Method for detecting underwater target detection performance of laser radar system

Abstract

The invention relates to the technical field of laser radar detection, in particular to a method for detecting the underwater target detection performance of a laser radar system, and solves the problem that a traditional detection method in the prior art lacks a unified judgment standard, and particularly, when the maximum detection distance is determined, part of methods depend on water profile estimation, so that the maximum detection distance is determined. And the other parts are judged according to target echo signals, but the detection result lacks consistency and comparability due to the fact that the target type, the size and the reflectivity are not uniformly stipulated. A method for detecting the underwater target detection performance of a laser radar system comprises the steps that a light path is changed through a reflector, a Lamberg body plate is used as a target, and the detection height is adjusted through a lifting platform. According to the invention, by introducing a standardized target, a unified criterion and a repeatable test process, the accuracy, consistency and comparability of a detection result are significantly improved, and a scientific basis and a technical support are provided for performance evaluation of a laser radar system.

Description

Technical Field

[0001] This invention relates to the field of lidar detection technology, and in particular to a method for detecting the underwater target detection performance of a lidar system. Background Technology

[0002] LiDAR systems, as an active detection technology that obtains information about the distance, shape, and surface features of a target by emitting a laser beam and receiving the reflected signal, have been widely used in various fields such as surveying, autonomous driving, robot navigation, security monitoring, and underwater exploration. With the continuous advancement of LiDAR technology, its application in underwater target detection has gradually attracted widespread attention. Especially in tasks such as marine resource exploration, underwater facility inspection, and military reconnaissance, LiDAR, with its advantages of high precision, high resolution, and non-contact measurement, has become one of the important means to achieve rapid identification and location of underwater targets.

[0003] However, due to the complex and variable underwater environment, including the influence of factors such as water turbidity, scattering and absorption characteristics, and temperature gradients, the propagation characteristics of lasers underwater differ significantly from those in air. This places higher demands on the detection performance of lidar systems. Therefore, accurately evaluating key performance indicators of lidar systems in underwater environments, such as maximum detection range, horizontal resolution, and vertical resolution, is crucial for ensuring their effective practical applications.

[0004] Specifically, a series of technical problems still need to be solved in the current process of testing the detection performance of lidar systems. Traditional detection methods lack unified judgment standards, especially when determining the maximum detection distance. Some methods rely on the water profile in the absence of a target for estimation, while others rely on the echo signal of a specific target for judgment. However, the type, size and reflectivity of the target are not clearly defined, resulting in a lack of consistency and comparability of detection results.

[0005] Therefore, existing methods for testing the performance of lidar systems in underwater environments suffer from problems such as low detection accuracy, inconsistent standards, complex operation, and poor practicality. There is an urgent need for a method to test the detection performance of lidar systems that can achieve standardized, repeatable, and efficient evaluation of the maximum detection range, horizontal resolution, and vertical resolution of lidar systems while ensuring detection accuracy. This would provide reliable technical support for the performance optimization and engineering applications of underwater lidar systems. Summary of the Invention

[0006] The purpose of this invention is to provide a method for detecting the underwater target detection performance of a lidar system. This method solves the problem that traditional detection methods in the prior art lack a unified judgment standard. In particular, when determining the maximum detection distance, some methods rely on the water profile in the absence of a target for estimation, while others rely on the echo signal of a specific target for judgment. However, the type, size and reflectivity of the target are not clearly defined, which leads to a lack of consistency and comparability in the detection results.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for detecting the underwater target detection performance of a lidar system includes a reflector group comprising reflector 1 and reflector 2, employing a high damage threshold emitting mirror to adjust the direction of the laser beam emitted by the laser, causing the laser beam to change from vertical propagation to horizontal propagation;

[0009] A reflector fixture is used to fix the reflector and adjust the spatial angle and position of the reflector to ensure that the laser beam propagates stably along a set path;

[0010] The target, used as a test object to simulate the reflection characteristics of a typical target in an underwater environment, is a diffuse reflector with standard Lambauer body characteristics;

[0011] A measuring tape is used to accurately measure the straight-line distance between a lidar system and a target.

[0012] The lifting platform is used to support and adjust the installation height of the lidar system to simulate the detection environment under different water depth conditions.

[0013] Preferably, when evaluating the maximum detection range of a lidar system, a three-standard-deviation criterion is used as the standard for determining whether the echo signal is distinguishable.

[0014] By statistically analyzing the echo signal data collected multiple times, the standard deviation of its noise background is calculated. Three times the standard deviation is used as the signal-to-noise ratio (SNR) threshold. When the SNR at the peak of the target echo signal drops to 3, it is determined that the target is at the maximum detection limit of the lidar. The target distance at this time is the maximum detection distance of the lidar system.

[0015] Preferably, when detecting the horizontal resolution of the lidar system, the laser beam emission direction is kept unchanged, and the target is moved along a direction perpendicular to the laser beam propagation direction;

[0016] The target is placed at a set detection distance and gradually moved laterally. After each movement, echo signal data is collected for a certain period of time, and the relationship curve of target signal intensity changing with position is recorded.

[0017] By extracting the lateral displacement distance corresponding to the rising edge of the signal from 10% to 90%, this distance difference is defined as the horizontal resolution of the lidar system.

[0018] Preferably, when detecting the vertical resolution of the lidar system, the laser beam emission direction is kept unchanged, and two target targets are set along the laser beam propagation direction, namely a movable plate A and a fixed plate B.

[0019] Initially, there is a certain gap between board A and board B. As board A gradually moves closer to board B, data is collected after each fixed step, and it is observed whether two distinguishable signal peaks appear in the echo signal.

[0020] When two signal peaks can no longer be distinguished, the minimum resolvable distance is determined according to the Rayleigh criterion, and this distance is the vertical resolution of the lidar system.

[0021] Preferably, it includes the following steps:

[0022] (a) Using a set of reflectors to fold the laser beam emitted by the lidar from the vertical direction to the horizontal direction for propagation;

[0023] (b) Place a Lambertian target with a certain reflectivity at a set detection range, and evaluate the maximum detection range of the lidar system for the target with that reflectivity by moving the target position and combining the three-standard-deviation criterion;

[0024] (c) Keeping the laser beam emission direction unchanged, move the target laterally along the direction perpendicular to the laser beam and measure the distance difference corresponding to 10%-90% of the signal rise edge to evaluate the horizontal resolution of the lidar system;

[0025] (d) Keep the laser beam emission direction unchanged, set two target targets along the laser beam propagation direction, one fixed and one moving. Determine the minimum vertical distance when the two signal peaks cannot be distinguished based on the changes in the echo signal and the Rayleigh criterion, and use it to evaluate the vertical resolution of the lidar system.

[0026] Preferably, during the evaluation of the maximum detection range, the target is moved gradually along the laser beam emission direction, and the echo signal strength of the lidar system is tested in real time.

[0027] After each target movement, echo signal data is collected over a certain period of time, and the signal strength changes are used to determine whether to continue moving the target away from the lidar.

[0028] When the echo signal strength drops below three standard deviations, i.e. the signal-to-noise ratio drops to 3, the movement stops. At this point, the distance between the target location and the lidar system is the maximum detection range.

[0029] Preferably, during the evaluation of horizontal resolution, the laser beam direction is kept constant, the target is moved in a direction perpendicular to the laser beam, and the horizontal resolution parameters are extracted by the relationship curve between the echo signal intensity and the moving distance.

[0030] The target moves gradually from the initial no-signal area towards the center of the laser spot. Data is collected after each certain distance, and a normalized signal intensity curve is plotted. The horizontal displacement distance between 10% and 90% of the signal rise edge is defined as the horizontal resolution.

[0031] The present invention has at least the following beneficial effects: The present invention provides a method for testing the underwater detection performance of a lidar system based on a unified standard, which can accurately and quantitatively evaluate the maximum detection range, horizontal resolution and vertical resolution of the lidar system, avoiding the problems of lack of unified judgment standards and unclear reflectivity in traditional methods.

[0032] By employing a Lamborghini body as the target, the reflection characteristics of common objects in the underwater environment are effectively simulated, making the detection results closer to reality and improving detection accuracy and consistency. The design of the reflector and its tooling allows for flexible adjustment of the optical path, facilitating multi-angle and multi-distance testing within a limited space, thus solving the error problem caused by inconvenient operation in traditional methods. The application of the lifting platform not only allows for convenient adjustment of the lidar system's height but also simulates detection scenarios at different depths, further enhancing the comprehensiveness and practicality of the testing. The use of a measuring tape for distance measurement is simple and direct, ensuring the accuracy of distance in each test and contributing to the establishment of unified detection standards. The entire device has a reasonable structure and is easy to operate, overcoming the problems of lack of unified standards, complex operation, and poor practicality in existing technologies. It provides reliable technical support for achieving standardized, repeatable, and efficient evaluation of the maximum detection distance, horizontal resolution, and vertical resolution of lidar systems, significantly improving the efficiency and accuracy of performance evaluation of lidar systems in underwater detection applications, and meeting the needs of modern marine detection and engineering applications. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the underwater target detection device using a lidar system according to the present invention.

[0035] Figure 2 This is a schematic diagram of the test method for the horizontal resolution of the lidar system of the present invention;

[0036] Figure 3 This is a schematic diagram of the test method for the vertical resolution of the lidar system of the present invention;

[0037] Figure 4 This is a schematic diagram showing the test results of the maximum detection distance of the lidar system of the present invention;

[0038] Figure 5 This is a schematic diagram of the horizontal resolution test results at different distances (20m, 30m, 35m, 40m) in an example of the present invention;

[0039] Figure 6 This is a schematic diagram of the vertical resolution test results of the lidar system of this invention at the maximum detection distance. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0041] Example 1

[0042] Please see Figure 1-6 As shown, a method for detecting the underwater target detection performance of a lidar system according to this embodiment includes: a reflector group including a reflector 1 and a reflector 2, using a high damage threshold emitting mirror to adjust the direction of the laser beam emitted by the laser, so that the laser beam changes from vertical propagation to horizontal propagation;

[0043] A reflector fixture is used to fix the reflector and adjust the spatial angle and position of the reflector to ensure that the laser beam propagates stably along a set path;

[0044] The target, used as a test object to simulate the reflection characteristics of a typical target in an underwater environment, is a diffuse reflector with standard Lambauer body characteristics;

[0045] A measuring tape is used to accurately measure the straight-line distance between a lidar system and a target.

[0046] The lifting platform is used to support and adjust the installation height of the lidar system to simulate the detection environment under different water depth conditions.

[0047] In testing the detection performance of the lidar system, the position and angle of the reflector are first fixed and adjusted using a reflector fixture to ensure that the lidar beam is accurately reflected and guided to the target. A Lambertian plate is used as the target to simulate typical reflection conditions in a real underwater environment. The height of the lidar system is changed by adjusting the height of the lifting platform, thereby testing the detection effect at different heights. During the measurement process, a measuring tape is used to accurately measure the distance between the lidar system and the target, and the data for each measurement is recorded. To evaluate the maximum detection range, horizontal resolution, and vertical resolution of the lidar system, different detection ranges and angles can be simulated by moving the target or changing the angle of the reflector, while keeping the lidar system stable. Performance is evaluated by analyzing the received echo signal data.

[0048] The performance indicators of underwater target detection lidar systems generally include: maximum detection range, horizontal resolution, and vertical resolution. Traditional performance testing methods involve placing targets along the water profile or vertically for detection. This method is difficult to implement and lacks unified and clear judgment criteria. Therefore, this invention proposes a simpler detection method with clearly defined judgment criteria. For example... Figure 1 The diagram illustrates the experimental scheme employed in this invention. A vertically oriented laser beam pointing towards the bottom of the water is deflected into a horizontal laser beam using a set of reflectors. The reflectors are large enough to encompass both the laser beam and the telescope's field of view. A 30cm x 30cm diffuse reflector is placed in the water as the target. When measuring the maximum detection range of the lidar system, the target is slowly moved away from the lidar while simultaneously calculating the signal-to-noise ratio (SNR) at the peak of the target signal in the echo signal. Movement is stopped when the SNR drops to 3, and this target detection range is considered the maximum detection range of the lidar. Figure 4 This is the result of the farthest detection distance of the underwater target detection lidar system.

[0049] The horizontal resolution detection method of underwater target detection lidar is as follows: Figure 2As shown, the target is placed 20m perpendicular to the laser propagation direction. The initial position of the square target is where the right edge of the square plate does not intersect with the left edge of the laser spot, and there is no target signal at 20m in the echo signal. Then, the target is slowly moved to the right, with each movement being 2cm. After each movement, the water surface is calmed, and data is collected for 1 minute. Movement is stopped when the left edge of the target does not intersect with the right edge of the laser spot, and there is no target signal at 20m in the echo signal. Let the initial position of the target be x=0, and the subsequent positions be x=2, 4, 6, 8... The data collected at different x positions are processed, and the target signal intensity is obtained by integrating the target signal peak in the echo signal. A scatter plot of the target signal intensity corresponding to different x positions is plotted and normalized to obtain a trapezoidal image. Here, the difference between x corresponding to 10% to 90% of the rising or falling side of the trapezoid is defined as the horizontal resolution of the underwater target detection lidar system. The target was moved to positions of 30m, 35m, and 40m respectively, and the above process was repeated. The obtained data were plotted on a single graph, and the results are as follows. Figure 5 As shown.

[0050] The vertical resolution detection process of underwater target detection lidar is as follows: Figure 3 As shown, two target plates are placed at a distance, offset from each other. The closer target plate is movable (defined as plate A), while the farther target plate is fixed (defined as plate B). The positions of plates A and B are adjusted so that part of the laser spot falls on plate A and the other part on plate B, with both target plates perpendicular to the laser propagation direction. The initial vertical distance between the two plates is 2m. Then, plate A is moved closer to plate B along the laser propagation direction, with each movement spaced 10cm apart. After each movement, the water surface is allowed to calm down before data is collected for 1 minute. Observing the echo signal reveals two signal peaks at the target location. The Rayleigh criterion is used for discrimination. When the two target signal peaks are just distinguishable, the movement of plate A is stopped. The vertical distance between plates A and B at this point is considered the vertical resolution distance of the underwater target detection lidar. The vertical resolution results tested at 50m are shown below. Figure 6 As shown.

[0051] Example 2

[0052] Please see Figure 1-6 As shown in this embodiment, a method for detecting underwater target detection performance of a lidar system includes a three-standard-deviation criterion. This criterion is used to determine whether the echo signal of the lidar signal is resolvable. Specifically, by setting the three-standard-deviation criterion, during the process of detecting whether the lidar signal echo is resolvable, the standard deviation of the echo signals obtained from multiple measurements is calculated through statistical analysis. The three-standard-deviation criterion is then used as the threshold for determining whether the signal is effectively identified, thereby improving the accuracy and consistency of the maximum detection distance determination and avoiding subjective misjudgment.

[0053] The maximum detection range of a lidar is determined by moving the target along a direction perpendicular to the laser beam while keeping the laser beam emission direction unchanged. This is used to test the horizontal resolution of the lidar. Specifically, the maximum detection range setting of the lidar is determined by changing the position of the target. While keeping the laser beam emission direction unchanged, the target is moved back and forth along the laser beam propagation direction, and the changes in echo signal intensity are used for judgment. This achieves the effect of accurately assessing whether the lidar system can effectively identify targets and obtain stable data at different distances.

[0054] By keeping the laser beam emission direction unchanged and moving the target along the laser beam direction, the vertical resolution of the lidar is detected. The Rayleigh criterion is used to determine the distance between two echo signal peaks when they cannot be distinguished, thus determining the vertical resolution. Specifically, by keeping the laser beam emission direction unchanged and moving the target perpendicular to the laser beam direction, the horizontal resolution setting is detected. During the test, the changes in echo signal intensity at different lateral positions are recorded, and the distance difference corresponding to 10%-90% of the signal rise edge is extracted. This achieves the effect of accurately evaluating the lidar system's ability to distinguish adjacent targets in the horizontal direction and improving the accuracy of spatial resolution testing.

[0055] Example 3

[0056] Please see Figure 1-6 As shown in this embodiment, a method for detecting the underwater target detection performance of a lidar system includes the following steps: adjusting the laser beam emission direction to horizontal underwater propagation using a reflector; changing the target's position and evaluating the maximum detection range based on the three-standard-deviation criterion; keeping the laser beam direction unchanged, adjusting the target position laterally, and measuring the distance corresponding to 10%-90% of the signal rise edge to evaluate the horizontal resolution; keeping the laser beam direction unchanged, adjusting the target position longitudinally, and using the Rayleigh criterion to determine the vertical distance when echo signal peaks cannot be distinguished to evaluate the vertical resolution. Specifically, by keeping the laser beam emission direction unchanged, moving the target along the laser beam propagation direction to detect the vertical resolution setting, and combining the Rayleigh criterion to determine whether two adjacent echo peaks can be distinguished, the minimum distance when the two peaks cannot be distinguished is determined in the data analysis, thus achieving the effect of scientifically quantifying the vertical resolution of the lidar system and improving the reliability of the test results.

[0057] When evaluating the maximum detection range, the target is moved along the emission direction of the laser beam, and the lidar signal is tested. The echo signal is used to determine whether to continue moving the target backward. Specifically, the laser beam emission direction is adjusted to underwater horizontal propagation by using a reflector. The maximum detection range, horizontal resolution, and vertical resolution settings of the lidar system are comprehensively evaluated by combining the moving target, the three-standard-deviation criterion, and the Rayleigh criterion. Multi-dimensional performance tests are completed under unified experimental conditions, which achieves the effect of establishing a standardized detection process and enhancing the repeatability and operability of detection.

[0058] When evaluating horizontal resolution, the laser beam direction is kept constant, and the target is moved in a direction perpendicular to the laser beam. The horizontal resolution is extracted by the relationship between the echo signal intensity and the moving distance. Specifically, by gradually moving the target backward along the laser beam emission direction when evaluating the maximum detection distance, and deciding whether to continue moving based on the real-time echo signal, dynamic feedback control is achieved during the test. This ensures accurate capture of the detection limit point, further optimizing test efficiency, reducing invalid operations, and improving detection integrity and practicality.

[0059] This solution includes the following workflow:

[0060] Throughout the testing process of the lidar system's detection performance, the device utilizes a reflector and a reflector fixture to flexibly adjust the laser beam propagation direction. Specifically, the reflector deflects the laser beam, originally pointing vertically towards the bottom, into a horizontal direction, allowing the laser beam to simulate the actual path of underwater target detection. The reflector fixture is used to precisely fix and adjust the angle and position of the reflector, ensuring a stable and controllable optical path. The target is made of Lamborghian material to realistically simulate the reflection characteristics of typical targets in an underwater environment, thereby improving the representativeness and reliability of the test data. A measuring tape is used to measure the precise distance between the lidar system and the target, ensuring the accuracy of the detection distance in each experiment. The lifting platform is used to adjust the installation height of the lidar system to adapt to the detection simulation requirements under different depth conditions.

[0061] During the detection of the maximum detection range, the target is moved back and forth along the laser beam propagation direction, and the change in echo signal intensity is used for judgment. A three-standard-deviation criterion is introduced as the standard for signal indistinguishability. Through statistical analysis of multiple measurement results, three standard deviations are set as the effective identification threshold, avoiding subjective misjudgment and improving the consistency and scientific rigor of the judgment. Movement stops when the signal-to-noise ratio drops to 3; the distance at this point is considered the maximum detection range of the lidar system, achieving precise capture of the detection limit.

[0062] In horizontal resolution detection, the laser beam emission direction is kept constant, and the target is moved laterally along a direction perpendicular to the laser beam. By recording the changes in echo signal intensity at different lateral positions and extracting the distance difference corresponding to 10%-90% of the signal rise time, the ability of the lidar system to distinguish adjacent targets in the horizontal direction is accurately evaluated, significantly improving the accuracy of spatial resolution testing. This process, combined with repeated testing of the target at different distances (20m, 30m, 35m, 40m), produces a complete horizontal resolution curve, further validating the stability and applicability of the method.

[0063] In vertical resolution detection, a dual-target structure is employed. One target (plate A) can move along the laser beam direction, while the other (plate B) remains stationary, with an initial distance of 2 meters between the two plates. As plate A gradually moves closer to plate B, data is collected and the changes in the echo signal peaks are observed after each 10cm movement. When the two signal peaks can no longer be distinguished, the minimum resolvable distance is determined according to the Rayleigh criterion; this distance is the vertical resolution of the lidar system. This method achieves a quantitative evaluation of vertical resolution capability, improving the reliability and repeatability of the test results.

[0064] This invention constructs a standardized, high-precision lidar detection performance testing system through the coordinated operation of the aforementioned components. The placement of the reflectors and their fixtures allows for flexible laser beam redirection, suitable for various experimental layouts; the target material, made of Lamborghini material, enhances the comparability and versatility of experimental data; the use of a measuring tape ensures the accuracy of the detection distance; the lifting platform supports multi-height detection simulation, expanding application scenarios; the application of the three-standard-deviation criterion and the Rayleigh criterion improves the accuracy of determining the maximum detection distance and vertical resolution, respectively; and the dynamic feedback-based movement control method further optimizes testing efficiency, reduces invalid operations, and enhances the integrity and practicality of the detection. This overall solution not only solves the problems of lack of unified standards, complex operation, and large errors in traditional detection methods, but also provides a scientific, efficient, and repeatable technical means for the performance evaluation of underwater lidar systems, possessing broad engineering application prospects and promotional value.

[0065] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A method for detecting the underwater target detection performance of a lidar system, characterized in that, include: The reflector group includes reflector 1 and reflector 2, and adopts a high damage threshold emission mirror to adjust the direction of the laser beam emitted by the laser, so that the laser beam changes from vertical propagation to horizontal propagation. A reflector fixture is used to fix the reflector and adjust the spatial angle and position of the reflector to ensure that the laser beam propagates stably along a set path; The target, used as a test object to simulate the reflection characteristics of a typical target in an underwater environment, is a diffuse reflector with standard Lambauer body characteristics. A measuring tape is used to accurately measure the straight-line distance between a lidar system and a target. The lifting platform is used to support and adjust the installation height of the lidar system to simulate the detection environment under different water depth conditions.

2. The method for detecting the underwater target detection performance of a lidar system according to claim 1, characterized in that, When evaluating the maximum detection range of a lidar system, the three-standard-deviation criterion is used as the standard for judging whether the echo signal is distinguishable. By statistically analyzing the echo signal data collected multiple times, the standard deviation of its noise background is calculated. Three times the standard deviation is used as the signal-to-noise ratio (SNR) threshold. When the SNR at the peak of the target echo signal drops to 3, it is determined that the target is at the maximum detection limit of the lidar. The target distance at this time is the maximum detection distance of the lidar system.

3. The method for detecting the underwater target detection performance of a lidar system according to claim 1, characterized in that, When detecting the horizontal resolution of a lidar system, keep the laser beam emission direction unchanged and move the target along a direction perpendicular to the laser beam propagation direction; The target is placed at a set detection distance and gradually moved laterally. After each movement, echo signal data is collected for a certain period of time, and the relationship curve of target signal intensity changing with position is recorded. By extracting the lateral displacement distance corresponding to the rising edge of the signal from 10% to 90%, this distance difference is defined as the horizontal resolution of the lidar system.

4. The method for detecting the underwater target detection performance of a lidar system according to claim 1, characterized in that, When testing the vertical resolution of a lidar system, keep the laser beam emission direction unchanged and set two target targets along the laser beam propagation direction, namely a movable plate A and a fixed plate B. Initially, there is a certain gap between board A and board B. As board A gradually moves closer to board B, data is collected after each fixed step, and it is observed whether two distinguishable signal peaks appear in the echo signal. When two signal peaks can no longer be distinguished, the minimum resolvable distance is determined according to the Rayleigh criterion, and this distance is the vertical resolution of the lidar system.

5. The method for detecting the underwater target detection performance of a lidar system according to claim 1, characterized in that, Includes the following steps: (a) Using a set of reflectors to fold the laser beam emitted by the lidar from the vertical direction to the horizontal direction for propagation; (b) Place a Lambertian target with a certain reflectivity at a set detection range, and evaluate the maximum detection range of the lidar system for the target with that reflectivity by moving the target position and combining the three-standard-deviation criterion; (c) Keeping the laser beam emission direction unchanged, move the target laterally along the direction perpendicular to the laser beam and measure the distance difference corresponding to 10%-90% of the signal rise edge to evaluate the horizontal resolution of the lidar system; (d) Keep the laser beam emission direction unchanged, set two target targets along the laser beam propagation direction, one fixed and one moving. Determine the minimum vertical distance when the two signal peaks cannot be distinguished based on the changes in the echo signal and the Rayleigh criterion, and use it to evaluate the vertical resolution of the lidar system.

6. The method for detecting the underwater target detection performance of a lidar system according to claim 5, characterized in that, During the assessment of the maximum detection range, the target is moved step by step along the laser beam emission direction, and the echo signal strength of the lidar system is tested in real time. After each target movement, echo signal data is collected over a certain period of time, and the signal strength changes are used to determine whether to continue moving the target away from the lidar. When the echo signal strength drops below three standard deviations, i.e. the signal-to-noise ratio drops to 3, the movement stops. At this point, the distance between the target location and the lidar system is the maximum detection range.

7. The method for detecting the underwater target detection performance of a lidar system according to claim 6, characterized in that, In the process of evaluating horizontal resolution, the laser beam direction is kept constant, the target is moved in a direction perpendicular to the laser beam, and the horizontal resolution parameters are extracted by the relationship curve between the echo signal intensity and the moving distance. The target moves gradually from the initial no-signal area towards the center of the laser spot. Data is collected after each certain distance, and a normalized signal intensity curve is plotted. The horizontal displacement distance between 10% and 90% of the signal rise edge is defined as the horizontal resolution.

Images