Tilted wavefront subaperture stitching interferometry based on spatial light modulator

Abstract

This invention discloses a tilted wavefront sub-aperture stitching interferometric detection method based on a spatial light modulator, relating to the field of optical detection. Light emitted from a laser is collimated and expanded before being incident on a polarizing beam splitter; the reflected light serves as a reference beam, and the transmitted light as a test beam; the test beam is incident on a spatial light modulator, and after phase modulation by the spatial light modulator and passing through a lens, it forms standard spherical waves with different tilt angles, allowing for zero-position detection of sub-apertures divided into different regions. Using a spatial light modulator as an ideal point source array generator in conjunction with an imaging lens can generate the required ideal tilted spherical waves for different test parameters, offering strong versatility compared to traditional point source generators. Furthermore, for large-aperture complex curved surfaces, sub-aperture stitching can be achieved without moving the interferometric device, reducing errors introduced by mechanical movement.

Description

Technical Field

[0001] This invention pertains to photoelectric detection technology, and specifically relates to a tilted wavefront sub-aperture splicing interferometric detection method based on a spatial light modulator. Background Technology

[0002] Optical freeform surfaces, with their extremely high degree of design freedom and excellent optical performance, are receiving increasing attention. However, high-precision machining of freeform surfaces relies on high-precision surface shape inspection. Due to their characteristics such as large surface gradient changes, high degree of surface shape freedom, lack of a unified axis of symmetry, and non-compliance with rotational symmetry, the difficulty of high-precision machining and precision inspection is increased. The level of development of freeform surface shape inspection technology restricts the level of its manufacturing.

[0003] Optical interferometry, especially tilted wavefront interferometry, offers advantages such as comprehensive synchronous detection, large dynamic measurement range, good versatility, and high detection accuracy, providing an effective detection solution for high-gradient, highly complex freeform surfaces. However, due to its non-zero-position interferometry, it introduces significant optical path backtracking errors during detection, limiting the improvement of detection accuracy.

[0004] Meanwhile, the sub-aperture interferometry method divides the surface to be measured into multiple small regions (sub-apertures) for detection. Since the asphericity of the sub-apertures is much lower than that of the entire surface to be measured, the detection difficulty is also much easier. Finally, after demodulating the wavefront information of all sub-apertures, the surface shape to be measured is synthesized using different methods. However, errors caused by mechanical movement are unavoidable during the stitching process.

[0005] Unlike traditional microlens arrays and fiber arrays, the dynamic point source generation method based on spatial light modulators can generate the most suitable sub-aperture zero-position detection point source according to different test surface shapes, and can simultaneously apply a certain degree of modulation to the point source, providing a new approach for free-form surface interferometry detection. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention proposes a tilted wavefront sub-aperture stitching interferometric detection method based on a spatial light modulator. This dynamic point source generation method using a spatial light modulator can generate the most suitable point source for sub-aperture zero-position detection based on different surface shapes of the test surface. By using the spatial light modulator as a phase compensation element to dynamically generate a point source array, it can generate the required ideal tilted spherical waves for different test surface parameters, exhibiting strong versatility compared to traditional point source generators. Furthermore, for large-aperture complex curved surfaces, sub-aperture stitching can be achieved without moving the interferometric device, reducing errors introduced by mechanical movement.

[0007] The technical solution of the present invention is as follows: a tilted wavefront sub-aperture splicing interferometric detection method based on spatial light modulators, comprising the following steps:

[0008] Step 1: Set up the measurement optical path:

[0009] The measurement optical path includes a laser, a first lens, a second lens, an aperture, a polarizer, a polarizing beam splitter, a first quarter-wave plate, a mirror, a spatial light modulator, a second quarter-wave plate, an imaging lens, a surface to be measured, a third quarter-wave plate, a third lens, a fourth lens, a polarizing camera, and a PC control terminal.

[0010] A laser, a first lens, a second lens, an aperture, a polarizer, a polarizing beam splitter, and a spatial light modulator are arranged sequentially along the first optical axis. A second optical axis perpendicular to the first optical axis also exists after passing through the polarizing beam splitter. A mirror, a first quarter-wave plate, a polarizing beam splitter, a third quarter-wave plate, a third lens, a fourth lens, and a polarizing camera are arranged sequentially along the second optical axis. A second quarter-wave plate, an imaging lens, and the surface to be measured are arranged sequentially along the reflected light path of the spatial light modulator. The spatial light modulator and the polarizing camera are respectively connected to the PC control terminal.

[0011] The linearly polarized light emitted from the laser passes through the first and second lenses to become expanded parallel light. Then, it passes through an aperture stop to limit the beam diameter, resulting in a parallel beam with high intensity uniformity. After passing through a polarizer, it is split into two parallel beams with mutually perpendicular polarization directions. These beams are then separated into a test beam and a reference beam by a polarizing beam splitter. The test beam is on the first optical axis, reflected by a spatial light modulator, and passes through a second quarter-wave plate and an imaging lens to reach the surface under test. After recording the surface profile information, it returns to the polarizing beam splitter along the imaging lens, the second quarter-wave plate, and the spatial light modulator. Because the test beam passes through the quarter-wave plate twice, its polarization direction is... When the beam is rotated 90° and reaches the polarizing beam splitter again, it will be reflected and will travel along the second optical axis through the third quarter-wave plate, the third lens, and the fourth lens to reach the polarizing camera. The reference beam is on the second optical axis, passes through the first quarter-wave plate, reaches the mirror, is reflected, and then passes through the first quarter-wave plate again to reach the polarizing beam splitter. Since the reference beam rotates 90° twice through the quarter-wave plate and reaches the polarizing beam splitter again, it will be transmitted and will travel along the second optical axis through the third quarter-wave plate, the third lens, and the fourth lens to reach the polarizing camera. Finally, the polarizing camera captures the interference fringe pattern that records the surface shape information of the surface under test.

[0012] Step 2: Based on the lens parameters of the surface to be tested, divide the detection area of ​​the surface to be tested, and determine the position parameters and ideal spherical wave modulation amount required for the spatial light modulator and imaging lens to generate a dynamic point source array when detecting the interference surface type based on the parameters of the divided detection area.

[0013] Step 3: Replace the surface to be tested with a standard spherical mirror, and use the iterative generation algorithm and wavefront iterative algorithm to calibrate the position parameters and ideal spherical wave modulation amount of the dynamic point source array generated by the spatial light modulator and imaging lens.

[0014] Step 4: Remove the standard spherical mirror and place it on the surface to be tested. Turn on the laser and use the dynamic point source array of the spatial light modulator and imaging lens generated in Step 3 to perform interference detection on the surface shape of the surface to be tested.

[0015] Step 5: The polarization camera acquires four sub-aperture interferograms for each point source corresponding to the surface under test.

[0016] Step 6: Perform a four-step phase shift on the above sub-aperture interferogram to obtain the encapsulated phase.

[0017] Step 7: Use a stitching algorithm to stitch together the wrapped phase to obtain surface shape information. Compare the surface shape information with the lens parameters of the surface to be tested to complete the detection of surface shape error of the surface to be tested.

[0018] Compared with the prior art, the present invention has the following significant advantages:

[0019] This invention uses a spatial light modulator as a phase compensation element to dynamically generate a point source array, which can generate the required ideal tilted spherical wave for different test parameters. Compared with traditional point source generators, it has strong versatility. Furthermore, for large-aperture complex curved surfaces, it can achieve sub-aperture splicing without moving the interference device, reducing errors introduced by mechanical movement. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the measurement optical path of the present invention.

[0021] In the figure: laser 1, first lens 2, second lens 3, aperture 4, polarizer 5, polarizing beam splitter 6, first quarter wave plate 7, mirror 8, spatial light modulator 9, second quarter wave plate 10, imaging lens 11, surface to be measured 12, third quarter wave plate 13, third lens 14 and fourth lens 15 form an imaging device, polarizing camera 16, PC control terminal 17.

[0022] Figure 2 This is a flowchart of the tilted wavefront sub-aperture splicing interferometry detection method based on a spatial light modulator according to the present invention. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings.

[0024] Combination Figure 2 The tilted wavefront sub-aperture stitching interferometry detection method based on spatial light modulator described in this invention comprises the following steps:

[0025] Step 1, Combining Figure 1 Set up the measurement optical path:

[0026] The measurement optical path includes a laser 1, a first lens 2, a second lens 3, an aperture 4, a polarizer 5, a polarizing beam splitter 6, a first quarter-wave plate 7, a mirror 8, a spatial light modulator 9, a second quarter-wave plate 10, an imaging lens 11, a surface to be measured 12, a third quarter-wave plate 13, a third lens 14, a fourth lens 15, a polarization camera 16, and a PC control terminal 17.

[0027] A laser 1, a first lens 2, a second lens 3, an aperture 4, a polarizer 5, a polarizing beam splitter 6, and a spatial light modulator 9 are arranged sequentially along the first optical axis. A second optical axis perpendicular to the first optical axis also exists after passing through the polarizing beam splitter 6. A mirror 8, a first quarter-wave plate 7, a polarizing beam splitter 6, a third quarter-wave plate 13, a third lens 14, a fourth lens 15, and a polarizing camera 16 are arranged sequentially along the second optical axis. A second quarter-wave plate 10, an imaging lens 11, and a surface to be measured 12 are arranged sequentially on the reflected light path of the spatial light modulator 9. The spatial light modulator 9 and the polarizing camera 16 are respectively connected to the PC control terminal 17.

[0028] The laser 1 emits light from the main optical axis; the polarization direction of the linearly polarized light emitted from the laser 1 forms a 45° angle with the polarization direction of the polarizer 5; the laser 1, after passing through the first lens 2 and the second lens 3, becomes beam-expanded parallel light.

[0029] The expanded parallel light beam passes through the aperture 4 to limit the beam aperture, becoming a parallel beam with high intensity uniformity. It then passes through the polarizer 5 to split into two parallel beams with mutually perpendicular polarization directions. The optical path is then divided into a test optical path and a reference optical path by the polarizing beam splitter 6. Since the beam splitting surface of the polarizing beam splitter 6 has an angle of 45° with the principal optical axis, the principal optical axes of the two optical paths are perpendicular to each other.

[0030] The test optical path is on the first optical axis. After being reflected by the spatial light modulator 9, it passes through the second quarter wave plate 10 and the imaging lens 11 to generate an ideal point source array, forming standard spherical waves with different tilt angles, which arrive at the test surface 12. The sub-apertures of different regions of the test surface are zero-position detected, and the surface shape information of the test surface is recorded. Then, it returns to the polarization beam splitter 6 along the imaging lens 11, the second quarter wave plate 10, and the spatial light modulator 9. Since the test beam is reflected when it passes through the quarter wave plate twice and rotates 90° in polarization direction to reach the polarization beam splitter 6 again, it will travel along the second optical axis through the third quarter wave plate 13, the third lens 14, and the fourth lens 15 to reach the polarization camera 16.

[0031] The reference beam travels along the second optical axis, passes through the first quarter-wave plate 7, reaches the reflecting mirror 8, is reflected, and then passes through the first quarter-wave plate 7 again to reach the polarizing beam splitter 6. Since the reference beam rotates 90° in polarization direction twice as it passes through the quarter-wave plate and reaches the polarizing beam splitter 6 again, it will be transmitted and travel along the second optical axis through the third quarter-wave plate 13, the third lens 14, and the fourth lens 15 to reach the polarizing camera 16.

[0032] The reference beam and the test beam, after passing through the third quarter-wave plate 13, form circularly polarized light p and s with opposite rotation directions, respectively. After passing through the two-dimensional checkerboard grating, the two circularly polarized lights generate four light fields (±1st order diffraction field in the x direction and ±1st order diffraction field in the y direction) by the diffraction effect.

[0033] After the four optical fields of each of the two circularly polarized lights pass through a 2×2 waveplate delay array, the phases of the four polarized optical fields are shifted by 0, π / 2, π, and 3π / 2, respectively.

[0034] The four optical fields of the phase-shifted circularly polarized light s interfere pairwise with the four optical fields of the phase-shifted circularly polarized light p along the polarization direction of the polarizer, generating four interference fields with phase differences of 0, π / 2, π, and 3π / 2, respectively, thus completing the spatial polarization phase-shifting interferometry measurement. The interferogram is displayed on the PC control terminal, and the surface shape under test is restored. The fast axis azimuth angle of the first quarter-wave plate 7, the second quarter-wave plate 10, and the third quarter-wave plate 13 is 45 degrees.

[0035] The polarization camera 16 is a polarization camera with a pixel-level polarization mask. The polarization mask covers the photodiode of the camera and is arranged in groups of four pixels with polarization angles of 0 degrees, 45 degrees, 90 degrees and 135 degrees, respectively. It can output images with four different polarization angles at the same time.

[0036] The angle between the normal of the reflective surface of the spatial light modulator and the principal optical axis of the test light is 3 to 10°, and the specific tilt angle can be adjusted according to the specific surface shape of the surface being tested.

[0037] Step 2: Divide the detection area of ​​the test surface 12 according to the lens parameters of the test surface 12, and determine the position parameters and ideal spherical wave modulation amount required for the spatial light modulator 9 and imaging lens 11 to generate a dynamic point source array when the interference surface type is detected based on the parameters of the divided detection area.

[0038] The sub-apertures of the surface to be measured are divided using a sub-aperture planning mathematical model:

[0039] For any complex surface of any form, it can be discretized, and then the discretized data can be used to find the closest solution to a sphere. An arbitrarily complex surface can be represented by the following equation:

[0040] z = P(x,y)

[0041] Consider the position closest to the center of the sphere (x) c y c , z c The nearest radius of the sphere is h, and the discrete point on the measured part is (x). i y i , z i ).

[0042] Due to the symmetry of the mirror, to simplify the solution model, we assume that both the mirror and the detector aperture are symmetrical along the X-axis, thus the closest point to the center of the sphere is...

[0043] x c =0

[0044] The objective function is then optimized as follows:

[0045]

[0046] Where M is the number of mirror sampling points, which can be obtained by solving based on an iterative algorithm (y c , z c The solution of h is used to obtain the position of the complex surface that is closest to the sphere. That is, the best fitting radius h of each sub-aperture obtained by the solution has a corresponding relationship with the off-axis position R of the center of the sub-aperture:

[0047] h = h(R)

[0048] It can be seen that there is a corresponding relationship between the radius r of each sub-aperture and the position h of the sub-aperture center off the axis:

[0049]

[0050] In the formula, F is the F-number of the standard mirror.

[0051] Assuming there are n aperture planning possibilities for a certain circle, then according to the constraints of k:

[0052]

[0053] Where k is the chord distance between the centers of adjacent sub-apertures in the same circle, and k0 is the maximum value of k, which is determined by the predefined overlap area between adjacent sub-apertures.

[0054] k0 (the maximum value of the distance k between the center of adjacent sub-apertures in the same ring) can be obtained from the ratio p of the overlapping area of ​​adjacent sub-apertures to the size of the sub-aperture. Therefore:

[0055]

[0056] S represents the area of ​​the sub-aperture. To ensure the overlap area, the number of sub-apertures should be minimized.

[0057] [x] is the integer part of x.

[0058] Therefore, the radii of the inner and outer circles contained in this circle can be determined as follows:

[0059]

[0060] First, determine the size r0 of the center sub-aperture of the test piece. Then, based on the requirement of overlapping area between adjacent rings and the fact that the R1 value of the (N+1)th ring should be less than the R2 value of the Nth ring, the size of R1 of the (N+1)th ring can be solved. The overlapping area between adjacent rings is defined as follows:

[0061]

[0062] Using R1, we can solve for the position R of the (N+1)th sub-aperture center from the mirror center, the number of sub-apertures n, and R2:

[0063]

[0064]

[0065] In a recursive manner, assuming that the sub-apertures within N rings are planned, the selection of the N+1 ring should make its R1 value less than the R2 value of the N ring, and the difference should be given by the percentage of overlapping area; once R1 is determined, the position R of the aperture center distance from the optical axis, the number of sub-apertures n, and the R2 value of the N+1 ring are derived from the R1 expression; the recursive process continues until the R2 of a certain ring is greater than half of the mirror aperture.

[0066] Step 3: Replace the surface to be tested 12 with a standard spherical mirror. Use the iterative generation algorithm and the wavefront iterative algorithm to calibrate the position parameters and ideal spherical wave modulation amount of the dynamic point source array generated by the spatial light modulator 9 and the imaging lens 11, which is used for high-precision generation of the dynamic point source array.

[0067] This invention is the first to propose an interference fringe feedback algorithm using a weighted Gerchberg-Saxton (GSW) algorithm combined with Newton iteration to obtain a spatial light modulator that generates an ideal point source array.

[0068] The method for detecting complex curved surfaces based on spatial light modulators mainly needs to solve two problems in generating dynamic point sources: accurate compensation for the tilt amount required for zero-position detection of point sources and accurate compensation for the required wavefront phase.

[0069] The weighted Gerchberg-Saxton iterative algorithm (GSW) used to calculate the light wave field of the 3D image generated from the hologram can accurately compensate for the tilt amount required for point source null detection. When calculating the hologram, the GSW algorithm introduces weighting factors to improve the brightness distribution of the image, reduce errors, and optimize the iterative process, thereby achieving more accurate and high-quality holographic image reconstruction. In conjunction with the generation of the point source array using the SLM and imaging lens, by setting the required point source position coordinate parameters, the algorithm automatically calculates the point intensity distribution on the corresponding Fourier plane and compares it with the target point intensity distribution to obtain the weighted correction coefficient. Because a weighting coefficient that changes with the number of iterations is used—that is, the ratio of the energy of the optical trap in the input image to the energy of the optical trap in the restored image obtained in each iteration multiplied by the weighting coefficient in the previous iteration—the introduction of weights ensures that the energy of the optical trap in the restored image obtained from the hologram is closer to the design value. This ultimately achieves accurate compensation for the required tilt amount, generating a dynamically oriented point source with precise pose. Finally, the required pose phase map generated on the SLM is obtained.

[0070] The proposed interference fringe feedback algorithm based on Newton's iteration innovatively uses a standard spherical mirror as a calibration surface to perform wavefront feedback calibration on point sources at different tilt angles, generating an ideal spherical wavefront phase map. J+1 Zernike fringe coefficients are selected as inputs, and an interference fringe processing algorithm is used for fringe extraction. Fringe information entropy is selected as the fringe gradient loss function f(x), and the fringe gradient loss value is selected as the output. The Newton's iteration algorithm is used as the gradient descent optimizer loss to find c. j The set of values ​​allows the loss to quickly reach zero.

[0071] Use e j Indicated It can be written as:

[0072]

[0073] The intensity information after polarization shift is:

[0074]

[0075] Eliminating A and B yields the relationship between the pixel information of the four frames:

[0076]

[0077] An initial random phase surface is input via SLM to obtain an initial interferogram, and the wavefront phase function information is obtained by polarization shifting. Perform Zernike fitting on the phase surface and define the weighted fitting coefficients.

[0078] Loss function:

[0079]

[0080] q j Using the weighting coefficients, the new phase function is applied to the SLM to obtain new fringes and a new phase function.

[0081] The phase function is based on Newton's iteration:

[0082]

[0083] The loss function is defined to decrease along the derivative direction, eventually yielding an ideal wavefront where the evaluation function approaches 0.

[0084] Step 4: Remove the standard spherical mirror and place it on the surface to be tested 12. Turn on the laser 1 light source and use the spatial light modulator 9 and imaging lens 11 to generate a dynamic point source array to perform interference detection on the surface shape of the surface to be tested.

[0085] During interferometric testing, the overlapping area of ​​the emitted light from the two outermost point light sources of the dynamic point source array onto the test surface 12 is larger than the freeform surface aperture of the test surface 12.

[0086] Step 5: Collect four interferograms for each point source corresponding to the aperture of the surface to be measured.

[0087] Step 6: Perform a four-step phase shifting and unwrapping phase on the sub-aperture interferogram.

[0088] Step 7: Compare the surface shape information obtained by stitching through the stitching algorithm with the lens parameters of the surface to be tested to complete the detection of surface shape error of the surface to be tested.

[0089] The stitching algorithm plans a mathematical model to restore the surface shape of the surface to be tested:

[0090] For two sub-apertures with overlapping regions, their surface profile data are represented by w1(x,y) and w2(x,y) respectively. Theoretically, their values ​​in the overlapping region should be consistent. However, due to errors in the two measurements, there is a certain deviation in the overlapping region. Therefore, it is necessary to eliminate the error through coordinate transformation. The transformation relationship is as follows:

[0091]

[0092] In the formula, w 10 (x,y) and w 20 (x, y) represent the theoretical surface profile data of the two sub-apertures, respectively; A1 and A2 represent the tilt coefficients in the x-direction, respectively; B1 and B2 represent the tilt coefficients in the y-direction, respectively; C1 and C2 are their corresponding defocus coefficients; D1 and D2 are their corresponding translation coefficients, respectively.

[0093] Ideally, the surface profile data of the two sub-apertures remains unchanged within the overlapping region, i.e., w 10 (x,y)=w 20 (x,y), therefore, for any two sub-apertures with overlapping regions, the relationship between their surface shapes is:

[0094] w1(x,y)-w2(x,y)=ΔAx+ΔBy+ΔC(x 2 +y 2 )+ΔD

[0095] In the formula, ΔA = A1 - A2, ΔB = B1 - B2, ΔC = C1 - C2, and ΔD = D1 - D2. It can be seen that to determine the deviation between the two surface types, it is only necessary to solve for the splicing coefficients ΔA, ΔB, ΔC, and ΔD. Theoretically, four unknowns can be calculated from the four equations. Therefore, by arbitrarily selecting four points not on the same straight line within the overlapping area, the specific values ​​of the four splicing coefficients ΔA, ΔB, ΔC, and ΔD can be obtained. To reduce errors caused by insufficient calculation data and improve the accuracy of the calculation results, a certain number of sampling points are selected and quantized. Then, the least squares method is used to fit the data to obtain the corresponding splicing parameters when the sum of squared residuals G is minimized. The objective function G can be expressed as:

[0096] G=∑{w1(x,y)-w2(x,y)-ΔAx-ΔBy-ΔC(x 2 +y 2 )-ΔD} 2

[0097] Taking the partial derivatives of the splicing coefficients in the above formula and setting them to 0, the specific formula is as follows:

[0098]

[0099] Solving the equations above, we obtain the following equation:

[0100]

[0101] Where H is the number of sampling points in the overlapping area, and Δw = w1(x,y) - w2(x,y), the splicing coefficients can be obtained. For two or more sub-apertures, each sub-aperture is spliced ​​and its coordinates transformed in turn. Then, by adding the various surface profiles, the measurement data of the full-aperture surface profile can be obtained, and finally, the surface profile error of the surface to be measured can be obtained.

[0102] This invention addresses the shortcomings of traditional tilted wavefront interferometry and sub-aperture stitching interferometry by proposing for the first time a tilted wavefront sub-aperture stitching interferometry detection device based on a spatial light modulator. Furthermore, taking into account the modulation characteristics of the spatial light modulator, it innovatively proposes a method combining a weighted Gerchberg-Saxton algorithm (GSW) with a Newton-based iterative interference fringe feedback algorithm to generate a dynamic point source array with high positional accuracy and good wavefront quality. This dynamic point source generation method based on the spatial light modulator can generate the most suitable point source for sub-aperture zero-position detection according to different surface shapes of the test surface. By using the spatial light modulator as a phase compensation element to dynamically generate the point source array, it can generate the required ideal tilted spherical waves for different test surface parameters, exhibiting strong versatility compared to traditional point source generators. Moreover, for large-aperture complex curved surfaces, sub-aperture stitching can be achieved without moving the interferometer, reducing errors introduced by mechanical movement.

[0103] The above description is merely a specific embodiment of the present invention and is not intended to limit it. Although, with reference to this embodiment, those skilled in the art should readily understand that they can still make equivalent substitutions for some of the technical features in the foregoing solution. These modifications and substitutions do not change the essence of the solution and should all be included within the protection scope of the present invention.

Claims

1. A tilted wavefront sub-aperture stitching interferometry detection method based on spatial light modulators, characterized in that, The steps are as follows: Step 1: Set up the measurement optical path: The measurement optical path includes a laser (1), a first lens (2), a second lens (3), an aperture (4), a polarizer (5), a polarizing beam splitter (6), a first quarter wave plate (7), a mirror (8), a spatial light modulator (9), a second quarter wave plate (10), an imaging lens (11), a surface to be measured (12), a third quarter wave plate (13), a third lens (14), a fourth lens (15), a polarizing camera (16), and a PC control terminal (17). A laser (1), a first lens (2), a second lens (3), an aperture (4), a polarizer (5), a polarizing beam splitter (6), and a spatial light modulator (9) are arranged sequentially along the first optical axis. A second optical axis perpendicular to the first optical axis also exists after passing through the polarizing beam splitter (6). A mirror (8), a first quarter wave plate (7), a polarizing beam splitter (6), a third quarter wave plate (13), a third lens (14), a fourth lens (15), and a polarizing camera (16) are arranged sequentially along the second optical axis. A second quarter wave plate (10), an imaging lens (11), and a surface to be measured (12) are arranged sequentially along the reflected light path of the spatial light modulator (9). The spatial light modulator (9) and the polarizing camera (16) are respectively connected to the PC control terminal (17). The linearly polarized light emitted from the laser (1) passes through the first lens (2) and the second lens (3) to become an expanded parallel beam. Then, it passes through the aperture stop (4) to limit the beam aperture, becoming a parallel beam with high intensity uniformity. After passing through the polarizer (5), it is split into two parallel beams with mutually perpendicular polarization directions. Then, it passes through the polarizing beam splitter (6) to be divided into a test beam path and a reference beam path. The test beam path is on the first optical axis. After being reflected by the spatial light modulator (9), it passes through the second quarter wave plate (10) and the imaging lens (11) to reach the surface to be tested (12). After recording the surface shape information of the surface to be tested, it returns to the polarizing beam splitter (6) along the imaging lens (11), the second quarter wave plate (10), and the spatial light modulator (9). Since the test beam passes through the quarter wave plate twice, the polarization direction rotates. When the beam reaches the polarizing beam splitter (6) again after rotating 90°, it will be reflected and will travel along the second optical axis through the third quarter wave plate (13), the third lens (14), and the fourth lens (15) to reach the polarizing camera (16). The reference beam is on the second optical axis, passes through the first quarter wave plate (7), reaches the reflecting mirror (8), is reflected, and then passes through the first quarter wave plate (7) again to reach the polarizing beam splitter (6). Since the reference beam rotates 90° twice through the quarter wave plate and reaches the polarizing beam splitter (6) again, it will be transmitted and will travel along the second optical axis through the third quarter wave plate (13), the third lens (14), and the fourth lens (15) to reach the polarizing camera (16). Finally, the interference fringe pattern that records the surface shape information of the surface to be measured is captured at the polarizing camera. Step 2: According to the lens parameters of the surface to be tested (12), the detection area of ​​the surface to be tested (12) is divided, and the position parameters and ideal spherical wave modulation amount required for the spatial light modulator (9) and imaging lens (11) to generate a dynamic point source array during interference surface detection are determined according to the parameters of the divided detection area. Step 3: Replace the surface to be tested (12) with a standard spherical mirror, and use the iterative generation algorithm and wavefront iterative algorithm to calibrate the position parameters and ideal spherical wave modulation amount of the dynamic point source array generated by the spatial light modulator (9) and the imaging lens (11); Step 4: Remove the standard spherical mirror and place it on the surface to be tested (12). Turn on the laser (1) and use the dynamic point source array of the spatial light modulator (9) and imaging lens (11) generated in step 3 to perform interference detection on the surface shape of the surface to be tested (12). Step 5: The polarization camera (16) acquires four sub-aperture interferograms of the test surface (12) corresponding to each point source; Step 6: Perform a four-step phase shift on the above sub-aperture interferogram to obtain the encapsulated phase; Step 7: The phase is spliced ​​by the splicing algorithm to obtain the surface information. The surface information is compared with the lens parameters of the surface to be tested (12) to complete the detection of the surface error of the surface to be tested.

2. The tilted wavefront sub-aperture stitching interferometry detection method based on a spatial light modulator as described in claim 1, characterized in that, In step 1, the polarization direction of the linearly polarized light emitted from the laser (1) is at an angle of 45° to the polarization direction of the polarizer (5); the angle between the beam splitting surface of the polarizing beam splitter (6) and the principal optical axis is 45°, and the angle between the normal of the reflecting surface of the spatial light modulator (9) and the first optical axis is 3 to 10°.

3. The tilted wavefront sub-aperture stitching interferometry detection method based on a spatial light modulator as described in claim 1, characterized in that, In step 3, the surface to be tested (12) is replaced with a standard spherical mirror, and the position parameters of the dynamic point source array generated by the spatial light modulator (9) and the imaging lens (11) are calibrated using an iterative generation algorithm, as follows: Based on the required dynamic point source position parameters, a precisely positioned point source array is generated using a spatial light modulator (9) and an imaging lens (11) based on the GSW weighted iterative algorithm. The GSW algorithm improves the brightness distribution of an image by introducing weighting factors, reducing errors and optimizing the iterative process, thereby achieving holographic image reconstruction. When the spatial light modulator (9) and imaging lens (11) generate a dynamic point source array, the GSW calculates the intensity distribution of the point array on the corresponding Fourier plane by setting the required point source position coordinate parameters, and compares it with the target point array intensity distribution to obtain the weight correction coefficient, and finally completes the accurate compensation of the required tilt amount to generate a dynamic point source with precise position.

4. The tilted wavefront sub-aperture stitching interferometry detection method based on a spatial light modulator as described in claim 3, characterized in that, In step 3, the wavefront iteration algorithm is used to calibrate the ideal spherical wave modulation amount generated by the spatial light modulator (9) and the imaging lens (11), as follows: The wavefront modulation of the ideal point source generated by the spatial light modulator (9) and imaging lens (11) is obtained by an interferometric fringe feedback algorithm based on Newton iteration: Using a standard spherical mirror as the calibration surface, wavefront feedback calibration was performed on point sources at different tilt angles to obtain the ideal spherical wavefront phase diagram; n+1 Zernike coefficients Z were selected. n As input, an interference fringe processing algorithm is used for fringe extraction. Fringe information entropy is selected as the fringe gradient loss function f(x), and the fringe gradient loss value is used as the output. Newton's iterative algorithm is used as the gradient descent optimizer loss to find the loss value c. n The set of values ​​allows the loss to quickly reach zero; Use c n Phase represented Written as: Among them, Z n This represents the nth Zernike coefficient; After polarization shifting, the pixel information relationship of the four frames of images is obtained, where the light intensity is I. i Image numbers i = 0, 1, 2, 3: in, This indicates information about the phase function of the light wavefront; An initial random phase surface is input through a spatial light modulator (9) to obtain an initial interference pattern, and the phase function information of the light wavefront is obtained by polarization shift. A Zernike fit is performed on the phase surface, and a loss function f(x) is defined by weighting the fit coefficients: q n As weighting coefficients, the new phase function is loaded onto the spatial light modulator (9) to obtain new fringes and a new phase function. The new phase function is then applied based on Newton's iteration: Where, f'(x) j ) represents the phase function after the j-th iteration; x j Let j represent the phase function variable of the j-th iteration, where j = 1, 2, 3, ...; The loss function is defined to decrease along the derivative direction, eventually yielding an ideal wavefront where the evaluation function approaches 0.

5. The tilted wavefront sub-aperture stitching interferometry detection method based on a spatial light modulator as described in claim 1, characterized in that, In step 7, the phase is stitched together using a stitching algorithm to obtain the surface shape information, as follows: Select a central sub-aperture as the reference sub-aperture, and then stitch the reference sub-aperture with other sub-apertures in turn. Perform a four-step phase shift unwrapping phase on the divided sub-apertures, transform the phase information into phase information in the global coordinate system, and then stitch them together using a stitching algorithm to obtain the surface information.

6. The tilted wavefront sub-aperture stitching interferometry detection method based on a spatial light modulator as described in claim 1, characterized in that, In step 4, during interference detection, the overlapping area of ​​the outgoing light from the two point light sources at the outermost edge of the dynamic point source array onto the test surface (12) is larger than the freeform surface aperture of the test surface (12).

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