Low-altitude optical attitude determination three-component magnetic measurement system correction test device and correction test method

Abstract

The invention discloses a correction test device and a correction test method for a low-altitude optical attitude determination three-component magnetic measurement system. The correction test device and the correction test method are used for carrying out correction test on the low-altitude optical attitude determination three-component magnetic measurement system. The low-altitude optical attitude determination three-component magnetic measurement system correction test device comprises a correction test bench and a VCSEL laser point light source plate, and the correction test bench is provided with an aircraft and cooperates with the VCSEL laser point light source plate to obtain test data of a magnetic vector element and a camera in the aircraft. Operation correction is carried out according to the detection data and accurate data of the correction test device, correction test of the magnetic vector element and the camera on the aviation aircraft is achieved, higher measurement precision is obtained, and then the measurement precision of the low-altitude optical attitude determination three-component magnetic measurement system is obviously improved.

Description

Technical Field

[0001] This invention relates to the field of geophysical exploration, specifically to a calibration and testing device and method for a low-altitude optical attitude-determining three-component magnetometry system. Background Technology

[0002] Three-component magnetic measurement is a method for measuring magnetic fields that provides information on the three components of the magnetic field: the intensity of the magnetic field in the vertical, horizontal, and tilt directions. This measurement method has wide applications in many fields, such as geological surveys, mineral resource exploration, and marine geomagnetic research.

[0003] In airborne geophysical exploration, the three-component airmagnetic measurement technique can obtain comprehensive information on the geomagnetic field, including magnetic declination, magnetic inclination, and vertical and horizontal components. This is highly beneficial for qualitative analysis and quantitative interpretation of magnetic anomalies. Currently, airborne magnetic surveying primarily focuses on measuring the total geomagnetic field strength or gradient. Compared to total field measurements, vector measurements can simultaneously acquire information on the magnitude and direction of the geomagnetic field modulus, effectively reducing ambiguity in inversion and aiding in the quantitative interpretation of magnetic bodies. This improves the resolution and positioning accuracy of underground ore bodies, making vector magnetic surveying one of the main development directions of airborne magnetic surveying.

[0004] The magnetic triaxial components are vector data, requiring the determination of the testing equipment's own attitude and orientation. Based on the equipment's attitude and orientation and the measured magnetic triaxial component data, the magnetic component values ​​in the true geographic coordinate environment are calculated. Attitude control of the magnetic measuring instrument during movement is a key aspect of this technology. The technical difficulties of high-precision attitude control during movement have hindered the development and application of magnetic field vector measurement technology in geophysical exploration.

[0005] Miniature inertial devices (IMUs) have been widely used in the civilian technology field, such as in drones, AR / VR devices, and optical image stabilization. IMU-based combined sensors can be miniaturized into chips with small size and weight, but these devices cannot meet the attitude determination accuracy requirements for magnetic field vector measurement.

[0006] The applicant has developed a low-altitude optical attitude determination three-component magnetometry system by utilizing and integrating technologies such as optics, satellite navigation and communication, machine vision, microelectronics, space attitude control, magnetic vector elements, and software. This system achieves rapid and high-precision measurement of the Earth's magnetic field vector. The system operates through a ground-based host and several aircraft equipped with magnetic vector elements and cameras. The cameras on each aircraft collect light samples from other aircraft, and the data collected by the magnetic vector elements on each aircraft are used to calculate the three-component magnetic vector data, thus avoiding the need for expensive inertial navigation systems for attitude determination. The accuracy of this system is limited by the accuracy of the subsystems on each aircraft. To further improve the accuracy of the final magnetic three-component vector data measurement, calibration of the aircraft components and other subsystems within the system is necessary. Summary of the Invention

[0007] To address the aforementioned problems mentioned in the background art, a device and a method for calibration testing of an aircraft in a low-altitude optical attitude determination three-component magnetic measurement system designed by the applicant are proposed.

[0008] The objective of this invention is achieved through the following technical measures: A calibration and testing device for a low-altitude optical attitude determination three-component magnetic measurement system is characterized by comprising a calibration test platform and a VCSEL laser point source plate. The calibration test platform includes a base platform and legs. The base platform includes an upper base platform and a lower base platform. The legs are installed on the lower part of the lower base platform. A leveling device is installed between the upper base platform and the lower base platform. A first rotating shaft is rotatably mounted in the middle of the upper base platform. The first rotating shaft is installed perpendicular to the upper base platform. The first rotating shaft has two symmetrically arranged shaft holes. A second rotating shaft orthogonal to the first rotating shaft is rotatably mounted in the two shaft holes. A third rotating shaft orthogonal to the second rotating shaft is rotatably mounted in the middle of the second rotating shaft. A laser point source is mounted on the side of the third rotating shaft. The laser beam direction of the laser point source is perpendicular to the second rotating shaft. The third rotating shaft has a connecting structure. An angle sensor is provided on the first rotating shaft, the second rotating shaft, and the third rotating shaft.

[0009] Furthermore, the first and third rotating shafts are arranged with their axes coinciding in a perpendicular state.

[0010] Furthermore, a first leveling device is installed on the upper foundation platform, and a second leveling device is installed on the upper surface of the third rotating shaft.

[0011] Furthermore, the aircraft includes a magnetic vector element and a camera assembly. After the aircraft is mounted on the calibration test bench via a connecting structure, the camera assembly is positioned at the same height as the center of the VCSEL laser point source board.

[0012] Furthermore, the connection structure is used to connect the magnetic vector element and the camera assembly. The calibration test platform is made entirely of non-magnetic materials. The base platform is fixed by support legs and leveled using a first leveling device, ensuring the first rotating shaft axis is perpendicular to the horizontal plane. A second rotating shaft is installed at the upper part of the first rotating shaft in a direction orthogonal to it, with its axis parallel to the horizontal plane. A third rotating shaft is installed in the middle of the second rotating shaft in a direction orthogonal to it. The rotation of the first, second, and third rotating shafts is recorded using angle sensors.

[0013] A calibration test method for a low-altitude optical attitude determination three-component magnetic measurement system calibration test device is characterized by: fixing an aircraft in the low-altitude optical attitude determination three-component magnetic measurement system onto the connection structure of the aforementioned low-altitude optical attitude determination three-component magnetic measurement system calibration test device; the aircraft having magnetic vector elements and camera components; and the method for calibrating and testing the aircraft including magnetic vector element calibration calculation, magnetic vector element orthogonality adjustment test, camera component position calibration, and image distortion correction.

[0014] The magnetic vector element calibration calculation is performed. The angle between the third rotating shaft and the magnetic field direction is defined as α1, and the angles at different positions of the third rotating shaft itself are defined as β1. The magnetic vector element is mounted on the third rotating shaft, and the two are installed nearly perpendicularly. Due to installation errors, the small angle between the magnetic vector element and the plane perpendicular to the third rotating shaft is defined as γ1. When the third rotating shaft rotates, the magnetic field vector magnitude measured by the magnetic vector element is: The angle γ1 between the magnetic vector element and the vertical plane relative to the third rotation axis is a fixed angle value, and the angle α1 between the magnetic vector element and the vertical plane relative to the third rotation axis is a fixed angle value.

[0015] In the above formula, The angle (in radians) between the direction of the α1 magnetic field and the third rotation axis ranges from 0 to +90°. The angle (in radians) of the third axis of rotation at different positions of β1, ranging from 0 to +360°; The angle (in radians) between the γ1 magnetic vector element and the perpendicular plane of the relative rotating third axis, ranging from 0 to +90°; T0 is the total field modulus of the magnetic field (nT). The value (nT) obtained by measuring the magnetic vector element at different angles.

[0016] The test steps for adjusting the orthogonality of magnetic vector elements are as follows: In a non-magnetic laboratory or an outdoor location with a small magnetic field gradient, fix and level the platform. Set up a VCSEL laser point source board at a distance of 5 meters or more, ensuring that the light source points are vertical from top to bottom. The laser point source board also serves as a marker board. Turn on the laser point source installed on one side of the third rotating shaft, projecting it onto the laser point source board and record the position. Then rotate both the first and second rotating shafts 180 degrees; the laser point should now be projected onto the same position.

[0017] The magnetic vector element and camera assembly are rigidly connected as one unit by a rigid rod. The centerline of the line of sight of camera #1 in the camera assembly is basically aligned with the positive direction of the magnetic field vector element X. The magnetic vector element and camera assembly are mounted on the rotating body of the third rotating shaft via fastening accessories and a connection structure of the third rotating shaft, and are connected to the magnetic vector host and camera data receiving device using flexible connecting wires. The magnetic field vector elements X and Y are basically perpendicular to the third rotating shaft, with the X element horizontally close to the preset 0-degree orientation of the camera assembly platform. The Z element is approximately in the same direction as the axis of the third rotating shaft.

[0018] Rotate the first and second shafts separately or alternately to minimize the change in the magnitude of the magnetic field vector obtained by the magnetic vector element. At this point, the vector magnitude should be constant regardless of the position of the third shaft. If the magnetic field vector element X is completely perpendicular to the third shaft, the vector magnitude should be 0. If the angle γ1 between the magnetic vector element and the plane perpendicular to the third shaft is not zero, the vector magnitude should be positive or negative, but without change. Fix the first shaft and record the orientation of the second shaft. The axis of the third shaft should then be the direction of the total magnetic field vector.

[0019] Rotate the second axis so that the third axis is vertically downward. Turn on the power to the VCSEL laser point source board, so that the laser from the third axis is projected onto the light source board. With the camera assembly platform horizontal, adjust the horizontal position of the VCSEL laser point source board through image data processing of camera #1, so that the image of the VCSEL laser point source and the laser projection point of the third axis coincide on a vertical line. At this time, record the angular orientation of the third axis as 0 degrees.

[0020] Rotate the second axis so that the axis of the third axis is aligned with the total magnetic field vector. Adjust the unidirectional orientation of the magnetic field vector X element so that the magnitude of the X element vector tends to 0 at any position of the third axis. Similarly, adjust the unidirectional orientation of the magnetic field vector Y element so that the magnitude of the Y element vector tends to 0 at any position of the third axis. At this point, the directions of the magnetic field vectors X and Y elements should be in the same plane perpendicular to the axis of rotation of the third axis, but the angle between them is not necessarily perfectly orthogonal.

[0021] By observing the data from the angle sensor, the second shaft is rotated 90 degrees, and then the third shaft is rotated so that the direction of the magnetic field vector X element is close to the axis of the second shaft. At this point, the third shaft is slightly moved, and the data of the magnetic field vector X element is observed. When the data approaches 0, there are two positions where the third shaft is rotated, approximately 90 degrees or 270 degrees. The accurate angle of the positive direction of the magnetic field vector X element, marked in one of these positions, is subtracted from 90 or 270 degrees to obtain the data ψ3. After the adjustment in the previous step, the θ3 data of the magnetic field vector X element can now be recorded as 0.

[0022] Rotate the third axis to bring the direction of the magnetic field vector Y element close to the axis of the second axis. Then, slightly move the third axis and observe the data of the magnetic field vector Y element. When the data approaches 0, there are two positions when rotating the third axis: approximately 0 degrees or 180 degrees. Subtract the accurate angle of the positive direction of the magnetic field vector Y element (marked in one of these positions) from 0 or 180 degrees to obtain the data ψ4. At this point, the θ4 data of the magnetic field vector Y element can be recorded as 0.

[0023] Rotate the third axis back to the initial 0-degree orientation. Based on the data recorded from the second axis, rotate the second axis until the third axis is perpendicular to the magnetic field direction, and record the orientation of the second axis. At this point, the magnetic field vector Y element is approximately perpendicular to the magnetic field direction. Slightly move the second axis and observe the data of the magnetic field vector Z element. Stop when the data approaches 0. Record the difference between the orientation of the second axis at this point and the previously recorded orientation as θ. zx, Rotate the third axis to a 90-degree position relative to the initial setting. Similarly, based on the data recorded from the second axis, rotate the second axis until the third axis is perpendicular to the magnetic field direction, and record the orientation of the second axis. Then, slightly move the second axis again and observe the magnetic field vector Z element data. Stop when the data approaches 0. Record the difference between the orientation of the second axis at this point and the previously recorded orientation as θ. zy .

[0024] It can be concluded that: because so θ zx The angle (in radians) between the direction of the vector Z element and the YZ plane is relatively small, generally -2 to +2°. θ zy The angle (in radians) between the direction of the vector Z element and the XZ plane is relatively small, generally -2 to +2°.

[0025] The camera component position correction method is as follows: Since the camera assembly consists of multiple cameras arranged in a circle, each camera is located on one side of the center point. The virtual focus of the camera does not coincide with the center point, and the distance is about 5 to 10 cm. In actual work, the target point of VCSEL is generally hundreds of meters away, so the resulting viewing angle error can be ignored. During calibration testing, the VCSEL laser point source board is located at a distance of 5 m or other slightly farther from the camera, and the resulting viewing angle error will affect the calibration accuracy.

[0026] Let the camera's virtual focus be at point A, and the VCSEL laser point source board be at point B. OB = r, representing the distance from the laser point source board to the axis, and OA = x, representing the distance from the lens's virtual focus to the axis. After the lens rotates around its axis by an angle β2, due to the lens being relatively forward, the angle it receives is α2, which is greater than β2. α2 varies depending on x, r, and β2. Draw an auxiliary line OF∥AB, extending downwards from B to intersect at point C, where ∠OCB = 90°.

[0027] so: After conversion: When calibrating the camera, the angle data recorded for the orientation of the third axis should be solved to obtain α2 using the above formula. The angle data obtained from the preliminary calculation based on geometric relationships in the vertical direction of the VCSEL laser point source board should also be processed in the same way.

[0028] In the above formula, The angle of view or camera line of sight (in radians) after α2 correction, ranging from -33 to +33°; β2 axis line of sight angle (radians), range -33 to +33°; x. Distance from the virtual focus of the lens to the axis (m); r measures the distance (m) from the laser point source plate to the axis.

[0029] The steps for image distortion correction are as follows: Camera image sensors are generally planar. Internally, the sensor and lens form a triangular geometry. The camera records the angle values ​​of its external pixel positions linearly, meaning the pixel position and the external field of view are not perfectly linearly correlated, with differences between the image center and edges. Ideally, the pixel position could be directly calculated as the viewing angle using analytical formulas, providing the tilt and angle of the light source relative to the camera. However, absolutely precise camera mounting is impossible; nonlinear distortion of the camera lens prevents analytical formulas from achieving the required accuracy; and even within the same batch of cameras, there are slight differences in lens focal length during installation. Therefore, each camera image needs to be calibrated. This system uses a dedicated test bench and a test laser point source board to simulate actual working conditions, combining the orientation of the magnetic three-component elements with the camera orientation, thus integrating the calibrated camera image light point position angle with the magnetic three-component element orientation angle.

[0030] In the above magnetic vector element calibration, the position of the VCSEL laser point source board was adjusted by processing the image data of camera #1 so that the image of the VCSEL laser point source and the laser projection point of the third rotating axis coincided on a vertical line, and the angular orientation of the third rotating axis was recorded as 0 degrees, and the third rotating axis was adjusted to be perpendicular to the horizontal plane.

[0031] At this point, adjust the vertical position of the VCSEL laser point source board so that the viewing axis of camera #1 is aligned with the height of the center spot of the VCSEL laser point source board. Since the installation position of the camera assembly is difficult to measure precisely, other leveling instruments can be used to calibrate the VCSEL laser point source boards at different distances.

[0032] Rotate the third axis sequentially at certain angular intervals (1-2 degrees is preferred), with the VCSEL laser point source and camera lighting up and off synchronously. Acquire two frames of image data, similar to actual operation, until more than one revolution is achieved. At each position, record the tilt angle and the tilt angle of the light spot relative to the rotation center from different positions above and below the VCSEL laser point source board. Correct both data using the β2 to α2 conversion method. Record the test data for all cameras as L1 and H1.

[0033] First, determine the camera's focal length: Solve for the equivalent focal length: The ideal viewpoint to pixel conversion problem is solved to obtain the theoretical pixel light spot's horizontal and numerical position: Using all L1 and H1 data within the camera's field of view as grid nodes, and the difference between their respective L1 and H1 and L0 and H0 data as the grid node elevation, representing the correction amount for each node, a new grid file q is regenerated using the grid kriging method. L (i,j), q H (i,j). q L q represents the new left-right direction correction. H This represents the new vertical correction amount. The numbers i and j in parentheses indicate integer pixel positions; i values ​​increase from left to right, and j values ​​increase from top to bottom. The L1 and H1 data grid group nodes are not complete squares, and the L1 and H1 data values ​​are not integers. The new grid file nodes, however, are complete squares, with integer coordinate values, and the square side length K... n Values ​​range from 10 to 40.

[0034] Let L2 and H2 be the initial positions of any image light spots obtained during the second verification or normal operation. Project them onto the grid file represented by the new integer nodes and solve for the positions represented by L2 and H2 in the new grid coordinates.

[0035] New left and right direction correction mesh file q L In (i,j), the grid nodes around the projection point, from left to right and from top to bottom, can be represented as q. L (i,j), q L (i+1,j), q L (i,j+1),q L (i+1,j+1).

[0036] Solve for the horizontal correction value at the initial position of any image spot obtained during normal operation: Similarly, the vertically corrected mesh file q H In (i,j), the grid nodes around the projection point can be represented as q from left to right and from top to bottom. H (i,j), q H (i+1,j), q H (i,j+1),q H (i+1,j+1).

[0037] Solve for the vertical correction at the initial position of any image spot obtained during normal operation: New horizontal and vertical corrected mesh file q L(i,j), q H In (i,j), the diagonal method should be used to check the accuracy: If δ L δ H If the pixel spacing is greater than 0.05, the square side length K should be adjusted. n The value is reduced, and the grid data is encrypted. If the grid data accuracy meets the requirements, the corrected spot position data can be obtained directly by subtracting the correction amount from the initial position data obtained from the inter-frame difference. Based on the inverse calculation from the ideal viewpoint to the pixel, the orientation data of the pixel light point is obtained: Cameras at different positions convert α4 data into azimuth angle ψ based on adjacent accurate angles obtained from the calibration, while tilt angle data θ can be directly obtained from β4 data.

[0038] In the above formula, f-camera lens focal length (mm); The horizontal dimensions (mm) of the L2 image sensor; θ w The horizontal field of view (in radians) of the camera is generally 64° when there are 6 cameras. f' Camera equivalent focal length; N w The number of pixels in the horizontal direction of the camera image can be set to 1280; M w The horizontal dimension (mm) of the camera's image sensor; The ideal angle (in radians) of the light spot in the horizontal or left-right direction of the α3 camera ranges from -33 to +33°. The ideal angle (in radians) of the light spot in the vertical or up-down direction of the β3 camera ranges from -20 to +20°. L0 is the theoretical position of the pixel spot in the horizontal or left-right direction under α3 and β3 conditions; H0 is the theoretical vertical or up-down position of the pixel light spot under α3 and β3 conditions; L1 calibration tests the position of the pixel spot in the horizontal or left-right direction; H2 correction test pixel spot position in the vertical or up-down direction; q L(i,j) Correction amount for the complete grid, correcting the file data in the left and right directions; q H (I,j) Correction amount for the complete grid, adjusting the file data, numerical direction; K n The spacing between data squares; The initial position of the pixel spot in the horizontal or left-right direction during actual operation; The initial position of the pixel light spot in the vertical or up-down direction during actual operation of H2; W L The proportion of the horizontal position of the pixel light spot within the complete grid during actual operation; W H The vertical position and proportion of the pixel light spot within the complete grid during actual operation; L3 is the amount of correction for the pixel light spot in the horizontal or left-right direction during actual operation; The vertical or up-down correction amount of the pixel light spot during actual operation of H3; δ L The correction coefficient in the horizontal or left-right direction; δ H The correction coefficient in the vertical or up-down direction; The horizontal or left-right position of the pixel spot after L4 compensation correction; The vertical or up-down position of the pixel spot after H4 compensation correction; The angle (in radians) of the light spot in the horizontal or left-right direction of the camera after α4 correction, ranging from -33 to +33°; The vertical or up-down angle (in radians) of the camera after β4 correction, ranging from -20 to +20°.

[0039] Due to the adoption of the above technical solution, compared with the prior art, the advantages of the present invention are as follows: The present invention discloses a calibration test device and calibration test method for a low-altitude optical attitude-determining three-component magnetic measurement system. It is a device and method for calibrating and testing a low-altitude optical attitude-determining three-component magnetic measurement system. The calibration test device of the present invention includes a calibration test platform and a VCSEL laser point source board. The calibration test platform is installed on an aircraft and cooperates with the VCSEL laser point source board to acquire test data of the magnetic vector elements and camera in the aircraft. Based on the above detection data and the precise data of the calibration test device, calculations and calibrations are performed to achieve calibration testing of the magnetic vector elements and camera on the aircraft and obtain higher measurement accuracy, thereby significantly improving the measurement accuracy of the low-altitude optical attitude-determining three-component magnetic measurement system.

[0040] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0041] Appendix Figure 1 This is a schematic diagram of the aircraft structure in the low-altitude optical attitude determination three-component magnetic measurement system corrected by the present invention.

[0042] Appendix Figure 2 This is a schematic diagram of the installation structure of the camera component in the aircraft in the low-altitude optical attitude determination three-component magnetic measurement system corrected by the present invention.

[0043] Appendix Figure 3 This is a schematic diagram of the structure of the low-altitude optical attitude determination three-component magnetometry system calibration test device of the present invention, which is equipped with a camera component in an aircraft for calibration testing.

[0044] Appendix Figure 4 This is a schematic diagram of the calibration test bench in this invention.

[0045] Appendix Figure 5 This is a simulation calculation diagram of the magnetic vector element correction in this invention.

[0046] Appendix Figure 6 This refers to the magnetic vector values ​​at different angles α1 in this invention.

[0047] Appendix Figure 7 This refers to the magnetic vector values ​​at different angles γ1 in this invention.

[0048] Appendix Figure 8 This is a diagram showing the viewing angle deviation caused by the eccentricity of the camera focus position in this invention.

[0049] In the attached diagram: 1. Aircraft; 2. Camera; 3. Calibration test stand; 4. VCSEL laser point source board; 5. Base platform; 6. Support leg; 51. Upper base platform; 52. Lower base platform; 7. Leveling device; 8. First leveling device; 9. First rotating shaft; 91. Rotating shaft hole; 10. Second rotating shaft; 11. Third rotating shaft; 12. Second leveling device; 13. Laser point source; 14. Connecting structure. Detailed Implementation

[0050] Example 1: As shown in the attached document Figure 1 To be continued Figure 4As shown, the calibration and testing device for a low-altitude optical attitude-fixing three-component magnetic measurement system includes a calibration test platform 3 and a VCSEL laser point source plate 4. The calibration test platform 3 includes a base platform 5 and support legs 6. The base platform 5 includes an upper base platform 51 and a lower base platform 52. Support legs 6 are installed on the lower part of the lower base platform 52. A leveling device 7 is installed between the upper base platform 51 and the lower base platform 52. A first leveling device 8 is installed on the upper base platform 51. A first rotating shaft 9 is rotatably installed in the middle of the upper base platform 51. The first rotating shaft 9 is installed perpendicular to the upper base platform 51 and has two... A symmetrically arranged pivot hole 91 houses a second pivot 10, orthogonal to the first pivot 9, which is rotatably mounted within the two pivot holes 91. A third pivot 11, orthogonal to the second pivot 10, is rotatably mounted at the center of the second pivot 10. A second leveling device 12 is mounted on the upper surface of the third pivot 11, and a laser point light source 13 is mounted on the side of the third pivot 11. The laser beam direction of the laser point light source 13 is perpendicular to the second pivot 10. The third pivot 11 has a connecting structure 14. Angle sensors are respectively provided on the first pivot 9, the second pivot 10, and the third pivot 11. (Angle sensors are not shown in the attached figure.) Figure 3 As shown, the calibration test stand 3 and the VCSEL laser point source board 4 of this application are arranged opposite each other, several meters apart. The aircraft 1 can be detachably installed on the calibration test stand 3 via the connection structure 14 to calibrate and test the camera 2 and magnetic vector element on the aircraft 1. The magnetic vector element installed inside the aircraft is not shown in the figure. The connection structure 14 is a conventionally used threaded connection, which is also the connection scheme used on the aircraft 1.

[0051] In this embodiment, the first rotating shaft 9 and the third rotating shaft 11 are arranged with their axes coinciding in a perpendicular state.

[0052] In this embodiment, the aircraft 1 includes a VCSEL laser point source, a magnetic vector element, and a camera assembly. After the aircraft is installed on the calibration test bench via a connecting structure, the camera assembly is set at the same height as the center of the VCSEL laser point source plate 4.

[0053] In this embodiment, the connecting structure 14 is used to connect the magnetic vector element of the aircraft 1 to the camera assembly, which consists of several cameras 2. The calibration test bench 3 is made of non-magnetic material. The base platform 5 is fixed by the support legs 6 and leveled by the first leveling device 8, so that the axis of the first rotating shaft 9 is perpendicular to the horizontal plane. A second rotating shaft 10 is installed on the upper part of the first rotating shaft 9 in a direction orthogonal to it, and the axis of the second rotating shaft 10 is parallel to the horizontal plane. A third rotating shaft 11 is installed in the middle of the second rotating shaft 10 in a direction orthogonal to it. The rotation of the first rotating shaft 9, the second rotating shaft 10, and the third rotating shaft 11 is recorded using angle sensors.

[0054] Example 2: Calibration test method for a calibration test device for a low-altitude optical attitude determination three-component magnetic measurement system. The aircraft 1 in the low-altitude optical attitude determination three-component magnetic measurement system is fixedly installed on the connection structure 14 of the calibration test device for the low-altitude optical attitude determination three-component magnetic measurement system in Example 1. The aircraft 1 has magnetic vector elements and camera components. The calibration test method for the aircraft 1 includes magnetic vector element calibration calculation, magnetic vector element orthogonality adjustment test, camera component position calibration, and image distortion correction.

[0055] The calculation method for magnetic vector element correction is as follows: See appendix Figure 5 As shown, the magnetic vector element calibration calculation is performed. The angle between the third rotating shaft 11 and the magnetic field direction is defined as α1, and the angles at different positions of the third rotating shaft 11 are defined as β1. The magnetic vector element is mounted on the third rotating shaft 11, and the two are installed nearly perpendicularly. Due to installation errors, the small angle between the magnetic vector element and the plane perpendicular to the third rotating shaft 11 is defined as γ1. When the third rotating shaft 11 rotates, the magnetic field vector magnitude measured by the magnetic vector element is: In the above formula, The angle (in radians) between the direction of the α1 magnetic field and the third rotating axis 11 has a range of 0 to +90°. The angle (radians) of the third rotating axis 11 at different positions of β1 itself, ranging from 0 to +360°; The angle (in radians) between the γ1 magnetic vector element and the perpendicular plane of the relative rotating third axis 11, ranging from 0 to +90°; T0 is the total field modulus of the magnetic field (nT). The value (nT) obtained by measuring the magnetic vector element at different angles.

[0056] Figure 6 The diagram shows the situation where the angle γ1 between the magnetic vector element and the plane perpendicular to the third rotating shaft 11 is fixed at 0.05 degrees, while the angle α1 between the third rotating shaft 11 and the direction of the magnetic field is different. When α1 is 0 degrees, the magnetic vector value is constant regardless of the rotation angle β1, even when the magnetic vector element itself is not perfectly calibrated. When the angle α1 is different, the magnetic vector value exhibits a sinusoidal fluctuation, with the fluctuation amplitude increasing as the angle α1 increases.

[0057] Figure 7 The diagram shows the situation where the angle α1 between the magnetic vector element and the vertical plane relative to the third rotating shaft 11 is fixed at 0.05 degrees, and the angle γ1 between the third rotating shaft 11 and the direction of the magnetic field is different. When γ1 is 0 degrees, the magnetic vector value exhibits a sinusoidal fluctuation state, and the amplitude of the positive and negative half-cycles of the fluctuation is the same. As the angle γ1 increases, the difference between the positive and negative half-cycles of the fluctuation amplitude increases.

[0058] The test steps for adjusting the orthogonality of magnetic vector elements are as follows: like Figure 3 As shown, in a non-magnetic laboratory or an outdoor location with a small magnetic field gradient, fix and level the platform. Set up the VCSEL laser point source plate 4 at a distance of 5 meters or more, ensuring that the light source points are vertical from top to bottom. The laser point source plate 4 also serves as a marker board. Turn on the laser point source 13 installed on one side of the third rotating shaft 11, projecting it onto the laser point source plate 4 and record the position. Then, rotate both the first rotating shaft 9 and the second rotating shaft 10 by 180 degrees. At this point, the laser point should be projected onto the same position.

[0059] This step only checks and records the orthogonality of each component of the magnetic vector. The zero-point deviation and nonlinear error of the magnetic vector components should be checked and recorded in the laboratory beforehand, and correction formulas should be provided. If the calibration is performed outdoors, another magnetic vector measuring instrument should be used simultaneously to observe the diurnal variation of the magnetic field vector, record the diurnal variation data, and correct the calibration parameters in a timely manner, adjusting the angles of the first rotating shaft 9 and the second rotating shaft 10 as needed.

[0060] In aircraft 1, the magnetic vector element and camera assembly are rigidly connected as a single unit, with the line of sight of camera #1 in the camera assembly essentially aligned with the positive direction of the magnetic field vector X element. The magnetic vector element and camera assembly are mounted on the rotating body of the third rotating shaft 11 via fastening fittings and a connection structure 14, and are connected to the magnetic vector host and camera data receiving device using flexible cables. The magnetic field vector X and Y elements are essentially perpendicular to the third rotating shaft, with the X element positioned horizontally close to the preset 0-degree orientation of the camera assembly platform. The Z element is approximately aligned with the axial direction of the third rotating shaft 11.

[0061] Rotate the first shaft 9 and the second shaft 10 respectively, or alternately, to minimize the change in the magnitude of the magnetic field vector obtained by the magnetic vector element. At this point, the vector magnitude should be constant regardless of the position of the third shaft 11. If the magnetic field vector element X is completely perpendicular to the third shaft 11, the vector magnitude should be 0. If the angle γ1 between the magnetic vector element and the plane perpendicular to the third shaft 11 is not 0, the vector magnitude should be positive or negative, but without change. Fix the first shaft 9 and record the orientation of the second shaft 10. At this point, the axis of the third shaft 11 should be the direction of the total magnetic field vector.

[0062] Rotate the second shaft 10 so that the third shaft 11 is vertically downward. Turn on the power to the VCSEL laser point source board 4 so that the laser from the third shaft 11 is projected onto the VCSEL laser point source board 4. With the camera assembly platform horizontal, adjust the horizontal position of the VCSEL laser point source board 4 through image data processing of camera #1 so that the image of the VCSEL laser point source on aircraft 1 and the laser projection point of the third shaft 11 coincide on a vertical line. At this time, record the angular orientation of the third shaft 11 as 0 degrees.

[0063] Rotate the second shaft 10 so that the axis of the third shaft 11 is aligned with the total magnetic field vector. Adjust the unidirectional orientation of the magnetic field vector X element so that the magnitude of the X element vector tends to 0 at any position of the third shaft 11. Similarly, adjust the unidirectional orientation of the magnetic field vector Y element so that the magnitude of the Y element vector tends to 0 at any position of the third shaft 11. At this point, the directions of the magnetic field vectors X and Y should be in the same plane perpendicular to the axis of rotation of the third shaft 11, but the angle between them is not necessarily perfectly orthogonal.

[0064] By observing the data from the angle sensor, the second rotating shaft 10 is rotated 90 degrees, and then the third rotating shaft 11 is rotated so that the direction of the magnetic field vector X element is close to the axial direction of the second rotating shaft 10. At this time, the third rotating shaft 11 is slightly moved, and the data of the magnetic field vector X element is observed. When the data approaches 0, there are two positions when the third rotating shaft 11 is rotated, approximately 90 degrees or 270 degrees. The accurate angle of the positive direction of the magnetic field vector X element marked in one of these positions is subtracted from 90 or 270 degrees to obtain the data ψ3. After the adjustment in the previous step, the θ3 data of the magnetic field vector X element can be recorded as 0.

[0065] Rotate the third shaft 11 so that the direction of the magnetic field vector Y element is close to the axis of the second shaft 10. At this time, slightly move the third shaft 11 and observe the data of the magnetic field vector Y element. When the data approaches 0, there are two positions when rotating the third shaft, approximately 0 degrees or 180 degrees. Subtract the accurate angle of the positive direction of the magnetic field vector Y element marked by one of these positions from 0 or 180 degrees to obtain the data ψ4. At this time, the θ4 data of the magnetic field vector Y element can be recorded as 0.

[0066] Rotate the third axis 11 back to the initial 0-degree orientation. Based on the data recorded from the second axis 10, rotate the second axis 10 until the third axis 11 is perpendicular to the magnetic field direction, and record the orientation of the second axis 10. At this point, the magnetic field vector Y element is approximately perpendicular to the magnetic field direction. Slightly move the second axis 10 and observe the data of the magnetic field vector Z element. Stop when the data approaches 0. Record the difference between the orientation of the second axis 10 at this point and the previously recorded orientation as θ. zx,Rotate the third axis 11 to a 90-degree position relative to the initial setting. Similarly, based on the data recorded from the second axis 10, rotate the second axis 10 until the third axis 11 is perpendicular to the magnetic field direction, and record the orientation of the second axis 10. Then, slightly move the second axis 10 again and observe the magnetic field vector Z element data. Stop when the data approaches 0. The difference between the orientation of the second axis 10 at this point and the previously recorded orientation is recorded as θ. zy .

[0067] It can be concluded that: because so θ zx The angle (in radians) between the direction of the vector Z element and the YZ plane is relatively small, generally -2 to +2°. θ zy The angle (in radians) between the direction of the vector Z element and the XZ plane is relatively small, generally -2 to +2°.

[0068] The camera component position correction method is as follows: Since the camera assembly consists of multiple cameras 2 arranged in a circle, each camera 2 is located on one side of the center point. The virtual focus of the camera 2 does not coincide with the center point, and the distance is about 5 to 10 cm. In actual work, the target point of VCSEL is generally hundreds of meters away, so the resulting viewing angle error can be ignored. During the calibration test, the VCSEL laser point source board 4 is located at a distance of 5 m or other slightly farther from the camera 2, and the resulting viewing angle error will affect the calibration accuracy.

[0069] like Figure 8 As shown, the virtual focus of camera 2 is located at point A, and the VCSEL laser point source plate 4 is located at point B. OB = r, which is the distance from the laser point source plate 4 to the axis. OA = x, which is the distance from the lens's virtual focus to the axis. After the lens rotates around the axis by an angle β2, because the lens is relatively forward, the angle it receives is α2, which is greater than β2. α2 varies depending on x, r, and β2. Draw an auxiliary line OF∥AB, extending downwards from B to intersect at point C, where ∠OCB = 90°.

[0070] so: After conversion: When calibrating camera 2, the angle data recorded for the orientation of the third rotating axis 11 should be solved for α2 according to the above formula. The angle data obtained from the preliminary calculation based on geometric relationships in the vertical direction of VCSEL laser point source plate 4 should also be processed in the same way.

[0071] The angle of view or camera line of sight (in radians) after α2 correction, ranging from -33 to +33°; β2 axis line of sight angle (radians), range -33 to +33°; x. Distance from the virtual focus of the lens to the axis (m); r measures the distance (m) from the laser point source plate to the axis.

[0072] The steps for image distortion correction are as follows: Camera image sensors are generally planar. Inside the camera, the sensor and lens form a triangular geometry. Since the camera records the angle values ​​of its external pixel positions linearly, the relationship between camera pixels and the external field of view is not perfectly linear, with differences between the image center and edges. Ideally, the pixel position could be directly calculated as the viewing angle using analytical formulas, providing the tilt and inclination data of the light source relative to the camera. However, due to the impossibility of absolutely accurate camera installation, the nonlinear distortion of the camera lens, and the slight differences in lens focal length even within the same batch of cameras, each camera image needs to be calibrated. This system uses a dedicated test bench and a test laser point source board to simulate actual working conditions, combining the orientation of the magnetic three-component elements with the camera orientation. This integrates the calibrated camera image light point position angle with the magnetic three-component element orientation angle.

[0073] In the above magnetic vector element correction, the position of VCSEL laser point source board 4 has been adjusted by image data processing of camera #1 so that the image of the VCSEL laser point source on aircraft 1 coincides with the laser projection point of the third rotating axis 11 on a vertical line, and the angular orientation of the third rotating axis is recorded as 0 degrees, and the third rotating axis 11 is adjusted to be perpendicular to the horizontal plane.

[0074] At this point, adjust the vertical position of the VCSEL laser point source plate 4 so that the viewing axis of camera #1 is aligned with the height of the center spot of the VCSEL laser point source plate 4. Since the installation position of the camera assembly is not easy to measure precisely, other leveling instruments can be used to calibrate the VCSEL laser point source plate 4 at different distances.

[0075] The third axis is rotated sequentially at certain angular intervals (1-2 degrees). The VCSEL laser point source of aircraft 1 illuminates and extinguishes synchronously with the camera, acquiring two frames of image data as in actual operation. This process is repeated until more than one revolution is completed. At each position, the tilt angle and the tilt angle of the light spot relative to the rotation center at different positions above and below the VCSEL laser point source plate are recorded. Both data are corrected using the β2 to α2 conversion method. The test data for all cameras are recorded as L1 and H1.

[0076] First, determine the camera's focal length: Solve for the equivalent focal length: The ideal viewpoint to pixel conversion problem is solved to obtain the theoretical pixel light spot's horizontal and numerical position: Using all L1 and H1 data within the field of view of camera 2 as grid nodes, and the difference between their respective L1 and H1 and L0 and H0 data as the grid node elevation, representing the correction amount for each node, a new grid file q is regenerated using the grid kriging method. L (i,j), q H (i,j). q L q represents the new left-right direction correction. H This represents the new vertical correction amount. The numbers i and j in parentheses indicate integer pixel positions; i values ​​increase from left to right, and j values ​​increase from top to bottom. The L1 and H1 data grid group nodes are not complete squares, and the L1 and H1 data values ​​are not integers. The new grid file nodes, however, are complete squares, and the grid file node coordinates are rounded down. The square side length K... n Values ​​range from 10 to 40.

[0077] Let L2 and H2 be the initial positions of any image light spots obtained during the second verification or normal operation. Project them onto the grid file represented by the new integer nodes and solve for the positions represented by L2 and H2 in the new grid coordinates.

[0078] New left and right direction correction mesh file q L In (i,j), the grid nodes around the projection point, from left to right and from top to bottom, can be represented as q. L (i,j), q L (i+1,j), q L (i,j+1),qL (i+1,j+1).

[0079] Solve for the horizontal correction value at the initial position of any image spot obtained during normal operation: Similarly, the vertically corrected mesh file q H In (i,j), the grid nodes around the projection point can be represented as q from left to right and from top to bottom. H (i,j), q H (i+1,j), q H (i,j+1),q H (i+1,j+1).

[0080] Solve for the vertical correction at the initial position of any image spot obtained during normal operation: New horizontal and vertical corrected mesh file q L (i,j), q H In (i,j), the diagonal method should be used to check the accuracy: If δ L δ H If the pixel spacing is greater than 0.05, the square side length K should be adjusted. n The value is reduced, and the grid data is encrypted. If the grid data accuracy meets the requirements, the corrected spot position data can be obtained directly by subtracting the correction amount from the initial position data obtained from the inter-frame difference. Based on the inverse calculation from the ideal viewpoint to the pixel, the orientation data of the pixel light point is obtained: Cameras at different positions convert α4 data into azimuth angle ψ based on adjacent accurate angles obtained from the calibration, while tilt angle data θ can be directly obtained from β4 data.

[0081] In the above formula, f-camera lens focal length (mm); The horizontal dimensions (mm) of the L2 image sensor; θ w The horizontal field of view (in radians) of the camera is generally 64° when there are 6 cameras. f' Camera equivalent focal length; N w The number of pixels in the horizontal direction of the camera image can be set to 1280; M w The horizontal dimension (mm) of the camera's image sensor; The ideal angle (in radians) of the light spot in the horizontal or left-right direction of the α3 camera ranges from -33 to +33°. The ideal angle (in radians) of the light spot in the vertical or up-down direction of the β3 camera ranges from -20 to +20°. L0 is the theoretical position of the pixel spot in the horizontal or left-right direction under α3 and β3 conditions; H0 is the theoretical vertical or up-down position of the pixel light spot under α3 and β3 conditions; L1 calibration tests the position of the pixel spot in the horizontal or left-right direction; H2 correction test pixel spot position in the vertical or up-down direction; q L (i,j) Correction amount for the complete grid, correcting the file data in the left and right directions; q H (I,j) Correction amount for the complete grid, adjusting the file data, numerical direction; K n The spacing between data squares; The initial position of the pixel spot in the horizontal or left-right direction during actual operation; The initial position of the pixel light spot in the vertical or up-down direction during actual operation of H2; W L The proportion of the horizontal position of the pixel light spot within the complete grid during actual operation; W H The vertical position and proportion of the pixel light spot within the complete grid during actual operation; L3 is the amount of correction for the pixel light spot in the horizontal or left-right direction during actual operation; The vertical or up-down correction amount of the pixel light spot during actual operation of H3; δ L The correction coefficient in the horizontal or left-right direction; δ H The correction coefficient in the vertical or up-down direction; The horizontal or left-right position of the pixel spot after L4 compensation correction; The vertical or up-down position of the pixel spot after H4 compensation correction; The angle (in radians) of the light spot in the horizontal or left-right direction of the camera after α4 correction, ranging from -33 to +33°; The vertical or up-down angle (in radians) of the camera after β4 correction, ranging from -20 to +20°.

[0082] After the above calibration tests, the calibration test bench, in conjunction with the VCSEL laser point source board, acquires test data of the magnetic vector components and cameras in the aircraft. Based on the aforementioned test data and the precise data from this calibration test device, calculations and calibrations are performed to achieve the calibration test of the magnetic vector components and cameras on the aircraft and obtain higher measurement accuracy. It should be noted that the low-altitude optical attitude determination three-component magnetic measurement system of this invention has been patented, published, and granted authorization; its system composition and magnetic measurement method are existing publicly available technologies.

Claims

1. A calibration and testing device for a low-altitude optical attitude determination three-component magnetic measurement system, characterized in that: The system includes a calibration test stand and a VCSEL laser point source board. The calibration test stand includes a base platform and legs. The base platform includes an upper base platform and a lower base platform. The legs are installed on the lower part of the lower base platform. A leveling device is installed between the upper and lower base platforms. A first rotating shaft is rotatably installed in the middle of the upper base platform. The first rotating shaft is installed perpendicular to the upper base platform. The side wall of the first rotating shaft has two symmetrically arranged rotating shaft holes. A second rotating shaft orthogonal to the first rotating shaft is rotatably installed in the two rotating shaft holes. A third rotating shaft orthogonal to the second rotating shaft is rotatably installed in the middle of the second rotating shaft. A laser point source is installed on the side of the third rotating shaft. The laser beam direction of the laser point source is perpendicular to the second rotating shaft. The third rotating shaft has a connection structure for connecting to the aircraft in the low-altitude optical attitude determination three-component magnetometry system. Angle sensors are respectively installed on the first, second, and third rotating shafts.

2. The calibration and testing device for the low-altitude optical attitude determination three-component magnetometry system according to claim 1, characterized in that: The first and third rotating shafts are arranged with their axes coinciding in a perpendicular state.

3. The calibration and testing device for the low-altitude optical attitude determination three-component magnetometry system according to claim 1, characterized in that: A first leveling device is installed on the upper foundation platform, and a second leveling device is installed on the upper surface of the third rotating shaft.

4. The calibration and testing device for the low-altitude optical attitude determination three-component magnetometry system according to claim 1, characterized in that: The aircraft includes a magnetic vector element and a camera assembly. After the aircraft is installed on the calibration test bench via a connecting structure, the camera assembly is set at the same height as the center of the VCSEL laser point source board.

5. A calibration and testing method for a low-altitude optical attitude determination three-component magnetic measurement system calibration and testing device, characterized in that: The aircraft in the low-altitude optical attitude determination three-component magnetic measurement system is fixedly installed on the connection structure of the low-altitude optical attitude determination three-component magnetic measurement system calibration test device as described in claim 1. The aircraft has magnetic vector elements and camera components. The method for calibrating and testing the aircraft includes magnetic vector element calibration calculation, magnetic vector element orthogonality adjustment test, camera component position calibration, and image distortion correction.

6. The calibration and testing method for the low-altitude optical attitude determination three-component magnetometry system calibration and testing device according to claim 5, characterized in that: The magnetic vector element correction calculation method is as follows: The angle between the third rotating shaft and the direction of the magnetic field is defined as α1, and the angles at different positions of the third rotating shaft are defined as β1. The magnetic vector element is mounted on the third rotating shaft, and the two are mounted nearly perpendicularly. The small angle between the magnetic vector element and the plane perpendicular to the third rotating shaft due to installation error is defined as γ1. When the third rotating shaft rotates, the magnitude of the magnetic field vector measured by the magnetic vector element is: The angle γ1 between the magnetic vector element and the vertical plane relative to the third rotation axis is a fixed angle value, and the angle α1 between the magnetic vector element and the vertical plane relative to the third rotation axis is a fixed angle value. In the above formula, The angle (in radians) between the direction of the α1 magnetic field and the third rotation axis ranges from 0 to +90°. The angle (in radians) of the third rotating shaft itself at different positions, ranging from 0 to +360°; The angle (in radians) between the γ1 magnetic vector element and the perpendicular plane of the relative rotating third axis, ranging from 0 to +90°; T0 is the total field modulus of the magnetic field (nT). The value (nT) obtained by measuring the magnetic vector element at different angles.

7. The calibration and testing method for the low-altitude optical attitude determination three-component magnetometry system calibration and testing device according to claim 5, characterized in that: The test steps for adjusting the orthogonality of the magnetic vector elements are as follows: In a non-magnetic laboratory or an outdoor location with a small magnetic field gradient, fix and level the platform, and set up a VCSEL laser point source plate at a distance of 5 meters or more, so that the light source point is vertical from top to bottom. Turn on the laser point light source installed on one side of the third rotating shaft, project it onto the laser point light source board, record the position, and then rotate both the first and second rotating shafts by 180 degrees. At this time, the laser point should be projected to the same position. The magnetic vector element and the camera assembly are rigidly connected together by a rigid rod. The center line of sight of camera #1 in the camera assembly is aligned with the positive direction of the magnetic field vector X element. The magnetic vector element and the camera assembly are mounted on the rotating body of the third rotating shaft through fastening accessories and a connection structure of the third rotating shaft. They are connected to the magnetic vector host and the camera data receiving device using flexible connecting wires. The magnetic field vector X element and Y element are basically perpendicular to the third rotating shaft, with the X element being close to the preset 0-degree orientation of the camera assembly platform in the horizontal direction. The Z element is approximately in the same direction as the axis of the third rotating shaft. Rotate the first and second shafts separately or alternately to minimize the change in the magnitude of the magnetic field vector obtained by the magnetic vector element. At this point, the vector magnitude should be constant regardless of the position of the third shaft. If the magnetic field vector element X is completely perpendicular to the third shaft, the vector magnitude should be 0. If the angle γ1 between the magnetic vector element and the plane perpendicular to the third shaft is not 0, the vector magnitude should be positive or negative, but without change. Fix the first shaft and record the orientation of the second shaft. At this point, the axis of the third shaft should be the direction of the total magnetic field vector. Rotate the second axis so that the third axis is vertically downward; turn on the power of the VCSEL laser point source board so that the laser of the third axis is projected onto the light source board. With the camera assembly platform horizontal, adjust the horizontal position of the VCSEL laser point source board through image data processing of camera #1 so that the image of the VCSEL laser point source and the laser projection point of the third axis coincide on a vertical line. At this time, record the angular orientation of the third axis as 0 degrees. Rotate the second axis so that the axis of the third axis is aligned with the total field vector of the magnetic field; adjust the unidirectional orientation of the magnetic field vector X element so that the vector magnitude of the X element tends to 0 when the third axis is in any position; similarly adjust the unidirectional orientation of the magnetic field vector Y element so that the vector magnitude of the Y element tends to 0 when the third axis is in any position; at this time, the directions of the magnetic field vectors X and Y elements should be in the same plane perpendicular to the axis of rotation of the third axis; By observing the data from the angle sensor, the second shaft is rotated 90 degrees, and then the third shaft is rotated so that the direction of the magnetic field vector X element is close to the axis of the second shaft. At this time, the third shaft is slightly moved, and the data of the magnetic field vector X element is observed. When the data approaches 0, there are two positions when the third shaft is rotated, approximately 90 degrees or 270 degrees. The accurate angle of the positive direction of the magnetic field vector X element marked in one of the steps is subtracted from 90 or 270 degrees to obtain the data ψ3. After the adjustment in the previous step, the θ3 data of the magnetic field vector X element can be recorded as 0. Rotate the third axis to bring the direction of the magnetic field vector Y element close to the axial direction of the second axis. At this time, slightly move the third axis and observe the data of the magnetic field vector Y element. When the data approaches 0, there are two positions when rotating the third axis, approximately 0 degrees or 180 degrees. Subtract the accurate angle of the positive direction of the magnetic field vector Y element marked by one of these positions from 0 or 180 degrees to obtain the data ψ4. At this time, the θ4 data of the magnetic field vector Y element can be recorded as 0. Rotate the third axis back to the initial 0-degree orientation. Based on the data recorded from the second axis, rotate the second axis until the third axis is perpendicular to the magnetic field direction. Record the orientation of the second axis. At this point, the magnetic field vector Y element is approximately perpendicular to the magnetic field direction. Finely move the second axis and observe the data of the magnetic field vector Z element. Stop when the data approaches 0. The difference between the orientation of the second axis at this point and the previously recorded orientation is recorded as θ. zx, Rotate the third axis to a 90-degree position relative to the initial setting. Similarly, based on the data recorded from the second axis, rotate the second axis until the third axis is perpendicular to the magnetic field direction, and record the orientation of the second axis. Then, slightly move the second axis again and observe the magnetic field vector Z element data. Stop when the data approaches 0. Record the difference between the orientation of the second axis at this point and the previously recorded orientation as θ. zy ; Conclusion: because so θ zx The angle (in radians) between the direction of the vector Z element and the YZ plane; θ zy The angle (in radians) between the direction of the vector Z element and the XZ plane.

8. The calibration and testing method of the low-altitude optical attitude determination three-component magnetometry system calibration and testing device according to claim 5, characterized in that: The camera component position correction steps are as follows: Let the camera's virtual focus be at point A, and the VCSEL laser point source board be at point B. OB = r, representing the distance from the laser point source board to the axis; OA = x, representing the distance from the camera lens's virtual focus to the axis. After the lens rotates around the axis by an angle β2, the angle it receives is α2, which is greater than β2. Draw an auxiliary line OF∥AB, extending downwards from B to intersect at point C. ∠OCB = 90°. so: After conversion: When calibrating the camera, the angle data recorded for the orientation of the third rotating axis should be solved for α2 according to the above formula. The angle data obtained from the preliminary calculation based on geometric relationships in the vertical direction of the VCSEL laser point source board should also be processed in the same way. In the above formula, The angle of view or camera line of sight (in radians) after α2 correction, ranging from -33 to +33°; β2 axis line of sight angle (radians), range -33 to +33°; x-distance from the lens virtual focus to the axis (m); r measures the distance (m) from the laser point source plate to the axis.

9. The calibration and testing method of the low-altitude optical attitude determination three-component magnetometry system calibration and testing device according to claim 5, characterized in that: The image distortion correction method is as follows: In the above magnetic vector element correction, the position of the VCSEL laser point source board has been adjusted by processing the image data of camera #1 so that the image of the VCSEL laser point source and the laser projection point of the third rotating axis coincides on a vertical line, and the angular orientation of the third rotating axis is recorded as 0 degrees, and the third rotating axis is adjusted to be perpendicular to the horizontal plane. At this point, adjust the vertical position of the VCSEL laser point source board so that the viewing axis of camera #1 is aligned with the height of the center point of the VCSEL laser point source board. The third axis is rotated sequentially at certain angular intervals, with the VCSEL laser point source and camera lighting up and off synchronously, acquiring two frames of image data. This process is repeated until more than one revolution is completed. At each position, the tilt angle and the tilt angle of the light spot relative to the rotation center at different positions above and below the VCSEL laser point source board are recorded. Both data are corrected using the β2 to α2 conversion method. The test data of all cameras are recorded as L1 and H1. First, determine the camera's focal length: Solve for the equivalent focal length: The ideal viewpoint to pixel conversion problem is solved to obtain the theoretical pixel light spot's horizontal and numerical position: Using all L1 and H1 data within the camera's field of view as grid nodes, and the difference between their respective L1 and H1 and L0 and H0 data as the grid node elevation, representing the correction amount for each node, a new grid file q is regenerated using the grid kriging method. L (i,j), q H (i,j); q L q represents the new left-right direction correction. H This indicates the new vertical correction amount. The i and j values ​​in parentheses represent integer pixel positions. The i value increases from left to right, and the j value increases from top to bottom. Let L2 and H2 be the initial positions of any image spot obtained during the second verification or normal operation. Project them onto the grid file represented by the new integer nodes and solve for the positions represented by L2 and H2 in the new grid coordinates. New left and right direction correction mesh file q L In (i,j), the grid nodes around the projection point, from left to right and from top to bottom, can be represented as q. L (i,j), q L (i+1,j), q L (i,j+1),q L (i+1,j+1); Solve for the horizontal correction value at the initial position of any image spot obtained during normal operation: Similarly, the vertically corrected mesh file q H In (i,j), the grid nodes around the projection point can be represented as q from left to right and from top to bottom. H (i,j), q H (i+1,j), q H (i,j+1),q H (i+1,j+1); Solve for the vertical correction at the initial position of any image spot obtained during normal operation: New horizontal and vertical corrected mesh file q L (i,j), q H In (i,j), the diagonal method should be used to check the accuracy: If δ L δ H If the pixel spacing is greater than 0.05, the square side length K should be adjusted. n The value is reduced, and the grid data is encrypted; if the grid data accuracy meets the requirements, the corrected spot position data can be obtained directly by subtracting the correction amount from the initial position data obtained by inter-frame difference. Based on the inverse calculation from the ideal viewpoint to the pixel, the orientation data of the pixel light point is obtained: Cameras at different positions convert α4 data into azimuth angle ψ based on adjacent accurate angles obtained from the correction, and tilt angle data θ can be directly used from β4 data; In the above formula, f-camera lens focal length (mm); The horizontal dimensions (mm) of the L2 image sensor; θ w The horizontal field of view (in radians) of the camera is generally 64° when there are 6 cameras. f' Camera equivalent focal length; N w The number of pixels in the horizontal direction of the camera image can be set to 1280; M w The horizontal dimension (mm) of the camera's image sensor; The ideal angle (in radians) of the light spot in the horizontal or left-right direction of the α3 camera ranges from -33° to +33°. The ideal angle (in radians) of the light spot in the vertical or up-down direction of the β3 camera ranges from -20 to +20°. L0 is the theoretical position of the pixel spot in the horizontal or left-right direction under α3 and β3 conditions; H0 is the theoretical vertical or up-down position of the pixel light spot under α3 and β3 conditions; L1 calibration tests the position of the pixel spot in the horizontal or left-right direction; H2 correction test pixel spot position in the vertical or up-down direction; q L (i,j) Correction amount for the complete grid, correcting the file data in the left and right directions; q H (I,j) Correction amount for the complete grid, correcting the file data, numerical direction; K n The spacing between data squares; L2 is the initial position of the pixel spot in the horizontal or left-right direction during actual operation; The initial position of the pixel light spot in the vertical or up-down direction during actual operation of H2; W L The proportion of the horizontal position of the pixel light spot within the complete grid during actual operation; W H The vertical position and proportion of the pixel light spot within the complete grid during actual operation; L3 is the amount of correction for the pixel light spot in the horizontal or left-right direction during actual operation; The vertical or up-down correction amount of the pixel light spot during actual operation of H3; δ L The correction coefficient in the horizontal or left-right direction; δ H Vertical or up-down direction correction coefficient; The horizontal or left-right position of the pixel spot after L4 compensation correction; The vertical or up-down position of the pixel spot after H4 compensation correction; The angle (in radians) of the light spot in the horizontal or left-right direction of the camera after α4 correction, ranging from -33 to +33°; The vertical or up-down angle (in radians) of the camera after β4 correction, ranging from -20 to +20°.

Images