Single-photon laser radar three-dimensional imaging system and method

Abstract

The invention relates to a single-photon laser radar three-dimensional imaging system and method. An optical fiber laser is used for actively illuminating an imaging target; the single-photon APD array detector is used for receiving a laser echo signal reflected by a target; the near-infrared detector is used for realizing aiming; the upper computer is used for parameter setting and data receiving of the optical fiber laser, the single-photon APD array detector and the near-infrared detector, receiving active laser three-dimensional imaging data in a three-dimensional imaging state and realizing real-time display of a depth image and an intensity image; and the information processing board card is used for realizing synchronous triggering of the fiber laser and the single-photon APD array detector and data communication between the upper computer and the fiber laser and the single-photon APD array detector, and realizing preprocessing and three-dimensional reconstruction of APD data based on a time correlation single-photon counting method and in combination with space-time correlation characteristics of laser echo signals. According to the invention, the problem of insufficient detection capability of a single-photon laser three-dimensional imaging method under all-weather and low-signal-to-noise-ratio conditions is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lidar three-dimensional imaging, and relates to a single-photon lidar three-dimensional imaging system and method. Background Art

[0002] Compared with traditional lidars that can only achieve the detection ability of echo signals by increasing the emission power of lasers and the optical aperture of receiving detectors, single-photon lidars based on Geiger APDs have the characteristics of high sensitivity, fast response time, small volume, and easy integration, and have outstanding advantages in terms of detection sensitivity, spatial resolution, and range resolution. They are one of the important development directions for long-distance three-dimensional imaging detection.

[0003] The literature "High-precision three-dimensional imaging device based on Geiger APD array and its usage method, Nanjing Institute of Astronomical Optics and Technology, Chinese Academy of Sciences 2014, Kou Songfeng et al." proposed a high-precision three-dimensional imaging device based on Geiger APD array and its usage method, which uses multiple small-scale Geiger APD arrays to be coupled to achieve staring three-dimensional imaging, and a common optical path design for high-frequency lasers and detector arrays is realized through a beam splitter.

[0004] The literature "A method and system for Gm-APD array lidar imaging under strong background noise, Huazhong University of Science and Technology 2019, Zhang Tianxu et al." proposed a method for obtaining lidar range images by performing histogram statistics and differential operations on the cumulative detection data of Gm-APD array lidars obtained under two sets of range gate opening time conditions under strong background noise, and then combining the peak discrimination method, which can achieve strong background noise interference in other range ranges and improve the quality of laser three-dimensional images.

[0005] The literature "A method and system for denoising detection data of a Gm-APD detector array, Huazhong University of Science and Technology 2022, Sang Hongshi et al." proposed a data denoising method based on a Gm-APD detector array. By statistically analyzing the echo count distribution histogram, segmentally fitting the noise distribution, taking the difference, and then combining the statistical imaging method, the effects of effectively removing noise and enhancing the signal-to-noise ratio of the target three-dimensional range image are achieved, making the target information more complete.

[0006] Although single-photon lidars have developed rapidly in recent years, in the application of long-distance three-dimensional imaging, there are deficiencies such as weak target echo signals and being easily submerged by strong background noise. Therefore, how to construct a single-photon lidar system to meet the improvement of the signal-to-noise ratio of echo signals and three-dimensional reconstruction under all-weather conditions is also one of the research focuses of current single-photon active laser three-dimensional imaging. Summary of the Invention

[0007] The technical problem solved by the present invention is: aiming at the problem of insufficient detection ability of the existing single-photon laser three-dimensional imaging method under all-weather and low signal-to-noise ratio conditions, a single-photon lidar three-dimensional imaging system and method are proposed to meet the requirement of real-time acquisition of the three-dimensional range image of the target under long-distance and low signal-to-noise ratio conditions.

[0008] The solution of the present invention to solve the technical problem is: a single-photon lidar three-dimensional imaging system, including a fiber laser, a single-photon APD array detector, a near-infrared detector, a pan-tilt head, a filter, a host computer and an information processing board;

[0009] The fiber laser is used for active illumination of the imaging target;

[0010] The single-photon APD array detector is used for receiving the laser echo signal reflected by the target;

[0011] The near-infrared detector is used for aiming. By observing the position of the laser spot in the field of view through the near-infrared detector, the laser emission azimuth is adjusted so that the laser spot is located at the center of the field of view of the near-infrared detector;

[0012] The pan-tilt head is used for realizing the detection field of view selection, and the filter is used for band selection;

[0013] The host computer is used for parameter setting and data reception of the fiber laser, the single-photon APD array detector and the near-infrared detector, and receives the active laser three-dimensional imaging data in the three-dimensional imaging state and realizes the real-time display and storage functions of the depth image and the intensity image;

[0014] The information processing board is used for realizing the synchronous triggering of the fiber laser and the single-photon APD array detector, the data communication between the host computer and the fiber laser and the single-photon APD array detector, and based on the time-correlated single-photon counting method, combining the spatio-temporal correlation characteristics of the laser echo signal, realizing the preprocessing of the APD data and the three-dimensional reconstruction.

[0015] Further, the fiber laser is a high-frequency fiber laser. After being output by a fiber lens, it is connected to two collimating lenses with different collimating and beam expanding effects through the thread of the output head to realize the switching of the divergence angle of the output beam.

[0016] Further, the two collimating lenses with different collimating and beam expanding effects are divided into a fine beam collimating lens and a beam expanding collimating lens;

[0017] The fine beam collimating lens is used for collimating the large divergence angle laser emitted by the fiber to form a fine beam with a divergence angle of several tenths of a mrad for forming a strong echo light spot on the surface of the measured target, or for adding a scanning mechanism on the laser optical path to realize the laser scanning of the target area;

[0018] The beam expander and collimator lens is used to shape the large divergence angle of the optical fiber output, so as to obtain a wide beam with a divergence angle of several rad, which is used to cover and irradiate the target at a distance of several kilometers, and to achieve the effect of staring imaging of the target area.

[0019] Furthermore, the way for the information processing board to achieve synchronous triggering of the fiber laser and the single-photon APD array detector is as follows:

[0020] A clock signal is generated by hardware, and the fiber laser and the single-photon APD array detector are triggered simultaneously by external triggering, so that the number of pulse signals generated by the fiber laser is consistent with the detection frame rate of the single-photon APD array detector, ensuring that each frame of the detector's imaging data can receive the laser echo signal, thereby realizing TOF ranging.

[0021] Furthermore, the way for the information processing board to achieve data communication is as follows:

[0022] The FPGA on the information processing board is used to transmit the commands of the laser repetition frequency, pulse width, power, and trigger mode input from the host computer side, the cooling temperature, bias voltage amplitude, trigger mode, and gating width commands of the single-photon APD array detector, and the exposure time command of the near-infrared detector, and feedback the states of the fiber laser and the single-photon APD array detector to the host computer for display through RS422 serial communication. The depth distance image, intensity image of the single-photon APD array detector, and the image of the near-infrared detector are uploaded to the host computer through the USB port for real-time display.

[0023] Furthermore, the method for the information processing board to achieve preprocessing and three-dimensional reconstruction of APD data is as follows:

[0024] Statistical echo photon count distribution histogram, and identify whether it is a strong noise background through threshold judgment method. If it is a strong noise background, first perform background extraction based on curve fitting on the echo photon count distribution histogram to remove the influence of the strong noise background, and then enter the signal-to-noise ratio improvement step; if it is not a strong noise background, directly enter the signal-to-noise ratio improvement step;

[0025] The signal-to-noise ratio improvement step is as follows: Re-statistical echo photon count distribution histogram through the nine-neighborhood in the spatial domain, and judge whether it is a few-photon echo situation. If it is a few-photon echo situation, use the peak method to judge the position of the echo moment to estimate the distance image; if it is not a few-photon echo situation, statistically the peak position of the histogram, and judge whether it is the only peak. If it is the only peak, use this peak position as the echo moment. If it is not the only peak position, first perform Gaussian filtering in the time domain neighborhood range of the peak, and perform peak threshold method statistics on the filtered result to achieve the estimation of the echo moment and the three-dimensional reconstruction of APD data.

[0026] Further, the threshold judgment method is as follows: it is judged whether it is a strong noise situation by the ratio of the front-end mean value and the overall mean value of the echo photon count distribution histogram. If the front-end mean value is greater than the overall mean value, it is a strong noise situation.

[0027] A three-dimensional imaging method for a single-photon lidar, comprising the following steps:

[0028] Power on the single-photon lidar three-dimensional imaging system and set it to a state capable of completing three-dimensional imaging;

[0029] Field of view alignment: Replace the collimating lens of the fiber laser output with a fine beam collimating lens. Observe the position of the laser spot in the field of view through the near-infrared detector, adjust the laser emission direction so that the laser spot is located at the center of the field of view of the near-infrared detector, and at the same time adjust the orientation of the single-photon APD array detector so that the laser spot in the range image is also located at the center of the field of view, ensuring that the near-infrared detector, the single-photon APD array detector, and the laser emission beam are in a nearly coaxial state at the long-distance imaging target.

[0030] Turn off the fiber laser through the upper computer, and replace the collimating lens with an expanded beam collimating lens to achieve flood illumination and three-dimensional imaging of a long-distance target. Observe the imaging effect of the range image through the upper computer and complete data storage.

[0031] The beneficial effects of the present invention compared with the prior art are as follows:

[0032] (1) The active laser three-dimensional imaging method and system based on a single-photon array detector built in the present invention adopt a modular design. The near-infrared camera can provide a field of view reference. At the same time, the design of the replaceable divergence angle of the laser emission beam can further improve the accuracy of field of view alignment and enhance the target alignment and detection capabilities of the lidar system.

[0033] (2) The distance information processing system based on time-of-flight counting constructed in the present invention includes a dual FPGA+DSP design, which is convenient for the subsequent upgrade of information processing algorithms, and can realize the embedded development of target detection and tracking algorithms based on single-photon lidar three-dimensional imaging data; it can also realize uploading the original data obtained by the single-photon array detector to the upper computer and developing corresponding information processing algorithms in the upper computer.

[0034] (3) The imaging system built in the present invention uses a filter to filter out signals outside the laser band in hardware, and at the same time combines a strong background judgment method, which can effectively improve the target three-dimensional imaging ability under strong background interference during the day. Description of the Drawings

[0035] Figure 1 It is the active laser three-dimensional range image acquisition system of the present invention;

[0036] Figure 2 Schematic diagram of the overall information processing architecture of the present invention;

[0037] Figure 3 Preprocessing flowchart of the present invention;

[0038] Figure 4 shows the reconstruction result using the single peak method in the embodiment, where Figure 4(a) is the intensity image and Figure 4(b) is the distance image;

[0039] Figure 5 shows the result of the reconstruction method of the present invention, where Figure 5(a) is the intensity image and Figure 5(b) is the distance image. Detailed implementation manners

[0040] The present invention obtains three-dimensional imaging data of a target to be measured by constructing a set of acquisition systems based on a fiber laser, a Geiger-mode single-photon APD array detector, and a short-wave infrared camera; realizes internal communication and preprocessing of three-dimensional imaging data through an information processing board, and writes a host computer through software such as MFC to realize the display and storage operations of imaging data. The active laser three-dimensional imaging method and system realized by the present invention can provide relatively sufficient verification for the implementation of software and hardware algorithms for the landing of long-distance laser imaging detection products.

[0041] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0042] Embodiment 1

[0043] The single-photon lidar three-dimensional imaging system proposed in this embodiment includes a set of active laser three-dimensional distance image acquisition systems based on a single-photon APD array and a set of distance information processing systems based on time-of-flight counting;

[0044] The active laser three-dimensional distance image acquisition system based on a single-photon APD array, as Figure 1 shown, includes a fiber laser, a single-photon APD array detector, a near-infrared detector, a pan-tilt, and a filter;

[0045] The fiber laser is used for active illumination of the imaging target;

[0046] The single-photon APD array detector is used to receive the laser echo signal reflected by the target;

[0047] The near-infrared detector is used for aiming. By observing the position of the laser spot in the field of view through the near-infrared detector, the laser emission azimuth is adjusted so that the laser spot is located at the center of the field of view of the near-infrared detector;

[0048] The pan-tilt is used for realizing the selection of the detection field of view, and the filter is used for band selection.

[0049] Among them, the fiber laser is a high-frequency fiber laser. After being output through a fiber lens, it is connected to collimating lenses with two different collimation and beam expansion effects through the threads of the output head to realize the switching of the divergence angle of the output beam.

[0050] The collimating lenses with the two different collimation and beam expansion effects are divided into a fine beam collimating lens and a beam expanding collimating lens. Among them, the fine beam collimating lens is used to collimate the laser with a large divergence angle emitted from the fiber to form a fine beam with a divergence angle of several tenths of a mrad for output, which can be used to form a strong reflected light spot on the surface of the measured target or to add a scanning mechanism to the laser optical path to realize laser scanning of the target area; the beam expanding collimating lens is used to obtain a wide beam with a divergence angle of several rads after shaping the large divergence angle emitted from the fiber for output, which can be used to cover and irradiate typical targets at a distance of several kilometers to achieve the effect of staring imaging of the target area.

[0051] The distance information processing system based on time-of-flight counting, such as Figure 2 shown, includes a host computer and an information processing board;

[0052] The host computer is used for parameter setting and data reception of the fiber laser, the single-photon APD array detector, and the near-infrared detector, and receives active laser three-dimensional imaging data in the three-dimensional imaging state to realize the real-time display and storage functions of the depth image and the intensity image;

[0053] The information processing board is used to realize the synchronous triggering of the fiber laser and the single-photon APD array detector, the data communication between the host computer and the fiber laser and the single-photon APD array detector, and based on the time-correlated single-photon counting method, combined with the spatio-temporal correlation characteristics of the laser echo signal, to realize the preprocessing of the APD data and three-dimensional reconstruction.

[0054] Among them, the way for the host computer to realize parameter setting and data reception is: the host computer conducts signal and data interaction with the active laser three-dimensional distance image acquisition system in real time through interfaces such as USB and RS422 at the test computer end, and inputs through the host computer interface to control the states of the fiber laser and the single-photon APD array detector.

[0055] The information processing board realizes the synchronous triggering of the fiber laser and the single-photon APD array detector as follows: a clock signal is generated by hardware, and the fiber laser and the single-photon APD array detector are triggered simultaneously by an external trigger method, so that the number of pulse signals generated by the fiber laser is consistent with the detection frame rate of the single-photon APD array detector, ensuring that the imaging data of each frame of the detector can receive the laser echo signal, thereby realizing TOF ranging.

[0056] The information processing board realizes data communication in the following ways: Through the FPGA on the information processing board, commands such as the repetition frequency, pulse width, power, and trigger mode of the laser from the host computer, commands such as the cooling temperature, bias voltage amplitude, trigger mode, and gating width of the single-photon APD array detector, and commands such as the exposure time of the near-infrared detector are transmitted downward. The states of the fiber laser and the single-photon APD array detector are fed back to the host computer for display through RS422 serial communication. The depth distance image, intensity image of the single-photon APD array detector, and the image of the near-infrared detector are uploaded to the host computer through the USB port for real-time display.

[0057] As Figure 3 shown, the method for the information processing board to realize the preprocessing and three-dimensional reconstruction of APD data is specifically as follows:

[0058] Statistically analyze the echo photon count distribution histogram, and use the threshold judgment method to identify whether it is a strong noise background. If it is a strong noise background, first perform background extraction based on curve fitting on the echo photon count distribution histogram to remove the influence of the strong noise background, and then enter the signal-to-noise ratio improvement step; if it is not a strong noise background, directly enter the signal-to-noise ratio improvement step;

[0059] Among them, the threshold judgment method is: judge whether it is a strong noise situation by the ratio of the front-end mean value and the overall mean value of the echo photon count distribution histogram. If the front-end mean value is greater than the overall mean value, that is, the ratio is greater than 1, it is a strong noise situation.

[0060] The signal-to-noise ratio improvement step is: re-statistically analyze the echo photon count distribution histogram through the nine-neighborhood in the spatial domain to judge whether it is a few-photon echo situation. If it is a few-photon echo situation, use the peak method to judge the position of the echo moment to estimate the distance image; if it is not a few-photon echo situation, statistically analyze the peak position of the histogram to judge whether it is the only peak. If it is the only peak, use this peak position as the echo moment. If it is not the only peak position, first perform Gaussian filtering within the time-domain neighborhood range of the peak, and perform peak threshold method statistics on the filtered result to realize the estimation of the echo moment and the three-dimensional reconstruction of APD data.

[0061] In this embodiment, in terms of the hardware architecture, the output head of the fiber laser used is equipped with the function of being connected to collimating lenses with two different collimation and beam expansion effects through threads, thereby enabling the switching of the divergence angle of the output beam, adapting to the switching of the alignment and imaging functions for distant targets, and improving the alignment and imaging effects of the targets. In terms of information processing, the intensity image and distance image results obtained by preprocessing the target imaging data of the aircraft model using the single peak method are shown in Figures 4(a) and 4(b). There are many noise points in the imaging results, the target signal-to-noise ratio is low, it is difficult to obtain an obvious outline of the aircraft target, and it is not conducive to subsequent tasks such as target contour detection, feature extraction, and category recognition. The intensity image and distance image results obtained by preprocessing the imaging data of the same aircraft model using the optimized depth estimation method based on spatio-temporal correlation of the present invention are shown in Figures 5(a) and 5(b). It can be seen from the figures that the background has a higher signal-to-noise ratio compared to the imaging using the single peak method, the target contour and local feature information are richer, and the imaging data preprocessed by the spatio-temporal correlation algorithm of the present invention will be more conducive to improving the accuracy of subsequent target detection and recognition tasks.

[0062] This embodiment proposes a three-dimensional imaging method for a single-photon lidar, including the following steps:

[0063] (1) Power on the three-dimensional imaging system of the single-photon lidar and set it to the state where three-dimensional imaging can be completed;

[0064] (2) Field of view alignment: Replace the collimating lens of the fiber laser output with a fine beam collimating lens. Observe the position of the laser spot in the field of view through the near-infrared detector, adjust the laser emission direction so that the laser spot is located at the center of the field of view of the near-infrared detector, and at the same time adjust the orientation of the single-photon APD array detector so that the laser spot in the distance image is also located at the center of the field of view, ensuring that the near-infrared detector, the single-photon APD array detector, and the laser emission beam are in a nearly coaxial state at the distant imaging target.

[0065] (3) Close the fiber laser through the upper computer and replace the collimating lens with an expanded beam collimating lens to achieve flood illumination of distant targets and three-dimensional imaging of targets such as typical buildings. Observe the imaging effect of the distance image through the upper computer and complete the storage of data in a timely manner.

[0066] Although the present invention has been disclosed above with preferred embodiments, it is not used to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes, and decorations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention all belong to the protection scope of the technical solution of the present invention.

[0067] The content not detailed in the specification of the present invention belongs to the well-known technology of those skilled in the art.

Claims

1. A single-photon lidar three-dimensional imaging system, characterized in that, It includes a fiber laser, a single-photon APD array detector, a near-infrared detector, a pan-tilt head, a filter, a host computer, and an information processing board; The fiber laser is used for actively illuminating the imaging target; The single-photon APD array detector is used for receiving the laser echo signal reflected by the target; The near-infrared detector is used for aiming. By observing the position of the laser spot in the field of view through the near-infrared detector, the laser emission azimuth is adjusted so that the laser spot is located at the center of the field of view of the near-infrared detector; The pan-tilt head is used for realizing the detection field of view selection, and the filter is used for band selection; The host computer is used for parameter setting and data reception of the fiber laser, the single-photon APD array detector, and the near-infrared detector. When entering the three-dimensional imaging state, it receives the active laser three-dimensional imaging data and realizes the real-time display and storage functions of the depth image and the intensity image; The information processing board is used for realizing the synchronous triggering of the fiber laser and the single-photon APD array detector, the data communication between the host computer and the fiber laser and the single-photon APD array detector, and based on the time-correlated single-photon counting method, combined with the spatio-temporal correlation characteristics of the laser echo signal, realizing the preprocessing of the APD data and three-dimensional reconstruction.

2. The three-dimensional imaging system of a single-photon lidar according to claim 1, characterized in that The fiber laser is a high-frequency fiber laser. After being output by a fiber lens, it is connected to two collimating lenses with different collimation and beam expansion effects through the thread of the output head to realize the switching of the output beam divergence angle.

3. The three-dimensional imaging system of a single-photon lidar according to claim 2, wherein, The two collimating lenses with different collimation and beam expansion effects are divided into a fine-beam collimating lens and an expanded-beam collimating lens; The fine-beam collimating lens is used for collimating the laser with a large divergence angle emitted from the fiber to form a fine beam with a divergence angle of several tenths of a mrad for emitting, which is used to form a strong reflected light spot on the surface of the measured target, or is used to add a scanning mechanism on the laser optical path to realize the laser scanning of the target area; The expanded-beam collimating lens is used for shaping the large divergence angle emitted from the fiber to obtain a wide beam with a divergence angle of several rads for emitting, which is used for covering and irradiating the target at a distance of several kilometers to realize the effect of staring imaging of the target area.

4. A three-dimensional imaging system for a single-photon lidar according to claim 1, wherein The way for the information processing board to realize the synchronous triggering of the fiber laser and the single-photon APD array detector is: A clock signal is generated by hardware, and the fiber laser and the single-photon APD array detector are simultaneously triggered by an external trigger method, so that the number of pulse signals generated by the fiber laser is consistent with the detection frame rate of the single-photon APD array detector, ensuring that each frame of the detector's imaging data can receive the laser echo signal, thereby realizing TOF ranging.

5. A three-dimensional imaging system for a single-photon lidar according to claim 1, wherein, The way for the information processing board to realize data communication is: The FPGA on the information processing board is used to transmit the commands of the laser repetition rate, pulse width, power, and trigger mode input from the host computer side, the cooling temperature, bias voltage amplitude, trigger mode, and gating width commands of the single-photon APD array detector, and the exposure time command of the near-infrared detector. The statuses of the fiber laser and the single-photon APD array detector are fed back to the host computer for display through RS422 serial communication. The depth distance image, intensity image of the single-photon APD array detector, and the image of the near-infrared detector are uploaded to the host computer through the USB port for real-time display.

6. A three-dimensional imaging system for a single-photon lidar according to claim 1, characterized in that, The method for the information processing board to implement the preprocessing and three-dimensional reconstruction of APD data is as follows: Statistically analyze the echo photon count distribution histogram, and use the threshold judgment method to identify whether it is a strong noise background. If it is a strong noise background, first perform background extraction based on curve fitting on the echo photon count distribution histogram to remove the influence of the strong noise background, and then enter the signal-to-noise ratio improvement step; if it is not a strong noise background, directly enter the signal-to-noise ratio improvement step; The signal-to-noise ratio improvement step is as follows: Statistically analyze the echo photon count distribution histogram again through the nine-neighborhood in the spatial domain, and judge whether it is a few-photon echo situation. If it is a few-photon echo situation, use the peak method to judge the position of the echo moment to estimate the distance image; if it is not a few-photon echo situation, statistically analyze the peak position of the histogram and judge whether it is the only peak. If it is the only peak, use this peak position as the echo moment. If it is not the only peak position, first perform Gaussian filtering in the time domain neighborhood of the peak, and statistically analyze the filtered result using the peak threshold method to estimate the echo moment and perform three-dimensional reconstruction of the APD data.

7. A single-photon lidar three-dimensional imaging system according to claim 6, characterized in that, The threshold judgment method is as follows: Judge whether it is a strong noise situation by the ratio of the front-end mean value and the overall mean value of the echo photon count distribution histogram. If the front-end mean value is greater than the overall mean value, it is a strong noise situation.

8. A three-dimensional imaging method for a single-photon lidar based on the system according to claims 1 to 7, characterized in that, It includes the following steps: The single-photon lidar three-dimensional imaging system is powered on and set to a state where three-dimensional imaging can be completed; Field of view alignment: Replace the collimating lens of the fiber laser output with a fine beam collimating lens. Observe the position of the laser spot in the field of view through the near-infrared detector, adjust the laser emission direction so that the laser spot is located at the center of the field of view of the near-infrared detector. At the same time, adjust the orientation of the single-photon APD array detector so that the laser spot in the distance image is also located at the center of the field of view, ensuring that the near-infrared detector, the single-photon APD array detector, and the laser emission beam are in a state close to coaxial at the long-distance imaging target. Turn off the fiber laser through the host computer and replace the collimating lens with an expanded beam collimating lens to achieve flood illumination and three-dimensional imaging of the long-distance target. Observe the imaging effect of the distance image through the host computer and complete data storage.

Images