An automatic detection device for the surface shape of large-aperture aspheric concave reflector

Abstract

A large-aperture aspheric concave reflector surface shape automatic detection device includes a dynamic interferometer, a compensation lens group, a primary image observation screen, a digital camera, a kinematic hexapod microrobot, and a control computer. The dynamic interferometer, the compensation lens group, and the primary image observation screen are placed on the top platform of the kinematic hexapod microrobot, sequentially along the optical path from left to right. The control computer controls the dynamic interferometer to emit a reference beam; controls the kinematic hexapod microrobot to perform six-dimensional posture adjustment so that the positions of the primary imaging point and the convergent imaging point coincide; drives the dynamic interferometer to perform interference detection, and reads the coma, spherical aberration, and defocus data obtained by the interference detection. The present invention can achieve rapid and automatic adjustment, improving the efficiency of reflector surface shape detection.

Description

Technical Field

[0001] The invention belongs to the technical field of remote sensor optical assembly and adjustment, and relates to a device for detecting the surface shape of a reflector. Background Art

[0002] Large-aperture aspheric concave reflectors are commonly used optical components in space telescopes and ground-based astronomical telescopes, and their surface shape is one of the key indicators.

[0003] The surface shape of large-aperture aspheric concave mirrors is typically inspected using a zero-compensation interferometry method based on a compensating lens. This method requires the use of a dynamic interferometer, compensating lenses, and other equipment and components. After being self-collimated by the reflector under test, the light beam returns along its original optical path, interfering with the outgoing beam to form fringes. The aberration information carried by the fringes is then used to determine the surface shape of the reflector under test. The relative position of the interferometer and compensating lens assembly to the reflector under test is very sensitive. Errors in these positions can lead to additional aberrations such as coma, spherical aberration, and defocus in the fringe information caused by optical path errors, necessitating precise adjustment.

[0004] At present, the surface shape inspection of large-aperture aspheric concave reflectors mainly relies on the experience of inspectors. By analyzing the interference fringes, the positions of the interferometer and compensation lens group are manually adjusted using a combined multi-dimensional adjustment table to complete the test. As a result, it is difficult to ensure the adjustment accuracy and efficiency, and a large number of highly skilled inspectors are required. Summary of the Invention

[0005] The technical problem solved by the present invention is: in view of the difficulty in adjusting the optical path of the current large-aperture aspheric concave reflector for zero-position compensation interference detection, an automatic detection device for the surface shape of a large-aperture aspheric concave reflector is proposed, which can realize fast and automatic adjustment and improve the detection efficiency of the reflector surface shape.

[0006] The technical solution of the present invention is: an automatic detection device for the surface shape of a large-aperture aspheric concave reflector, including a dynamic interferometer, a compensation lens group, a primary image observation screen, a digital camera, a motion hexapod displacement platform micro robot, a test reference platform and a control computer, wherein:

[0007] The test reference platform is used to provide stable support. The kinematic hexapod microrobot and the large-aperture aspheric concave reflector to be measured are both placed on the test reference platform. The dynamic interferometer, compensation lens group, and primary image observation screen are placed on the top platform of the kinematic hexapod microrobot in order from left to right along the optical path.

[0008] Dynamic interferometer: emits a reference beam and enters the compensation lens group; the CCD camera built into the dynamic interferometer receives the interference fringes after the reflected beam carrying the surface shape information of the large-aperture aspheric concave reflector being measured interferes with the reference beam, and outputs the interference fringes to the control computer;

[0009] Compensation lens group: used to compensate for the aberration in the aspheric interference test optical path, and convert the spherical wave reference beam emitted by the dynamic interferometer into an aspheric beam that matches the large-aperture aspheric concave mirror to be tested;

[0010] Primary image observation screen: used for primary imaging of the outgoing reference beam and convergent imaging of the reflected beam from the large-aperture aspheric concave reflector under test;

[0011] Digital camera: takes pictures of the positions of the imaging point and the convergent imaging point and sends them to the control computer;

[0012] Hexapod microrobot: used to adjust the six-dimensional posture of the combination of dynamic interferometer, compensation lens group, and primary image observation screen;

[0013] Control computer: controls the dynamic interferometer to emit a reference beam; controls the hexapod microrobot to adjust the six-dimensional posture of the assembly according to the positions of the primary imaging point and the convergent imaging point transmitted by the digital camera, so that the positions of the primary imaging point and the convergent imaging point coincide; drives the dynamic interferometer to perform interference detection, and reads the coma, spherical aberration, and defocus data obtained by the interference detection.

[0014] Preferably, the test reference platform is an air-floating platform, the dynamic interferometer is a 4DPhaseCam 6000 series interferometer, and the compensation lens assembly is an Offner compensator.

[0015] Furthermore, the primary image observation screen is a flat white cardboard with a small hole in the center.

[0016] Preferably, the diameter of the small hole is 1 mm.

[0017] Preferably, the resolution of the digital camera is better than 1024×1024 pixels and the frame rate is better than 60 frames.

[0018] Furthermore, the digital camera is placed in a position where the test light is not blocked, and can capture the entire image of the observation screen at one time.

[0019] Preferably, the hexapod microrobot is a PI 8XX series hexapod microrobot.

[0020] A method for detecting a large-aperture aspheric concave reflector using an automatic detection device for the surface shape of the aspheric reflector comprises the following steps:

[0021] Step 1: Set up the various components of the detection device and the large-aperture aspheric concave reflector to be tested;

[0022] Step 2: Adjust the position of the primary image observation screen so that the primary image point of the output beam of the dynamic interferometer passes through the small hole located on the primary image observation screen; adjust the position of the large-aperture aspheric concave reflector to be measured so that the beam convergence point of the output beam after passing through the large-aperture aspheric concave reflector to be measured is projected onto the primary image observation screen;

[0023] Step 3: Start the control computer, drive the digital camera to capture the projected position of the reflected light beam convergence point on the primary image observation screen, and read the image; calculate the distance between the projected position of the reflected light beam convergence point on the primary image observation screen and the pinhole based on the image, solve the six-dimensional pose error of the dynamic interferometer, compensation lens group, and primary image observation screen assembly, output the six-dimensional pose error to the motion hexapod micro-robot, and drive the motion hexapod micro-robot to perform six-degree-of-freedom adjustment until the reflected light beam convergence point coincides with the primary image point;

[0024] Step 4: Use a control computer to drive a dynamic interferometer to perform interference detection; read the coma, spherical aberration, and defocus data obtained from the interference detection, and continuously drive the hexapod microrobot to adjust the six-dimensional posture error of the dynamic interferometer, compensation lens group, and primary image observation screen assembly until the coma, spherical aberration, and defocus data meet the requirements;

[0025] Step 5: Use the control computer to drive the dynamic interferometer to perform the final interference detection, save the final surface detection data, and complete the detection.

[0026] The advantages of the present invention compared with the prior art are:

[0027] (1) The present invention provides a device for automatically detecting the surface shape of a large-aperture aspheric concave reflector. When performing surface shape detection of a large-aperture aspheric concave reflector, the device uses automatic analysis and control technology to automatically adjust a dynamic interferometer and a compensation lens group. This device provides a quick and effective solution to the problem of difficulty in adjusting the position of the interferometer and the compensation lens group in the optical path of large-aperture aspheric concave reflector detection.

[0028] (2) The present invention enables the large-aperture aspheric concave reflector to simultaneously have the advantage of automatic position adjustment of the interferometer and the compensation lens group when performing surface shape detection, which is of great significance for improving the intelligent level of surface shape detection and realizing unmanned assembly and detection;

[0029] (3) The present invention uses a hexapod microrobot to adjust the interferometer and the compensation lens group, which has the advantages of simple structure, strong versatility and high adjustment accuracy;

[0030] (4) The present invention uses a digital camera to obtain the positional relationship between the convergence point of the reflected light beam and the primary image of the outgoing light beam, which has the characteristic of a high degree of digitization and is conducive to realizing an unmanned detection process. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a block diagram of the composition principle of the device of the present invention. DETAILED DESCRIPTION

[0032] like Figure 1 As shown, the detection device of the present invention mainly includes a dynamic interferometer 2, a compensation lens group 3, a primary image observation screen 4, a digital camera 5, a kinematic hexapod microrobot 6, a test reference platform 7, and a control computer 1. The kinematic hexapod microrobot 6 and the large-aperture aspheric concave reflector to be tested are placed on the test reference platform 7. The dynamic interferometer 2, the compensation lens group 3, and the primary image observation screen 4 are placed on the top platform of the kinematic hexapod microrobot in order from left to right along the optical path. The digital camera 5 is placed in a position that does not block the test light and is used to capture the primary image observation screen 4. The control computer 1 is connected to the dynamic interferometer 2, the digital camera 5, and the kinematic hexapod microrobot 6 via cables.

[0033] The test reference platform 7 is used to provide a stable support, and an air-floating platform for optical testing can be selected.

[0034] Dynamic interferometer 2 emits a reference beam, which is incident on compensation lens group 3. Furthermore, the reflected beam, which carries the surface shape information of the large-aperture aspheric concave reflector being measured, interferes with the reference beam. The CCD camera built into dynamic interferometer 2 receives the interference fringes and outputs them to control computer 1. Dynamic interferometer 2 can use a 4D PhaseCam6000 series interferometer.

[0035] Compensating lens group 3 is used to compensate for aberrations in the optical path of aspheric interferometry testing. Compensating lens group 3 is an Offner-type compensator, consisting of two or three lenses. It converts the spherical wave reference beam emitted by dynamic interferometer 2 into an aspheric beam that matches the large-aperture aspheric concave mirror being tested. For details, please refer to the literature "Structural Design and Assembly of the Offner Compensator" (Optical Precision Engineering, Vol. 18, No. 1, 2010, pp. 88-93).

[0036] The primary image observation screen 4 is used to receive the real image of the convergence point of the reflected light beam. The primary image observation screen 4 is a flat white cardboard with a small hole in the center, and the diameter of the hole is 1 mm.

[0037] The digital camera 5 is used to take pictures of the positions of the convergence point of the reflected light beam and the primary image of the outgoing light beam, and output them to the control computer 1. The resolution of the digital camera 5 is better than 1024×1024 pixels and the frame rate is better than 60 frames.

[0038] The hexapod microrobot 6 is used to perform six-dimensional posture adjustment on the assembly of the dynamic interferometer 2, the compensation lens assembly 3, and the primary image observation screen 4. The hexapod microrobot 6 can be a PI 8XX series hexapod microrobot. For more information, please refer to the document "Design and Implementation of a Parallel Six-Degree-of-Freedom Motion Platform" (Journal of Jilin University of Architecture, Vol. 39, No. 2, 2022, pp. 84-88).

[0039] Control computer 1 is the control unit of the detection device of the present invention, responsible for controlling and processing the digital camera 5 for image capture, controlling the hexapod microrobot 6 for six-dimensional position adjustment, and controlling the dynamic interferometer 2 for surface shape detection. Control computer 1 deploys four software programs: digital camera 5 control software, hexapod microrobot 6 control software, dynamic interferometer 2 control software, and analysis and control instruction generation software. The analysis and control instruction generation software is used to calculate the six-dimensional position error of the dynamic interferometer 2 and compensation lens assembly 3 combination based on images captured by the digital camera 5 or measurement data from the dynamic interferometer 2. It also exchanges instructions and data with the digital camera 5 control software, the hexapod microrobot 6 control software, and the dynamic interferometer 2 control software. The analysis and control instruction generation software drives the digital camera 5 to capture the reflected beam's convergence point on the primary image observation screen 4, reads the image, and calculates the distance between the reflected beam's convergence point on the primary image observation screen 4 and the pinhole based on the image. The software then calculates the six-dimensional pose error of the dynamic interferometer 2, compensation lens assembly 3, and primary image observation screen 4 assembly. This six-dimensional error data is then output to the control software for the hexapod microrobot 6, which then drives the hexapod microrobot 6 to perform six-degree-of-freedom adjustments until the reflected beam's convergence point also passes through the pinhole on the primary image observation screen 4, coinciding with the primary image point. The software then drives the dynamic interferometer 2 to perform interferometry, reading the coma, spherical aberration, and defocus data obtained from the interferometry. The sensitivity matrix of the detection optical path is then calculated using optical design software. See the document "Zero-compensation Interferometry Detection Implementation and Error Law" (Journal of Harbin Institute of Technology, Vol. 38, No. 8, 2006, pp. 1247-1250). According to the detection optical path sensitivity matrix, the 6-dimensional posture error of the combination of dynamic interferometer 2, compensation lens group 3, and primary image observation screen 4 is solved; the dynamic interferometer 2 is driven to perform the final interference detection and the final surface detection data is saved.

[0040] The specific working process of the device of the present invention is as follows:

[0041] Step 1: According to the surface shape test drawing of the large-aperture aspheric concave reflector to be tested, Figure 1 Set up various equipment and the large-aperture aspheric concave mirror to be measured.

[0042] The relative position relationship between the dynamic interferometer 2 and the compensation lens group 3 can be adjusted using the compensator's alignment reference. The initial distance between the compensation lens group 3 and the large-aperture aspheric concave reflector under test should deviate from the dimensions marked on the drawing by less than 1 mm.

[0043] The primary image observation screen 4 is placed at the primary image of the outgoing light beam of the dynamic interferometer 2 after passing through the compensation lens group 3. The digital camera 5 is placed where it does not block the test light and can capture the entire image of the primary image observation screen 4.

[0044] Step 2: Adjust the position of the primary image observation screen 4 so that the primary image point of the output beam from the dynamic interferometer 2 passes through the small hole located on the primary image observation screen 4. Adjust the position of the large-aperture aspheric concave reflector under test so that the output beam passes through the large-aperture aspheric concave reflector under test and then is reflected by the large-aperture aspheric concave reflector under test. The convergence point of the beam is projected onto the primary image observation screen 4.

[0045] Step 3: Start the analysis and control command generation software of the control computer 1. Drive the digital camera 5 to capture the position of the reflected beam convergence point on the primary image observation screen 4 and read the image. Based on the image, calculate the distance between the projected position of the reflected beam convergence point on the primary image observation screen 4 and the pinhole, and solve for the six-dimensional position error of the dynamic interferometer 2, compensation lens assembly 3, and primary image observation screen 4 combination. Output this six-dimensional error data to the control software of the hexapod micro-robot 6, which drives the hexapod micro-robot 6 to adjust the six degrees of freedom. Repeat the above steps until the reflected beam convergence point also passes through the pinhole of the primary image observation screen 4, i.e., coincides with the primary image point.

[0046] Step 4: The analysis and control instruction generation software of the control computer 1 starts the dynamic interferometer 2 control software, drives the dynamic interferometer 2 to perform interference detection; reads the coma, spherical aberration, and defocus data obtained by the interference detection; and solves the 6-dimensional posture error of the combination of the dynamic interferometer 2, the compensation lens group 3, and the primary image observation screen 4 according to the detection optical path sensitivity matrix.

[0047] Step 5: The 6-dimensional error data obtained in step 4 is output to the control software of the hexapod microrobot 6 to drive the hexapod microrobot 6 to perform six-degree-of-freedom adjustment on the combination of the dynamic interferometer 2 and the compensation lens group 3.

[0048] Step 6: Repeat steps 4 and 5 until coma, spherical aberration, and defocus all meet the requirements, generally less than 0.05λ, where λ = 0.6328 microns.

[0049] Step 7: Drive the dynamic interferometer 2 to perform the final interference detection, save the final surface detection data, and complete the detection.

[0050] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. An automatic detection device for the surface shape of a large-aperture aspheric concave reflector, characterized by: The invention comprises a dynamic interferometer (2), a compensation lens group (3), a primary image observation screen (4), a digital camera (5), a motion hexapod displacement platform micro-robot (6), a test reference platform (7) and a control computer (1), wherein: The test reference platform (7) is used to provide a stable support. The kinematic hexapod displacement platform microrobot (6) and the large-aperture aspheric concave reflector to be measured are both placed on the test reference platform (7). A dynamic interferometer (2), a compensation lens group (3), and a primary image observation screen (4) are sequentially placed on the top platform of the kinematic hexapod displacement platform microrobot (6) along the optical path from left to right. A dynamic interferometer (2) emits a reference beam and enters a compensation lens group (3); a CCD camera built into the dynamic interferometer (2) receives interference fringes generated by the interference between the reflected beam carrying the surface shape information of the large-aperture aspheric concave reflector to be measured and the reference beam, and outputs the interference fringes to a control computer (1); Compensating lens group (3): used to compensate for the aberration in the aspheric interference test optical path, and convert the spherical wave reference beam emitted by the dynamic interferometer (2) into an aspheric beam that matches the large-aperture aspheric concave mirror to be tested; Primary image observation screen (4): used for primary imaging of the outgoing reference beam and convergent imaging of the beam reflected by the large-aperture aspheric concave reflector under test; Digital camera (5): takes pictures of the positions of the primary imaging point and the convergent imaging point and sends them to the control computer (1); A hexapod micro robot (6) is used to adjust the six-dimensional posture of a combination of a dynamic interferometer (2), a compensation lens group (3), and a primary image observation screen (4); The control computer (1) controls the dynamic interferometer (2) to emit a reference beam; controls the hexapod microrobot (6) to adjust the six-dimensional posture of the assembly according to the positions of the primary imaging point and the convergent imaging point transmitted by the digital camera (5), so that the positions of the primary imaging point and the convergent imaging point coincide; drives the dynamic interferometer (2) to perform interference detection, and reads the coma, spherical aberration, and defocus data obtained by the interference detection.

2. The large-aperture aspheric concave reflector surface shape automatic detection device according to claim 1, characterized in that: The test reference platform (7) is an air-floating platform.

3. The automatic detection device for the surface shape of a large-aperture aspheric concave reflector according to claim 1, characterized in that: The dynamic interferometer (2) is a 4D PhaseCam 6000 series interferometer.

4. The large-aperture aspheric concave reflector surface shape automatic detection device according to claim 1, characterized in that: The compensating lens group (3) is an Offner type compensator.

5. The automatic detection device for the surface shape of a large-aperture aspheric concave reflector according to claim 1, characterized in that: The primary image observation screen (4) is a flat white cardboard with a small hole in the center.

6. The large-aperture aspheric concave reflector surface shape automatic detection device according to claim 5, characterized in that: The diameter of the small hole is 1 mm.

7. The automatic detection device for the surface shape of a large-aperture aspheric concave reflector according to claim 5, characterized in that: The resolution of the digital camera (5) is better than 1024×1024 pixels, and the frame rate is better than 60 frames.

8. The large-aperture aspheric concave reflector surface shape automatic detection device according to claim 1, characterized in that: The digital camera (5) is placed in a place where the test light is not blocked, and can capture the entire image of the observation screen (4).

9. The large-aperture aspheric concave reflector surface shape automatic detection device according to claim 1, characterized in that: The hexapod microrobot (6) is a PI 8XX series hexapod microrobot.

10. A method for detecting a large-aperture aspheric concave reflector using the automatic detection device for detecting the surface shape of the large-aperture aspheric concave reflector according to claim 1, characterized in that: The steps include: Step 1: Set up the various components of the detection device and the large-aperture aspheric concave reflector to be tested; Step 2: adjusting the position of the primary image observation screen (4) so ​​that the primary image point of the output light beam of the dynamic interferometer (2) passes through the small hole located on the primary image observation screen (4); adjusting the position of the large-aperture aspheric concave reflector to be measured so that the light beam convergence point after the output light beam passes through the large-aperture aspheric concave reflector to be measured is projected onto the primary image observation screen (4); Step 3: Start the control computer (1), drive the digital camera (5) to shoot the projection position of the reflected light beam convergence point on the primary image observation screen (4), and read the image; calculate the distance between the projection position of the reflected light beam convergence point on the primary image observation screen (4) and the pinhole according to the image, solve the six-dimensional posture error of the dynamic interferometer (2), the compensation lens group (3), and the primary image observation screen (4) combination, output the six-dimensional posture error to the motion hexapod displacement platform micro robot (6), and drive the motion hexapod displacement platform micro robot (6) to perform six-degree-of-freedom adjustment until the reflected light beam convergence point coincides with the primary image point; Step 4: Using a control computer (1) to drive a dynamic interferometer (2) to perform interference detection; reading coma, spherical aberration, and defocus data obtained by the interference detection, and adjusting the six-dimensional posture error of the dynamic interferometer (2), the compensation lens group (3), and the primary image observation screen (4) by continuously driving the hexapod displacement stage microrobot (6) until the coma, spherical aberration, and defocus data all meet the requirements; Step 5: Use the control computer (1) to drive the dynamic interferometer (2) to perform the final interference detection, save the final surface shape detection data, and complete the detection.

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