Off-axis reflective collimator focal plane assembly position calibration device and method

Abstract

This invention discloses a device and method for calibrating the focal plane assembly position of an off-axis reflective collimator, solving the problem that existing technologies cannot achieve accurate calibration of the focal plane position of an off-axis reflective collimator. The calibration device includes an autocollimation component, an angle measuring component, a translation stage calibration component, and a digital microscopy system. The autocollimation component and the angle measuring component work together to calibrate the actual central field of view of the off-axis reflective collimator; the translation stage calibration component is used to calibrate the movement direction of the translation stage; the autocollimation component, the angle measuring component, and the digital microscopy system work together to calibrate the position of the target plate, ensuring that it is parallel to the focal plane of the off-axis reflective collimator and that its center coincides with the actual central field of view of the off-axis reflective collimator. This calibration device can quickly and optimally adjust the principal ray direction of the central field of view of the off-axis reflective collimator and the relative position between the focal plane and the target plate and translation stage, thereby improving calibration accuracy.

Description

Technical Field

[0001] This invention pertains to calibration devices and methods for optical precision measurement components, specifically relating to a device and method for calibrating the position of an off-axis reflective collimator focal plane component. Background Technology

[0002] Collimators are key testing equipment in the development of precision optoelectronic devices. They are used to detect imaging quality parameters such as the speckle of confusion, modulation transfer function (MTF), and resolution of optical systems or cameras, as well as geometric parameters such as focal length and distortion. Compared to traditional transmission collimators and coaxial reflection collimators, off-axis reflection collimators can simulate infinitely distant targets without central obstruction while achieving large apertures.

[0003] When using an off-axis reflective collimator to test camera performance parameters, the scribed surface of the test target plate must be precisely aligned with the theoretical focal plane position of the collimator to simulate targets at infinity. During stages such as camera focal plane alignment, mechanical testing, and thermal vacuum testing, the test target plate typically needs to be able to move back and forth along the principal ray (optical axis) of the off-axis reflective collimator's central field of view to simulate targets at finite distances at different imaging distances, and to test imaging quality parameters such as the camera's speckle and MTF. Based on this, an overfocus curve is plotted to determine whether the camera's focal plane position meets the expected requirements. Fixing the test target plate on a translation stage that can move back and forth along the principal ray of the off-axis reflective collimator's central field of view constitutes the focal plane assembly of the off-axis reflective collimator. This focal plane assembly must meet the following basic requirements:

[0004] a) The direction of movement of the translation stage is parallel to the direction of the principal ray in the central field of view of the off-axis reflective collimator;

[0005] b) The scribing surface of the test target is parallel to the focal plane of the off-axis reflective collimator;

[0006] c) The center field of view of the off-axis reflective collimator coincides with the center of the test target.

[0007] Off-axis reflective collimator focal plane assembly must be rigorously calibrated to avoid problems such as inconsistency between the translation stage of the focal plane assembly and the principal ray direction of the collimator's central field of view, incorrect collimator focal plane position, tilt of the test target's scribed surface relative to the collimator focal plane, and deviation of the test target's scribed surface from the actual collimator focal plane. Otherwise, it will cause testing errors in camera performance parameters, as well as the detection accuracy of the camera's focal plane position during focal plane contact, before and after mechanical tests, and thermal vacuum tests.

[0008] Traditional calibration methods for the focal plane assembly of coaxial reflective collimators, such as the invention patent with publication number CN107727368A, directly utilize the perpendicularity between the focal plane and the optical axis to calibrate based on the cat's-eye optical path formed by the laser interferometer and the test target. However, the principal ray in the central field of view of off-axis reflective collimators is usually not perpendicular enough to the image plane, causing the laser interferometer's output beam to not return along its original path and thus failing to construct a cat's-eye optical path with the test target. Therefore, precise calibration specifically for the focal plane assembly of off-axis reflective collimators is of great significance.

[0009] Based on this, invention patent CN111006855A discloses a method and device for calibrating the optical axis of a large-aperture off-axis reflective vacuum collimator. It mainly uses the off-axis primary mirror of the collimator as a reference mirror, combined with a laser interferometer for adjustment, thereby completing the calibration of the collimator's optical axis. However, this method can only calibrate the position of the central field of view, but cannot achieve precise calibration of the focal plane position. This leads to a deviation between the position of the focal plane assembly and its theoretical position, ultimately resulting in testing errors in the camera's performance parameters. Summary of the Invention

[0010] The purpose of this invention is to provide a device and method for calibrating the position of the focal plane assembly of an off-axis reflective collimator, so as to solve the technical problem that existing calibration methods cannot achieve accurate calibration of the focal plane position of an off-axis reflective collimator.

[0011] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0012] A device for calibrating the position of an off-axis reflective collimator focal plane assembly, wherein the off-axis reflective collimator focal plane assembly includes a translation stage and a target plate, the target plate being mounted on the translation stage by a fixing fixture; its special feature is that:

[0013] Includes autocollimation components, angle measurement components, translation stage calibration components, and digital microscopy measurement systems;

[0014] The autocollimation assembly includes a laser interferometer and a plane mirror. The laser interferometer is located at the incident end of the off-axis reflective collimator and is used to emit a reference spherical wave, which is collimated by the off-axis reflective collimator to form parallel light. The plane mirror is located at the output end of the off-axis reflective collimator and is used to reflect the parallel light emitted by the off-axis reflective collimator, allowing it to return to the laser interferometer along its original path. The laser interferometer and the plane mirror work together to detect wavefront aberrations at different fields of view of the off-axis reflective collimator.

[0015] The angle measuring assembly includes a cubic mirror and an angle measuring device; the cubic mirror is installed on the side of the plane mirror away from the off-axis reflective collimator, and the side of the cubic mirror away from the plane mirror faces the angle measuring device; the angle measuring device cooperates with the cubic mirror to measure the deflection angle of the plane mirror in real time.

[0016] The translation stage calibration component is used to calibrate the movement direction of the translation stage; the translation stage calibration component includes a light source, a star plate, and an imager; the light source is located at the light-incident end of the off-axis reflective collimator; the star plate is used to mount on the translation stage, it is set at the light-incident end of the off-axis reflective collimator, and is located in the light-out path of the light source; the imager is located at the light-out end of the off-axis reflective collimator, and is used to image the pattern on the star plate.

[0017] The digital microscopy measurement system is located at the light-incident end of the off-axis reflective collimator and close to the laser interferometer; the digital microscopy measurement system is used to acquire the spot size of the target plate in different postures in real time.

[0018] Furthermore, the light source is an integrating sphere light source;

[0019] The angle measuring device is an autocollimator;

[0020] The star-shaped plate and the target plate have the same shape and size.

[0021] The present invention also provides a method for calibrating the position of the focal plane assembly of an off-axis reflective collimator, using the above-mentioned off-axis reflective collimator focal plane assembly position calibration device, comprising the following steps:

[0022] Step 1: Determine the field of view to be calibrated and its field of view angle for the off-axis reflective collimator based on the size of the target plate; the field of view to be calibrated includes the central field of view and four peripheral fields of view evenly distributed around the central field of view;

[0023] Step 2: Construct the autocollimation assembly and the angle measuring assembly respectively. According to the field of view to be calibrated and its field of view angle, adjust the deflection angle of the plane mirror relative to the off-axis reflective collimator in sequence. At the same time, use a laser interferometer to detect the wavefront aberration at different fields of view of the off-axis reflective collimator in sequence.

[0024] Step 3: Based on the offset characteristics of the off-axis reflective collimator aberration design, and combined with the wave aberrations obtained in Step 2 at different fields of view, calibrate the actual central field of view of the off-axis reflective collimator, and adjust the plane mirror to the position corresponding to the actual central field of view.

[0025] Step 4: Install the translation stage at the focal plane of the off-axis reflective collimator, and install the star plate on the translation stage. Then remove the laser interferometer and install the light source and imager.

[0026] Step 5: Illuminate the star plate with a light source, and at the same time adjust the pose of the translation stage and move the star plate. During this process, the image of the pattern on the star plate is acquired and observed in real time by the imager. When the image position remains unchanged, the calibration of the translation stage's movement direction is completed.

[0027] Step 6: Remove the light source, star plate and imager, and install the target plate on the calibrated translation stage so that the center of the target plate coincides with the center of the actual central field of view calibrated in Step 3. Then install the laser interferometer and digital microscopy measurement system.

[0028] Step 7: Adjust the plane mirror to the different field-of-view positions corresponding to the off-axis reflective collimator, and move the translation stage back and forth in the direction it is calibrated. At the same time, use the digital micro-measurement system to obtain the image of the light spot projected by the laser interferometer on the target plate under different fields of view and its size in real time, so as to obtain the optimal focal plane position corresponding to each field of view.

[0029] Step 8: Based on the optimal focal plane position corresponding to each field of view, obtain the relative pose between the target plate and the focal plane of the off-axis reflective collimator, and adjust the pose of the target plate accordingly until the focal plane of the target plate and the off-axis reflective collimator are parallel.

[0030] Step 9: Adjust the plane mirror to the position corresponding to the actual center field of view of the off-axis reflective collimator, and then adjust the front and rear position of the target plate by means of the translation stage until the center of the target plate coincides with the actual center field of view of the off-axis reflective collimator, thereby completing the calibration of the focal plane component position of the off-axis reflective collimator.

[0031] Furthermore, in step 1, the four edge fields of view are the upper edge field of view, the lower edge field of view, the left edge field of view, and the right edge field of view.

[0032] Furthermore, in step 2, when adjusting the deflection angle of the plane mirror relative to the off-axis collimator, the deflection angle of the plane mirror is monitored in real time by the angle measuring component.

[0033] Furthermore, in step 4, when installing the star plate, first adjust the position of the star plate so that the light spot emitted by the laser interferometer is projected onto the center of the star plate, and then remove the laser interferometer.

[0034] Furthermore, in step 5, after the translation stage is calibrated, its direction of movement is parallel to the direction of the principal ray in the actual central field of view of the off-axis reflective collimator.

[0035] Furthermore, in step 7, the optimal focal plane position corresponding to each field of view is obtained in the following manner:

[0036] Based on the images and sizes of the light spots projected onto the target plate by the laser interferometer under different fields of view obtained by the digital microscopy measurement system, the size of the projected light spot when the translation stage is defocused at different distances at the corresponding field of view of the off-axis reflective collimator is fitted by a quadratic polynomial, and then the optimal focal plane position corresponding to each field of view is calculated.

[0037] Furthermore, in step 8, the relative pose between the target plate and the focal plane of the off-axis reflective collimator is obtained in the following manner:

[0038] By combining the optimal focal plane positions of the left and right edge fields of view of the off-axis reflective collimator, the horizontal angle between the target plate and the focal plane of the off-axis reflective collimator is determined. Then, by combining the optimal focal plane positions of the upper and lower edge fields of view of the off-axis reflective collimator, the vertical angle between the target plate and the focal plane of the off-axis reflective collimator is determined. ;

[0039] The specific method of adjusting the attitude of the target plate is as follows: based on and The fixture for fixing the target plate is trimmed until the target plate is parallel to the focal plane of the off-axis reflective collimator.

[0040] Further, step 9 specifically involves adjusting the plane mirror to a position corresponding to the actual center field of view of the off-axis reflective collimator, then adjusting the front and rear positions of the target plate using a translation stage, and observing the size of the spot projected by the laser interferometer on the target plate using a digital microscopic measurement system until the grid line marker at the center of the target plate coincides with the spot projected by the laser interferometer's output beam on the target plate. This indicates that the center of the target plate coincides with the actual center field of view of the off-axis reflective collimator, thereby completing the calibration of the focal plane component position of the off-axis reflective collimator.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] 1. The off-axis reflective collimator focal plane assembly position calibration device of the present invention includes an autocollimation assembly, an angle measuring assembly, a translation stage calibration assembly, and a digital microscopy measurement system. The autocollimation assembly and the angle measuring assembly cooperate to calibrate the actual central field of view of the off-axis reflective collimator; the translation stage calibration assembly is used to calibrate the movement direction of the translation stage; the autocollimation assembly, the angle measuring assembly, and the digital microscopy measurement system cooperate to calibrate the position of the target plate, ensuring that it is parallel to the focal plane of the off-axis reflective collimator and that its center coincides with the actual central field of view of the off-axis reflective collimator. This calibration device can quickly and optimally adjust the principal ray direction of the central field of view of the off-axis reflective collimator and the relative position between the focal plane and the target plate and translation stage, thereby achieving accurate calibration of the focal plane position of the off-axis reflective collimator.

[0043] 2. This invention monitors the rotation angle of the plane mirror in real time through the angle measuring component, thereby ensuring that the fixed field of view position of the off-axis reflective collimator can be repeatedly tested during the calibration of the focal plane component, which helps to improve the reliability of the relevant trimming parameters in the calibration process.

[0044] 3. This invention illuminates the star plate with an integrating sphere light source and observes it with an imager. By combining the characteristics of the image position change corresponding to the pattern on the star plate when the translation stage moves, the direction of the translation stage can be adjusted to be parallel to the direction of the principal ray of the center field of view of the off-axis reflective collimator, thereby improving the calibration accuracy of the direction of the translation stage.

[0045] 4. The present invention employs a digital microscopic measurement system, which further improves the calibration accuracy.

[0046] 5. The off-axis reflective collimator focal plane assembly position calibration method provided by the present invention is convenient to operate and has high calibration accuracy. Attached Figure Description

[0047] Figure 1 This is a reference diagram showing the usage status of the autocollimation component and the angle measuring component in an embodiment of the off-axis reflective collimator focal plane component position calibration device of the present invention.

[0048] Figure 2 This is a schematic diagram of the determined field of view position to be calibrated in step 1 of an embodiment of the off-axis reflective collimator focal plane assembly position calibration method of the present invention.

[0049] Figure 3 This is a reference diagram showing the usage state of the translation stage calibration component in an embodiment of the off-axis reflective collimator focal plane component position calibration device of the present invention;

[0050] Figure 4 This is a reference diagram showing the usage status of the digital microscopic measurement system in an embodiment of the off-axis reflective collimator focal plane assembly position calibration device of the present invention;

[0051] Figure 5 This is a schematic diagram of the target plate in the off-axis reflective collimator focal plane assembly specified in this invention;

[0052] Figure 6 This is a schematic diagram of the digital microscopic measurement system in an embodiment of the off-axis reflective collimator focal plane assembly position calibration device of the present invention.

[0053] The annotations in the attached figures are explained as follows:

[0054] 1-Laser interferometer, 2-Off-axis reflective collimator, 3-Plane mirror, 4-Cube mirror, 5-Angle measuring device, 6-Field of view to be calibrated, 7-Central field of view, 8-Left edge field of view, 9-Right edge field of view, 10-Upper edge field of view, 11-Lower edge field of view, 12-Star plate, 13-Translation stage, 14-Light source, 15-Imager, 16-Target plate, 17-Digital microscopy measurement system, 18-Target, 19-Microscopic objective lens, 20-Relay mirror, 21-Detector, 22-Illumination source, 23-Adjustable aperture. Detailed Implementation

[0055] To make the objectives, advantages, and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0056] Reference Figures 1 to 6 As shown, this embodiment provides a calibration device for the focal plane assembly position of an off-axis reflective collimator, including an autocollimation assembly, an angle measuring assembly, a translation stage calibration assembly, and a digital microscopy measurement system 17. This calibration device is used to calibrate the position of the focal plane assembly of the off-axis reflective collimator 2. The focal plane assembly includes a translation stage 13 and a target plate 16. The translation stage 13 is movable relative to the off-axis reflective collimator 2. The target plate 16 is mounted on the translation stage 13 using a fixing fixture. Grid line markers are respectively provided at the corresponding positions of each calibration field of view on the target plate 16. Figure 5 As shown, it can be used for precise alignment of the digital microscopy measurement system 17.

[0057] Reference Figure 1 The self-collimating assembly includes a laser interferometer 1 and a plane mirror 3. The laser interferometer 1 is located at the incident end of the off-axis reflective collimator 2, and its standard lens is used to emit a reference spherical wave. This reference spherical wave, after being collimated by the off-axis reflective collimator 2, forms parallel light, which, together with the plane mirror 3, constitutes a self-collimating optical path. The plane mirror 3 is located at the output end of the off-axis reflective collimator 2 and is used to reflect the parallel light emitted from the off-axis reflective collimator 2, returning it to the laser interferometer 1 along its original path. The plane mirror 3 can be angularly deflected relative to the off-axis reflective collimator 2. The laser interferometer 1 and the plane mirror 3 work together to detect wavefront aberrations at different fields of view of the off-axis reflective collimator 2, thereby calibrating the actual central field of view of the off-axis reflective collimator 2.

[0058] The angle measuring assembly includes a cubic mirror 4 and an angle measuring device 5. The cubic mirror 4 is mounted on the side of the plane mirror 3 away from the off-axis collimator 2, with the side of the cubic mirror 4 away from the plane mirror 3 facing the angle measuring device 5. The angle measuring device 5 works in conjunction with the cubic mirror 4 to measure the specific deflection angle of the plane mirror 3 in real time. The angle measuring device 5 can be an autocollimator, or other angle measuring devices capable of performing the corresponding functions.

[0059] Reference Figure 3 The translation stage calibration assembly is used to calibrate the movement direction of the translation stage. The assembly includes a light source 14, a dot plate 12, and an imager 15. The light source 14 is an integrating sphere light source, located at the incident end of the off-axis reflective collimator 2. The dot plate 12 is mounted on the translation stage 13, positioned at the incident end of the off-axis reflective collimator 2, and located in the output light path of the light source 14. The dot plate 12 has the same shape and size as the target plate 16. The imager 15 is located at the output end of the off-axis reflective collimator 2 and is used to image the pattern on the dot plate 12.

[0060] Reference Figure 4 The digital microscopy measurement system 17 is set at the light-incident end of the off-axis reflective collimator 2 and close to the laser interferometer 1; the digital microscopy measurement system 17 is used to acquire the spot size of the target plate 16 in different postures in real time.

[0061] Furthermore, this embodiment also provides a method for calibrating the position of the focal plane assembly of an off-axis reflective collimator, specifically including the following steps:

[0062] Step 1: Based on the size of the target plate 16, determine the field of view to be calibrated and its field of view angle of the off-axis reflective collimator 2; the field of view to be calibrated 6 includes the central field of view and four edge fields of view evenly distributed around the central field of view 7, namely the upper edge field of view 10, the lower edge field of view 11, the left edge field of view 8 and the right edge field of view 9.

[0063] Step 2: Construct the autocollimation assembly and the angle measuring assembly respectively. According to the field of view to be calibrated and its field of view angle, adjust the deflection angle of the plane mirror 3 relative to the off-axis reflective collimator 2 in sequence. At the same time, use the laser interferometer 1 to detect the wavefront aberration at different fields of view of the off-axis reflective collimator 2 in sequence.

[0064] When adjusting the deflection angle of the plane mirror 3 relative to the off-axis reflective collimator 2, the deflection angle of the plane mirror 3 is monitored in real time by the angle measuring component to ensure the deflection accuracy of the plane mirror 3.

[0065] Step 3: Based on the offset characteristics of the off-axis reflective collimator 2 aberration design, and combined with the wave aberrations obtained in Step 2 at different fields of view, calibrate the actual central field of view of the off-axis reflective collimator 2. Then, adjust the plane mirror 3 to the position corresponding to the actual central field of view, and proceed to Step 4.

[0066] Step 4: Install the translation stage 13 at the focal plane of the off-axis reflective collimator 2, and install the star plate 12 on the translation stage 13 so that it can perform defocusing motion. During the installation process, first adjust the position of the star plate 12 so that the light spot emitted from the laser interferometer 1 is projected onto the center of the star plate 12. Then, remove the laser interferometer 1 and install the light source 14 and the imager 15.

[0067] Step 5: Illuminate the star plate 12 with the light source 14, and at the same time adjust the pose of the translation stage 13 and move the star plate 12. During this process, the imager 15 collects and observes the image of the pattern on the star plate 12 in real time and extracts the centroid position of the image. When the centroid position of the image remains unchanged, it means that the moving direction of the translation stage 13 is parallel to the principal ray direction of the actual center field of view of the off-axis reflective collimator 2, thereby completing the calibration of the moving direction of the translation stage 13.

[0068] Step 6: Remove the light source 14, star plate 12 and imager 15 respectively, and install the target plate 16 on the calibrated translation stage 13 using a fixing fixture, so that the center of the target plate 16 coincides with the center of the actual center field of view calibrated in Step 3. Then install the laser interferometer 1 and digital microscopic measurement system 17.

[0069] Step 7: According to the field of view and its field of view angle determined in Step 1, adjust the plane mirror 3 to the different field of view positions corresponding to the off-axis reflective collimator 2 in sequence (real-time monitoring is required through the angle measuring component). At the same time, move the translation stage 13 back and forth in the direction calibrated in Step 6, and obtain the image of the light spot projected by the laser interferometer 1 on the target plate 16 and its size in real time under different fields of view through the digital micro-measurement system 17, so as to obtain the optimal focal plane position corresponding to each field of view.

[0070] During this process, each time the translation stage 13 moves to a different position, the attitude of the digital microscopic measurement system 17 is adjusted so that it can clearly image the grid line markers at the corresponding positions on the target plate 16. At this time, the image of the light spot projected on the target plate 16 by the light emitted from the laser interferometer 1 is acquired, and the size of the light spot is obtained.

[0071] The structure and working principle of the digital microscopy measurement system 17 are as follows: Figure 6As shown, the target 18 on the target plate 16 is imaged by the microscope objective 19 and then focused onto the detector 21 by the relay mirror 20. The illumination source 22 is a ring-shaped light strip with an adjustable aperture 23 installed in front of it. This structural design effectively increases the slenderness of the entire system, thereby avoiding structural conflicts between the digital microscopy measurement system 17 and the laser interferometer 1. When imaging the markers on the calibration target plate, the adjustable aperture 23 is opened for illumination. When it is necessary to acquire the light spot projected by the laser interferometer 1 onto the target plate 16, the adjustable aperture 23 is closed to avoid interference between its illumination and the projected light spot.

[0072] During operation, after the autocollimating optical path for a certain field of view is established, the target plate 16 is inserted, the adjustable aperture 23 is opened, and the position of the digital microscopy system 17 is adjusted so that it can clearly image the grid line markers on the target plate 16. Then, the adjustable aperture 23 is closed, and the digital microscopy system 17 acquires the image of the light spot projected by the laser interferometer 1 onto the target plate 16 and obtains its size. Subsequently, a quadratic polynomial is used to fit the projected light spot size at different defocusing distances of the translation stage 13 at the corresponding field of view angle of the off-axis reflective collimator 2, resulting in the following fitting formula:

[0073]

[0074] In the formula: To characterize the defocus distance of translation stage 13 The corresponding projection spot size; i represents the field of view number of the off-axis reflective collimator 2; , , These are the fitting coefficients of the quadratic polynomial.

[0075] Based on the above, the optimal focal plane position for each field of view is further calculated. :

[0076]

[0077] Step 8: Based on the optimal focal plane position corresponding to each field of view, and in conjunction with the optimal focal plane positions of the left edge field of view 8 and the right edge field of view 9 of the off-axis reflective collimator 2. , Determine the horizontal angle between the calibration target plate 16 (generally referring to the target plate 16 with a patterned etched surface) and the focal plane of the off-axis reflective collimator 2. The formula is as follows:

[0078]

[0079] In the formula: This indicates the distance between the two fields of view on the target plate 16 corresponding to the left edge field of view 8 and the right edge field of view 9 of the off-axis reflective collimator 2.

[0080] Similarly, the optimal focal plane positions of the upper edge field of view 10 and lower edge field of view 11 of the off-axis reflective collimator 2 are combined. , Determine the vertical angle between the calibration target plate 16 and the focal plane of the off-axis reflective collimator 2. The formula is as follows:

[0081]

[0082] In the formula: This indicates the distance between the two fields of view on the target plate 16 corresponding to the upper edge field of view 10 and the lower edge field of view 11 of the off-axis reflective collimator 2.

[0083] Afterwards, according to and The fixture for fixing the target plate 16 is trimmed to adjust the relative attitude of the target plate 16 and the off-axis reflective collimator 2 until the focal planes of the target plate 16 and the off-axis reflective collimator 2 are parallel.

[0084] Step 9: Adjust the plane mirror 3 to the position corresponding to the actual center field of view of the off-axis reflective collimator 2. Then, adjust the front and rear positions of the target plate 16 through the translation stage 13. Observe the size of the light spot projected by the laser interferometer 1 on the target plate 16 through the digital micro-measurement system 17 until the grid line marker at the center of the target plate 16 coincides with the light spot projected by the laser interferometer 1's output beam on the target plate 16. This is the optimal focal plane position of the off-axis reflective collimator 2, thus completing the calibration of the focal plane component position of the off-axis reflective collimator.

[0085] The present invention proposes an off-axis reflective collimator focal plane assembly position calibration device and method, which can make the relative positional relationship between the central field of view principal ray direction, focal plane, target plate 16 and translation stage 13 of the off-axis reflective collimator 2 meet the usage requirements, thereby ensuring the accuracy of imaging quality detection and camera focal plane position determination.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A device for calibrating the position of an off-axis reflective collimator focal plane assembly, wherein the off-axis reflective collimator focal plane assembly includes a translation stage (13) and a target plate (16), the target plate (16) being mounted on the translation stage (13) by a fixing fixture; characterized in that: Including autocollimation components, angle measurement components, translation stage calibration components and digital microscopy measurement system (17); The self-collimation assembly includes a laser interferometer (1) and a plane mirror (3); the laser interferometer (1) is located at the light-incident end of the off-axis reflective collimator (2) and is used to emit a reference spherical wave, which is collimated by the off-axis reflective collimator (2) to form parallel light; the plane mirror (3) is located at the light-outcident end of the off-axis reflective collimator (2) and is used to reflect the parallel light emitted by the off-axis reflective collimator (2) so that it returns to the laser interferometer (1) along the original path; the laser interferometer (1) and the plane mirror (3) cooperate with each other to detect wavefront aberrations at different fields of view of the off-axis reflective collimator (2); The angle measuring assembly includes a cubic mirror (4) and an angle measuring device (5); the cubic mirror (4) is installed on the side of the plane mirror (3) away from the off-axis reflective collimator (2), and the side of the cubic mirror (4) away from the plane mirror (3) faces the angle measuring device (5); the angle measuring device (5) cooperates with the cubic mirror (4) to measure the deflection angle of the plane mirror (3) in real time; The translation stage calibration assembly is used to calibrate the movement direction of the translation stage (13); the translation stage calibration assembly includes a light source (14), a star plate (12), and an imager (15); the light source (14) is located at the light-incident end of the off-axis reflective collimator (2); the star plate (12) is used to be mounted on the translation stage (13), and it is set at the light-incident end of the off-axis reflective collimator (2) and located in the light-out path of the light source (14); the imager (15) is located at the light-out end of the off-axis reflective collimator (2) and is used to image the pattern on the star plate (12); The digital microscopy measurement system (17) is set at the light-incident end of the off-axis reflective collimator (2) and close to the laser interferometer (1); the digital microscopy measurement system (17) is used to acquire the spot size of the target plate (16) in different postures in real time.

2. The off-axis reflective collimator focal plane assembly position calibration device according to claim 1, characterized in that: The light source (14) is an integrating sphere light source; The angle measuring device (5) is an autocollimator; The star plate (12) has the same shape and size as the target plate (16).

3. A method for calibrating the position of a focal plane assembly in an off-axis reflective collimator, characterized in that, The off-axis reflective collimator focal plane assembly position calibration device according to claim 1 or 2 includes the following steps: Step 1: Determine the field of view (6) to be calibrated and its field of view angle of the off-axis reflective collimator (2) according to the size of the target plate (16); the field of view (6) to be calibrated includes the central field of view (7) and four edge fields of view evenly distributed around the central field of view (7); Step 2: Construct the autocollimation assembly and the angle measuring assembly respectively. According to the field of view (6) to be calibrated and its field of view angle, adjust the deflection angle of the plane mirror (3) relative to the off-axis reflective collimator (2) in sequence. At the same time, use the laser interferometer (1) to detect the wavefront aberration at different fields of view of the off-axis reflective collimator (2) in sequence. Step 3: Based on the offset characteristics of the off-axis reflective collimator (2) aberration design, combined with the wave aberrations obtained in Step 2 at different fields of view, the actual central field of view of the off-axis reflective collimator (2) is calibrated, and the plane mirror (3) is adjusted to the position corresponding to the actual central field of view. Step 4: Install the translation stage (13) at the focal plane of the off-axis reflective collimator (2), and install the star plate (12) on the translation stage (13). Then remove the laser interferometer (1) and install the light source (14) and the imager (15). Step 5: Illuminate the star plate (12) with the light source (14), and at the same time adjust the pose of the translation stage (13) and move the star plate (12). During this process, the image of the pattern on the star plate (12) is collected and observed in real time by the imager (15). When the image position remains unchanged, the calibration of the movement direction of the translation stage (13) is completed. Step 6: Remove the light source (14), star plate (12) and imager (15), and install the target plate (16) on the calibrated translation stage (13) so that the center of the target plate (16) coincides with the center of the actual central field of view calibrated in Step 3. Then install the laser interferometer (1) and digital microscopy measurement system (17). Step 7: Adjust the plane mirror (3) to the different field of view positions corresponding to the off-axis reflective collimator (2), and move the translation stage (13) back and forth in the direction it is calibrated. At the same time, the digital micro-measurement system (17) acquires the light spot image and its size projected by the laser interferometer (1) on the target plate (16) under different fields of view in real time, so as to obtain the optimal focal plane position corresponding to each field of view. Step 8: Based on the optimal focal plane position corresponding to each field of view, obtain the relative pose between the target plate (16) and the focal plane of the off-axis reflective collimator (2), and adjust the pose of the target plate (16) accordingly until the focal plane of the target plate (16) and the off-axis reflective collimator (2) are parallel. Step 9: Adjust the plane mirror (3) to the position corresponding to the actual center field of view of the off-axis reflective collimator (2), and then adjust the front and rear positions of the target plate (16) by means of the translation stage (13) until the center of the target plate (16) coincides with the actual center field of view of the off-axis reflective collimator (2), thereby completing the calibration of the focal plane component position of the off-axis reflective collimator.

4. The method for calibrating the position of the focal plane assembly of an off-axis reflective collimator according to claim 3, characterized in that: In step 1, the four edge fields of view are the upper edge field of view (10), the lower edge field of view (11), the left edge field of view (8), and the right edge field of view (9).

5. The method for calibrating the position of the focal plane assembly of an off-axis reflective collimator according to claim 4, characterized in that: In step 2, when adjusting the deflection angle of the plane mirror (3) relative to the off-axis reflective collimator (2), the deflection angle of the plane mirror (3) is monitored in real time by the angle measuring component.

6. The method for calibrating the position of the focal plane assembly of an off-axis reflective collimator according to claim 5, characterized in that: In step 4, when installing the star plate (12), first adjust the position of the star plate (12) so that the light spot emitted by the laser interferometer (1) is projected onto the center of the star plate (12), and then remove the laser interferometer (1).

7. The method for calibrating the position of the focal plane assembly of an off-axis reflective collimator according to claim 6, characterized in that: In step 5, after the translation stage (13) is calibrated, its direction of movement is parallel to the direction of the principal ray of the actual central field of view of the off-axis reflective collimator (2).

8. The method for calibrating the position of the focal plane assembly of an off-axis reflective collimator according to claim 7, characterized in that: In step 7, the optimal focal plane position corresponding to each field of view is obtained in the following way: Based on the images and sizes of the light spots projected by the laser interferometer (1) on the target plate (16) under different fields of view obtained by the digital microscopy measurement system (17), the size of the projected light spot when the translation stage (13) is defocused at different distances at the corresponding field of view of the off-axis reflective collimator (2) is fitted by a quadratic polynomial, and then the optimal focal plane position corresponding to each field of view is calculated.

9. The method for calibrating the position of the focal plane assembly of an off-axis reflective collimator according to claim 8, characterized in that: In step 8, the relative pose between the target plate (16) and the focal plane of the off-axis reflective collimator (2) is obtained in the following way: by combining the optimal focal plane positions of the left edge field of view (8) and the right edge field of view (9) of the off-axis reflective collimator (2), the angle between the target plate (16) and the focal plane of the off-axis reflective collimator (2) in the horizontal direction is determined. Then, by combining the optimal focal plane positions of the upper edge field of view (10) and lower edge field of view (11) of the off-axis reflective collimator (2), the angle between the target plate (16) and the focal plane of the off-axis reflective collimator (2) in the vertical direction is determined. ; The adjustment of the attitude of the target plate (16) refers to, according to and The fixture for fixing the target plate (16) is trimmed until the target plate (16) is parallel to the focal plane of the off-axis reflective collimator (2).

10. The method for calibrating the position of the focal plane assembly of an off-axis reflective collimator according to claim 9, characterized in that: Step 9 specifically involves adjusting the plane mirror (3) to a position corresponding to the actual center field of view of the off-axis reflective collimator (2), then adjusting the front and rear positions of the target plate (16) using the translation stage (13), and observing the size of the spot projected by the laser interferometer (1) on the target plate (16) using the digital micro-measurement system (17) until the grid line marker at the center of the target plate (16) coincides with the spot projected by the laser interferometer (1) beam on the target plate (16). This indicates that the center of the target plate (16) coincides with the actual center field of view of the off-axis reflective collimator (2), thereby completing the calibration of the focal plane component position of the off-axis reflective collimator.

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