CGH detection optical path automatic adjustment method

Abstract

The invention discloses a CGH detection light path automatic adjustment method, which comprises the following steps: S1, building a CGH detection light path according to a distance given by optical design; s2, measuring and calculating to obtain a pose error; s3, generating an adjustment instruction based on the pose error; s4, based on the adjustment instruction, driving a six-dimensional adjustment mechanism to perform pose adjustment on the laser interferometer and the CGH diffraction type compensator; s5, repeating the steps S2 to S4 until a preset error threshold value is met, and completing rough adjustment; and S6, performing interference imaging on the measured reflector by using the laser interferometer, and finishing fine adjustment according to an interference imaging result. According to the method, rapid adjustment of the CGH detection optical path of the reflector can be realized, the surface shape detection capability of the optical element is improved, the surface shape detection precision and consistency are improved, the manpower demand in the surface shape detection link is reduced, the detection period is shortened, and the installation and adjustment efficiency of an optical system is improved; the problems that a large-aperture optical system is too long in installation and adjustment period and poor in consistency are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of large-aperture optics, and in particular relates to a CGH detection optical path automatic adjustment method. Background Art

[0002] In recent years, space optical systems such as remote sensing cameras have increasingly adopted large-aperture off-axis structures, and their reflectors are all off-axis secondary aspheric surfaces or high-order aspheric surfaces. Traditional refractive compensators are difficult to fully match the aberration of the surface to be measured, and the compensation ability is limited. Diffraction compensators have gradually become the preferred method for detecting off-axis mirrors. The commonly used diffraction compensator is the CGH (Computer Generated Hologram) diffraction compensator. The detection optical path based on the CGH diffraction compensator is called the CGH detection optical path. The basic principle of the CGH detection optical path is to convert the spherical wave generated by the front system into an aspheric wave that matches the shape of the aspheric surface to be measured through diffraction, so that when there is no surface deviation on the surface to be measured, the interference system is in a completely self-collimated state to achieve zero-position detection.

[0003] Since the CGH detection optical path of the off-axis aspheric mirror needs to be calibrated for the off-axis amount and spin, the traditional method of using a laser tracker can only calibrate the position but not the angle. At the same time, CGH has problems such as interference level and projection distortion. It is highly sensitive to posture errors (mainly including tilt, eccentricity and axial positioning). Therefore, before entering the interferometric measurement stage, the posture adjustment accuracy of CGH is more critical, especially in vacuum, low temperature and other environments where personnel cannot intervene. Certain automatic testing methods are required, so the adjustment of the CGH detection optical path is usually time-consuming and labor-intensive. Summary of the invention

[0004] The technology of the present invention solves the problem: overcomes the shortcomings of the prior art, provides a CGH detection light path automatic adjustment method, can realize the rapid adjustment of the CGH detection light path of the reflector, improves the surface detection capability of the optical element, improves the surface detection accuracy and consistency, reduces the manpower demand in the surface detection link, shortens the detection cycle, improves the optical system installation efficiency, and solves the problem of long installation cycle and poor consistency of large-aperture optical systems.

[0005] In order to solve the above technical problems, the present invention discloses a CGH detection optical path automatic adjustment method, comprising:

[0006] S1, placing the laser interferometer, CGH diffraction compensator and the measured reflector in sequence according to the spacing given by the optical design, and constructing a CGH detection optical path; wherein the laser interferometer is placed on the first six-dimensional adjustment mechanism, the CGH diffraction compensator is placed on the second six-dimensional adjustment mechanism, and the measured reflector is placed on the third six-dimensional adjustment mechanism;

[0007] S2, measure and calculate the posture error S between the laser interferometer and the measured reflector A , and the position error S between the CGH diffraction compensator and the measured reflector B ;

[0008] S3, according to the posture error S A and posture error S B , respectively generating a first six-dimensional adjustment mechanism adjustment instruction and a second six-dimensional adjustment mechanism adjustment instruction;

[0009] S4, according to the adjustment instruction of the first six-dimensional adjustment mechanism and the adjustment instruction of the second six-dimensional adjustment mechanism, respectively drive the first six-dimensional adjustment mechanism and the second six-dimensional adjustment mechanism to adjust the position and posture of the laser interferometer and the CGH diffraction compensator;

[0010] S5, repeating steps S2 to S4 until the posture error between the adjusted laser interferometer and the measured reflector, and the posture error between the CGH diffraction compensator and the measured reflector both meet the preset error threshold, completing the coarse adjustment of the CGH detection optical path, and entering step S6;

[0011] S6, using a laser interferometer to perform interference imaging on the reflector to be measured, and completing fine adjustment of the CGH detection optical path according to the interference imaging result.

[0012] The above-mentioned CGH detection optical path automatic adjustment method also includes: establishing a laser interferometer body coordinate system, a CGH diffraction compensator body coordinate system and a measured reflector body coordinate system; and determining the measured reflector body coordinate system as a reference coordinate system; determining a conversion matrix T between the CGH diffraction compensator body coordinate system and the reference coordinate system. A , and the transformation matrix T between the laser interferometer body coordinate system and the reference coordinate system B .

[0013] In the above-mentioned CGH detection optical path automatic adjustment method, the laser interferometer body coordinate system, the CGH diffraction compensator body coordinate system and the measured reflector body coordinate system are established, including:

[0014] The optical axis of the laser interferometer is Z A Axis; Use the laser tracker target ball to collect several points on the non-etched part of the upper end face of the laser interferometer to establish the X A O A Y A plane; in Z A Axis and X A O A Y A The intersection of the planes is taken as the coordinate origin O A ; in X A OA Y A Choose any point on the plane as Y A Points on the axis; based on this, the laser interferometer body coordinate system is established;

[0015] The optical axis of the CGH diffraction compensator is Z B Axis; Use the laser tracker target ball to collect several points on the non-etched part of the upper end surface of the CGH diffraction compensator to establish the X B O B Y B plane; in Z B Axis and X B O B Y B The intersection of the planes is taken as the coordinate origin O B ; in X B O B Y B Choose any point on the plane as Y B The point on the axis; based on this, the coordinate system of the CGH diffraction compensator body is established;

[0016] Take the optical axis of the reflector to be measured as Z C Axis; Use the laser tracker target ball to collect several points on the non-etched part of the upper end face of the reflector to establish the X C O C Y C plane; in Z C Axis and X C O C Y C The intersection of the planes is taken as the coordinate origin O C ; in X C O C Y C Choose any point on the plane as Y C The point on the axis; in this way, the coordinate system of the reflector body to be measured is established.

[0017] In the above CGH detection optical path automatic adjustment method, the conversion matrix T A and the transformation matrix T B The expression is as follows:

[0018]

[0019] Among them, u A 、v A and w A They represent the laser interferometer body coordinate system around X A Axis, Y A Axis and Z A Angle of axis rotation, dx A ,dy A and dz AThey represent the laser interferometer body coordinate system along X A Axis, Y A Axis and Z A Axis translation; u B 、v B and w B They represent the coordinate system of the CGH diffraction compensator body around X B Axis, Y B Axis and Z B Angle of axis rotation, dx B ,dy B and dz B They represent the coordinate system of the CGH diffraction compensator along the X B Axis, Y B Axis and Z B The amount of translation of the axis.

[0020] In the above CGH detection optical path automatic adjustment method, the position error S between the laser interferometer and the measured reflector is measured and calculated. A , and the position error S between the CGH diffraction compensator and the measured reflector B ,include:

[0021] Select n points as nominal points on the reference planes of the laser interferometer, the CGH diffraction compensator and the reflector to be measured respectively;

[0022] At each nominal point A on the reference plane of the laser interferometer i At each nominal point B on the reference plane of the CGH diffraction compensator i At, and each nominal point C on the reference surface of the measured reflector i At each of the locations, target ball seats are pasted and target balls are placed; where i = 1, 2, ..., n;

[0023] The laser tracker automatically collects the coordinates of the target ball at each nominal point in sequence to obtain the coordinates of each nominal point A. i Coordinate value A in the laser interferometer body coordinate system i (x i ,y i ,z i ), each nominal point B i Coordinate value B in the CGH diffraction compensator body coordinate system i (x i ,y i ,z i ), and each nominal point C i Coordinate value C in the reference coordinate system i (x i ,y i ,z i );

[0024] According to the measured A i (x i ,y i ,z i ), combined with the transformation matrix T A , calculate each nominal point A i Coordinate value A in the reference coordinate system i ′(x i ,y i ,z i );and according to A i ′(x i ,y i ,z i ) and C i (x i ,y i ,z i ), calculate the pose error S A ;

[0025] According to the measured B i (x i ,y i ,z i ), combined with the transformation matrix T B , calculate each nominal point B i Coordinate value B in the reference coordinate system i ′(x i ,y i ,z i ) and according to B i ′(x i ,y i ,z i ) and C i (x i ,y i ,z i ), calculate the pose error S B .

[0026] In the above CGH detection optical path automatic adjustment method,

[0027] Pose error S A , including: the rotation angle error of the laser interferometer relative to the measured reflector (Δu A ,Δv A ,Δw A ) and the position error of the laser interferometer relative to the measured reflector (Δdx A ,Δdy A ,Δdz A ), where Δu A , Δv A and Δw AThey represent the laser interferometer relative to the measured reflector at X C Axis, Y C Axis and Z C Rotation angle error in the axis direction, Δdx A , Δdy A and Δdz A They represent the laser interferometer relative to the measured reflector at X C Axis, Y C Axis and Z C Position error in the axis direction;

[0028] Pose error S B , including: the rotation angle error of the CGH diffraction compensator relative to the measured reflector (Δu B ,Δv B ,Δw B ) and the position error (Δdx) of the CGH diffraction compensator relative to the measured reflector B ,Δdy B ,Δdz B ), where Δu B , Δv B and Δw B They represent the CGH diffraction compensator relative to the measured reflector at X C Axis, Y C Axis and Z C Rotation angle error in the axis direction, Δdx B , Δdy B and Δdz B They represent the CGH diffraction compensator relative to the measured reflector at X C Axis, Y C Axis and Z C Position error in the axis direction.

[0029] In the above-mentioned CGH detection optical path automatic adjustment method, the preset error threshold is ±0.05 mm.

[0030] In the above-mentioned CGH detection optical path automatic adjustment method, a laser interferometer is used to perform interference imaging on the reflector to be measured, and the CGH detection optical path is finely adjusted according to the interference imaging result, including:

[0031] S61, performing interference imaging on the reflector to be measured by using a laser interferometer, and acquiring an interference fringe image;

[0032] S62, semantically segmenting and extracting the features of "defocus", "horizontal coma" and "vertical coma" in the collected interference fringe image through an image processing algorithm, and comparing and interpreting them with the data in the standard aberration graphic library to obtain the misalignment amount;

[0033] S63, generating a third six-dimensional adjustment mechanism adjustment instruction according to the misadjustment amount;

[0034] S64, driving the third six-dimensional adjustment mechanism to adjust the position and posture of the measured reflector according to the adjustment instruction of the third six-dimensional adjustment mechanism;

[0035] S65, repeating steps S61 to S64 until the obtained offset data decays to within a set threshold or reaches a set maximum number of iterations.

[0036] In the above CGH detection optical path automatic adjustment method, the misalignment includes: the angle adjustment amount of the measured reflector (Δu C ,Δv C ) and the position adjustment of the reflector under test (Δdx C ,Δdy C ,Δdz C ), where Δu C Indicates the reflector being measured around X C Angular adjustment of the shaft, Δv C Indicates the reflector under test revolves around Y C The angle adjustment of the measured reflector along the X axis. Δdx represents the angle adjustment of the measured reflector along the X axis. C Axis translation, Δdy C Indicates that the reflector being measured is along the Y C Axis translation, Δdz C Indicates the measured reflector along Z C The amount of translation along the axis.

[0037] In the above CGH detection optical path automatic adjustment method, "defocus" corresponds to the indication Δdz C , "Horizontal coma" corresponds to the indication Δdx and Δv C , "Vertical coma" corresponds to the indication Δdy C and Δu C .

[0038] The present invention has the following advantages:

[0039] (1) The present invention discloses a method for automatically adjusting a CGH detection optical path, which uses a laser tracker to measure distance to achieve rapid adjustment of the CGH detection optical path, has high adjustment accuracy, is simple to operate, and has good versatility.

[0040] (2) The present invention discloses a method for automatically adjusting the CGH detection optical path, which uses large-scale three-dimensional spatial coordinate measurement technology to adjust the CGH detection optical path, thereby improving the test accuracy.

[0041] (3) The present invention discloses a method for automatic adjustment of the CGH detection optical path, which uses active posture control based on coordinate calculation and image understanding, and automatically drives the six-dimensional adjustment mechanism through an algorithm to achieve rapid convergence of the CGH detection optical path and improve detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is an overall flow chart of a CGH detection optical path automatic adjustment method in an embodiment of the present invention;

[0043] Figure 2 This is a schematic diagram of a CGH detection optical path in an embodiment of the present invention;

[0044] Figure 3 It is a schematic diagram of a standard aberration graphic library in an embodiment of the present invention. DETAILED DESCRIPTION

[0045] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments disclosed in the present invention will be further described in detail below with reference to the accompanying drawings.

[0046] The surface quality of each optical element of the space camera is a key factor affecting its on-orbit imaging quality. During the development of the space camera, the reflector surface test runs through the entire optical component assembly stage. Among them, the CGH diffraction compensator is widely used in the test of large-aperture off-axis aspheric reflectors. The corresponding hologram is obtained according to the surface shape of the aspheric surface to be tested. Since the wavefront corresponding to each diffraction order is uniquely determined by its hologram pattern, zero position compensation can be achieved by matching it with the surface to be tested.

[0047] The method of the invention is based on the CGH surface test principle of aspheric reflectors, and is mainly used for surface test of reflectors at various stages during the assembly and adjustment process of large-aperture optical systems. It can solve the problems of long detection cycle and poor consistency for large-volume and batch production tasks.

[0048] The method of the present invention coordinates the benchmarks of each component through a laser tracking coordinate measurement method, obtains an interference fringe pattern collected by a laser interferometer, performs image preprocessing and recognition on the interference fringe pattern, calculates the misalignment information of each component in a reflector surface shape test optical path, generates adjustment instructions for a six-dimensional adjustment mechanism, drives the six-dimensional adjustment mechanism to automatically adjust, thereby replacing the judgment and adjustment of a tester, realizing the automation of the reflector surface shape test process, and promoting the digitalization and automation transformation of a remote sensing camera production model.

[0049] Reference Figure 1 In this embodiment, the CGH detection optical path automatic adjustment method includes:

[0050] S0, establish the laser interferometer body coordinate system, the CGH diffraction compensator body coordinate system and the measured reflector body coordinate system.

[0051] In this embodiment, before constructing the CGH detection optical path, it is necessary to establish the laser interferometer body coordinate system, the CGH diffraction compensator body coordinate system and the measured reflector body coordinate system, and determine the conversion matrix between the coordinate systems. Specifically:

[0052] Set up the laser tracker.

[0053] Laser interferometer body coordinate system: The optical axis of the laser interferometer is Z A Axis; Use the laser tracker target ball to collect several points on the non-etched part of the upper end face of the laser interferometer to establish the X A O A Y A plane; in Z A Axis and X A O A Y A The intersection of the planes is taken as the coordinate origin O A ; in X A O A Y A Choose any point on the plane as Y A The point on the axis; in this way, the laser interferometer body coordinate system is established.

[0054] CGH diffractive compensator body coordinate system: The optical axis of the CGH diffractive compensator is the Z axis. B Axis; Use the laser tracker target ball to collect several points on the non-etched part of the upper end surface of the CGH diffraction compensator to establish the X B O B Y B plane; in Z B Axis and X B O B Y B The intersection of the planes is taken as the coordinate origin O B ; in X B O B Y B Choose any point on the plane as Y B The point on the axis; based on this, the coordinate system of the CGH diffraction compensator body is established.

[0055] Coordinate system of the reflector under test: The optical axis of the reflector under test is Z C Axis; Use the laser tracker target ball to collect several points on the non-etched part of the upper end face of the reflector to establish the X C O C Y C plane; in Z C Axis and X C OC Y C The intersection of the planes is taken as the coordinate origin O C ; in X C O C Y C Choose any point on the plane as Y C The points on the axis are used to establish the coordinate system of the reflector body under test. At the same time, the coordinate system of the reflector body under test is determined as the reference coordinate system.

[0056] On this basis, the transformation matrix T between the CGH diffraction compensator body coordinate system and the reference coordinate system can be obtained: A , and the transformation matrix T between the laser interferometer body coordinate system and the reference coordinate system B :

[0057]

[0058] Among them, u A 、v A and w A They represent the laser interferometer body coordinate system around X A Axis, Y A Axis and Z A Angle of axis rotation, dx A ,dy A and dz A They represent the laser interferometer body coordinate system along X A Axis, Y A Axis and Z A Axis translation; u B 、v B and w B They represent the coordinate system of the CGH diffraction compensator body around X B Axis, Y B Axis and Z B Angle of axis rotation, dx B ,dy B and dz B They represent the coordinate system of the CGH diffraction compensator along the X B Axis, Y B Axis and Z B The amount of translation of the axis.

[0059] S1. According to the spacing given by the optical design, place the laser interferometer, CGH diffraction compensator and the reflector to be measured in sequence to build the CGH detection optical path. At this time, the optical axes of the laser interferometer, CGH diffraction compensator and the reflector to be measured basically coincide with each other and are basically located at the theoretical position given by the design.

[0060] In this embodiment, if Figure 2As shown, the laser interferometer is placed on the first six-dimensional adjustment mechanism, the CGH diffraction compensator is placed on the second six-dimensional adjustment mechanism, and the measured reflector is placed on the third six-dimensional adjustment mechanism.

[0061] After the preparation process is completed, enter the rough adjustment stage:

[0062] S2, measure and calculate the posture error S between the laser interferometer and the measured reflector A , and the position error S between the CGH diffraction compensator and the measured reflector B .

[0063] In this embodiment, the specific implementation of step S2 is as follows:

[0064] S21, selecting n points as nominal points on the reference planes of the laser interferometer, the CGH diffraction compensator and the measured reflector respectively.

[0065] S22, nominal points A on the reference surface of the laser interferometer i At each nominal point B on the reference plane of the CGH diffraction compensator i At, and each nominal point C on the reference surface of the measured reflector i At each location, stick the target ball holders and place the target balls. Where i = 1, 2, ..., n.

[0066] S23, the coordinates of the target ball at each nominal point are automatically collected in sequence by a laser tracker to obtain the coordinates of each nominal point A i Coordinate value A in the laser interferometer body coordinate system i (x i ,y i ,z i ), each nominal point B i Coordinate value B in the CGH diffraction compensator body coordinate system i (x i ,y i ,z i ), and each nominal point C i Coordinate value C in the reference coordinate system i (x i ,y i ,z i ).

[0067] S24, according to the measured A i (x i ,y i ,z i ), combined with the transformation matrix T A , calculate each nominal point A i Coordinate value A in the reference coordinate system i ′(xi ,y i ,z i );and according to A i ′(x i ,y i ,z i ) and C i (x i ,y i ,z i ), calculate the pose error S A Among them, the posture error S A Mainly includes: the rotation angle error of the laser interferometer relative to the measured reflector (Δu A ,Δv A ,Δw A ) and the position error of the laser interferometer relative to the measured reflector (Δdx A ,Δdy A ,Δdz A );Δu A , Δv A and Δw A They represent the laser interferometer relative to the measured reflector at X C Axis, Y C Axis and Z C Rotation angle error in the axis direction, Δdx A , Δdy A and Δdz A They represent the laser interferometer relative to the measured reflector at X C Axis, Y C Axis and Z C Position error in the axis direction.

[0068] S25, based on the measured B i (x i ,y i ,z i ), combined with the transformation matrix T B , calculate each nominal point B i Coordinate value B in the reference coordinate system i ′(x i ,y i ,z i ) and according to B i ′(x i ,y i ,z i ) and C i (x i ,y i ,z i ), calculate the pose error S B Among them, the posture error S BMainly includes: the rotation angle error (Δu B ,Δv B ,Δw B ) and the position error (Δdx) of the CGH diffraction compensator relative to the measured reflector B ,Δdy B ,Δdz B );Δu B , Δv B and Δw B They represent the CGH diffraction compensator relative to the measured reflector at X C Axis, Y C Axis and Z C Rotation angle error in the axis direction, Δdx B , Δdy B and Δdz B They represent the CGH diffraction compensator relative to the measured reflector at X C Axis, Y C Axis and Z C Position error in the axis direction.

[0069] S3, according to the posture error S A and posture error S B , respectively generate a first six-dimensional adjustment mechanism adjustment instruction and a second six-dimensional adjustment mechanism adjustment instruction.

[0070] S4, according to the adjustment instructions of the first six-dimensional adjustment mechanism and the adjustment instructions of the second six-dimensional adjustment mechanism, respectively drive the first six-dimensional adjustment mechanism and the second six-dimensional adjustment mechanism to adjust the posture of the laser interferometer and the CGH diffraction compensator.

[0071] In this embodiment, as mentioned above, the posture error S obtained by step S2 is A and posture error S B They all include errors in six dimensions (three rotation angle errors and three position errors). When an adjustment instruction is generated to drive the six-dimensional adjustment mechanism to adjust the posture, the six-dimensional adjustment mechanism is driven to adjust the errors in the dimensions that exceed the preset error threshold.

[0072] S5, repeat steps S2 to S4 until the posture error between the adjusted laser interferometer and the measured reflector, and the posture error between the CGH diffraction compensator and the measured reflector meet the preset error threshold, complete the coarse adjustment of the CGH detection optical path, and enter step S6.

[0073] In this embodiment, the preset error threshold is ±0.05 mm, that is, when the errors in the six dimensions all meet the preset error threshold, it is considered that the coarse adjustment stage is ended and the fine adjustment stage begins.

[0074] Fine-tuning phase:

[0075] S6, using a laser interferometer to perform interference imaging on the reflector to be measured, and completing fine adjustment of the CGH detection optical path according to the interference imaging result.

[0076] In this embodiment, the specific implementation of step S6 is as follows:

[0077] S60, pre-constructing a standard aberration graphic library. The standard aberration graphic library includes aberration-free theoretical fringes and aberration diagrams of various magnitudes, such as Figure 3 shown.

[0078] S61, using a laser interferometer to perform interference imaging on the reflector to be measured, and collecting an interference fringe image.

[0079] S62, semantically segment and extract the "defocus", "horizontal coma" and "vertical coma" features in the collected interference fringe image through an image processing algorithm, and compare and interpret them with the data in the standard aberration graphic library to obtain the misalignment. The misalignment mainly includes: the angle adjustment amount (Δu C ,Δv C ) and the position adjustment of the reflector under test (Δdx C ,Δdy C ,Δdz C );Δu C Indicates the reflector being measured around X C Angular adjustment of the shaft, Δv C Indicates the reflector under test revolves around Y C The angle adjustment of the measured reflector along the X axis. Δdx represents the angle adjustment of the measured reflector along the X axis. C Axis translation, Δdy C Indicates that the reflector being measured is along the Y C Axis translation, Δdz C Indicates the measured reflector along Z C The amount of translation in the axial direction. Further, the “defocus” corresponds to the indication Δdz C , "Horizontal coma" corresponds to the indication Δdx and Δv C , "Vertical coma" corresponds to the indication Δdy C and Δu C .

[0080] S63, generating a third six-dimensional adjustment mechanism adjustment instruction according to the misalignment amount.

[0081] S64, according to the adjustment instruction of the third six-dimensional adjustment mechanism, drive the third six-dimensional adjustment mechanism to adjust the position and posture of the measured reflector.

[0082] S65, repeating steps S61 to S64 until the obtained misalignment data decays to within the set threshold (less than one wavelength), and the collected interference fringe image is close to the ideal state without aberration, and the fine adjustment stage is considered to be over. If the measured reflector itself has a poor surface shape, the measured reflector can be terminated by setting the maximum number of iterations to obtain the optimal solution.

[0083] S7, testing the reflector surface shape by laser interferometer, taking the average value through multiple tests, performing error processing and storing, and completing the automatic test of the reflector surface shape.

[0084] Based on the above embodiments, it can be seen that the CGH detection optical path automatic adjustment method of the present invention mainly includes two stages of adjustment:

[0085] The first stage (coarse adjustment stage):

[0086] According to the spacing given by the optical design, the laser interferometer, CGH diffraction compensator and the reflector to be measured are placed in sequence to build the CGH detection optical path. At this time, the optical axes of the laser interferometer, CGH diffraction compensator and the reflector to be measured basically coincide, and are basically located at the theoretical position given by the design.

[0087] A laser tracker is set up to establish the laser interferometer body coordinate system, the CGH diffraction compensator body coordinate system and the measured reflector body coordinate system respectively, and the measured reflector body coordinate system is determined as the reference coordinate system.

[0088] Six laser tracker target balls (SMRs) are firmly attached to the reference surface of each component as nominal points. The six target balls are evenly distributed and have basically the same spacing.

[0089] The coordinate values ​​of each target ball are automatically collected in sequence, and an autocollimator is set up to collect the angle data of the CGH diffraction compensator and the measured reflector. The collected coordinate values ​​are recorded as: A1(x1,y1,z1),...,A6(x6,y6,z6), B1(x1,y1,z1),...,B6(x6,y6,z6), C1(x1,y1,z1),...,C6(x6,y6,z6).

[0090] Through the conversion relationship between each coordinate system and the reference coordinate system, the position calculation software is used to calculate the posture error S between the laser interferometer and the measured reflector. A , and the position error S between the CGH diffraction compensator and the measured reflector B , and then get the angle (Δu A ,Δv A ,Δw A ) and (Δdx A ,Δdy A ,ΔdzA ), and the angle (Δu B ,Δv B ,Δw B ) and (Δdx B ,Δdy B ,Δdz B ); on this basis, the first six-dimensional adjustment mechanism adjustment instruction and the second six-dimensional adjustment mechanism adjustment instruction are generated to drive the first six-dimensional adjustment mechanism and the second six-dimensional adjustment mechanism that respectively carry the laser interferometer and the CGH diffraction compensator to adjust the position of the laser interferometer and the CGH diffraction compensator.

[0091] After multiple iterations, when the error is within ±0.05mm, it enters the next stage.

[0092] The second stage (fine-tuning stage):

[0093] The laser interferometer is used to perform interference imaging on the reflector under test, and the interference fringe image is collected for preprocessing. The preprocessed image is used as input data and compared with the standard aberration graphic library for interpretation. The "defocus", "horizontal coma" and "vertical coma" features in the image are semantically segmented, extracted and identified through the image processing algorithm. The magnitude of "defocus", "horizontal coma" and "vertical coma" contained in the current interference fringe image is identified, and the misalignment (angle (Δu C ,Δv C ) and the translation (Δdx C ,Δdy C ,Δdz C )).

[0094] The obtained misalignment is input into the controller to generate the adjustment instruction of the third six-dimensional adjustment mechanism, and the third six-dimensional adjustment mechanism is driven to adjust the position of the measured reflector. At this time, the optical axis (Z C No angle adjustment is made in the (axis) direction.

[0095] After multiple iterations, when the interference fringe image is adjusted to a state close to the ideal state without aberration (straight fringe), the surface shape at this time can be considered as the actual surface shape of the measured reflector. After fine adjustment, the laser interferometer tests the measured reflector multiple times, takes the average of the multiple test results and stores them, and completes the automatic test of the measured reflector. If the measured reflector itself has a poor surface shape (aberration is greater than one wavelength) and the ideal aberration-free image cannot be obtained, the maximum number of iterations is set to obtain the optimal solution.

[0096] The method of the present invention can realize unmanned automatic adjustment of the CGH detection optical path of the aspheric reflector, effectively reduce the airflow disturbance in the detection environment, and thus improve the detection accuracy of the reflector surface shape (the surface shape detection accuracy can be improved from 0.0015λ to 0.0008λ). Compared with manual testing, the detection efficiency of the method of the present invention is improved by 30%; the automated testing time accounts for more than 70% of the entire testing process time.

[0097] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

[0098] The contents not described in detail in the specification of the present invention belong to the common knowledge of the professionals in this field.

Claims

1. A method for automatically adjusting a CGH detection optical path, characterized in that: include: S1, placing the laser interferometer, CGH diffraction compensator and the measured reflector in sequence according to the spacing given by the optical design, and constructing a CGH detection optical path; wherein the laser interferometer is placed on the first six-dimensional adjustment mechanism, the CGH diffraction compensator is placed on the second six-dimensional adjustment mechanism, and the measured reflector is placed on the third six-dimensional adjustment mechanism; S2, measure and calculate the posture error S between the laser interferometer and the measured reflector A , and the position error S between the CGH diffraction compensator and the measured reflector B ; S3, according to the posture error S A and posture error S B , respectively generating a first six-dimensional adjustment mechanism adjustment instruction and a second six-dimensional adjustment mechanism adjustment instruction; S4, according to the adjustment instruction of the first six-dimensional adjustment mechanism and the adjustment instruction of the second six-dimensional adjustment mechanism, respectively drive the first six-dimensional adjustment mechanism and the second six-dimensional adjustment mechanism to adjust the position and posture of the laser interferometer and the CGH diffraction compensator; S5, repeating steps S2 to S4 until the posture error between the adjusted laser interferometer and the measured reflector, and the posture error between the CGH diffraction compensator and the measured reflector both meet the preset error threshold, completing the coarse adjustment of the CGH detection optical path, and entering step S6; S6, using a laser interferometer to perform interference imaging on the reflector to be measured, and completing fine adjustment of the CGH detection optical path according to the interference imaging result.

2. The CGH detection optical path automatic adjustment method according to claim 1, characterized in that: Also includes: Establishing the laser interferometer body coordinate system, the CGH diffraction compensator body coordinate system and the measured reflector body coordinate system; and determining the measured reflector body coordinate system as the reference coordinate system; Determine the transformation matrix T between the CGH diffractive compensator body coordinate system and the reference coordinate system A , and the transformation matrix T between the laser interferometer body coordinate system and the reference coordinate system B .

3. The CGH detection optical path automatic adjustment method according to claim 2, characterized in that: Establish the laser interferometer body coordinate system, the CGH diffraction compensator body coordinate system and the measured reflector body coordinate system, including: The optical axis of the laser interferometer is Z A Axis; Use the laser tracker target ball to collect several points on the non-etched part of the upper end face of the laser interferometer to establish the X A O A Y A plane; in Z A Axis and X A O A Y A The intersection of the planes is taken as the coordinate origin O A ; in X A O A Y A Choose any point on the plane as Y A The point on the axis; based on this, the laser interferometer body coordinate system is established; The optical axis of the CGH diffraction compensator is Z B Axis; Use the laser tracker target ball to collect several points on the non-etched part of the upper end surface of the CGH diffraction compensator to establish the X B O B Y B plane; in Z B Axis and X B O B Y B The intersection of the planes is taken as the coordinate origin O B ; in X B O B Y B Choose any point on the plane as Y B The point on the axis; based on this, the coordinate system of the CGH diffraction compensator body is established; Take the optical axis of the reflector to be measured as Z C Axis; Use the laser tracker target ball to collect several points on the non-etched part of the upper end face of the reflector to establish the X C O C Y C plane; in Z C Axis and X C O C Y C The intersection of the planes is taken as the coordinate origin O C ; in X C O C Y C Choose any point on the plane as Y C The point on the axis; in this way, the coordinate system of the reflector body to be measured is established.

4. The CGH detection optical path automatic adjustment method according to claim 3, characterized in that: Transformation Matrix T A and the transformation matrix T B The expression is as follows: Among them, u A 、v A and w A They represent the laser interferometer body coordinate system around X A Axis, Y A Axis and Z A Angle of axis rotation, dx A ,dy A and dz A They represent the laser interferometer body coordinate system along X A Axis, Y A Axis and Z A Axis translation; u B 、v B and w B They represent the coordinate system of the CGH diffraction compensator body around X B Axis, Y B Axis and Z B Angle of axis rotation, dx B ,dy B and dz B They represent the coordinate system of the CGH diffraction compensator along the X B Axis, Y B Axis and Z B The amount of translation of the axis.

5. The CGH detection optical path automatic adjustment method according to claim 4, characterized in that: Measure and calculate the position error S between the laser interferometer and the measured reflector A , and the position error S between the CGH diffraction compensator and the measured reflector B ,include: Select n points as nominal points on the reference planes of the laser interferometer, the CGH diffraction compensator and the reflector to be measured respectively; At each nominal point A on the reference plane of the laser interferometer i At each nominal point B on the reference plane of the CGH diffraction compensator i At, and each nominal point C on the reference surface of the measured reflector i At each of the locations, target ball seats are pasted and target balls are placed; where i = 1, 2, ..., n; The laser tracker automatically collects the coordinates of the target ball at each nominal point in sequence to obtain the coordinates of each nominal point A. i Coordinate value A in the laser interferometer body coordinate system i (x i ,y i ,z i ), each nominal point B i Coordinate value B in the CGH diffraction compensator body coordinate system i (x i ,y i ,z i ), and each nominal point C i Coordinate value C in the reference coordinate system i (x i ,y i ,z i ); According to the measured A i (x i ,y i ,z i ), combined with the transformation matrix T A , calculate each nominal point A i Coordinate value A in the reference coordinate system i ′(x i ,y i ,z i ) and according to A i ′(x i ,y i ,z i ) and C i (x i ,y i ,z i ), calculate the pose error S A ; According to the measured B i (x i ,y i ,z i ), combined with the transformation matrix T B , calculate each nominal point B i Coordinate value B in the reference coordinate system i ′(x i ,y i ,z i ) and according to B i ′(x i ,y i ,z i ) and C i (x i ,y i ,z i ), calculate the pose error S B .

6. The CGH detection optical path automatic adjustment method according to claim 5, characterized in that: Position error S A , including: the rotation angle error of the laser interferometer relative to the measured reflector (Δu A ,Δv A ,Δw A ) and the position error of the laser interferometer relative to the measured reflector (Δdx A ,Δdy A ,Δdz A ), where Δu A , Δv A and Δw A They represent the laser interferometer relative to the measured reflector at X C Axis, Y C Axis and Z C Rotation angle error in the axis direction, Δdx A , Δdy A and Δdz A They represent the laser interferometer relative to the measured reflector at X C Axis, Y C Axis and Z C Position error in the axis direction; Position error S B , including: the rotation angle error of the CGH diffraction compensator relative to the measured reflector (Δu B ,Δv B ,Δw B ) and the position error (Δdx) of the CGH diffraction compensator relative to the measured reflector B ,Δdy B ,Δdz B ), where Δu B , Δv B and Δw B They represent the CGH diffraction compensator relative to the measured reflector at X C Axis, Y C Axis and Z C Rotation angle error in the axis direction, Δdx B , Δdy B and Δdz B They represent the CGH diffraction compensator relative to the measured reflector at X C Axis, Y C Axis and Z C Position error in the axis direction.

7. The CGH detection optical path automatic adjustment method according to claim 4, characterized in that: The preset error threshold is ±0.05mm.

8. The CGH detection optical path automatic adjustment method according to claim 3, characterized in that: The laser interferometer is used to perform interference imaging on the reflector to be tested. Based on the interference imaging results, the CGH detection optical path is fine-tuned, including: S61, performing interference imaging on the reflector to be measured by using a laser interferometer, and acquiring an interference fringe image; S62, semantically segmenting and extracting the features of "defocus", "horizontal coma" and "vertical coma" in the collected interference fringe image through an image processing algorithm, and comparing and interpreting them with the data in the standard aberration graphic library to obtain the misalignment amount; S63, generating a third six-dimensional adjustment mechanism adjustment instruction according to the misadjustment amount; S64, driving the third six-dimensional adjustment mechanism to adjust the position and posture of the measured reflector according to the adjustment instruction of the third six-dimensional adjustment mechanism; S65, repeating steps S61 to S64 until the obtained offset data decays to within a set threshold or reaches a set maximum number of iterations.

9. The CGH detection optical path automatic adjustment method according to claim 8, characterized in that: Misalignment, including: angle adjustment of the reflector under test (Δu C ,Δv C ) and the position adjustment of the reflector under test (Δdx C ,Δdy C ,Δdz C ), where Δu C Indicates the reflector being measured around X C Angular adjustment of the shaft, Δv C Indicates the reflector under test revolves around Y C The angle adjustment of the measured reflector along the X axis. Δdx represents the angle adjustment of the measured reflector along the X axis. C Axis translation, Δdy C Indicates that the reflector being measured is along the Y C Axis translation, Δdz C Indicates the measured reflector along Z C The amount of translation along the axis.

10. The CGH detection optical path automatic adjustment method according to claim 9, characterized in that: "Out of focus" corresponds to the indication Δdz C , "horizontal coma" corresponds to the indication Δdx and Δv C , "Vertical coma" corresponds to the indication Δdy C and Δu C .

Images