A single-photon lidar detection system based on double-gm-apd camera delay detection

Abstract

The application discloses a kind of single-photon laser radar detection systems based on double Gm-APD camera delay detection, the single-photon laser radar detection system includes equipment mechanism, radar data acquisition and control unit, positioning orientation system, single-photon laser radar based on double Gm-APD camera delay detection, host computer.The application is realized twice detection to the same target by using two Gm-APD detectors and introducing delay between two Gm-APD detectors, by comparing and analyzing the signal of two Gm-APD detectors, noise photon can be effectively identified and rejected, and the detection accuracy of signal photon is improved.In addition, the data rate can be improved by signal accumulation effect of double Gm-APD detector delay detection technology.Compared with single-camera detection, the detection system of the application has significant advantages in improving ranging accuracy, noise reduction, improving data rate and distance resolution.

Description

Technical Field

[0001] This invention belongs to the field of single-photon lidar technology and relates to a single-photon lidar detection system, specifically a single-photon lidar detection system based on time-delay detection using dual Gm-APD cameras. Background Technology

[0002] LiDAR (Light Detection and Ranging) technology is an important technology that uses lasers for distance measurement and target detection, and it is widely used in fields such as autonomous driving, environmental monitoring, and industrial inspection. Traditional LiDAR systems typically use a single detector for distance measurement, but in complex environments, they are susceptible to noise interference, leading to a decrease in ranging accuracy. Furthermore, single-detector systems also have limitations in terms of data rate and distance resolution.

[0003] In recent years, Gm-APDs, as highly sensitive photon detectors, have been widely used in lidar systems due to their detection capabilities at the single-photon level. However, single Gm-APD cameras still struggle to effectively distinguish between signal photons and noise photons when faced with strong background noise or complex target reflections, reducing the accuracy and reliability of the acquired data. To improve the accuracy of the acquired data, in addition to optimizations in algorithm processing and theory, new approaches should also be explored in the configuration of lidar systems. Summary of the Invention

[0004] To overcome the problems of single-photon detectors being susceptible to interference from noisy photons, having limited dynamic range, and constrained data rates in environments with strong background noise, complex target reflections, and high-precision data requirements, this invention provides a single-photon lidar detection system based on delayed detection using dual Gm-APD cameras. This system employs two Gm-APD detectors and introduces a delay between them, enabling two detections of the same target. By comparing and analyzing the signals from the two Gm-APD detectors, noisy photons can be effectively identified and eliminated, improving the detection accuracy of signal photons. Furthermore, the delayed detection technique using two Gm-APD detectors can also improve the data rate through signal accumulation. The detection system of this invention can simulate the motion of a lidar in three-dimensional space by controlling the assembly mechanism. Moreover, this detection system, based on delayed detection using dual Gm-APD cameras, has significant advantages over single-camera detection in terms of improved ranging accuracy, noise reduction, increased data rate, and range resolution.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A single-photon lidar detection system based on time-delay detection using dual Gm-APD cameras includes an assembly and adjustment mechanism, a radar data acquisition and control unit, a positioning and orientation system (POS), a single-photon lidar based on time-delay detection using dual Gm-APD cameras, and a host computer, wherein:

[0007] The assembly and adjustment mechanism includes a base and an installation platform. The data acquisition and control unit, POS, and single-photon lidar based on the time-delay detection of dual Gm-APD cameras are installed on the installation platform. The installation platform is connected to the rotating shaft and the base via a slide rail.

[0008] The radar data acquisition and control unit is fixedly installed on the installation platform. The working parameters of the POS and the working parameters of the single-photon lidar based on the delay detection of the dual Gm-APD camera are set through the radar data acquisition and control unit, and the return data of the positioning and orientation system and the single-photon lidar are collected.

[0009] The POS is fixed on the installation platform and connected to the radar data acquisition and control unit. It transmits the data frames output by the POS, which include latitude, longitude, altitude, attitude angle information and timestamps, to the radar data acquisition and control unit, thereby realizing the transmission of data frames and the reception of control commands.

[0010] The single-photon lidar based on time-delay detection by dual Gm-APD cameras is fixed at the front of the mounting platform and includes Gm-APD detector 1, Gm-APD detector 2, high repetition rate sub-nanosecond laser and high-precision coaxial transceiver conical scanning system.

[0011] The Gm-APD detector 1 and Gm-APD detector 2 communicate with the radar data acquisition and control unit respectively to realize detector control and detector measurement of photon flight time data output; the signals acquired by Gm-APD detector 1 and Gm-APD detector 2 are compared and analyzed by the upper computer through algorithms to remove noisy photons and perform data fusion.

[0012] The high-repetition-rate sub-nanosecond laser receives the trigger command from the radar data acquisition and control unit and synchronously emits a narrow-pulse-width, high-repetition-rate sub-nanosecond laser with a wavelength of 1064nm.

[0013] The high-precision coaxial transceiver conical scanning system is fixed at the front of the mounting platform. By constructing a coaxial optical path for transmission and reception and deflecting the laser beam emitted by the high-repetition-rate sub-nanosecond laser, it enables the transmission of laser pulses and the reception of echo signal photons through the same telescope.

[0014] The host computer is connected to the radar data acquisition and control unit to obtain the real-time relative position of the laser spot in the field of view. It reads the data collected by the radar data acquisition and control unit through the local area network, processes and analyzes the data to generate a radar point cloud and correct errors, thereby realizing the radar correction and calibration accuracy of the Gm-APD detector.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1. This invention can simulate the movement of a real three-dimensional space lidar along with the carrier by moving and rotating the detection and installation platform.

[0017] 2. The radar data acquisition and control unit of the present invention has a highly parallel architecture, which can process photon signals from multiple Gm-APD detectors, achieve extremely low latency, and complete data acquisition and processing in a short time.

[0018] 3. By using two Gm-APD detectors and setting a delay between the two detectors, this invention acquired two sets of data from the same object during the experiment. After comparison and analysis, it can effectively distinguish between noise photons and signal photons, achieving a good denoising effect and improving the data rate.

[0019] 4. This invention uses a computer and corresponding software to process the data obtained from each part, and uses an algorithm in the software to analyze the data of the two Gm-APDs, thereby improving the accuracy of lidar detection. Attached Figure Description

[0020] Figure 1 This is a schematic block diagram of the overall structure of a single-photon lidar detection system based on time-delay detection using dual Gm-APD cameras;

[0021] Figure 2 This is a schematic diagram of data processing from two Gm-APD detectors in a single-photon lidar detection system based on time-delay detection using dual Gm-APD cameras;

[0022] Figure 3 This is a simplified structural diagram of a conical scanning system in a single-photon lidar detection system based on time-delay detection using dual Gm-APD cameras. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0024] This invention provides a single-photon lidar detection system based on time-delay detection using dual Gm-APD cameras, such as... Figure 1 As shown, the system includes an assembly and adjustment mechanism, a radar data acquisition and control unit, a positioning and orientation system (POS), a single-photon lidar based on time-lapse detection using dual Gm-APD cameras, and a host computer, wherein:

[0025] The assembly and adjustment mechanism includes a base and an installation platform, which carries all components of the single-photon lidar detection system. The installation platform is the carrier of the data acquisition and control unit, the POS, and the single-photon lidar based on the time-delay detection of dual Gm-APD cameras. Except for the host computer, the data acquisition and control unit, the POS, and the single-photon lidar based on the time-delay detection of dual Gm-APD cameras are all installed on the installation platform. The installation platform is connected to the rotating shaft and the base through slide rails, thereby realizing the translation and multi-angle rotation of the installation platform and the equipment it carries in space, achieving the effect of simulating the movement of the single-photon lidar based on the time-delay detection of dual Gm-APD cameras in three-dimensional space.

[0026] The radar data acquisition and control unit is the core component of the single-photon lidar detection system. It is responsible for controlling the positioning and orientation system (POS) and the single-photon lidar based on the time-delay detection of dual Gm-APD cameras, and for acquiring data. The radar data acquisition and control unit is fixedly installed on the mounting platform. The operating parameters of the positioning and orientation system (POS system) and the single-photon lidar based on the time-delay detection of dual Gm-APD cameras are set through the radar data acquisition and control unit, and the return data of the positioning and orientation system and the single-photon lidar are acquired.

[0027] The Positioning and Orientation System (POS) provides the single-photon lidar detection system with the altitude, latitude and longitude of its location, as well as the heading angle, roll angle, and pitch angle of the system's own angular offset measuring instrument. The POS is fixed on the mounting platform and is used to collect the attitude information of the mounting platform. The data frames output by the POS include latitude and longitude, altitude, attitude angle information, and timestamps. It is connected to the radar data acquisition and control unit through a serial port to realize the transmission of data frames and the reception of control commands.

[0028] The single-photon lidar based on dual Gm-APD camera time-lapse detection is mounted at the front of the installation platform and moves with the platform. It includes two Gm-APD detectors: Gm-APD detector 1 and Gm-APD detector 2, a high-repetition-rate sub-nanosecond laser, and a high-precision coaxial transceiver conical scanning system. Specifically: Gm-APD detector 1 and Gm-APD detector 2 communicate with the radar data acquisition and control unit via corresponding interfaces to achieve detector control and output of photon time-of-flight data. Each Gm-APD detector is equipped with an independent communication interface to ensure efficient data transmission and command interaction with the radar data acquisition and control unit, guaranteeing that the radar system can accurately control the detector's operating state while receiving and processing the photon time-of-flight data measured by the detector. Gm-APD detector 1 and Gm-APD detector 2 have a certain time delay, used sequentially to receive the photon time-of-flight data reflected from the target object. The system processes laser signals; signals acquired by Gm-APD detector 1 and Gm-APD detector 2 in the host computer, compares and analyzes the data from Gm-APD detector 1 and Gm-APD detector 2 through algorithms, removes noisy photons, and performs data fusion to achieve noise reduction and data rate improvement; the high-repetition-rate sub-nanosecond laser receives trigger commands from the radar data acquisition and control unit through a BNC interface and synchronously emits a narrow-pulse-width, high-repetition-rate sub-nanosecond laser with a wavelength of 1064nm; the high-precision coaxial transceiver conical scanning system is fixed at the front of the mounting platform. The high-precision coaxial conical scanning system constructs a coaxial optical path for transmission and reception by using multiple mirrors, prisms, filters, and concave and convex lenses, and deflects the emitted laser beam to achieve the emission of laser pulses and the reception of echo signal photons through the same telescope; the high-precision coaxial conical scanning system is equipped with a beam deflection element (wedge mirror) and a movable mirror mount (hollow disk scanning motor) to achieve rapid adjustment of the beam direction;

[0029] The host computer is connected to the radar data acquisition and control unit to acquire the real-time relative position of the laser spot in the field of view and adjust the movable lens mount in the high-precision coaxial transceiver conical scanning system to ensure coaxiality. It reads the data collected by the radar data acquisition and control unit through the local area network. This data includes key information such as photon flight time and spot position. After processing and analyzing the data through software, a radar point cloud is generated and the error is corrected, thereby realizing the radar correction and calibration accuracy of the Gm-APD detector.

[0030] In this invention, the radar data acquisition and control unit includes a data acquisition and storage module and a control and synchronization triggering module. The data acquisition and storage module receives position and attitude information and timestamps sent by the POS, scanning angle position data provided by the high-precision coaxial transceiver conical scanning optical system, and photon flight time data measured by two Gm-APD detectors. It stores the information from different data sources in the NAND-flash memory of the radar data acquisition and control unit. The control and synchronization triggering module stably provides a time-delayed synchronization triggering signal to the POS, the high-precision coaxial transceiver conical scanning optical system, the two Gm-APD detectors, and the high-repetition-rate sub-nanosecond laser.

[0031] In this invention, the POS includes a GPS system and a dynamic offset angle measurement system. The GPS system receives GPS and BeiDou satellite positioning data at a frequency of 20Hz via an antenna, obtains the latitude, longitude and elevation information of the lidar system, and outputs it to the radar data acquisition and control unit. The dynamic offset angle measurement system measures the heading angle, pitch angle and roll angle in real time at a frequency of 20Hz via a built-in IMU, and outputs the data to the radar data acquisition and control unit.

[0032] In this invention, the Gm-APD detector uses a domestically produced GD5551 type 64*64InGaAs Geiger avalanche focal plane camera.

[0033] In this invention, the high repetition rate sub-nanosecond laser consists of a DC power supply, a sub-nanosecond laser, and a laser controller. The DC power supply supplies power to the laser and the laser controller, and the laser controller receives a trigger signal from the radar data acquisition and control unit and starts the sub-nanosecond laser output.

[0034] In this invention, such as Figure 3 As shown, the high-precision coaxial transceiver conical scanning system includes a laser optical path, a receiving telescope, a hollow disk scanning motor and its controller, a beam deflection element (wedge mirror), and a high-precision grating encoder. The laser optical path consists of a reflector, a filter, and a prism assembly, allowing for partial sharing of the transmission and reception optical paths. The receiving telescope is composed of a concave-convex lens assembly, matched with a Gm-APD detector to receive echo signal photons. The concave-convex lens assembly can adjust the divergence angle of the laser pulse to match the field of view of the receiving telescope. The beam direction is changed by rotating the hollow disk scanning motor after passing through the beam deflection element. The high-precision grating encoder includes a circular grating code disk and a grating read head, used to provide high-precision beam direction information.

[0035] In this invention, the host computer can receive output data from the radar data acquisition and control unit; by simplifying the modeling and optimization process, data processing and analysis are performed to reduce computational complexity while ensuring accuracy; and the data acquired from the two Gm-APD detectors are compared using corresponding algorithms.

[0036] In this invention, the POS operates at 20Hz. After the system initialization is completed, it continuously sends position and attitude information to the radar data acquisition and control unit, and attaches the timestamp of the data in each frame.

[0037] In this invention, a schematic diagram of data processing from two Gm-APD detectors in a single-photon lidar detection system based on delay detection using dual Gm-APD cameras is shown below. Figure 2 As shown, it specifically includes:

[0038] 1. Two Gm-APD detectors: Gm-APD detector 1 and Gm-APD detector 2, which receive reflected signals in different time windows (door opening times t1 and t2, respectively);

[0039] 2. Two signal processing units: Signal Processing Unit 1 and Signal Processing Unit 2. Their main task is to process the signals received from the Gm-APD detector, extract the timestamp information of the signal photons, and distinguish between signal photons and noise photons. Specifically, their tasks are:

[0040] (1) Timestamp extraction: Record the precise time when each photon arrives at the detector;

[0041] (2) Noise suppression: Identify and eliminate noisy photons (such as dark count noise and after-pulse noise);

[0042] (3) Signal enhancement: The signal-to-noise ratio is improved by accumulating signal photons;

[0043] (4) Data formatting: Convert the processed data into a format suitable for subsequent analysis.

[0044] 3. A data fusion unit: has the following functions:

[0045] (1) Signal photon identification: By comparing the timestamp sequences of Gm-APD detector 1 and Gm-APD detector 2, the data fusion unit can identify signal photons more accurately. Signal photons usually appear simultaneously in the timestamp sequences of Gm-APD detector 1 and Gm-APD detector 2, while noise photons are randomly distributed.

[0046] (2) Time difference analysis: By analyzing the timestamp difference between Gm-APD detector 1 and Gm-APD detector 2, the data fusion unit can more accurately determine the arrival time of the signal photon, thereby improving the ranging accuracy.

[0047] (3) Noise photon removal: The data fusion unit can identify and remove noise photons by comparing the signals of Gm-APD detector 1 and Gm-APD detector 2. For example, if a certain timestamp appears in the timestamp sequences of both Gm-APD detector 1 and Gm-APD detector 2, it is more likely to be a signal photon; if it appears only in one Gm-APD detector, it is likely to be a noise photon.

[0048] (4) Background noise suppression: Through comparative analysis, the data fusion unit can effectively suppress the influence of background noise and improve the signal-to-noise ratio of the signal.

[0049] (5) Signal accumulation: By accumulating the signals from Gm-APD detector 1 and Gm-APD detector 2, the data fusion unit can improve the data rate. For example, the signals collected by Gm-APD detector 1 and Gm-APD detector 2 in different time windows can be weighted averaged or estimated by maximum likelihood, thereby improving the reliability and efficiency of ranging.

[0050] (6) Data optimization: By optimizing the data processing algorithm, the data fusion unit can reduce data redundancy and improve the overall performance of the system.

[0051] (7) Enhanced temporal resolution: By analyzing the timestamp sequences of Gm-APD detector 1 and Gm-APD detector 2, the data fusion unit can more accurately determine the arrival time of signal photons, thereby improving the distance resolution.

[0052] (8) Multi-frame fusion: By fusing signals within multiple time windows, the data fusion unit can further improve distance resolution.

[0053] Its specific implementation can be divided into two main aspects: hardware and software.

[0054] (1) Hardware implementation:

[0055] FPGA (Field-Programmable Gate Array): FPGAs have high parallel processing capabilities and low latency, making them suitable for real-time data processing. Data fusion units can be implemented using FPGAs, and functions such as timestamp comparison, noise photon removal, and signal accumulation can be achieved by writing hardware description language (HDL) code.

[0056] DSP (Digital Signal Processor): DSPs possess highly efficient digital signal processing capabilities, making them suitable for implementing complex algorithms. Data fusion units can be implemented using DSPs, with functions such as correlation analysis and maximum likelihood estimation achieved through C or assembly language code.

[0057] (2) Software implementation:

[0058] Algorithm Design: The algorithm design of the data fusion unit is crucial for improving system performance. Common algorithms include timestamp comparison algorithms, correlation analysis algorithms, and maximum likelihood estimation algorithms.

[0059] Software tools: MATLAB, Python, and other software tools can be used for algorithm design and simulation. Simulation verifies the algorithm's performance, optimizes algorithm parameters, and improves the system's ranging accuracy and noise resistance.

[0060] Finally, we obtained data with high accuracy.

Claims

1. A single-photon lidar detection system based on time-delay detection using dual Gm-APD cameras, characterized in that... The single-photon lidar detection system includes a radar data acquisition and control unit, a positioning and orientation system (POS), a single-photon lidar based on time-delay detection using dual Gm-APD cameras, and a host computer, wherein: The radar data acquisition and control unit sets the operating parameters of the POS and the operating parameters of the single-photon lidar based on the delay detection of the dual Gm-APD camera, and acquires the return data of the positioning and orientation system and the single-photon lidar. The POS is connected to the radar data acquisition and control unit. The POS acquires data frames containing latitude, longitude, altitude, attitude angle information and timestamps and transmits them to the radar data acquisition and control unit to realize the transmission of data frames and the reception of control commands. The single-photon lidar based on time-delay detection by dual Gm-APD cameras includes Gm-APD detector 1, Gm-APD detector 2, a high-repetition-rate sub-nanosecond laser, and a high-precision coaxial transceiver conical scanning system. The Gm-APD detector 1 and Gm-APD detector 2 communicate with the radar data acquisition and control unit respectively to realize detector control and detector measurement of photon flight time data output; the signals acquired by Gm-APD detector 1 and Gm-APD detector 2 are compared and analyzed by the upper computer through algorithms to remove noisy photons and perform data fusion. The Gm-APD detector 1 and Gm-APD detector 2 have a time delay and are used to receive the laser signal reflected back from the target object, respectively. The high-repetition-rate sub-nanosecond laser receives the trigger command from the radar data acquisition and control unit and synchronously emits a narrow-pulse-width, high-repetition-rate sub-nanosecond laser with a wavelength of 1064nm. The high-precision coaxial transceiver conical scanning system achieves the transmission of laser pulses and the reception of echo signal photons through the same telescope by constructing a coaxial optical path for transmission and reception and deflecting the laser beam emitted by a high repetition rate sub-nanosecond laser. The high-precision coaxial transceiver conical scanning system includes a laser optical path, a receiving telescope, a hollow disk scanning motor, a beam deflection element, and a high-precision grating encoder. The laser optical path consists of a reflector, a filter, and a prism assembly, allowing for partial sharing of the transmission and reception optical paths. The receiving telescope is composed of a concave-convex lens assembly, matched with a Gm-APD detector to receive echo signal photons. The concave-convex lens assembly adjusts the divergence angle of the laser pulse to match the field of view of the receiving telescope. The beam direction is changed by rotating the hollow disk scanning motor after passing through the beam deflection element. The high-precision grating encoder provides high-precision beam direction information. The host computer is connected to the radar data acquisition and control unit to obtain the real-time relative position of the laser spot in the field of view. It reads the data collected by the radar data acquisition and control unit through the local area network, processes and analyzes the data to generate a radar point cloud and correct errors, thereby realizing the radar correction and calibration accuracy of the Gm-APD detector.

2. The single-photon lidar detection system based on delay detection using dual Gm-APD cameras according to claim 1, characterized in that... The single-photon lidar detection system also includes an assembly and adjustment mechanism, which includes a base and an installation platform. The data acquisition and control unit, POS, and single-photon lidar based on dual Gm-APD camera time-delay detection are installed on the installation platform, which is connected to the rotating shaft and the base via a slide rail.

3. The single-photon lidar detection system based on delay detection using dual Gm-APD cameras according to claim 1, characterized in that... The radar data acquisition and control unit includes a data acquisition and storage module and a control and synchronization triggering module. The data acquisition and storage module receives position and attitude information and timestamps sent by the POS, scanning angle position data provided by the high-precision coaxial transceiver conical scanning optical system, and photon flight time data measured by two Gm-APD detectors. It stores the information from different data sources in the NAND-flash memory of the radar data acquisition and control unit. The control and synchronization triggering module provides a synchronization trigger signal with a fixed time delay for the POS, the high-precision coaxial transceiver conical scanning optical system, the two Gm-APD detectors, and the high-repetition-rate sub-nanosecond laser.

4. The single-photon lidar detection system based on delay detection using dual Gm-APD cameras according to claim 1, characterized in that... The POS includes a GPS system and a dynamic offset angle measurement system. The GPS system receives GPS and BeiDou satellite positioning data at a frequency of 20Hz through an antenna, obtains the latitude, longitude and elevation information of the lidar system, and outputs it to the radar data acquisition and control unit. The dynamic offset angle measurement system measures the heading angle, pitch angle and roll angle in real time at a frequency of 20Hz through a built-in IMU, and outputs the data to the radar data acquisition and control unit.

5. The single-photon lidar detection system based on delay detection using dual Gm-APD cameras according to claim 1 or 3, characterized in that... The high repetition rate sub-nanosecond laser consists of a DC power supply, a sub-nanosecond laser, and a laser controller. The DC power supply powers the laser and the laser controller, and the laser controller receives a trigger signal from the radar data acquisition and control unit and starts the sub-nanosecond laser output.

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