Laser imaging system based on Gm-APD array

Abstract

The invention discloses a laser imaging system based on a Gm-APD array. The laser imaging system comprises a transmitting end, a receiving end, a Gm-APD single photon array sensor, a reading circuit unit, a TCSPC unit, a DAQ unit and a control and calculation unit. The control and calculation unit is connected with the transmitting end, the receiving end is connected with the Gm-APD single photon array sensor, the Gm-APD single photon array sensor is connected with the reading circuit unit, the reading circuit unit is connected with the TCSPC unit, the TCSPC unit is connected with the DAQ unit through a CamLink cable, and the DAQ unit is connected with the control and calculation unit. The laser imaging system based on the Gm-APD array is simple, low in cost and high in ranging and point cloud imaging capacity.

Description

Technical Field

[0001] The present invention relates to the field of single-photon lidar imaging, and particularly to a laser imaging system based on a Gm-APD array. Background Art

[0002] "Single-Photon Lidar" (SPL) is a detection and ranging technology based on individual photons, which uses extremely sensitive detectors to detect individual photons reflected back from targets. Compared with traditional lidars, single-photon lidars have higher sensitivity and longer operating ranges, and are particularly suitable for applications in low-light conditions or those requiring high-precision measurements.

[0003] In actual use, the operating range, imaging resolution, imaging sampling rate, point cloud generation rate, etc. of a single-photon lidar are key factors affecting ranging and imaging. Traditional single-photon lidar systems use the TCSPC (Time-Correlated Single Photon Counting) technique in a point-by-point scanning manner to accumulate multiple laser pulse echo signals at each pixel point, forming raw histogram data, obtaining the flight time of laser pulses, and thus obtaining the distance information and spatial point cloud of the target. When imaging at close range, high-repetition-rate laser pulses can be used to increase the counting rate of the imaging system, forming more effective data points per unit time, thereby improving the imaging point cloud generation rate, resolution, and sampling rate of the lidar system.

[0004] However, high-repetition-rate laser pulses will result in a shorter imaging ambiguity distance. Prior Art 1 (CN202410476676.1) discloses a high-repetition-rate lidar imaging system and method with weak light detection capabilities, which are used to solve technical problems such as the reduction of imaging accuracy in a streak tube system for single-laser-pulse imaging due to the inability to eliminate the jitter of the scanning circuit and system, the susceptibility of single-photon lidars to interference from background noise photons during detection, which affects their detection accuracy, and the relatively low detection efficiency and photon energy utilization rate of single-photon lidars. However, it fails to solve the problem of the shorter imaging ambiguity distance caused by high repetition rates, and thus is not suitable for long-range detection.

[0005] In the application of long-distance imaging, the accumulation of several laser pulses required by the low laser repetition frequency and TCSPC technology makes the long-distance imaging system have the disadvantages of low point cloud generation rate, low imaging resolution and sampling rate. In this case, the multi-beam single-photon laser radar can improve the working efficiency of the system, and the imaging efficiency of the system can be improved by covering a larger field of view angle during scanning with a multi-beam laser. However, the multi-beam single-photon laser radar system usually requires multiple lasers and detectors, which increases the system cost. Prior art 2 (CN202210356769.1) discloses an airport bird detection laser radar system and its working method, in which the multi-beam laser emission module in the system is used to generate and emit a multi-beam laser line array according to a preset safety wavelength and a preset beam angle to illuminate a small volume target, solving the technical problems of short detection distance, small detection field of view and severe clutter interference. However, the multi-beam laser emission module and receiving module of the system not only increase the complexity of the optical system, but also have the problems of being too large and too heavy, and the higher system cost also leads to an increase in the workload of assembly and later maintenance.

[0006] At the receiving end of the single-photon laser radar, the traditional single-pixel detector is combined with a two-dimensional galvanometer to adopt a continuous scanning method, which has a high lateral and longitudinal ranging resolution at close distances. However, when imaging at long distances, the rotation resolution characteristics of the galvanometer itself directly restrict the detector's ability to perform high-resolution 3D imaging measurements at long distances. Prior art 3 (Shen Guangyue. Research on near-infrared single-photon imaging technology [D]. East China Normal University, 2021. DOI: 10.27149 / d.cnki.ghdsu.2021.000067.) discloses research on near-infrared single-photon imaging technology, specifically involving a self-selected single-photon imaging system based on continuous scanning of a two-dimensional galvanometer. Since its continuous scanning does not perform the TCSPC process on the same position in space, it is necessary to divide several consecutive pulses into one pixel during data processing to form raw data and obtain the target distance, which not only increases the difficulty of system post-processing, but also increases the sampling time of point cloud imaging.

[0007] Therefore, how to improve the ranging and point cloud imaging capabilities of single-photon lidar while controlling the complexity and cost of the system has become one of the key issues that need to be urgently addressed in this field. Summary of the invention

[0008] In order to overcome the above-mentioned deficiencies of the prior art, the present invention provides a laser imaging system based on a Gm-APD array to solve the problems of high complexity, high cost, and poor ranging and point cloud imaging capabilities of single-photon laser radar systems in the prior art.

[0009] The present invention provides a laser imaging system based on a Gm-APD array, comprising: a transmitting end, a receiving end, a Gm-APD single-photon array sensor, a readout circuit unit, a TCSPC unit, a DAQ unit, and a control and calculation unit.

[0010] The control and calculation unit is connected to the transmitting end, the receiving end is connected to the Gm-APD single-photon array sensor, the Gm-APD single-photon array sensor is connected to the readout circuit unit, the readout circuit unit is connected to the TCSPC unit, the TCSPC unit is connected to the DAQ unit through a CamLink cable, and the DAQ unit is connected to the control and calculation unit.

[0011] The transmitting end is configured to emit pulsed laser towards the object to be measured.

[0012] The receiving end is configured to receive the echo signal reflected by the object to be measured and focus the echo signal to generate a focused signal.

[0013] The Gm-APD single-photon array sensor is configured to receive the focused signal, record the number of photons and time, and generate a detectable electrical signal.

[0014] The readout circuit unit is configured to convert the electrical signal into electrical pulses and transmit the arrival time to the TCSPC unit.

[0015] The TCSPC unit is configured to receive the electrical pulses and generate time-correlated single-photon numbers.

[0016] The DAQ unit is configured to receive the single-photon numbers and generate an analog signal.

[0017] The control and calculation unit is configured to receive the analog signal and obtain a two-dimensional array image.

[0018] Optionally, the transmitting end includes: a pulsed laser and a laser emitting lens, the pulsed laser is connected to the control and calculation unit, and the control and calculation unit controls the pulsed laser to emit laser.

[0019] The laser emitting lens is configured to receive the laser emitted by the pulsed laser and adjust the divergence angle of the laser.

[0020] Optionally, it further includes: a sight, and the sight is configured to assist the transmitting end and the receiving end in aiming at the object to be measured.

[0021] Optionally, the transmitting end includes: a fiber laser, an erbium-doped fiber amplifier, a fiber collimator, a perforated mirror, and a mirror.

[0022] The fiber laser is configured to generate seed light.

[0023] The erbium-doped fiber amplifier is used to amplify the seed light.

[0024] The fiber collimator is used to receive the amplified seed light and emit laser light.

[0025] The perforated mirror is used to reflect the laser light.

[0026] The mirror is used to emit the laser light.

[0027] Optionally, the receiving end is coaxial with the transmitting end, and the receiving end includes: a first convex lens, a second convex lens, a concave lens, a narrowband filter, and a detector.

[0028] The first convex lens, the concave lens, the narrowband filter, the second convex lens, and the detector are coaxially arranged in sequence. The return light emitted by the target passes through the first convex lens, the concave lens, the narrowband filter, and the second convex lens in sequence, and converges onto the detector.

[0029] Optionally, the detector includes:

[0030] InGaAs Gm-APD array chip and TDC conversion chip;

[0031] The InGaAs Gm-APD array chip is used to convert photons of each pixel into electrical pulses; the TDC conversion chip is used to measure the time difference between the start signal and the photon event of each pixel point after programmable delay, and the start signal is generated by the detector.

[0032] Optionally, the time resolution of the TDC chip is 1 ns, which can be quantized to 12 bits, the corresponding time measurement range is 4096 ns, the distance range is 600 m, and the effective distance gating signal adjustment range is 25 - 4090 ns.

[0033] Optionally, it includes: when the TCSPC unit receives an external trigger signal, after the inherent delay and gating delay of the signal link, a distance gating signal is generated.

[0034] The distance gating signal uses the readout circuit unit as the start signal of the high-frequency clock counter in each pixel.

[0035] When the laser pulse echo signal returns to reach the photosensitive target surface, the photosensitive pixel will generate a Geiger avalanche signal. After the threshold discrimination circuit in the readout circuit unit detects the avalanche signal, a CMOS-compatible voltage pulse STOP signal is generated.

[0036] The pulse STOP signal stops the TDC counting of the pixel and serially outputs the TDC count values of each pixel after the distance gating signal ends.

[0037] The conversion relationship between the TDC count value and time is:

[0038] T0 = TDC × T bin

[0039] T0 is the starting time of the laser pulse emission, and T bin is the time bin.

[0040] The flight time of the laser pulse is obtained from the following model:

[0041] D f = (T0 + T d + T ind - T u ) × c

[0042] c is the time constant 3×10 8 m / s, D f is the flight time of the laser pulse, T u is the delay between the laser emission and the synchronization signal, T d is the gating delay, T ind is the inherent delay of the signal link.

[0043] The distance of the object to be detected is obtained from the following model:

[0044] D T = D f ÷ 2

[0045] D T is the distance of the object to be detected.

[0046] As can be seen from the above technical solutions, the present invention provides a laser imaging system based on a Gm-APD array, including: a transmitting end, a receiving end, a Gm-APD single-photon array sensor, a readout circuit unit, a TCSPC unit, a DAQ unit, and a control and calculation unit. The control and calculation unit is connected to the transmitting end, the receiving end is connected to the Gm-APD single-photon array sensor, the Gm-APD single-photon array sensor is connected to the readout circuit unit, the readout circuit unit is connected to the TCSPC unit, the TCSPC unit is connected to the DAQ unit through a CamLink cable, and the DAQ unit is connected to the control and calculation unit. The transmitting end is used to emit pulsed laser towards the object to be measured. The receiving end is used to receive the echo signal feedback from the object to be measured and focus the echo signal to generate a focused signal. The Gm-APD single-photon array sensor is used to receive the focused signal, record the number of photons and time, and generate a detectable electrical signal. The readout circuit unit is used to convert the electrical signal into electrical pulses and transmit the arrival time to the TCSPC unit. The TCSPC unit is used to receive the electrical pulses and generate time-correlated single-photon numbers. The DAQ unit is used to receive the single-photon numbers and generate an analog signal. The control and calculation unit is used to receive the analog signal to obtain a two-dimensional column array image. The laser imaging system based on a Gm-APD array provided by the present invention has a simple system, low cost, and strong ranging and point cloud imaging capabilities.

[0047] The following are the beneficial effects of the present invention:

[0048] Aiming at the defect that the high-repetition-rate lidar imaging system in the prior art fails to solve the problem of short imaging ambiguity distance caused by high repetition rate, resulting in inapplicability to long-distance detection, the present invention uses an imaging method with multiple repetition-rate laser pulses in cooperation, which increases the ambiguity distance of the imaging system and improves the counting rate and point cloud generation rate of the imaging system at the same time.

[0049] Compared with the multi-beam single-photon lidar, although the multi-beam single-photon lidar can solve the problem of short imaging distance ambiguity caused by high repetition rate and cover a larger field of view angle. However, the multi-beam single-photon lidar system usually requires multiple lasers and detectors, which increases the system complexity and cost. While increasing the ambiguity distance of the imaging system, the optical system structure of the present invention changes little, saving system cost and reducing the workload of system assembly and maintenance.

[0050] Compared with the self-gating single-photon imaging system based on two-dimensional galvanometer continuous scanning, this system is limited by the upper limit value of the scanning rate of the two galvanometers in the X-Y axes and it is difficult to achieve panoramic scanning of the local field of view in a short time. Compared with the scanning point detector, the technical solution provided by the present invention can achieve simultaneous photon counting of up to 4096 channels at the two-dimensional level, improving the system sampling rate and meeting the real-time requirement of the system at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0052] Figure 1 is a framework diagram of a laser imaging system based on a Gm-APD array provided by an embodiment of the present invention;

[0053] Figure 2 is a schematic diagram of the internal structure of the transmitting end and the receiving end provided by an embodiment of the present invention. Among them, RM is a reflecting mirror, PERM is a perforated reflecting mirror, L1 is a first convex lens, L2 is a second convex lens, CL is a concave lens, F is a narrowband filter, Detector is a detector, COL is an optical fiber collimator, SMF is a single-mode optical fiber, EDFA is an erbium-doped fiber amplifier, LD is a laser diode and its driver, FPGA is a timing board, and the thin beam and the thick beam respectively represent the outgoing path and the collection path;

[0054] Figure 3 is a schematic diagram of the working principle of the high-frequency clock counter TDC provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0055] The above describes the present invention and its embodiments. This description is not restrictive. What is shown in the drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto. Generally speaking, if those of ordinary skill in the art are inspired by it and, without departing from the purpose of the present invention, design similar structural forms and embodiments to this technical solution without creative efforts, they should all fall within the protection scope of the present invention.

[0056] In the field of single-photon lidar imaging, how to improve the ranging and point cloud imaging capabilities of single-photon lidar on the premise of controlling the complexity and cost of the control system is one of the key problems that need to be solved urgently.

[0057] Therefore, in order to solve the above technical problems, an embodiment of the present invention proposes a solution, that is, to provide a laser imaging system based on a Gm-APD array.

[0058] See Figure 1 , a framework diagram of a laser imaging system based on a Gm-APD array provided by an embodiment of the present invention; an embodiment of the present invention provides a laser imaging system based on a Gm-APD array, including:

[0059] A transmitting end, a receiving end, a Gm-APD single-photon array sensor, a readout circuit unit, a TCSPC unit, a DAQ unit, and a control and calculation unit. The control and calculation unit is connected to the transmitting end, the receiving end is connected to the Gm-APD single-photon array sensor, the Gm-APD single-photon array sensor is connected to the readout circuit unit, the readout circuit unit is connected to the TCSPC unit, the TCSPC unit and the DAQ unit are connected by a CamLink cable, and the DAQ unit is connected to the control and calculation unit. The transmitting end is used to emit pulsed laser towards the object to be measured. The receiving end is used to receive the echo signal fed back by the object to be measured and focus the echo signal to generate a focused signal. The Gm-APD single-photon array sensor is used to receive the focused signal, record the number of photons and time, and generate a detectable electrical signal. The readout circuit unit is used to convert the electrical signal into electrical pulses and transmit the arrival time to the TCSPC unit. The TCSPC unit is used to receive the electrical pulses and generate time-correlated single-photon numbers. The DAQ unit is used to receive the single-photon numbers and generate an analog signal. The control and calculation unit is used to receive the analog signal and obtain a two-dimensional column array image.

[0060] The transmitting end includes: a pulsed laser and a laser emission lens. The pulsed laser is connected to the control and calculation unit, and the control and calculation unit controls the pulsed laser to emit laser.

[0061] The laser emission lens is used to receive the laser emitted by the pulsed laser and adjust the divergence angle of the laser.

[0062] The transmitting end of the lidar uses a fiber laser to emit a pulsed laser beam with a wavelength of 1550 nm and a repetition frequency of 20 kHz. Its divergence angle is adjusted by the laser emission lens and can cover the receiving field of view. The echo light diffusely reflected by the object to be measured returns along the original path of the outgoing beam. After the echo signal of the object to be measured is filtered by a filter, the receiving lens focuses it on the photosensitive surface of the detection module.

[0063] The photosensitive surface of the Gm-APD (Geiger Mode Avalanche Photodiode) single-photon array sensor is one of its key components, which determines its detection ability and response characteristics to optical signals. The photosensitive surface is divided into multiple independent pixel units, and each pixel unit is an independent Gm-APD detector. These pixel units form an array to achieve spatial resolution and imaging function. The photosensitive area can range from as small as dozens of micrometers to several millimeters. A larger photosensitive area can improve the photon capture probability, but may increase the dark count rate and crosstalk effect; a smaller photosensitive area helps reduce noise and improve spatial resolution.

[0064] The system provided by the present invention further includes: a sight, which is used to assist the transmitting end and the receiving end in aiming at the object to be measured.

[0065] The detector is a Gm-APD single-photon array sensor with a resolution of 64*64 pixels, a receiving field of view of 19.2 mrad, and a single-pixel field of view of 0.3 mrad. The readout circuit converts the photons on each pixel of the photosensitive surface into electrical pulses and transmits the arrival time to the TCSPC unit to achieve time-correlated single-photon counting (TCSPC) measurement. The measurement results are transmitted to the DAQ unit through a CameraLink cable and delivered to the control and calculation unit after data processing. The control and calculation unit can input parameters and control commands for both the transmitting end and the receiving end simultaneously, and perform post-processing on the two-dimensional array image obtained by the receiving end and display it in real time on the host computer.

[0066] See Figure 2 , which is a schematic diagram of the internal structures of the transmitting end and the receiving end provided by an embodiment of the present invention. Among them, RM is a reflector, PERM is a perforated reflector, L1 is a first convex lens, L2 is a second convex lens, CL is a concave lens, F is a narrowband filter, Detector is a detector, COL is an optical fiber collimator, SMF is a single-mode optical fiber, EDFA is an erbium-doped fiber amplifier, LD is a laser diode and its driver, FPGA is a timing board, and the thin beam and the thick beam respectively represent the outgoing path and the collection path.

[0067] The transmitting end includes: a fiber laser, an erbium-doped fiber amplifier, an optical fiber collimator, a perforated reflector, and a reflector. The fiber laser is used to generate seed light. The erbium-doped fiber amplifier is used to amplify the seed light. The optical fiber collimator is used to receive the amplified seed light and emit laser light. The perforated reflector is used to reflect the laser light. The reflector is used to emit the laser light.

[0068] The receiving end is coaxial with the transmitting end, and the receiving end includes: a first convex lens, a second convex lens, a concave lens, a narrowband filter, and a detector.

[0069] The first convex lens, the concave lens, the narrowband filter, the second convex lens, and the detector are coaxially arranged in sequence. The backscattered light emitted by the target passes through the first convex lens, the concave lens, the narrowband filter, and the second convex lens in sequence and converges onto the detector.

[0070] The detector includes: an InGaAs Gm-APD array chip and a TDC conversion chip;

[0071] The InGaAs Gm-APD array chip is used to convert photons of each pixel into electrical pulses; the TDC conversion chip is used to measure the time difference between the start signal and the photon event of each pixel point after programmable delay, and the start signal is generated by the detector.

[0072] The seed light of the system is generated by a 1550 nm fiber laser (LD), and the electrical pulse signal is generated by a signal generator. An erbium-doped fiber amplifier (EDFA) is used to amplify the seed light by laser to increase the laser power of the imaging system and improve the working distance of the imaging system. The laser exits from the fiber collimator (COL), with a beam diameter of 14.5 mm and a divergence angle of 0.13 mrad. The laser beam passes through a perforated mirror (PERM) placed at 45°, with a reflectivity of 96% and an aperture of 16 mm. The laser beam can pass through the perforated mirror without loss and exits after passing through the mirror (RM). Since the receiving end and the transmitting end of the system are coaxial, the laser emission and receiving optical paths can also be kept coaxial. The backscattered light from the target diffuse reflection returns along the original path of the outgoing beam, passes through the convex lenses L1, L2 and the concave lens CL, and a narrowband filter (F) with a central wavelength of 1550 nm is used to suppress the interference of the background light, and finally converges on the receiving array target surface of the detector.

[0073] See Figure 3 , which is a schematic diagram of the working principle of the high-frequency clock counter TDC provided by the embodiment of the present invention.

[0074] The detection module of the lidar is an integrated device, including a 64*64 pixel InGaAs Gm-APD array chip, an integrated circuit and a time-digital (TDC) conversion chip. Photons incident on each pixel of the array chip are converted into electrical pulses, and its photon detection efficiency (PDE) is approximately 20%. The TDC chip measures the time difference between the start signal and the photon event of each pixel point after programmable delay. The start signal is generated by the detector installed in the emission optical path. The time resolution T bin of the TDC chip is 1 ns, which can be quantified to 12 bits, corresponding to a time measurement range of 4096 ns and a distance range of 600 m. However, due to reasons such as circuit reset, when the high-level width of the gating signal is 4096 ns, there is a small blind area at the start and end respectively. Therefore, the effective distance gating signal adjustment range is 25 - 4090 ns. Since the TDC chip can only obtain one photon event for each pixel in a single acquisition cycle, the photons scattered by the target may be masked by the background photons that arrive first. Finally, the photon events from the target scattering and the background are transmitted to the computer through CameraLink.

[0075] For this system, since the single-photon array lidar and the laser use the same signal trigger source, such as Figure 3As shown, after the TCSPC receives an external trigger signal through the external trigger interface, it passes through the inherent delay T of the signal link ind (the T of the external trigger ind is 225 ns), the gating delay T d and then generates a range gating signal EN. The range gating signal EN is used as the start signal of the TDC (high-frequency clock counter) in each pixel for the ROIC (readout circuit), and the TDC counting starts; when the laser pulse echo signal returns to the photosensitive target surface, the photosensitive pixel will generate a Geiger avalanche signal. After the threshold discrimination circuit in the ROIC detects the avalanche signal, it generates a CMOS-compatible voltage pulse STOP, which stops the TDC counting of the pixel, and then serially outputs the TDC count values of each pixel after the EN signal ends.

[0076] The conversion relationship between the count value (TDC, Time-to-Digital Converter) and time usually depends on the specific design parameters of the TDC device (such as time resolution, clock frequency, calibration coefficient, etc.). The conversion relationship between the TDC count value and time is:

[0077] T0 = TDC × T bin

[0078] T0 is the start time of the laser pulse emission, and T bin is the time bin.

[0079] In a lidar (LiDAR) or time-of-flight (ToF) measurement system, Tbin (Time Bin) usually refers to the time bin, that is, the time axis is divided into several discrete intervals (called "bins"), and each bin corresponds to a fixed time interval. The core function of Tbin is to discretize the continuous time-of-flight signal, which is convenient for subsequent digital signal processing and statistical analysis.

[0080] In the time-of-flight (ToF) measurement scenario of a lidar (LiDAR), the conversion relationship between the TDC count value and time directly determines the calculation of the target distance. When calculating, it should be noted that: clock synchronization: it is necessary to ensure that the TDC clock is strictly synchronized with the system timing; dead time: the interval between two measurements needs to meet the TDC reset and readout time; multi-target resolution: high repetition rate lasers may need to combine multiple measurements or waveform analysis.

[0081] The time of flight of the laser pulse is obtained from the following model:

[0082] D f =(T0 + T d + T ind - T u )×c

[0083] c is the time constant 3×108 m / s, D f is the flight time of the laser pulse, T u is the delay between the laser emission and the synchronization signal, T d is the gating delay, T ind is the inherent delay of the signal link.

[0084] The distance of the object to be detected is obtained by the following model:

[0085] D T = D f ÷ 2

[0086] D T is the distance of the object to be detected.

[0087] It can be seen that the laser imaging system based on the Gm-APD array provided by the embodiment of the present invention has a simple system, low cost, and strong ranging and point cloud imaging capabilities.

[0088] It should be noted that in the present invention, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

Claims

1. A laser imaging system based on a Gm-APD array, characterized in that, Including: A transmitting end, a receiving end, a Gm-APD single-photon array sensor, a readout circuit unit, a TCSPC unit, a DAQ unit, and a control and calculation unit; The control and calculation unit is connected to the transmitting end, the receiving end is connected to the Gm-APD single-photon array sensor, the Gm-APD single-photon array sensor is connected to the readout circuit unit, the readout circuit unit is connected to the TCSPC unit, the TCSPC unit is connected to the DAQ unit through a CamLink cable, and the DAQ unit is connected to the control and calculation unit; The transmitting end is used to emit pulsed laser towards the object to be measured; The receiving end is used to receive the echo signal fed back by the object to be measured and focus the echo signal to generate a focused signal; The Gm-APD single-photon array sensor is used to receive the focused signal, record the number of photons and time, and generate a detectable electrical signal; The readout circuit unit is used to convert the electrical signal into electrical pulses and transmit the arrival time to the TCSPC unit; The TCSPC unit is used to receive the electrical pulses and generate time-correlated single-photon numbers; The DAQ unit is used to receive the single-photon numbers and generate analog signals; The control and calculation unit is used to receive the analog signals to obtain a two-dimensional array image.

2. The laser imaging system based on a Gm-APD array according to claim 1, wherein The transmitting end includes: a pulsed laser and a laser emission lens. The pulsed laser is connected to the control and calculation unit, and the control and calculation unit controls the pulsed laser to emit laser; The laser emission lens is used to receive the laser emitted by the pulsed laser and adjust the divergence angle of the laser.

3. The laser imaging system based on a Gm-APD array according to claim 1, wherein, It also includes: A sight, which is used to assist the transmitting end and the receiving end to aim at the object to be measured.

4. The laser imaging system based on a Gm-APD array according to claim 1, characterized in that, The transmitting end includes: a fiber laser, an erbium-doped fiber amplifier, a fiber collimator, a perforated mirror, and a mirror; The fiber laser is used to generate seed light; The erbium-doped fiber amplifier is used to amplify the seed light; The fiber collimator is used to receive the amplified seed light and emit laser; The perforated mirror is used to reflect the laser; The mirror is used to emit the laser.

5. The laser imaging system based on a Gm-APD array according to claim 1, wherein The receiving end is coaxial with the transmitting end. The receiving end includes: a first convex lens, a second convex lens, a concave lens, a narrow-band filter, and a detector; The first convex lens, the concave lens, the narrow-band filter, the second convex lens, and the detector are arranged coaxially in sequence. The echo light emitted by the target passes through the first convex lens, the concave lens, the narrow-band filter, and the second convex lens in sequence and converges onto the detector.

6. The laser imaging system based on a Gm-APD array according to claim 5, characterized in that, The detector includes: An InGaAs Gm-APD array chip and a TDC conversion chip; The InGaAs Gm-APD array chip is used to convert the photons of each pixel into electrical pulses; the TDC conversion chip is used to measure the time difference between the start signal and the photon event of each pixel point after programmable delay, and the start signal is generated by the detector.

7. The laser imaging system based on a Gm-APD array according to claim 6, wherein The time resolution of the TDC chip is 1 ns, which can be quantized to 12 bits. The corresponding time measurement range is 4096 ns, the distance range is 600 m, and the effective distance gating signal adjustment range is 25 - 4090 ns.

8. A laser imaging system based on a Gm-APD array according to claim 1, characterized in that, Including: After the TCSPC unit receives an external trigger signal, a range gating signal is generated after the inherent delay and gating delay of the signal link; The range gating signal uses the readout circuit unit as the start signal of the high-frequency clock counter in each pixel; When the laser pulse echo signal returns and reaches the photosensitive target surface, the photosensitive pixel generates a Geiger avalanche signal. After the threshold discrimination circuit in the readout circuit unit detects the avalanche signal, a CMOS-compatible voltage pulse STOP signal is generated; The pulse STOP signal stops the TDC counting of the pixel and serially outputs the TDC count values of each pixel after the range gating signal ends; The conversion relationship between the TDC count value and time is: T0 = TDC × T bin T0 is the starting time of the laser pulse emission, and T bin is the time bin; The time of flight of the laser pulse is obtained from the following model: D f = (T0 + T d + T ind - T u ) × c c is the time constant of 3×10 8 m / s, D f is the flight time of the laser pulse, T u is the delay between the laser emission and the synchronization signal, T d is the gating delay, T ind is the inherent delay of the signal link; The distance of the object to be detected is obtained from the following model: D T = D f ÷ 2 D T is the distance of the object to be detected.

Images