Automatic detection device for surface shape of large-aperture aspheric concave reflector

Abstract

The invention discloses an automatic detection device for the surface shape of a large-aperture aspheric concave reflector. The automatic detection device comprises a dynamic interferometer, a compensation lens group, a primary image observation screen, a digital camera, a motion hexapod displacement table micro-robot and a control computer, a dynamic interferometer, a compensation lens group and a primary image observation screen are sequentially arranged on a top platform of the motion hexapod displacement platform micro robot from left to right along a light path. The control computer controls the dynamic interferometer to emit a reference light beam; controlling the motion six-foot displacement platform micro-robot to perform six-dimensional attitude adjustment, so that the positions of the primary imaging point and the convergence imaging point are overlapped; and driving the dynamic interferometer to perform interference detection, and reading coma, spherical aberration and out-of-focus data obtained by interference detection. According to the invention, rapid and automatic adjustment can be realized, and the detection efficiency of the reflector surface shape is improved.

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 reflectors is generally tested using a zero-position compensation interference test method based on a compensation lens, which requires the use of dynamic interferometers, compensation lenses and other equipment and components. The light beam is self-collimated and reflected by the reflector to be measured and then returns along the original optical path, interfering with the outgoing light beam to form fringes, and the surface shape data of the reflector to be measured is obtained through the aberration information carried by the fringes. The relative position of the interferometer and the compensation lens group to the measured mirror is very sensitive, and its position error will cause additional aberrations such as coma, spherical aberration, and defocus in the fringe information due to optical path errors, so precise adjustment is required.

[0004] At present, the surface shape detection of large-aperture aspheric concave reflectors mainly relies on the experience of the inspectors. Through the analysis of the interference fringes, the positions of the interferometer and the 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 zero-position compensation interference detection of large-aperture aspheric concave reflectors, an automatic surface shape detection device for large-aperture aspheric concave reflectors 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: a large-aperture aspheric concave reflector surface shape automatic detection device, including a dynamic interferometer, a compensation lens group, a primary image observation screen, a digital camera, a moving six-legged displacement platform micro robot, a test reference platform and a control computer, wherein:

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

[0008] Dynamic interferometer: emits a reference beam and incidents it on a compensation lens group; a CCD camera built into the dynamic interferometer receives 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 optical path of aspheric interference inspection, 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 primary imaging point and the convergent imaging point and sends them to the control computer;

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

[0013] Control computer: control the dynamic interferometer to emit a reference beam; control the moving hexapod displacement platform micro-robot to perform six-dimensional posture adjustment on the combination 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; drive the dynamic interferometer to perform interference detection, and read 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 4DPhaseCam6000 series interferometer, and the compensation lens group is an Offner type 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 using a large-aperture aspheric concave reflector surface shape automatic detection device comprises the following steps:

[0021] Step 1: Set up the 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 light beam of the dynamic interferometer passes through the small hole on the primary image observation screen; adjust 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 on the primary image observation screen;

[0023] Step 3, start the control computer, drive the digital camera to shoot the projection position of the reflected light beam convergence point on the primary image observation screen, and read the image; calculate the distance between the projection position of the reflected light beam convergence point on the primary image observation screen and the pinhole according to the image, solve the six-dimensional posture error of the dynamic interferometer, the compensation lens group, and the primary image observation screen assembly, output the six-dimensional posture error to the moving six-legged displacement platform micro-robot, and drive the moving six-legged displacement platform 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, using a control computer to drive a dynamic interferometer to perform interference detection; reading the coma, spherical aberration, and defocus data obtained by the interference detection, and adjusting the six-dimensional posture errors of the dynamic interferometer, the compensation lens group, and the primary image observation screen assembly by continuously driving the moving six-legged displacement stage micro-robot 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 large-aperture aspheric concave reflector surface shape automatic detection device. When performing large-aperture aspheric concave reflector surface shape detection, the device uses automatic analysis and control technology to achieve automatic adjustment of a dynamic interferometer and a compensation lens group, and provides a fast and effective solution to the problem of difficult position adjustment of an interferometer and a compensation lens group in the detection optical path of a large-aperture aspheric concave reflector;

[0028] (2) The present invention enables the large-aperture aspheric concave reflector to 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 adjustment 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 The figure 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 motion hexapod displacement platform micro robot 6, a test reference platform 7, and a control computer 1. The motion hexapod displacement platform micro robot 6 and the large-aperture aspheric concave reflector to be tested are placed on the test reference platform 7, and the dynamic interferometer 2, the compensation lens group 3, and the primary image observation screen 4 are placed on the top platform of the motion hexapod displacement platform micro robot in sequence from left to right along the optical path. The digital camera 5 is placed at a place where the test light is not blocked and is used to shoot the primary image observation screen 4. The control computer 1 is connected to the dynamic interferometer 2, the digital camera 5, and the motion hexapod displacement platform micro robot 6 through cables.

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

[0034] On the one hand, the dynamic interferometer 2 is used to emit a reference beam and enter the compensation lens group 3; on the other hand, the reflected beam carrying the surface shape information of the large-aperture aspheric concave reflector to be measured interferes with the reference beam, and the CCD camera built into the dynamic interferometer 2 receives the interference fringes and outputs them to the control computer 1. The dynamic interferometer 2 can use a 4D PhaseCam6000 series interferometer.

[0035] Compensation lens group 3 is used to compensate for the aberration in the optical path of the non-spherical interference test. Compensation lens group 3 is an Offner type compensator, which is composed of two or three lenses, and converts the spherical wave reference beam emitted by the dynamic interferometer 2 into an aspherical beam that matches the large-aperture non-spherical concave mirror to be tested. For details, please refer to the document "Structural Design and Adjustment of 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 small 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 emitted 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 motion hexapod displacement platform micro robot 6 is used to perform six-dimensional posture adjustment on the combination of the dynamic interferometer 2, the compensation lens group 3, and the primary image observation screen 4. The motion hexapod displacement platform micro robot 6 can use the PI 8XX series motion hexapod displacement platform micro robot product. For reference, the document "Design and Implementation of Parallel Six-Degree-of-Freedom Motion Platform" (Journal of Jilin Jianzhu University, Vol. 39, No. 2, 2022, pp. 84-88) can be used.

[0039] The control computer 1 is the control unit of the detection device of the present invention, which is used to control and process the digital camera 5 to take pictures, control the moving six-legged displacement platform micro-robot 6 to adjust the six-dimensional posture, and control the dynamic interferometer 2 to perform surface detection. The control computer 1 deploys 4 software, namely the digital camera 5 control software, the moving six-legged displacement platform micro-robot 6 control software, the dynamic interferometer 2 control software, and the analysis and control instruction generation software. The analysis and control instruction generation software is used to calculate the six-dimensional posture error of the combination of the dynamic interferometer 2 and the compensation lens group 3 according to the pictures taken by the digital camera 5 or the measurement data of the dynamic interferometer 2; and to exchange instructions and data with the digital camera 5 control software, the moving six-legged displacement platform micro-robot 6 control software, and the dynamic interferometer 2 control software. The analysis and control instruction generation software drives the digital camera 5 to shoot the projection position of the reflected light beam convergence point on the primary image observation screen 4, reads the image, and calculates the distance between the projection position of the reflected light beam convergence point on the primary image observation screen 4 and the small hole according to the image; solves the 6-dimensional posture error of the dynamic interferometer 2, the compensation lens group 3, and the primary image observation screen 4 combination, outputs the 6-dimensional error data to the control software of the motion hexapod displacement platform micro robot 6, drives the motion hexapod displacement platform micro robot 6 to perform six-degree-of-freedom adjustment until the reflected light beam convergence point also passes through the small hole of the primary image observation screen 4, that is, coincides with the primary image point; drives the dynamic interferometer 2 to perform interference detection, reads the coma, spherical aberration, and defocus data obtained by the interference detection; and uses the optical design software to calculate the sensitivity matrix of the detection optical path. See the document "Zero Compensation Interference Detection Implementation and Error Quantity 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 the dynamic interferometer 2, the compensation lens group 3, and the primary image observation screen 4 is solved; the dynamic interferometer 2 is driven to perform the final interference detection and the final surface shape 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 reflector to be tested.

[0042] The relative position relationship between the dynamic interferometer 2 and the compensation lens group 3 can be adjusted by using the alignment reference of the compensator. The initial distance between the compensation lens group 3 and the large-aperture aspheric concave reflector to be measured has a deviation of less than 1 mm from the dimension marked on the drawing.

[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 at a position where the test light is not blocked and the full view of the primary image observation screen 4 can be captured.

[0044] Step 2: adjust 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 on the primary image observation screen 4. Adjust the position of the large-aperture aspheric concave reflector to be measured so that the output light beam passes through the large-aperture aspheric concave reflector to be measured, and the light beam convergence point after being reflected by the large-aperture aspheric concave reflector to be measured is projected on the primary image observation screen 4.

[0045] Step 3, start the analysis and control instruction generation software of 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 small hole according to the image, and solve the 6-dimensional posture error of the dynamic interferometer 2, the compensation lens group 3, and the primary image observation screen 4 combination; output the 6-dimensional error data to the control software of the moving six-legged displacement platform micro robot 6, and drive the moving six-legged displacement platform micro robot 6 to adjust the six degrees of freedom; repeat the above steps until the reflected light beam convergence point also passes through the small hole of the primary image observation screen 4, that is, 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 to drive 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 dynamic interferometer 2, the compensation lens group 3, and the primary image observation screen 4 combination 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 moving hexapod displacement stage micro-robot 6, which drives the moving hexapod displacement stage micro-robot 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, which are generally less than 0.05λ, λ = 0.6328 microns.

[0049] Step seven, drive the dynamic interferometer 2 to perform 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. A large-aperture aspheric concave reflector surface shape automatic detection device, characterized in that: The invention comprises a dynamic interferometer (2), a compensation lens group (3), a primary image observation screen (4), a digital camera (5), a moving 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 moving hexapod displacement platform micro robot (6) and the large-aperture aspheric concave reflector to be tested 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 moving hexapod displacement platform micro robot (6) along the optical path from left to right. The dynamic interferometer (2) emits a reference beam and injects it into a compensation lens group (3); a CCD camera built into the dynamic interferometer (2) receives interference fringes after the reflected beam carrying the surface shape information of the large-aperture aspheric concave reflector to be measured interferes with the reference beam, and outputs the interference fringes to the control computer (1); Compensation lens group (3): used to compensate for the aberration in the non-spherical interference test optical path, and to convert the spherical wave reference beam emitted by the dynamic interferometer (2) into a non-spherical beam that matches the large-aperture non-spherical concave mirror to be tested; Primary image observation screen (4): used for primary imaging of the outgoing reference beam and convergent imaging of the reflected beam from the large-aperture aspheric concave reflector to be measured; Digital camera (5): photographs the positions of the primary imaging point and the convergent imaging point and sends them to the control computer (1); A moving hexapod displacement platform micro robot (6) is used to perform six-dimensional posture adjustment on 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 moving hexapod displacement platform micro robot (6) to perform six-dimensional posture adjustment on 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 with each other; 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 large-aperture aspheric concave reflector surface shape automatic detection device according to claim 1, characterized in that: The dynamic interferometer (2) is a 4D PhaseCam6000 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 large-aperture aspheric concave reflector surface shape automatic detection device 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 large-aperture aspheric concave reflector surface shape automatic detection device 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 position 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 using the large-aperture aspheric concave reflector surface shape automatic detection device according to claim 1, characterized in that: The steps include: Step 1: Set up the 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 a small hole 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, starting the control computer (1), driving the digital camera (5) to photograph the projection position of the reflected light beam convergence point on the primary image observation screen (4), and reading the image; calculating 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, solving the six-dimensional posture error of the dynamic interferometer (2), the compensation lens group (3), and the primary image observation screen (4) combination, outputting the six-dimensional posture error to the moving six-legged displacement platform micro robot (6), and driving the moving six-legged 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) assembly by continuously driving the hexapod displacement platform micro robot (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 final interference detection, save the final surface shape detection data, and complete the detection.

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