A digital calibration device and method for optical axis pointing error

Abstract

The invention discloses a digital calibration device for optical axis pointing errors, comprising a control cabinet, a light source, a platform body fixed on a foundation, and a six-degree-of-freedom swing table for placing optoelectronic devices to be calibrated, wherein a platform frame with an arc-shaped cross section is arranged on the platform body, an array target composed of a plurality of parallel light tubes is arranged on the platform frame, and the center of the arc surface of the platform frame in a horizontal plane is located directly above the center of the table surface of the six-degree-of-freedom swing table; a calibration method thereof is also disclosed; the inertial navigation installation error can be digitally calibrated simultaneously by exciting the six-degree-of-freedom swing table at the aiming target point, thereby improving the calibration efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of optical machinery, and specifically relates to a device and method for digitally calibrating pointing errors of optoelectronic equipment, and is particularly suitable for digitally calibrating pointing errors of optical axes of optical systems with complex optical paths. Background Art

[0002] For multi-channel, common-aperture complex optical path optical systems, the current main assembly and adjustment method is to align each mirror in the optical path through a hexahedron or a plane mirror to draw out the mirror normal, and then align them piece by piece through a theodolite and a collimator to ensure the direction of the optical axis.

[0003] The above-mentioned adjustment method has two obvious shortcomings: on the one hand, the efficiency is low, especially for optical systems containing a large number of reflectors and spectrometers in the optical path; on the other hand, this method can only guarantee the pointing accuracy of the optical axis at a single position (such as the zero position), but cannot guarantee the accuracy for other viewing angles within the field of view.

[0004] To address the above-mentioned problems, digital calibration of optical axis pointing error is an effective method.

[0005] Optical targets as digital calibration benchmarks are the prerequisite for digital calibration of optical axis errors. Currently, digital calibration targets for optical axis pointing errors include celestial collimators, etc. However, celestial collimators are only suitable for periscope optical axis calibration, and cannot meet the calibration requirements for complex two-axis two-frame pointers and complex optical systems. Summary of the invention

[0006] In order to overcome the defects of the existing technology, one of the purposes of the present invention is to provide a digital calibration device for optical axis pointing errors, which can meet the digital calibration of optical axis pointing errors of complex optical systems on the one hand, and the digital calibration of inertial navigation installation errors of strapdown optoelectronic systems on the other hand.

[0007] The technical solution adopted by the present invention to solve its technical problems is: a digital calibration device for optical axis pointing errors, including a control cabinet, a light source, a platform body fixed on a foundation, and a six-degree-of-freedom swing platform for placing optoelectronic equipment to be calibrated, the platform body is provided with a platform with an arc-shaped cross-section, the platform is provided with an array target composed of a plurality of parallel light tubes, and the center of the arc surface of the platform in the horizontal plane is located directly above the center of the table surface of the six-degree-of-freedom swing platform.

[0008] The optical axis pointing error digital calibration device has a collimator which is a reflective card-type collimator with a diameter of 300 mm and a focal length of 1200 mm.

[0009] The optical axis pointing error digital calibration equipment has a table center at a height of 1.5 m from the convergence point of the parallel light of the collimator.

[0010] The optical axis pointing error digital calibration device has a collimator that is tightly fixed to a mounting hole reserved on a stand by means of bolts and pins, and the mounting hole diameters in the azimuth and elevation directions are 380 mm.

[0011] The optical axis pointing error digital calibration equipment is formed by using cast iron in consideration of the stability of the collimator and the accuracy requirements of the deformation.

[0012] The optical axis pointing error digital calibration device has 20 parallel light tubes arranged in 4×5.

[0013] The optical axis pointing error digital calibration device has a platform body and a foundation of a six-degree-of-freedom rocking platform arranged on an external foundation via a vibration isolation belt.

[0014] The second object of the present invention is to provide a calibration method for a digital calibration device for optical axis pointing error, the steps are as follows:

[0015] S1, the premise of digital calibration of optical axis pointing error of optoelectronic system is to establish mathematical model of optical axis pointing with error parameters to be calibrated under geographic system LOS=f(e1,e2,...,e N ,ψ,θ), where e1,e2,...,e N is the optical path error parameter, and its physical meaning and number N vary with the structure of the device to be calibrated. ψ and θ are the azimuth and elevation angles respectively. Then, the optical axis pointing error objective function is established according to the optical axis pointing mathematical model. Where b i is the projection of the parallel light tube target point on the X / Y / Z axis of the geographic system; finally, the objective function A is minimized to obtain the optical axis error parameter vector E[e1,e2,...,e N ];

[0016] S2, use a gyrotheodolite to calibrate the benchmark of the collimator array target (this step needs to be calibrated every six months) to obtain the geographic system azimuth and elevation values ​​of 20 target points;

[0017] S3, placing the optoelectronic device to be calibrated at the center of the table of the six-degree-of-freedom swing table, and adjusting the position of the optoelectronic device to be calibrated on the six-degree-of-freedom swing table so that the imaging sensor of the optoelectronic device to be calibrated is located at the convergence intersection of the parallel light tube array target when in the zero position;

[0018] S4, control the optical axis of the imaging sensor of the optoelectronic device to be calibrated to point to the first collimator No. 1 in the lower left corner as a reference through servo control, and then start the target tracking mode so that the crosshairs of the collimator are located at the center of the image crosshairs;

[0019] S5, setting the rocking center of the six-degree-of-freedom rocking platform to be approximately located at the imaging sensor position of the optoelectronic device to be calibrated, the rocking amplitude to be ±6°, the rocking cycles to be 15s, 12s, and 8s, and then starting the six-degree-of-freedom rocking platform;

[0020] S6, record the azimuth and elevation angle readings of the optoelectronic equipment to be calibrated under different swing attitudes, the inertial navigation attitude data and the true value of the target collimator geographical system, with the amount of data being no less than 10 groups;

[0021] S7, switching the tracking mode to the aiming mode, turning the optical axis of the imaging sensor of the optoelectronic device to be calibrated to point to the collimator of the next target according to the true value of the collimator geographical system, and entering the target tracking mode after the crosshair image of the collimator enters the field of view and is guided by the wave gate, so that the crosshair image of the target is located at the center of the crosshairs of the image;

[0022] S8, repeating steps S6 and S7 until traversing 20 target parallel light tubes;

[0023] S9, bringing the true value of the target collimator geographic system, the angle measurement reading and the inertial navigation attitude data obtained from the test into the optical axis error solution method to perform digital calibration of the error parameters, and output the error parameter fitting results;

[0024] S10, set the original error parameter during the initial calibration to a zero vector, and convert the calibrated error parameter result E[e1,e2,...,e N ] replace the original error parameter E'[e1',e'2,...,e' N ], to correct the optical axis pointing error parameters;

[0025] S11, randomly select three parallel light tubes as target points, turn the optical axis of the imaging sensor of the optoelectronic device to be calibrated to the selected target points, and evaluate the pointing accuracy and stability accuracy;

[0026] S12, turn off the power of the six-degree-of-freedom swing stage and the collimator to complete the calibration.

[0027] In the optical axis pointing error digital calibration device, the optical path error in step S1 includes detector installation error, angular misalignment error between the azimuth axis and the elevation axis, and azimuth or elevation zero position error.

[0028] The beneficial effects of the present invention are:

[0029] 1. The collimator references of the present invention are evenly distributed within the field of view, and can collect optical axis pointing data at different azimuths and elevation angles, thereby improving the accuracy of digital calibration of pointing errors;

[0030] 2. The present invention can digitally calibrate the inertial navigation installation error by exciting the six-degree-of-freedom rocking platform at the aiming target point, thereby improving the calibration efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the working of the system of the present invention;

[0032] Figure 2 It is a structural schematic diagram of the card-type collimator used in the present invention;

[0033] Figure 3 To add a comparison curve of the optical axis pointing error of a certain optoelectronic device before and after calibration.

[0034] The reference numerals of the figures are: 1—stand, 2—collimator, 3—six-degree-of-freedom swing table, 4—photoelectric equipment to be calibrated, 5—foundation, 6—table body, 7—external foundation. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0036] Example 1

[0037] Reference Figure 1 As shown, a digital calibration device for optical axis pointing errors of the present invention comprises a control cabinet, a light source, a platform 6 fixed on a foundation 5, and a six-degree-of-freedom swing table 3 for placing an optoelectronic device 05 to be calibrated, wherein the platform 6 and the foundation 5 of the six-degree-of-freedom swing table 3 are arranged on an external foundation 7 through a vibration isolation belt, and a stand 1 with an arc-shaped cross-section is arranged on the platform 6, and a 4×5 array target composed of 20 parallel light tubes 2 is arranged on the stand 1, and the center of the arc surface of the stand 1 in the horizontal plane is located directly above the center of the table surface of the six-degree-of-freedom swing table 3. The present invention uses the arc center of the stand 1 as the center of the circle to provide a target reference for digital calibration, and the stand 1 realizes the array support of the parallel light tubes 2 and maintains the relative position stability of the light tubes for a long time.

[0038] Reference Figure 2 As shown, the collimator 2 is a reflective card-type collimator with a diameter of 300mm and a focal length of 1200mm; the center of the table is 1.5m away from the convergence point of the collimator 2; the collimator 2 is tightly fixed to the mounting holes reserved on the stand 1 by bolts and pins, and the mounting holes in the azimuth and pitch directions have a diameter of 380mm. Considering the stability and deformation accuracy requirements of the collimator 2, the stand 1 is formed by cast iron processing; and the six-degree-of-freedom swing table 3 provides a swing environment to realize the inertial guidance excitation function.

[0039] Example 2

[0040] The implementation process of the calibration method of the present invention is further described as follows:

[0041] S1, the premise of digital calibration of optical axis pointing error of optoelectronic system is to establish mathematical model of optical axis pointing with error parameters to be calibrated under geographic system LOS=f(e1,e2,...,e N ,ψ,θ), where e1,e2,...,e N is the optical path error parameter, such as the detector installation error, the azimuth axis and elevation axis non-correction error, the azimuth or elevation zero position error, etc. Its physical meaning and number N vary with the structure of the device to be calibrated. ψ and θ are the azimuth angle and elevation angle respectively. Then, the optical axis pointing error objective function is established according to the optical axis pointing mathematical model. Where b i is the projection of the target point of parallel light tube 2 on the X / Y / Z axis of the geographic system; finally, the objective function A is minimized to obtain the optical axis error parameter vector E[e1,e2,...,e N ];

[0042] S2, use a gyrotheodolite to calibrate the benchmark of the collimator 2 array target (this step needs to be calibrated every six months) to obtain the geographic system azimuth and elevation values ​​of 20 target points;

[0043] S3, place the optoelectronic device 4 to be calibrated at the center of the table top of the six-degree-of-freedom swing table 3, and adjust the position of the optoelectronic device 4 to be calibrated on the six-degree-of-freedom swing table 3 so that the imaging sensor of the optoelectronic device 4 to be calibrated is located at the convergence intersection of the parallel light tube 2 array targets when in zero position.

[0044] S4, through servo control, the optical axis of the imaging sensor of the optoelectronic device 4 to be calibrated points to the first collimator 2 No. 1 in the lower left corner as a reference, and then the target tracking mode is turned on so that the crosshairs of the collimator 2 are located at the center of the image crosshairs.

[0045] S5, set the rocking center of the six-degree-of-freedom rocking platform 3 to be approximately located at the imaging sensor position of the optoelectronic device 4 to be calibrated, the rocking amplitude is ±6°, the rocking period is 15s, 12s, and 8s, and then start the six-degree-of-freedom rocking platform 3.

[0046] S6, recording the azimuth and elevation angle readings of the optoelectronic device 4 to be calibrated under different swing postures, the inertial navigation attitude data and the true value of the geographic system of the target collimator 2, with the amount of data being no less than 10 groups.

[0047] S7, switch the tracking mode to the aiming mode, and adjust the optical axis of the imaging sensor of the optoelectronic device 4 to be calibrated to point to the next target collimator 2 according to the true value of the geographic system of the collimator 2. After the crosshair image of the collimator 2 enters the field of view, it is guided by the wave gate and enters the target tracking mode, so that the target crosshair image is located at the center of the image crosshairs.

[0048] S8, repeat steps S6 and S7 until 20 target parallel light tubes 2 are traversed.

[0049] S9, bringing the true value of the geographic system of the target collimator 2, the angle measurement reading and the inertial navigation attitude data obtained from the test into the optical axis error solution method to perform digital calibration of the error parameters, and output the error parameter fitting results.

[0050] S10, use the error parameter fitting result to correct the parameters of the optical axis pointing servo control model, and re-burn the code: set the original error parameter during the initial calibration to the 0 vector, and convert the calibrated error parameter result E[e1,e2,...,e N ] replace the original error parameter E'[e'1,e'2,...,e' N ] to correct the optical axis pointing error parameters.

[0051] S11, randomly select three parallel light tubes 2 as target points, turn the optical axis of the imaging sensor of the optoelectronic device 4 to be calibrated to the selected target point, and evaluate the pointing accuracy and stability accuracy.

[0052] S12, turn off the power of the six-degree-of-freedom swing platform 3 and the collimator 2 to complete the calibration.

[0053] The above device is based on the digital calibration device and method of optical axis pointing error to calibrate the front and back pointing error comparison. Figure 3 shown.

[0054] The above embodiments are only illustrative of the principles and effects of the present invention, as well as some embodiments of its application. For those skilled in the art, several modifications and improvements may be made without departing from the creative concept of the present invention, and all of these belong to the protection scope of the present invention.

Claims

1. A calibration method for a digital calibration device for optical axis pointing error, characterized in that: Based on a digital calibration device comprising a control cabinet, a light source, a platform (6) fixed on a foundation (5), and a six-degree-of-freedom swing platform (3) for placing an optoelectronic device (4) to be calibrated, the platform (6) is provided with a platform (1) with an arc-shaped cross section, the platform (1) is provided with an array target composed of a plurality of parallel light pipes (2) arranged, and the center of the arc surface of the platform (1) in the horizontal plane is located directly above the center of the table surface of the six-degree-of-freedom swing platform (3); the steps are: S1, first establish the mathematical model of optical axis pointing LOS=f(e1,e2,...,e N ,Ψ,θ), where e1,e2,...,e N is the optical path error parameter, Ψ and θ are the azimuth and elevation angles respectively; then the optical axis error solution model is established: the optical axis pointing error objective function is established according to the optical axis pointing mathematical model Where b i is the projection of the target point of the parallel light tube (2) on the X / Y / Z axis of the geographic system; finally, the objective function A is minimized to obtain the optical axis error parameter vector E[e1,e2,...,e N ]; S2, using a gyrotheodolite to calibrate the benchmark of the collimator (2) array target, and obtain the geographic azimuth and elevation values ​​of 20 target points; S3, placing the optoelectronic device to be calibrated (4) at the center of the tabletop of the six-degree-of-freedom swing table (3), and adjusting the position so that the imaging sensor of the optoelectronic device to be calibrated (4) is located at the convergence intersection of the array targets of the parallel light tube (2) when in the zero position; S4, controlling the optical axis of the imaging sensor of the optoelectronic device (4) to be calibrated to point to the first collimator (2), and then making the crosshairs of the collimator (2) located at the center of the image crosshairs; S5, setting the rocking center of the six-degree-of-freedom rocking platform (3) to the imaging sensor position of the optoelectronic device (4) to be calibrated, the rocking amplitude to ±6°, the rocking period to 15s, 12s, and 8s, and then starting the six-degree-of-freedom rocking platform (3); S6, recording the azimuth and elevation angle readings of the optoelectronic device (4) to be calibrated under different swing attitudes, the inertial navigation attitude data and the true value of the geographic projection of the collimator (2), the amount of data being no less than 10 groups; S7, according to the true value of the geographic system projection of the collimator (2), the optical axis of the imaging sensor of the optoelectronic device (4) to be calibrated is directed to the next collimator (2), and the crosshair image of the collimator (2) enters the field of view so that the target crosshair image is located at the center of the crosshairs of the image; S8, repeating steps S6 and S7 until traversing 20 target parallel light tubes (2); S9, bringing the true value of the geographic projection of the collimator (2), the angle measurement reading and the inertial navigation attitude data obtained from the test into the optical axis error solution method to perform digital calibration of the error parameters, and output the error parameter fitting result; S10, set the original error parameter during the initial calibration to a zero vector, and convert the calibrated error parameter result E[e1,e2,...,e N ] replace the original error parameter E'[e1',e'2,...,e' N ], to correct the optical axis pointing error parameters; S11, randomly selecting three parallel light tubes (2) as target points, turning the optical axis of the imaging sensor of the optoelectronic device (4) to be calibrated to the selected target points, and evaluating the pointing accuracy and stability accuracy; S12, turning off the six-degree-of-freedom rocking platform (3) and the collimator (2).

2. The calibration method of a digital calibration device for optical axis pointing error according to claim 1, characterized in that: The optical path error in step S1 includes detector installation error, angular misalignment error between the azimuth axis and the elevation axis, and azimuth or elevation zero position error.

3. The calibration method of a digital calibration device for optical axis pointing error according to claim 2, characterized in that: The collimator (2) is a reflective card-type collimator with a diameter of 300 mm and a focal length of 1200 mm.

4. The calibration method of a digital calibration device for optical axis pointing error according to claim 3 is characterized in that: The height between the center of the table and the convergence point of the parallel light of the parallel light pipe (2) is 1.5 m.

5. The calibration method of a digital calibration device for optical axis pointing error according to claim 4, characterized in that: The collimator (2) is fixedly connected to a mounting hole on the stand (1) by means of bolts and pins, and the mounting hole has a diameter of 380 mm.

6. The calibration method of a digital calibration device for optical axis pointing error according to claim 5, characterized in that: The stand (1) is formed by processing with cast iron.

7. The calibration method of a digital calibration device for optical axis pointing error according to claim 6, characterized in that: The collimator tubes (2) are 20 in number and are arranged in a 4×5 pattern.

8. The calibration method of a digital calibration device for optical axis pointing error according to claim 7, characterized in that: The foundation (5) is arranged on an external foundation (7) via a vibration isolation belt.

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