A resonance scanning-based laser imaging radar coordinate system detection method

Abstract

This invention discloses a coordinate system detection method for a laser imaging radar based on resonant scanning, comprising: establishing the alignment of the optical axis of a large field-of-view camera with the normal of a reference cubic mirror using a collimator; establishing the spatial position mapping relationship of the orthogonal plane of the reference cubic mirror on the focal plane of the large field-of-view camera using an opto-collimator; calibrating the orthogonality and angular error of the dynamic scanning axis of the laser radar using the large field-of-view camera; and installing a reference cubic mirror on the laser radar, with its spatial orientation consistent with that of the reference cubic mirror, using this cubic mirror as the reference coordinate reference to establish the radar's reference reference, and providing the relationship between the radar's optical axis and the reference coordinate reference system. This invention optimizes and solves the imaging distortion and coordinate transfer problems of a laser radar system by using a collimator, a large field-of-view camera, and a cubic reference mirror to detect the optical axis orientation and the relative reference relationship of the orthogonality of the resonant scanning axis.

Description

Technical Field

[0001] This invention relates to the field of lidar technology, and more specifically to a method for detecting the coordinate system of a lidar imaging radar based on resonant scanning. Background Technology

[0002] Laser 3D scanning imaging systems are mainly used for precise positioning and imaging measurement of large spatial targets. By non-contact scanning and measuring the surface of large objects, intuitive 3D point cloud data is obtained for 3D reverse modeling or relative pose calculation.

[0003] As a type of navigation and measurement system, optical axis coordinate transformation and calibration are indispensable. Coordinate transformation is the description of the position of a spatial entity, a process of changing from one coordinate system to another. This is achieved by establishing a one-to-one correspondence between the two coordinate systems. During lidar scanning and detection, the measurement results often need to be transferred to the geodetic coordinate system for subsequent conversion and measurement of various target parameters.

[0004] Existing calibration methods are only applicable to lidar using traditional laser scanning mirrors, requiring the lidar scanning mirror to remain stationary at certain fixed positions. However, resonant scanning mirrors can only be in a resonant state during operation and cannot remain stationary at a specific angle. Therefore, this method cannot be extended to various types of laser scanning equipment, lacks operational universality, and does not transfer the scanning coordinate system to the geodetic reference coordinate system for unified measurement data. Summary of the Invention

[0005] To address or partially address the problems existing in related technologies, this invention provides a coordinate system detection method for laser imaging radar based on resonant scanning. By utilizing a collimator, a large field-of-view camera, and a cubic reference mirror to detect the optical axis pointing and the relative reference relationship of the orthogonality of the resonant scanning axis of a three-dimensional scanning imaging laser radar, this method optimizes and solves the imaging distortion and coordinate transfer of the laser radar system.

[0006] This invention provides a method for coordinate system detection in laser imaging radar based on resonant scanning, comprising:

[0007] Using a collimator, the optical axis of the large field-of-view camera is aligned with the normal of the reference cubic mirror;

[0008] The spatial position mapping relationship of the orthogonal planes of the reference cubic mirror on the focal plane of the large field-of-view camera is established using an opto-collimator;

[0009] The orthogonality and angular error of the dynamic scanning axis of the lidar are calibrated using a large field-of-view camera;

[0010] A reference cubic mirror is also installed on the lidar, and its spatial orientation is consistent with that of the reference cubic mirror. The reference reference of the lidar is established by using this cubic mirror as the reference coordinate reference, and the relationship between the lidar optical axis and the reference coordinate reference system is given.

[0011] Optionally, the step of using a collimator to establish that the optical axis of the large field-of-view camera is aligned with the normal of the reference cubic mirror includes:

[0012] A test laser beam of moderate energy is injected into the inlet of the collimator. The laser beam is then positioned at the center of the camera's field of view by adjusting the multi-dimensional adjustment frame. The camera position is kept fixed, and the position of the reference cubic mirror is adjusted so that the reflected light from the front surface A of the cubic mirror reaches the center of the camera's field of view in the collimator.

[0013] Optionally, establishing the spatial position mapping relationship of the orthogonal planes of the reference cubic mirror on the focal plane of the large field-of-view camera using an opto-collimator includes:

[0014] Maintaining the positional relationship of each device, two photoelectric autocollimators are installed on the upper surface C and right surface B of the reference cubic mirror. The autocollimators are adjusted so that the backlight of surfaces C and B of the reference cubic mirror is at a certain value. First, the multidimensional adjustment frame is rotated around the Y-axis of the reference cubic mirror while keeping the value of the Y-axis autocollimator constant. The rotation angle α and the position of the corresponding camera point O are recorded by monitoring the Z-axis autocollimator reading. This operation is repeated multiple times to fit the Y-axis straight line of the camera's corresponding focal plane. Then, the mirror is returned to its original position, and the rotation is similarly performed around the Z-axis of the reference cubic mirror to fit the X-axis straight line of the camera's corresponding focal plane. At this point, the spatial position mapping relationship of the Y-axis and Z-axis of the reference cubic mirror can be mapped in the receiving field of view of the camera.

[0015] Optionally, the calibration of the orthogonality and angular error of the dynamic scanning axis of the lidar using a large field-of-view camera includes:

[0016] The lidar emits a moderately energetic laser beam to the focal plane of a large field-of-view camera. By adjusting the multi-dimensional adjustment frame, the initial optical axis of the lidar is aligned with the center of the field of view of the large field-of-view camera. Then, the lidar's resonant scanning is activated, and the scanning data of the lidar's emitted beam is displayed directly in the camera's receiving field of view. By analyzing the point trace information of the lidar's emitted laser beam on the camera surface, the orthogonality of the lidar's scanning axis and the distortion feedback of the scanning angle can be detected.

[0017] Optionally, a reference cubic mirror is also installed on the lidar, with its spatial orientation consistent with the reference cubic mirror. Using this cubic mirror as a reference coordinate system, a reference reference for the lidar is established, and the relationship between the lidar optical axis and the reference coordinate reference system is given, including:

[0018] The orthogonality of the lidar resonant scanning axis is corrected to the allowable error range. Then, a reference cubic mirror is installed on the lidar with its spatial orientation consistent with that of the reference cubic mirror. The relationship between the lidar optical axis and the reference coordinate reference system is solved by using the spatial mapping relationship and the point trace information of the corrected lidar resonant scanning axis in the camera's field of view.

[0019] Optionally, the wide field-of-view camera is a CCD camera with distortion correction and focal length calibration; the collimator has detection capability with coaxial transmission and reception; the cubic mirrors are spatially aligned and used to establish a reference coordinate system and transform the camera's optical axis.

[0020] The technical solution provided by this invention may include the following beneficial effects:

[0021] This invention establishes a method for monitoring and calibration of various laser scanning devices, which transfers the optical axis of resonant scanning to the coordinates of a standard reference cubic mirror, thereby establishing a reference plane. The resonant scanning axis of a laser radar based on resonant scanning is in a resonant state during operation and cannot remain stationary at any angle like a conventional scanning mirror; therefore, conventional calibration and testing methods are not applicable to this type of laser radar.

[0022] The detection method constructed in this invention can simultaneously measure and calibrate the perpendicularity and angular accuracy of the two-dimensional scanning axis of a laser scanning device.

[0023] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the technical solution of the laser imaging radar coordinate system detection method based on resonant scanning according to the present invention;

[0026] Figure 2 This is a schematic diagram illustrating how the optical axis of a large field-of-view camera is aligned with the normal of a reference cubic mirror using a collimator according to the present invention.

[0027] Figure 3 This is a schematic diagram illustrating the use of a photoelectric autocollimator to monitor coordinate axis transformations according to the present invention.

[0028] Figure 4 This is a schematic diagram of the resonant scanning axis of a lidar imaging system using a large field-of-view camera, as per the present invention. Detailed Implementation

[0029] Embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be more thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0030] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms “a,” “the,” and “the” used in this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0031] It should be understood that although the terms "first," "second," "third," etc., may be used in this invention to describe various radars, this information should not be limited to these terms. These terms are only used to distinguish radars of the same type from each other. For example, a first radar may also be referred to as a second radar without departing from the scope of this invention, and similarly, a second radar may also be referred to as a first radar. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0032] This invention provides an application example of a coordinate system detection method for laser imaging radar based on resonant scanning. As shown in the figure, this paper introduces a method for detecting the optical axis orientation and resonant scanning axis orthogonality relative reference relationship of a scanning imaging laser radar using a collimator, a large field-of-view camera, and a cubic reference mirror. The collimator has coaxial transmission and reception detection capabilities, the cubic reference mirror is used to establish a reference coordinate system and perform coordinate transformation of the camera's optical axis, and the large field-of-view camera is used to receive the resonant scanning light from the laser radar and measure and detect relevant radar data. This method is applicable to the monitoring and calibration of various laser scanning devices.

[0033] The detection method in this embodiment includes the following steps:

[0034] Step 1: Using collimator 4, align the optical axis of the large field-of-view camera 6 with the normal of the reference cubic mirror 7. Figure 2 );

[0035] A test laser 2 with appropriate energy is injected into the light inlet 3 of the collimator 4. Then, the laser beam is positioned at the center of the field of view of the camera 6 by adjusting the multidimensional adjustment frame 5. At this time, the position of the camera 6 is fixed and the position of the reference cubic mirror 7 is adjusted so that the reflected light from the front surface A of the cubic mirror reaches the center of the field of view of the camera in the collimator 4.

[0036] Step 2: Use an opto-collimator to establish the spatial position mapping relationship of the orthogonal plane of the reference cubic mirror 7 on the focal plane of the large field-of-view camera 6. Figure 3 );

[0037] Based on step 1, maintain the positional relationship of each device (state 0). As shown in step 1, install the following on the upper surface C (taken as the positive Z-axis) and right surface B (taken as the negative Y-axis) of the reference cubic mirror 7. Figure 3 The two photoelectric autocollimators shown are adjusted so that the reflected light from surfaces C and B of the reference cubic mirror 7 reaches a specific value (or zero position). First, the multi-dimensional adjustment frame 5 is rotated around the Y-axis of the reference cubic mirror 7, while keeping the Y-axis autocollimator reading constant. The rotation angle α and the corresponding position of point O on the camera are recorded by monitoring the Z-axis autocollimator reading. This process is repeated multiple times to fit the Y-axis line corresponding to the focal plane of camera 6. Then, returning to the original position (initial state 0), the rotation around the Z-axis of the reference cubic mirror 7 is repeated to fit the X-axis line corresponding to the focal plane of camera 6. At this point, the spatial position mapping relationship of the reference cubic mirror 7 along the Y-axis and Z-axis can be mapped within the receiving field of view of camera 6.

[0038] Step 3: Use a large field-of-view camera to calibrate the orthogonality and angular error of the dynamic scanning axes of the 10-axis LiDAR (6-axis calibration). Figure 4 );

[0039] The lidar 10 emits a moderately energetic laser beam to the focal plane of the large field-of-view camera 6. By adjusting the multi-dimensional adjustment frame 8, the initial optical axis of the lidar is aligned with the center of the field of view of the large field-of-view camera 6. Then, the resonant scanning of the lidar 10 is activated. The scanning data of the laser beam emitted by the lidar 10 is displayed directly in the receiving field of view of the camera 6. By analyzing the spot information of the laser beam emitted by the lidar 10 on the surface of the camera 6, the orthogonality of the lidar scanning axis and the distortion feedback of the scanning angle can be detected.

[0040] Step 4: Install a reference cube mirror 11 on the lidar 10, with its spatial (ABC plane) pointing in the same direction as the reference cube mirror 7. Use the cube mirror 11 as the reference coordinate reference to establish the radar's reference reference and give the relationship between the radar optical axis and the reference coordinate reference system.

[0041] Based on the test results from step 3, the orthogonality of the resonant scanning axis of the lidar 10 is corrected to the allowable error range. Then, a reference cubic mirror 11 is also installed on the lidar 10, with its spatial (ABC plane) orientation consistent with that of the reference cubic mirror 7. By utilizing the spatial mapping relationship obtained in step 2 and the point trace information of the corrected resonant scanning axis of the lidar 10 in the camera's field of view, the relationship between the radar optical axis and the reference coordinate system can be solved.

[0042] The large field-of-view camera is a CCD camera with distortion correction and focal length calibration; the collimator has detection capability with coaxial transmission and reception; the cubic mirrors are spatially aligned and are used to establish a reference coordinate system and transform the camera's optical axis.

[0043] The above description is merely an embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and scope of the present invention are included within the scope of protection of the present invention.

Claims

1. A method for detecting coordinate systems in a laser imaging radar based on resonant scanning, characterized in that, include: Using a collimator, the optical axis of the large field-of-view camera is aligned with the normal of the reference cubic mirror; The spatial position mapping relationship of the orthogonal planes of the reference cubic mirror on the focal plane of the large field-of-view camera is established using an opto-collimator; The orthogonality and angular error of the dynamic scanning axis of the lidar are calibrated using a large field-of-view camera; Install another reference cube mirror on the lidar that is aligned with the spatial orientation of the reference cube mirror. Use the reference cube mirror installed on the lidar as the reference coordinate reference to establish the radar's reference reference and give the relationship between the radar's optical axis and the reference coordinate reference system.

2. The laser imaging radar coordinate system detection method based on resonant scanning as described in claim 1, characterized in that, The method of using a collimator to establish that the optical axis of the large field-of-view camera is aligned with the normal of the reference cubic mirror includes: A test laser beam of moderate energy is injected into the inlet of the collimator. The laser beam is then positioned at the center of the camera's field of view by adjusting the multi-dimensional adjustment frame. The camera position is kept fixed, and the position of the reference cubic mirror is adjusted so that the reflected light from the front surface A of the cubic mirror reaches the center of the camera's field of view set in the collimator.

3. The laser imaging radar coordinate system detection method based on resonant scanning as described in claim 1, characterized in that, The method of establishing the spatial position mapping relationship of the orthogonal planes of the reference cubic mirror on the focal plane of the large field-of-view camera using an opto-collimator includes: Maintaining the positional relationship of each device, two photoelectric autocollimators are installed on the upper surface C and right surface B of the reference cubic mirror. The autocollimators are adjusted so that the backlight of surfaces C and B of the reference cubic mirror is at a certain value. First, the multidimensional adjustment frame is rotated around the Y-axis of the reference cubic mirror while keeping the value of the Y-axis autocollimator constant. The rotation angle α and the position of the corresponding camera point O are recorded by monitoring the Z-axis autocollimator reading. This operation is repeated multiple times to fit the Y-axis straight line of the camera's corresponding focal plane. Then, the mirror is returned to its original position, and the rotation is similarly performed around the Z-axis of the reference cubic mirror to fit the X-axis straight line of the camera's corresponding focal plane. At this point, the spatial position mapping relationship of the Y-axis and Z-axis of the reference cubic mirror can be mapped in the receiving field of view of the camera.

4. The laser imaging radar coordinate system detection method based on resonant scanning as described in claim 1, characterized in that, The calibration of the orthogonality and angular error of the dynamic scanning axis of the lidar using a large field-of-view camera includes: The lidar emits a moderately energetic laser beam to the focal plane of a large field-of-view camera. By adjusting the multi-dimensional adjustment frame, the initial optical axis of the lidar is aligned with the center of the field of view of the large field-of-view camera. Then, the lidar's resonant scanning is activated, and the scanning data of the lidar's emitted beam is displayed directly in the camera's receiving field of view. By analyzing the point trace information of the lidar's emitted laser beam on the camera surface, the orthogonality of the lidar's scanning axis and the distortion feedback of the scanning angle can be detected.

5. The laser imaging radar coordinate system detection method based on resonant scanning as described in claim 1, characterized in that, The process involves installing another reference cubic mirror on the lidar that maintains the same spatial orientation as the reference cubic mirror. Using this reference cubic mirror as the reference coordinate reference, a reference reference for the lidar is established, and the relationship between the lidar optical axis and the reference coordinate reference system is given, including: The orthogonality of the lidar resonant scanning axis is corrected to the allowable error range. Then, another reference cubic mirror is installed on the lidar, which is aligned with the spatial orientation of the reference cubic mirror. The relationship between the lidar optical axis and the reference coordinate reference system is solved by the spatial mapping relationship and the point trace information of the corrected lidar resonant scanning axis in the camera's field of view.

6. The laser imaging radar coordinate system detection method based on resonant scanning as described in claim 1, characterized in that, The wide field-of-view camera is a CCD camera with distortion correction and focal length calibration; the collimator has detection capability with coaxial transmission and reception; the cubic mirrors are spatially aligned and used to establish a reference coordinate system and transform the camera's optical axis.

Images