Water depth detection laser radar photomultiplier and echo data acquisition and storage cooperative gating method

Abstract

The invention discloses a water depth detection laser radar photomultiplier and echo data acquisition and storage cooperative gating method, and designs a water depth detection laser radar photomultiplier and echo data acquisition and storage cooperative gating method through an echo data delay acquisition technology and a photomultiplier gating technology. Comprising the following steps: step 1, preliminarily calculating the slant round-trip time from a current laser light outlet to the water surface according to the flight height when the radar is started, and completing the initial acquisition of the system; 2, after the laser radar system is started to work, according to the obtained water body echo information, the system can accurately calculate the water surface echo round-trip time according to the obtained data. And according to the obtained data, compensation time calculation is designed to carry out feedback regulation on the gating time. And step 3, according to the obtained delay time, respectively designing the acquisition time of the data acquisition and storage module and the detection starting time of the photomultiplier so as to realize selective receiving of multi-channel target echo signals.

Description

Technical Field

[0001] The present invention relates to the field of laser radar, and in particular to a water depth detection laser radar photomultiplier tube and echo data acquisition and storage collaborative gating system. Background Art

[0002] At present, in the process of receiving, collecting and storing the echo signal of the water depth detection lidar, photoelectric signal conversion is usually performed using photomultiplier detection, and then the data is collected using the relevant data acquisition and storage module. Generally speaking, when the photomultiplier tube opening time and the acquisition time are long enough, the complete water echo signal can be collected. However, the corresponding noise signal will also be collected, and the collected data will be very large, which will cause great difficulties in data acquisition and storage and increase the difficulty of echo data processing.

[0003] Patent number CN114167436A discloses a single-frequency water-measuring laser radar system, which solves the storage of echo data in complex multi-channel situations, but cannot cope with the impact of changes in the height of the laser radar from the water surface, and there is a possibility that the echo data cannot be effectively stored.

[0004] The patent with patent number 202110730164X proposes a new type of airborne lidar detection timing control system, which controls the opening and closing of the photomultiplier tube by controlling the gating signal to achieve phased reception of underwater echo signals. However, the gating signal designed by the system cannot be adjusted according to changes in the experimental environment, which may easily lead to system failure.

[0005] Patent No. 2023110464340 proposes a method for adaptively collecting and storing delay control of water depth detection laser radar echo signals. When the height of the laser radar from the water surface changes, the channel delay time of collection and storage is automatically adjusted to ensure the integrity of the surface and bottom echo data. However, this method cannot selectively receive echo signals.

[0006] Patent number CN114285486A discloses a high-speed receiving method based on the collaboration of SPAD arrays with external gating. Through a single gating control method, the equivalent acquisition time is effectively increased, the requirements for photon signal flux are reduced, and the interference of ambient light is avoided to a certain extent. However, this method cannot take into account the subsequent data acquisition and storage work, and cannot improve the data quality.

[0007] Patent number CN116626602A discloses a dual-platform airborne radar collaborative working timing control system, which aims to solve the problem that airborne radars cannot achieve collaborative depth sounding at the same time, but cannot optimize the timing and operation in a single radar working system.

[0008] Patent number CN109444829B discloses a unified timing control and collaborative processing method for a radar system. The method generates timing signals of different forms for distribution by analyzing the requirements of the transmitting system and the signal processing system, and extracts and processes the received echo signals to eliminate invalid signals.

[0009] Although the patents listed above have proposed relevant gating methods and adaptive acquisition and storage methods for problems such as the difficulty in acquiring laser radar echo signals and the easy loss of data, so far, there has not been a method that can achieve high-quality acquisition and storage of echo data while taking into account the selective reception of underwater echo signals under complex environmental changes during the laser radar operation process. Therefore, the present invention proposes a coordinated gating method for photomultiplier tubes and echo data acquisition and storage of water depth detection laser radars. Summary of the invention

[0010] The invention discloses a laser radar photomultiplier tube and echo data acquisition and storage coordinated gating method.

[0011] The design of this method requires analysis of many aspects, including the time from laser emission to the echo return from the water surface, water backscattering, and the signal transmission delay time within the system. At the same time, complex factors such as the flight altitude of manned aircraft need to be taken into account. Therefore, the calculation of the photomultiplier tube gating delay time and the echo acquisition and storage delay time needs to be considered.

[0012] First, the round trip time from the current laser light outlet to the water surface is preliminarily calculated according to the flight altitude when the radar is turned on, and the system initialization acquisition is completed. Then, according to the echo signal data solution, the photomultiplier tube gating and overall sampling delay time output by the echo signal acquisition storage and gating module are preliminarily calculated to ensure that the water echo signal is effectively collected at the beginning of the system operation.

[0013] Second, after the LiDAR system starts working, based on the acquired water echo information, the system can accurately calculate the round-trip time of the water surface echo based on the acquired data. At the same time, in order to ensure the complete filtering of the water surface echo and the anti-interference ability of the water body backscattering, the gate delay compensation time is designed by analyzing the deep-water channel echo signal. The compensation time is half of the position in the data packet where the water surface peak and the bottom peak are located. Half of the overall data packet acquisition time is used as the comparison value to fine-tune the delayed acquisition time to ensure that the overall echo data is located at half of the data packet. Based on the above results, the gate delay time calculation of the photomultiplier tube is redesigned and the gate signal is output.

[0014] Third, according to the obtained delay time, the data acquisition storage module acquisition time and the photomultiplier tube detection start time are designed respectively to achieve the selective reception of multi-channel target echo signals.

[0015] The present invention calculates the real-time water surface echo return time, thereby controlling the echo data collection and storage time and the photomultiplier tube opening time, and completes the high-quality collection and storage of echo data and the selective reception of bottom echo signals through the coordinated control of multiple optical receiving channels, effectively ensuring the validity of the data in the echo data packet and the utilization rate of limited memory. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a timing diagram of the collaborative gating method of laser radar photomultiplier tube and echo data acquisition and storage.

[0017] Figure 2 It is a structural block diagram of the laser radar photomultiplier tube and echo data acquisition and storage collaborative gating system.

[0018] Figure 3 It is a step diagram of the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, preferred embodiments are given below and the specific implementation of the present invention is further described in detail in conjunction with the accompanying drawings.

[0020] The collaborative gating method uses an echo data acquisition system designed based on FPGA, real-time echo detection, and based on the echo data of shallow water channels and deep water channels, analyzes the actual time when the water surface echo returns to the optical receiving system, and designs a photomultiplier tube and echo acquisition and storage collaborative gating method based on this time. Through the two-phase combination of delayed gating of the photomultiplier tube and delayed acquisition of the acquisition channel, while achieving the selective reception of the bottom echo by the deep water echo signal channel, it ensures that the complete water body echo information can be collected and stored with high quality and high efficiency.

[0021] Combination Figure 1 and Figure 2 , describing the implementation steps of the laser radar photomultiplier tube and echo data acquisition and storage collaborative gating method of the present invention:

[0022] First, the round-trip time from the current laser light outlet to the water surface is preliminarily calculated based on the flight altitude when the radar is turned on, completing the initial acquisition of the system. Then, based on the echo signal data solution, the photomultiplier tube gating and overall sampling delay time output by the echo data acquisition and gating output module are preliminarily calculated to ensure that the water echo signal is effectively collected at the beginning of the system operation. It is required to be less than the actual time of the water surface echo returning to the optical receiving channel. for:

[0023] (1)

[0024] (2)

[0025] in is the actual slope from the laser outlet to the water surface, is the speed of light, is the optical scanning angle. The aircraft platform pitch angle, roll angle and aircraft cruising altitude The changes of are affected. Then the overall acquisition time of the system is at least for:

[0026] (3)

[0027] in, is the maximum target measurement depth. In this system, the acquisition time of the echo data acquisition system is stably set to 0.5us when it is in working state. According to equations (1), (2), (3) and the inherent opening delay of the photomultiplier tube selected by the system, it can be calculated that theoretically, this system needs to be at least 37.5m away from the water surface to achieve full function. At the same time, according to the above equation, the initial acquisition delay can be obtained The range is:

[0028] (4)

[0029] In order to ensure the integrity and intuitiveness of the first waveform acquisition, the initial acquisition delay is designed for:

[0030] (5)

[0031] in It is helpful to collect the water surface echo completely in the initial state and the peak is located in the center of the entire echo data packet. The internal signal transmission delay of the acquisition system is to ensure that the next step of the system is completed. At this time, the normally closed PMT gate delay signal It can be expressed as:

[0032] (6)

[0033] in It is the response time required when the photomultiplier tube is turned on.

[0034] Second, after obtaining the water echo information, the system can accurately calculate the round-trip time of the water surface echo based on the obtained data. , at this time of this cycle It can also be expressed as:

[0035] (7)

[0036] That is, it is the delay time before the whole data packet starts to collect plus the time when the water surface peak appears after the collection starts, where Indicates the time when the water surface peak appears in the data packet.

[0037] At the same time, in order to ensure the complete filtering of water surface echoes and the anti-interference ability of water backscattering, the gate delay compensation time is designed by analyzing the echo signal of the deep water channel for:

[0038] (8)

[0039] The peak time of the bottom echo in the deep water channel obtained by solving the data package. It needs to be set in the calculation for At this time, in order to achieve high-quality acquisition of echo data, the acquisition delay time is calculated. for:

[0040] (9)

[0041] (10)

[0042] in As the gate correction time, Right now It represents the average value of the peak time of the water surface echo and the peak time of the bottom echo in the data packet. This value is used as the result value, and half of the gated pulse width time is used as the reference value. By comparing the two values, the following can be obtained: If the result is negative, it means that the acquisition delay is too long, so reduce the delay time. To ensure data quality. When it is a positive number, it is judged that the acquisition delay time is too short, and the Extend the acquisition time. When equal to 0, the delay time No more adjustments needed.

[0043] Based on the above results, the gate delay time calculation of the normally closed PMT is redesigned. for:

[0044] (11)

[0045] Third, according to the obtained delay time, the data acquisition and storage module acquisition delay time and the photomultiplier tube delay opening time are output respectively, and the selective reception of multi-channel target echo signals is realized by outputting the gating signal and controlling the acquisition and storage delay time inside the FPGA.

[0046] The above embodiments are only used to illustrate the present invention, but not to limit the present invention. A person skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also belong to the scope of the present invention, and the patent protection scope of the present invention shall be defined by the claims.

[0047] The technical contents not described in detail in the present invention are all known technologies.

Claims

1. A coordinated gating method for water depth detection laser radar photomultiplier tube and echo data acquisition and storage, characterized in that Follow these steps: First, the round-trip time from the current laser light outlet to the water surface is preliminarily calculated according to the flight altitude when the radar is turned on, and the system initialization acquisition is completed; then, the photomultiplier tube gating and overall sampling delay time output by the echo data acquisition and gating output module are preliminarily calculated according to the echo signal data solution, so as to ensure that the water echo signal is effectively collected at the beginning of the system operation; Its initial acquisition delay time It is required to be less than the actual time of the water surface echo returning to the optical receiving channel. for: （1） （2） in is the actual slope from the laser outlet to the water surface, is the speed of light, is the optical scanning angle. The aircraft platform pitch angle, roll angle and aircraft cruising altitude The changes of are affected; then the overall acquisition time of the system is at least for: （3） in, is the maximum target measurement depth; in this system, the acquisition time of the echo data acquisition system is stably set to 0.5us when it is in working state. According to equations (1), (2), (3) and the inherent opening delay of the photomultiplier tube selected by the system, it can be calculated that theoretically, this system needs to be at least 37.5m away from the water surface to achieve full function; at the same time, according to the above equation, the initial acquisition delay can be obtained The range is: （4） In order to ensure the integrity and intuitiveness of the first waveform acquisition, the initial acquisition delay is designed for: （5） in It is helpful to collect the water surface echo completely in the initial state and the peak is located in the center of the entire echo data packet. The internal signal transmission delay of the acquisition system is to ensure that the next step of the system is completed; at this time, the normally closed PMT gate delay signal It can be expressed as: （6） in It is the response time required when the photomultiplier tube is turned on; Second, after obtaining the water echo information, the system can accurately calculate the round-trip time of the water surface echo based on the obtained data. , at this time of this cycle It can also be expressed as: （7） That is, it is the delay time before the whole data packet starts to collect plus the time when the water surface peak appears after the collection starts, where Indicates the time when the water surface peak appears in the data packet; At the same time, in order to ensure the complete filtering of water surface echoes and the anti-interference ability of water backscattering, the gate delay compensation time is designed by analyzing the echo signal of the deep water channel for: （8） The peak time of the bottom echo in the deep water channel obtained by solving the data package. It needs to be set in the calculation for The minimum value of the acquisition delay time is calculated to achieve high-quality acquisition of echo data. for: （9） （10） in As the gate correction time, Right now It represents the average value of the peak time of the water surface echo and the peak time of the bottom echo in the data packet. This value is taken as the result value, and half of the gated pulse width time is taken as the reference value. When the two values ​​are compared, the following situations can be obtained: If the result is negative, it means that the acquisition delay is too long, so reduce the delay time. To ensure data quality; When it is a positive number, it is judged that the acquisition delay time is too short, and the Extend the acquisition time; when equal to 0, the delay time No more adjustments are needed; According to the above results, the gate delay time calculation of the photomultiplier tube is redesigned. for: （11） Third, according to the obtained delay time, the data acquisition and storage module acquisition delay time and the photomultiplier tube delay opening time are output respectively, and the acquisition and storage delay time and the output gating signal are controlled internally by FPGA to realize the selective reception of multi-channel target echo signals.

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