallel to each other, with their reflective surfaces facing each other.

[0051] The galvanometer 5 is a two-dimensional scanning galvanometer, including an X-lens and a Y-lens. The X-lens controls the horizontal deflection of the light beam (X-axis), while the Y-lens controls the vertical deflection of the light beam (Y-axis). It also includes a position sensor that provides real-time feedback on the lens' angle.

[0052] The bandpass filter 6 is located on the reflected light path of the first reflector 3 and is used to filter out background noise in the echo light. In this embodiment, the central wavelength of the bandpass filter 6 is 532 nm, corresponding to the emission band of the laser 1, and the bandwidth is 1 nm, which can effectively filter out the sunlight background noise.

[0053] The coupling lens 9 is located at the light output end of the bandpass filter 6 and is connected to the detector 11 through the multimode optical fiber 10 , and is used to couple the received echo light into the multimode optical fiber 10 and then couple it to the detector 11 through the multimode optical fiber 10 .

[0054] The emitted light from the laser 1 passes through the beam expander 2, the positioning hole of the first reflector 3, the second reflector 4, and the galvanometer 5 in sequence, then reaches the surface of the target object to scan the target scene, forming an echo light with target information. The echo light then returns along the original path. That is, after being reflected by the galvanometer 5, the second reflector 4, and the surface of the first reflector 3, it passes through the bandpass filter 6, the coupling lens 9, and the multimode optical fiber 10 in sequence before being received by the detector 11. The detector 11, the time-to-digital converter 12, and the main control unit 14 are connected in sequence. The detector 11 is used to convert the echo light into an electrical signal and transmit it to the main control unit 14 via the time-to-digital converter 12. The detector 11 of this embodiment adopts a silicon-based single-photon avalanche detector (Si SPAD). The detector's response detection band covers visible light and exhibits a good detection probability at 532nm laser detection.

[0055] In addition, in order to improve the coupling efficiency, this embodiment also provides a reduction assembly between the bandpass filter 6 and the coupling lens 9; the reduction assembly includes a first lens 7 and a second lens 8 arranged in sequence, wherein the first lens 7 is a convex lens with one side being flat and the other side being convex, which is arranged close to the bandpass filter 6, and the convex surface faces the bandpass filter 6; the second lens 8 is a concave lens with one side being flat and the other side being concave, and the concave surface is arranged toward the coupling lens 9.

[0056] The first and second lenses 7 and 8 are identical in size, with diameters ranging from 10 to 50.4 mm. Excessively large diameters would affect the overall system miniaturization requirements, while excessively small diameters would result in loss of the echo light returned by the galvanometer 5. In this embodiment, the diameters of the first and second lenses 7 and 8 are 25.4 mm, a moderate size that allows for full reception of the echo light. The focal length of the first lens 7 is 60 mm, while the focal length of the second lens 8 is -30 mm.

[0057] In this embodiment, the laser 1, beam expander 2, first reflector 3, second reflector 4, and galvanometer 5 constitute a transmitting system, and the galvanometer 5, second reflector 4, first reflector 3, bandpass filter 6, first lens 7, second lens 8, coupling lens 9, multimode optical fiber 10, and detector 11 constitute a receiving system. The coaxial integrated transmitting and receiving optical path design, the precise matching of the receiving field of view and the laser divergence angle, and the addition of the beam reducing component jointly improve the coupling efficiency and the suppression of background noise.

[0058] In the present invention, the signal delay generator 13 is connected to the laser 1, the detector 11 and the time-to-digital converter 12 respectively, so as to send out a synchronization signal and provide timing control.

[0059] The main control unit 14 is connected to the galvanometer control unit for sending deflection instructions to the galvanometer control unit; the galvanometer control unit is respectively connected to the galvanometer 5 and the time-to-digital converter 12 for controlling the deflection angle of the galvanometer 5, and at the same time obtaining the time information of the deflection state of the galvanometer 5 and transmitting it to the main control unit 14 via the time-to-digital converter 12.

[0060] The main control unit 14 is used to process the received electrical signal and time information and realize imaging. In this embodiment, the main control unit 14 can be realized by selecting a conventional PC controller to load the corresponding algorithm.

[0061] In this embodiment, the galvanometer control unit includes an FPGA (field programmable gate array), a digital-to-analog converter (DAC) 15 and an analog-to-digital converter (ADC) 16 connected to the FPGA respectively, and a galvanometer driving board 17 .

[0062] The FPGA is connected to the main control unit 14 and is used to receive the deflection instruction sent by the main control unit 14 and convert the deflection instruction into a precise control signal and send it to the digital-to-analog converter 15 .

[0063] The digital-to-analog converter 15 is connected to the galvanometer drive board 17, which is provided with an X-axis control pin and a Y-axis control pin electrically connected to the galvanometer 5 respectively; the digital-to-analog converter 15 is used to convert the control signal into a corresponding voltage signal and drive the X-axis or Y-axis control pin of the galvanometer 5 to deflect.

[0064] The analog-to-digital converter 16 is connected to the galvanometer driver board 17 to obtain the actual deflection information of the galvanometer 5 and feed it back to the FPGA in real time. The FPGA is connected to the time-to-digital converter 12 to calculate the received actual deflection information and obtain the time information of the deflection state of the galvanometer 5, which is then transmitted to the time-to-digital converter 12.

[0065] Existing technologies, due to insufficient optical-electronics collaborative design, suffer from significant shortcomings in timing synchronization accuracy, noise suppression, and adaptability to dynamic scenarios. This invention systematically addresses these issues through the dual-dimensional innovation of coaxial optical path optimization and FPGA closed-loop synchronization control, providing a reliable solution for high-dynamic, high-precision single-photon radar applications.

[0066] Optical architecture optimization: Construct a coaxial integrated transceiver optical path, achieve spatial filtering by precisely matching the receiving field of view with the laser divergence angle, and introduce a beam reduction system to suppress background noise to an extremely low level while ensuring high coupling efficiency.

[0067] Electronics control optimization: Developed an FPGA-based real-time synchronization control system. Through closed-loop timing matching of the 16-bit DAC galvanometer drive and the 80-Msps ADC photon timestamp acquisition, it achieved sub-microsecond synchronization of the galvanometer motion trajectory and photon events, effectively solving the depth estimation ambiguity problem.

[0068] Through the coordinated optimization of optical architecture and electronic control, the present invention systematically solves the depth estimation ambiguity problem in traditional single-photon lidar systems, significantly improving the ranging accuracy and three-dimensional imaging clarity in dynamic scanning scenarios.

[0069] In addition, this embodiment also provides a scanning single-photon laser radar imaging method, comprising the following steps:

[0070] Step 1: Assemble the above-mentioned scanning single-photon lidar imaging system.

[0071] Step 2: Generate a synchronization signal through the signal delay generator 13 and send it to the laser 1, the detector 11 and the time digital converter 12 respectively, so that the detector 11 and the time digital converter 12 are in working state, and the laser 1 emits outgoing light.

[0072] At the same time, according to the deflection angle requirement of the galvanometer 5 , a deflection instruction is sent to the galvanometer control unit via the main control unit 14 .

[0073] Step 3: The outgoing light passes through the beam expander 2, the positioning hole of the first reflector 3, the second reflector 4, and the galvanometer 5 (passing through the X-lens and Y-lens in sequence) before reaching the target surface, forming an echo light with target information. The echo light passes through the galvanometer 5 (passing through the Y-lens and X-lens in sequence), the second reflector 4, the first reflector 3, the bandpass filter 6, the coupling lens 9, and the multimode fiber 10 before being received by the detector 11. The detector 11 converts the received echo light into an electrical signal and transmits it to the time-to-digital converter 12. The time-to-digital converter 12 records the electrical signal in time-resolved mode, provides a timestamp when the marker signal arrives, and transmits the electrical signal to the main control unit 14.

[0074] At the same time, the galvanometer control unit controls the galvanometer 5 to deflect, obtains the time information of the deflection state of the galvanometer 5, and transmits it to the main control unit 14 via the time-to-digital converter 12, specifically:

[0075] 3.1. The FPGA receives the deflection instruction sent by the main control unit 14, converts it into a control signal, and then sends it to the digital-to-analog converter 15.

[0076] 3.2. The digital-to-analog converter 15 converts the control signal into a corresponding voltage signal, and drives the galvanometer 5 to deflect via the X-axis control pin or the Y-axis control pin on the galvanometer drive board 17 .

[0077] 3.3. The analog-to-digital converter 16 obtains the actual deflection state information of the galvanometer 5 in real time through the galvanometer driver board 17 and feeds it back to the FPGA.

[0078] 3.4. The time information of the deflection state of the galvanometer 5 is calculated by the FPGA and transmitted to the main control unit 14 via the time-to-digital converter 12 .

[0079] The detailed operating sequence of the FPGA in this embodiment is as follows: Figure 2 As shown, the figure describes four key operating parameters: modulation of the galvanometer control voltage, angle position feedback, synchronization marks Marker1 / Marker2 and time resolution characteristics of TDC (time to digital converter 12).

[0080] The measurement protocol operates as follows: When the FPGA modifies the voltage value of the digital-to-analog converter 15, this event is timestamped as t. After an inherent 0.5μs delay (attributed to the DAC serial peripheral interface configuration), the time-to-digital converter 12 records the actual deflection start time t1 of the galvanometer 5 via the Marker1 signal. Simultaneously, the analog-to-digital converter 16 obtains position feedback of the galvanometer 5 from the galvanometer driver board 17. After receiving this data, the FPGA executes an embedded algorithm to determine the stabilization time t2 of the galvanometer 5 and sends the Marker2 signal to the time-to-digital converter 12. The time-to-digital converter 12 then calculates the time interval between markers Marker1 and Marker2 to establish a valid data acquisition window for single-pixel measurement. Figure 2 In the figure, invalid data refers to the data collected during the deflection period of the galvanometer 5 between each pixel, and valid data refers to the data collected when the galvanometer 5 resides on the specified pixel. The FPGA can mark both valid data and invalid data, and finally the main control unit 14 performs corresponding calculations based on the time mark to obtain valid information about the target object.

[0081] This embodiment uses an FPGA-based real-time synchronous control system, and the closed-loop timing matching of the 16-bit DAC galvanometer drive and the 80-Msps ADC photon timestamp acquisition can achieve sub-microsecond synchronization of the galvanometer motion trajectory and photon events, thereby effectively solving the problem of depth estimation ambiguity caused by the asynchronous movement of the galvanometer 5 and pixel acquisition.

[0082] In step 4, the main control unit 14 uses a pixel-by-pixel depth reconstruction algorithm to perform calculations based on the electrical signal transmitted in step 3 and the time information of the deflection state of the galvanometer 5, and outputs a three-dimensional image of the target object, thereby achieving high-precision imaging of the scanning single-photon laser radar.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A scanning single-photon laser radar imaging system, characterized by: The invention comprises a signal acquisition unit, a time-to-digital converter (12), a signal delay generator (13), a galvanometer control unit and a main control unit (14); the signal acquisition unit comprises a laser (1), a beam expander (2), a first reflector (3), a second reflector (4), a galvanometer (5) arranged in sequence along the output light path of the laser (1), a bandpass filter (6), a coupling lens (9) and a detector (11); The beam expander (2) is arranged close to the laser (1) and is used to limit the divergence angle of the emitted light; the first reflector (3) is provided with a 45° positioning hole, and the central axis of the positioning hole coincides with the optical axis of the emitted light; The first reflector (3) and the second reflector (4) are arranged in parallel, and their reflection surfaces are opposite to each other; the galvanometer (5) is a two-dimensional scanning galvanometer; the bandpass filter (6) is located on the reflection light path of the first reflector (3) and is used to filter out background noise; the coupling lens (9) is located at the light output end of the bandpass filter (6) and is connected to the detector (11) through a multimode optical fiber (10); the output light of the laser (1) passes through the beam expander (2), the positioning hole of the first reflector (3), the second reflector (4), After the galvanometer (5), the light reaches the surface of the target object, forming an echo light with target information, and the echo light is received by the detector (11) after passing through the galvanometer (5), the second reflector (4), the first reflector (3), the bandpass filter (6), the coupling lens (9), and the multimode optical fiber (10); the detector (11), the time-to-digital converter (12), and the main control unit (14) are connected in sequence, and the detector (11) is used to convert the echo light into an electrical signal, and transmit it to the main control unit (14) via the time-to-digital converter (12); The signal delay generator (13) is connected to the laser (1), the detector (11) and the time-to-digital converter (12) respectively, and is used to send out a synchronization signal to provide timing control; The main control unit (14) is connected to the galvanometer control unit and is used to send a deflection instruction to the galvanometer control unit; the galvanometer control unit is respectively connected to the galvanometer (5) and the time-to-digital converter (12) and is used to control the deflection angle of the galvanometer (5), and simultaneously obtain time information of the deflection state of the galvanometer (5) and transmit it to the main control unit (14) via the time-to-digital converter (12); the main control unit (14) is used to process the received electrical signal and time information and realize imaging.

2. The scanning single-photon laser radar imaging system according to claim 1, characterized in that: The galvanometer control unit includes an FPGA, a digital-to-analog converter (15) and an analog-to-digital converter (16) respectively connected to the FPGA, and a galvanometer drive board (17); The FPGA is connected to the main control unit (14) and is used to receive a deflection instruction sent by the main control unit (14), and convert the deflection instruction into a control signal and send it to the digital-to-analog converter (15); The digital-to-analog converter (15) is connected to a galvanometer drive board (17), and the galvanometer drive board (17) is provided with an X-axis control pin and a Y-axis control pin respectively electrically connected to the galvanometer (5); the digital-to-analog converter (15) is used to convert the control signal into a corresponding voltage signal, and drive the galvanometer (5) to deflect via the X-axis control pin or the Y-axis control pin; The analog-to-digital converter (16) is connected to the galvanometer drive board (17) and is used to obtain actual deflection state information of the galvanometer (5) and feed it back to the FPGA; The FPGA is connected to a time-to-digital converter (12) and is used to calculate the received actual deflection state information and obtain time information of the deflection state of the galvanometer (5), and then transmit the information to the time-to-digital converter (12).

3. The scanning single-photon laser radar imaging system according to claim 1 or 2, characterized in that: Also included is a beam reduction assembly located between the bandpass filter (6) and the coupling lens (9); The shrinking assembly comprises a first lens (7) and a second lens (8) which are arranged in sequence; the first lens (7) is a convex lens with one plane surface and one convex surface, and is arranged close to the band-pass filter (6), with the convex surface facing the band-pass filter (6); the second lens (8) is a concave lens with one plane surface and one concave surface, and the concave surface is arranged facing the coupling lens (9).

4. The scanning single-photon laser radar imaging system according to claim 3, characterized in that: The diameters of the first lens (7) and the second lens (8) are consistent, both ranging from 10 to 50.4 mm. The focal length of the first lens (7) is 60 mm; and the focal length of the second lens (8) is -30 mm.

5. The scanning single-photon laser radar imaging system according to claim 4, characterized in that: The diameters of the first lens (7) and the second lens (8) are 25.4 mm.

6. The scanning single-photon laser radar imaging system according to claim 1, characterized in that: The laser (1) is a narrow pulse width laser with a central wavelength of 532 nm.

7. The scanning single-photon laser radar imaging system according to claim 6, characterized in that: The bandpass filter (6) has a central wavelength of 532 nm and a bandwidth of 1 nm; The detector (11) is a silicon-based single-photon avalanche detector.

8. The scanning single-photon laser radar imaging system according to claim 7, characterized in that: The main control unit (14) is a PC controller.

9. A scanning single-photon laser radar imaging method, characterized in that: The following steps are involved: Step 1: Assemble the scanning single-photon lidar imaging system according to any one of claims 1 to 8; Step 2: Generate a synchronization signal through a signal delay generator (13) and send it to the laser (1), the detector (11) and the time-to-digital converter (12) respectively, so that the detector (11) and the time-to-digital converter (12) are in an operating state, and the laser (1) emits output light at the same time; At the same time, according to the deflection angle requirement of the galvanometer (5), a deflection instruction is sent to the galvanometer control unit through the main control unit (14); Step 3: The outgoing light sequentially passes through the beam expander (2), the positioning hole of the first reflector (3), the second reflector (4), and the galvanometer (5) before reaching the surface of the target object, forming an echo light with target information; the echo light sequentially passes through the galvanometer (5), the second reflector (4), the first reflector (3), the bandpass filter (6), the coupling lens (9), and the multimode optical fiber (10) before being received by the detector (11); the detector (11) converts the received echo light into an electrical signal and transmits it to the time-to-digital converter (12); the time-to-digital converter (12) records the electrical signal in a time-resolved mode and transmits it to the main control unit (14); At the same time, the galvanometer control unit controls the galvanometer (5) to deflect, obtains time information of the deflection state of the galvanometer (5), and transmits it to the main control unit (14) via the time-to-digital converter (12); Step 4: The main control unit (14) uses a pixel-by-pixel depth reconstruction algorithm to perform calculations based on the electrical signal transmitted in step 3 and the time information of the deflection state of the galvanometer (5), and outputs a three-dimensional image of the target object, thereby realizing scanning single-photon laser radar imaging.

10. The scanning single-photon laser radar imaging method according to claim 9, characterized in that: In step 3, the galvanometer control unit controls the galvanometer (5) to deflect, obtains time information of the deflection state of the galvanometer (5), and transmits it to the main control unit (14) via the time-to-digital converter (12), specifically: 3.

1. The FPGA receives the deflection instruction sent by the main control unit (14), converts it into a control signal and sends it to the digital-to-analog converter (15); 3.

2. The digital-to-analog converter (15) converts the control signal into a corresponding voltage signal, and drives the galvanometer (5) to deflect via the X-axis control pin or the Y-axis control pin on the galvanometer drive board (17); 3.3, the analog-to-digital converter (16) obtains the actual deflection state information of the galvanometer (5) in real time through the galvanometer driver board (17) and feeds it back to the FPGA; 3.

4. The time information of the deflection state of the galvanometer (5) is calculated by FPGA and transmitted to the main control unit (14) via the time-to-digital converter (12).

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