A method for solving the smearing of single-line laser radar

Abstract

The present application relates to a kind of method for solving single line laser radar tailing, the method comprises the following steps: S1, by optical simulation software Zemax simulation simulation real laser radar being used, and according to actual situation setting obscuration diaphragm;S2, by the multiple configuration function in optical simulation software realizes the rotation of laser radar, and finds the angle that laser beam of laser radar is just all blocked by shelter;And S3, the transverse and longitudinal diameter size of laser beam is measured in the 3D layout of Zemax sequence mode, and the size of divergence angle is obtained using standard point column chart, collate the transverse and longitudinal diameter size of laser beam measured, finally light-absorbing material is coated to the edge position of shelter structure with this width and length rectangular.The present application solves the problem of single line laser radar tailing, so that single line radar measurement accuracy is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of radar detection technology, and in particular relates to a method for solving the trailing effect of single-line lidar. Background Technology

[0002] LiDAR uses laser light as its detection beam. The directional collimation, short pulse width, single spectral line, and high brightness of laser light give it advantages such as high spatial resolution, high sensitivity, and strong anti-interference capabilities. It is widely used in fields such as autonomous driving, automated guided vehicles (AGVs), security mapping, and industrial automation. LiDAR calculates the distance between the target object and the laser by emitting and receiving laser light, recording the time interval between emission and reception.

[0003] LiDAR contains numerous components, among which the transmitting and receiving lens groups are crucial optical elements. The laser source in a LiDAR emits laser light, which is collimated by the transmitting lens group before being projected onto the object being measured. Ideally, this laser beam should strike a point-like focal spot on the object's surface. However, in reality, because the actual divergence angle of the light source is within a range and the transmitting lens group has certain tolerances, the laser beam is not perfectly collimated upon exiting; instead, it exhibits a divergence angle, resulting in a surface focal spot on the object. When two objects are some distance apart, part of the laser beam strikes one object, and the other strikes the other. The LiDAR detector receives the superposition of two reflected beams with a time difference. This can cause the LiDAR to misjudge the object as being between the two objects, resulting in a trailing phenomenon in the LiDAR point cloud, commonly known as LiDAR trailing. This trailing phenomenon can cause difficulties in navigation, ranging, and path planning. In addition, reflections, scattering, and diffusion may occur on the inner wall of the lidar optical path and at the edge of the lens, which can also affect the quality of the laser beam and cause measurement errors.

[0004] In existing technologies, the solution to LiDAR trailing issues typically involves detecting outliers using algorithms. This treats trailing points in the point cloud as outliers and employs outlier detection principles based on statistics, distance, and density to locate and remove them. However, considering that LiDAR measurements can be performed in complex environments, including both indoors and outdoors, this mathematical calculation-based detection and removal algorithm is prone to false positives or missed detections, thus affecting the measurement accuracy of the LiDAR.

[0005] Chinese patent CN113345093B, entitled "A Filtering Method for Tail Points in LiDAR Point Clouds," provides a method for filtering out LiDAR trailing points. This method includes: filtering out trailing points from the point cloud generated by each laser line; then, for each point in the point cloud generated by the laser line, calculating the distance between each point and its left and right adjacent points; if both distance values ​​are greater than a set distance threshold, the point is initially determined to be a trailing point; for points initially determined to be trailing points, calculating the angle corresponding to the origin of the point cloud in the triangle formed by the point's left adjacent point, the point itself, and the origin of the point cloud; further calculating the angle corresponding to the origin of the point cloud in the triangle formed by the point's right adjacent point, the point itself, and the origin of the point cloud; if both angle values ​​are less than a set angle threshold, the point is considered a trailing point and filtered out; finally, superimposing the point clouds generated by each laser line that have had their trailing points filtered out to generate a frame of point cloud with trailing points removed. This invention has low computational complexity and a simple algorithm. However, the inventors of this invention did not explain the principle behind the entire method, nor did they provide details on how the first step, "filtering out trailing points from the point cloud generated by each laser line," is performed. Furthermore, this method is designed for multi-line lidar and cannot be used to remove trailing phenomena from single-line lidar. Moreover, as mentioned earlier, considering the complex working environment of lidar, this mathematical calculation-based detection and elimination algorithm is prone to missed or false detections, inevitably affecting the measurement accuracy of the lidar.

[0006] Single-line lidar refers to lidar where the laser source emits a single-line beam. There are two main types: triangulation lidar and Time-of-Flight (TOF) lidar. Single-line lidar features fast scanning speed, high resolution, and high reliability. Compared to multi-line lidar, single-line lidar responds faster in terms of angular frequency and sensitivity, resulting in more accurate distance measurement and precision for obstacles. Furthermore, single-line lidar is significantly cheaper than multi-line lidar, making it easier to promote and more widely accepted. In fact, due to its low cost, single-line lidar is currently the most widely used.

[0007] Unfortunately, the trailing phenomenon of LiDAR is unrelated to whether it is a single-line or multi-line LiDAR; in other words, both exhibit the trailing phenomenon. Summary of the Invention

[0008] To address the problems existing in the prior art, this invention provides a method for solving the trailing effect of a single-line lidar, comprising the following steps: a preprocessing step, in which the lidar currently in use is simulated in the optical simulation software Zemax, and the obstruction aperture is set according to the actual situation; a critical position analysis step, in which the lidar is rotated using the multi-state function in the optical simulation software, and the angle at which the lidar laser beam is exactly all on the obstruction; and a beam size calculation and analysis step, in which the lateral and longitudinal diameters of the laser beam are measured in the 3D layout diagram in the Zemax sequence mode, and the divergence angle obtained from the standard point array diagram is used to verify the measured lateral and longitudinal diameters, and the light-absorbing material is applied to the edge of the obstruction aperture in a rectangle of this width and length.

[0009] The preprocessing step is performed by the preprocessing module, the critical position analysis step by the critical position analysis module, and the beam size calculation and analysis step by the beam size calculation and analysis module. These steps are performed sequentially and the order cannot be changed.

[0010] Furthermore, the preprocessing steps include: a transmitter group simulation step, which measures the actual optical path of the lidar transmitter group and simulates it in Zemax; a receiver group simulation step, which measures the actual optical path of the lidar receiver group and simulates it in Zemax; and a blocking aperture setting step, which sets a blocking aperture in the optical path according to the relative position of the lidar. The transmitter group simulation step is completed by the laser source and the transmitter group lens, and the receiver group simulation step is completed by the receiver group lens and the high-speed PIN photodiode.

[0011] Furthermore, the critical position analysis step includes: a multi-state step, which sets the transmitting group and the receiving group in Zemax as a whole and thereby sets its y-axis deflection angle; and a critical angle analysis step, which finds an angle at which the laser beams are all at the edge of the obstruction aperture based on the deflection of the entire lidar system relative to the y-axis by the multi-state step, characterized in that when the lidar deflects again, the obstruction cannot completely block the entire laser beam.

[0012] Furthermore, the beam size calculation and analysis steps include: a laser beam measurement step, which measures the horizontal and vertical widths of the laser beam at the critical angle found in the critical angle analysis step; a laser beam verification step, which calculates the radar width using the formula W = A * D + L based on the size of the divergence angle in the standard point array diagram at this time, where W = the beam width of the laser on the blocking aperture, A = the laser divergence angle, D = the distance from the blocking aperture to the laser emitter, and L = the size of the laser radar beam when it is emitted; and a laser beam size application step, which applies a rectangular light-blocking area at the edge of the blocking object based on the length and width data obtained from the laser beam measurement step and the laser beam verification step.

[0013] The method of this invention provides a precise calculation of the beam size on the blocking aperture. Based on the calculated beam size, the edge of the blocking aperture is blackened with a light-absorbing material, preventing laser emission from the edge and thus solving the trailing problem in single-line lidar. This invention helps researchers simulate the position and size of different blocking aperture structures within different lidar blind zones, with the structure perfectly fitting the entire lidar device. Specifically, in practical operation, different emitting lens groups emit laser beams of different sizes, and blocking apertures with different reflectivities can be used. By accurately simulating the beam detected by the receiving group under this multivariable condition, the trailing phenomenon of single-line lidar is eliminated quickly and easily, greatly improving the accuracy of single-line lidar measurements. Attached Figure Description

[0014] Figure 1 A schematic diagram of a method for solving single-line lidar trailing according to an embodiment of the present invention is shown, mainly illustrating the relationship between the preprocessing module, the critical position analysis module, and the beam size calculation and analysis module. Figure 2 A flowchart illustrating a method for resolving single-line lidar trailing according to an embodiment of the present invention is shown. Figure 3 A flowchart illustrating the preprocessing steps in a method for resolving single-line lidar trailing according to an embodiment of the present invention is shown. Figure 4 A flowchart illustrating the critical position analysis steps in the method for resolving single-line lidar trailing according to an embodiment of the present invention is shown. Figure 5 A flowchart illustrating the steps for calculating and analyzing the beam size in a method for resolving single-line lidar trailing according to an embodiment of the present invention is shown. Detailed Implementation

[0015] To make the objectives and advantages of the present invention clearer, the present invention will be further described below in conjunction with embodiments; it should be noted that the specific embodiments described herein are merely for explaining the present invention and do not limit the present invention.

[0016] See appendix Figure 1 and Figure 2 Specifically, to solve the problem of single-line lidar trailing, this invention uses the optical simulation software Zemax to simulate the currently used lidar. This step is performed by the preprocessing module, and an obstruction stop is set according to the current lidar situation. The obstruction stop is set in the critical position analysis module. The lidar simulation software Zemax, like the actual lidar, has a simulated transmitting lens combination and a simulated receiving lens group. Then, the lidar is rotated through the multi-state function in the optical simulation software Zemax, and the angle at which the lidar laser beam is exactly all in the obstruction stop, that is, the critical angle, is found. The lateral and longitudinal diameters of the laser beam are measured in the 3D layout diagram in the sequence mode of the simulation software Zemax, and the laser divergence angle obtained from the standard point array diagram is used to verify the measured lateral and longitudinal diameters. Finally, the light-absorbing material is applied to the edge of the obstruction stop in a rectangle of this width and length.

[0017] See Figure 3 As a refinement of the simulation of the currently used lidar using the optical simulation software Zemax, it is necessary to measure the actual optical path of the lidar emitting group, and then simulate the actual optical path of the emitting group in the simulation software Zemax. It is also necessary to measure the actual optical path of the lidar receiving group and simulate the actual optical path of the receiving group in the simulation software Zemax. Finally, based on the relative position of the lidar, an obstruction aperture is set in the actual optical path.

[0018] See Figure 4 To refine the process of finding the critical angle, the transmitting and receiving groups in the simulation software Zemax need to be set as a whole, and the rotation angle of the receiving group relative to the y-axis needs to be set accordingly. Then, based on the deflection of the entire lidar system relative to the y-axis by multiple reconfigurations, an angle is found where the laser beams are exactly at the edge of the blocking aperture structure. This is how the critical angle is found. It is worth noting that when the lidar deflects again, the blocking aperture cannot completely block the entire laser beam.

[0019] See box Figure 5 Furthermore, this embodiment also requires detailed explanation. The key to this invention is to obtain the beam size through calculation and analysis. This process involves finding the critical angle, measuring the horizontal and vertical widths of the laser beam at this point, and then calculating the laser beam width using the formula W = A * D + L based on the standard dot matrix diagram. Here, W = the laser beam width on the blocking aperture, A = the laser divergence angle, D = the distance from the blocking aperture to the laser emitter, and L = the size of the laser radar beam when it is emitted. The calculated values ​​are then checked against the measured values. Finally, a rectangular light-blocking area is applied to the edge of the blocking aperture, thereby completing this embodiment of the invention.

[0020] In this summary, the inventors have described the technical solution of the present invention in detail with reference to the accompanying drawings and embodiments. However, those skilled in the art will readily understand that the scope of protection of the present invention is obviously not limited to the specific embodiments described above. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions resulting from these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for solving the trailing effect of a single-line lidar, specifically including: Step S1: Simulate the real lidar in use using the optical simulation software Zemax, and set the blocking aperture according to the actual situation. Step S2: Rotate the lidar using the multi-state function in the optical simulation software Zemax, and find the angle at which the lidar laser beam is exactly all in the blocking aperture; Step S3: Measure the horizontal and vertical diameters of the laser beam in the 3D layout diagram in Zemax sequence mode, and verify the measured horizontal and vertical diameters of the laser beam using the divergence angle obtained from the standard point array diagram, and apply the light-absorbing material to the edge of the blocking aperture in a rectangle of this width and length. Step S2 includes: Step S21, setting the transmitting group and receiving group in Zemax as a whole, and thereby setting its deflection angle relative to the y-axis; Step S22, based on the deflection of the entire lidar system relative to the y-axis by multiple reconfigurations, finding an angle at which the laser beams are all at the edge of the blocking aperture, which is the critical angle, so that when the lidar deflects again, the blocking aperture cannot completely block the entire laser beam. Step S3 includes: Step S31, measuring the horizontal and vertical widths of the laser beam at the critical angle found in step S22; Step S32, calculating the laser beam width using a formula based on a standard dot matrix diagram; Step S33, verifying the beam width measurement value obtained in step S31 against the calculated value obtained in step S32, and then applying a rectangular light-blocking area with a width equal to the obtained value at the edge of the blocking aperture.

2. The method for solving the trailing effect of a single-line lidar as described in claim 1, characterized in that: Step S1 includes: Step S11, measuring the actual optical path of the lidar transmitting group and simulating it in the optical simulation software Zemax; Step S12, measuring the actual optical path of the lidar receiving group and simulating it in the optical simulation software Zemax; Step S13, setting an obstruction aperture in the optical path according to the relative position of the lidar.

3. The method for solving the trailing effect of a single-line lidar as described in claim 1, characterized in that: The formula is: W=A*D+L, where W=the beam width of the laser on the blocking aperture, A=the laser divergence angle, D=the distance from the blocking aperture to the laser emitter, and L=the size of the laser radar beam when it is emitted.

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