Inclined wave surface sub-aperture stitching interference detection method based on spatial light modulator

Abstract

The invention discloses an inclined wave surface sub-aperture stitching interference detection method based on a spatial light modulator, and relates to the field of optical detection. Light emitted by the laser is collimated and expanded and then enters the polarizing beam splitter; the reflected light is used as a reference light beam, and the transmitted light is used as a test light beam; a test light beam enters the spatial light modulator, is subjected to phase modulation by the spatial light modulator, passes through the lens and then forms standard spherical waves with different inclination angles, and zero detection is carried out on sub-apertures divided in different regions. The spatial light modulator is used as an ideal point source array generator to be matched with the imaging lens, so that required ideal inclined spherical waves can be generated according to different parameters of a measured piece, and compared with a traditional point source generator, the device has high universality. And for a large-aperture complex curved surface, sub-aperture splicing can be realized without moving an interference device, and errors caused by mechanical movement are reduced.

Description

Technical Field

[0001] The invention belongs to the technology of photoelectric detection, and in particular relates to a tilted wave surface sub-aperture splicing interference detection method based on a spatial light modulator. Background Art

[0002] Optical free-form surfaces, with extremely high design freedom and excellent optical performance, are gaining more and more attention. However, high-precision free-form surface processing depends on high-precision surface detection. Due to its large surface gradient changes, high surface freedom, no unified symmetry axis, and non-satisfaction of rotational symmetry, it increases the difficulty of high-precision processing and precision detection. The development level of free-form surface detection restricts its manufacturing level.

[0003] Optical interferometry detection technology, especially tilted wavefront interferometry detection technology, has the advantages of comprehensive synchronous detection mode, large dynamic measurement range, good versatility, and high detection accuracy, and provides an effective detection solution for large gradient and high complexity free-form surface detection. However, due to its non-zero interferometry detection, there is a large optical path return error in the detection, which limits the improvement of detection accuracy.

[0004] At the same time, the idea of ​​sub-aperture interferometry is to divide the surface to be tested into multiple small areas (sub-apertures) for detection. Since the asphericity of the sub-aperture is much lower than that of the entire surface to be tested, the detection difficulty is much easier. Finally, after demodulating the wavefront information of all sub-apertures, different methods are used to synthesize the surface shape to be tested. However, errors caused by mechanical movement will inevitably be introduced during the splicing process.

[0005] Different from traditional microlens arrays and optical fiber arrays, the dynamic point source generation method based on spatial light modulator can generate the most suitable point source for sub-aperture zero-position detection according to the different surface shapes of the test surface, and can also apply a certain degree of modulation to the point source at the same time, providing a new idea for free-form surface interference detection. Summary of the invention

[0006] In view of the shortcomings of the above-mentioned prior art, the present invention proposes a tilted wave surface sub-aperture splicing interference detection method based on a spatial light modulator. The 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 the different surface types to be tested. The spatial light modulator is used as a phase compensation element to dynamically generate a point source array, which can generate the required ideal tilted spherical waves for different parameters of the tested object. Compared with the traditional point source generator, it has strong versatility. In addition, for large-caliber complex curved surfaces, sub-aperture splicing can be achieved without moving the interference device, reducing the error introduced by mechanical movement.

[0007] The technical solution of the present invention is as follows: a tilted wave surface sub-aperture splicing interference detection method based on a spatial light modulator, the steps are as follows:

[0008] Step 1: Build the measurement optical path:

[0009] The measuring optical path includes a laser, a first lens, a second lens, an aperture, a polarizer, a polarization beam splitter, a first 1 / 4 wave plate, a reflector, a spatial light modulator, a second 1 / 4 wave plate, an imaging lens, a surface to be measured, a third 1 / 4 wave plate, a third lens, a fourth lens, a polarization camera, and a PC control terminal.

[0010] A laser, a first lens, a second lens, an aperture, a polarizer, a polarization beam splitter prism, and a spatial light modulator are arranged in sequence along a common first optical axis; a second optical axis perpendicular to the first optical axis also exists through the polarization beam splitter prism; a reflector, a first 1 / 4 wave plate, a polarization beam splitter prism, a third 1 / 4 wave plate, a third lens, a fourth lens, and a polarization camera are arranged in sequence along the second optical axis; a second 1 / 4 wave plate, an imaging lens, and a surface to be measured are arranged in sequence on the reflected light path of the spatial light modulator; the spatial light modulator and the polarization camera are respectively connected to a PC control terminal.

[0011] The linearly polarized light emitted by the laser passes through the first lens and the second lens to become a beam-expanding parallel light, and then passes through the aperture to limit the beam aperture, becoming a parallel light beam with high light intensity uniformity; it passes through the polarizer to be divided into two parallel light beams with mutually perpendicular polarization directions, and then passes through the polarization beam splitter prism to be divided into a test light path and a reference light path; the test light path is on the first optical axis, and after being reflected by the spatial light modulator, it passes through the second 1 / 4 wave plate and the imaging lens to reach the surface to be tested, records the surface shape information of the surface to be tested, and then returns to the polarization beam splitter prism along the imaging lens, the second 1 / 4 wave plate, and the spatial light modulator; since the test light beam passes through the 1 / 4 wave plate polarization direction twice, the test light path is divided into a reference light path and a test light path. When the reference beam is rotated 90° and reaches the polarization beam splitter prism again, it will be reflected and will reach the polarization camera along the second optical axis through the third 1 / 4 wave plate, the third lens, and the fourth lens; on the second optical axis, the reference beam passes through the first 1 / 4 wave plate and reaches the reflector, where it is reflected and passes through the first 1 / 4 wave plate again to reach the polarization beam splitter prism; since the reference beam passes through the 1 / 4 wave plate twice and the polarization direction is rotated 90°, it will be transmitted when it reaches the polarization beam splitter prism again, and will reach the polarization camera along the second optical axis through the third 1 / 4 wave plate, the third lens, and the fourth lens; finally, an interference fringe pattern recording the surface information of the measured surface is taken at the polarization camera.

[0012] Step 2: divide the detection area of ​​the surface to be measured according to the lens parameters of the surface to be measured, 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 during interference surface type detection according to the divided detection area parameters.

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

[0014] Step 4: remove the standard spherical reflector, place it on the surface to be measured, turn on the laser, and use the spatial light modulator generated in step 3 and the dynamic point source array of the imaging lens to perform interference detection on the surface shape of the surface to be measured.

[0015] Step 5: The polarization camera collects four sub-aperture interference patterns corresponding to the measured surface for each point source.

[0016] Step 6: Perform four-step phase shifting on the above sub-aperture interference pattern to obtain the wrapped phase.

[0017] Step 7: Use a stitching algorithm to stitch the wrapped phases to obtain surface information, compare the surface information with the lens parameters of the surface to be measured, and complete the detection of the surface error of the surface to be measured.

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

[0019] The present 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 waves for different parameters of the device under test. Compared with traditional point source generators, it has strong versatility and can achieve sub-aperture splicing for large-aperture complex curved surfaces without moving the interference device, thereby reducing the error introduced by mechanical movement. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the measuring optical path of the present invention.

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

[0022] Figure 2 This is a flow chart of the tilted waveplane sub-aperture stitching interference detection method based on the spatial light modulator of the present invention. DETAILED DESCRIPTION

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

[0024] Combination Figure 2 The tilted wave surface sub-aperture stitching interferometry detection method based on the spatial light modulator of the present invention comprises the following steps:

[0025] Step 1: Combine Figure 1 , build the measurement optical path:

[0026] The measuring optical path includes a laser 1, a first lens 2, a second lens 3, an aperture 4, a polarizer 5, a polarization beam splitter prism 6, a first 1 / 4 wave plate 7, a reflector 8, a spatial light modulator 9, a second 1 / 4 wave plate 10, an imaging lens 11, a surface to be measured 12, a third 1 / 4 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 polarization beam splitter prism 6, and a spatial light modulator 9 are arranged in sequence along a common first optical axis. A second optical axis perpendicular to the first optical axis also exists through the polarization beam splitter prism 6. A reflector 8, a first 1 / 4 wave plate 7, a polarization beam splitter prism 6, a third 1 / 4 wave plate 13, a third lens 14, a fourth lens 15, and a polarization camera 16 are arranged in sequence along the second optical axis. A second 1 / 4 wave plate 10, an imaging lens 11, and a surface to be measured 12 are arranged in sequence on the reflected light path of the spatial light modulator 9. The spatial light modulator 9 and the polarization camera 16 are respectively connected to a PC control terminal 17.

[0028] The emission direction of the laser 1 is the main optical axis; the polarization direction of the linear polarized light emitted by the laser 1 is at an angle of 45° to the polarization direction of the polarizer 5; the laser 1 passes through the first lens 2 and the second lens 3 to become a beam-expanding parallel light.

[0029] The expanded parallel light passes through the aperture 4 to limit the beam aperture, becoming a parallel light beam with high light intensity uniformity, and then passes through the polarizer 5 to be divided into two parallel light beams with mutually perpendicular polarization directions; the light path is divided into a test light path and a reference light path after passing through the polarization beam splitter prism 6. Since the angle between the splitting surface of the polarization beam splitter prism 6 and the main optical axis is 45°, the main optical axes of the two light paths are perpendicular to each other.

[0030] The test light path is on the first optical axis, and after being reflected by the spatial light modulator 9, it passes through the second 1 / 4 wave plate 10 and the imaging lens 11 to generate an ideal point source array to form standard spherical waves with different inclination angles to reach the surface to be tested 12, and performs zero position detection on the sub-apertures divided into different areas of the surface to be tested, and after recording the surface information of the surface to be tested, it returns to the polarization beam splitter prism 6 along the imaging lens 11, the second 1 / 4 wave plate 10, and the spatial light modulator 9; since the test light beam passes through the 1 / 4 wave plate twice and the polarization direction is rotated 90°, it will be reflected when it reaches the polarization beam splitter prism 6 again, and will reach the polarization camera 16 along the second optical axis through the third 1 / 4 wave plate 13, the third lens 14, and the fourth lens 15.

[0031] The reference beam is on the second optical axis, passes through the first 1 / 4 wave plate 7 and reaches the reflector 8, where it is reflected, and then passes through the first 1 / 4 wave plate 7 again and reaches the polarization beam splitter prism 6. Since the reference beam is transmitted through the 1 / 4 wave plate twice and its polarization direction is rotated by 90°, it will be transmitted when it reaches the polarization beam splitter prism 6 again, and will pass through the third 1 / 4 wave plate 13, the third lens 14, and the fourth lens 15 along the second optical axis and reach the polarization camera 16.

[0032] The reference beam and the test beam respectively form circularly polarized light p and s with opposite rotation directions after passing through the third 1 / 4 wave plate 13. After the two circularly polarized lights pass through the two-dimensional chessboard grating, the diffraction effect generates four light fields (±1st order diffraction light field in the x direction, ±1st order diffraction light field in the y direction) respectively.

[0033] After the four light fields of the two circularly polarized lights pass through a 2×2 wave plate delay array, the phases of the four polarized light fields produce phase shifts of 0, π / 2, π, and 3π / 2, respectively.

[0034] The four light fields of the circularly polarized light s after the phase shift interfere with the four light fields of the circularly polarized light p after the phase shift in pairs in the polarization direction of the polarizer, generating four interference fields with phase differences of 0, π / 2, π, and 3π / 2, respectively, to complete the spatial polarization phase shift interferometry. The interference pattern is displayed on the PC control terminal and the surface type to be measured is restored. The fast axis azimuth angles of the first 1 / 4 wave plate 7, the second 1 / 4 wave plate 10, and the third 1 / 4 wave plate 13 are 45 degrees.

[0035] The polarization camera 16 is a polarization camera with a pixel-level polarization mask, which covers the photodiode of the camera. Four pixels are grouped together, and the polarization angles are 0 degrees, 45 degrees, 90 degrees, and 135 degrees, respectively. Images with four different polarization angles can be output simultaneously.

[0036] The angle between the normal line of the spatial light modulator reflection surface and the main optical axis of the test light is 3-10°, and the specific tilt angle can be adjusted according to the specific side surface shape.

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

[0038] The sub-aperture of the surface to be measured is divided into sub-apertures through the sub-aperture planning mathematical model:

[0039] For any complex surface, it can be discretized and then the discretized data can be solved as close to the sphere as possible. For any complex surface, it can be expressed as follows:

[0040] z=P(x,y)

[0041] Consider the position closest to the center of the sphere (x c ,y c , z c ), the radius of the closest sphere is h, and the discrete points on the measured object are (x i ,y i , z i ).

[0042] Due to the symmetry of the mirror, in order to simplify the solution model, it is assumed that the mirror and the detection sub-aperture are symmetrical along the X-axis, then the closest to the center of the sphere

[0043] x c =0

[0044] The optimization objective function is:

[0045]

[0046] Where M is the number of mirror sampling points. Based on the iterative algorithm, we can get (y c , z c ) and h, and thus the position of the complex surface closest to the spherical surface is obtained, 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 sub-aperture center:

[0047] h=h(R)

[0048] It can be obtained that the radius r of each sub-aperture corresponds to the off-axis position h of the sub-aperture center:

[0049]

[0050] Where F is the standard mirror F number.

[0051] Assuming that the number of planned apertures of a circle is n, according to the constraint relationship of k:

[0052]

[0053] Where k is the distance between the chords of adjacent subapertures in the same circle and the center of the subaperture, and k0 is the maximum value of k, which is determined by the pre-defined overlapping area between adjacent subapertures.

[0054] According to the ratio p of the overlapping area of ​​adjacent sub-apertures to the size of the sub-aperture, k0 (the maximum value of the distance k between the chords of adjacent sub-apertures in the same circle and the center of the sub-aperture) can be obtained. Therefore, we have:

[0055]

[0056] S represents the sub-aperture area. While ensuring the overlapping area, the number of sub-apertures should take the minimum value:

[0057] [x] is the integer of x

[0058] From this, we can determine that the inner and outer radii of this circle are:

[0059]

[0060] First determine the size r0 of the central sub-aperture of the DUT, and then solve the R1 size of the N+1th circle based on the overlapping area requirement of adjacent circles and the fact that the R1 value of the N+1th circle should be smaller than the R2 value of the Nth circle. The overlapping area of ​​adjacent rings is defined as:

[0061]

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

[0063]

[0064]

[0065] In a recursive manner, assuming that sub-apertures within N circles are planned, the selection of the N+1th circle should make its R1 value smaller than the R2 value of the Nth circle, and the difference should be given by the percentage of overlapping area; when R1 is determined, the position R of the aperture center of the N+1th circle from the optical axis, the number of sub-apertures n, and the R2 value are deduced from the R1 expression; the recursive process is continued until the R2 of a certain circle is larger than half the mirror aperture.

[0066] Step 3, replace the surface to be measured 12 with a standard spherical reflector, use the iterative generation algorithm and the wavefront iteration algorithm to calibrate the position parameters and the ideal spherical wave modulation amount of the dynamic point source array generated by the spatial light modulator 9 and the imaging lens 11, for high-precision generation of the dynamic point source array;

[0067] Among them, the present invention first proposes to obtain a spatial light modulator to generate an ideal point source array by using a weighted Gerchberg Saxton algorithm (GSW) and a Newton iterative interference fringe feedback algorithm:

[0068] The generation of a dynamic point source in the complex curved surface detection method based on a spatial light modulator mainly needs to solve two problems: accurate compensation of the tilt amount required for point source zero position detection and precise compensation of the required wavefront phase.

[0069] The weighted Gerchberg and Saxton iterative algorithm (GSW) for calculating the light wave field of a three-dimensional image generated by a hologram can solve the problem of accurate compensation of the tilt required for point source zero position detection. When calculating the hologram, the GSW algorithm introduces a weight factor to improve the brightness distribution of the image, reduce errors, and optimize the iteration process, thereby achieving more accurate high-quality holographic image reconstruction. When the SLM and the imaging lens generate a point source array, the algorithm automatically calculates the point lattice intensity distribution on the corresponding Fourier plane by setting the required point source position coordinate parameters, and compares it with the target point lattice intensity distribution to obtain a weight correction coefficient. Since a weight coefficient that changes with the number of iterations is used, the ratio of the energy of the light trap in the input image to the energy of the light trap in the restored image obtained in each iteration multiplied by the weight coefficient in the previous iteration is used as the weight of this iteration. The introduction of weights makes the light trap energy of the restored image obtained by hologram restoration approach the design value. Finally, the accurate compensation of the required tilt is completed, and a dynamic point source with accurate posture is generated. Finally, the posture phase map required to be generated on the SLM is pushed back.

[0070] The interference fringe feedback algorithm based on Newton iteration innovatively proposes to use a standard spherical mirror as a calibration surface, and perform wavefront feedback calibration on point sources with different tilt angles to generate an ideal spherical wavefront phase map. J+1 Zernike fringe coefficients are selected as input, and the interference fringe processing algorithm is used to extract the fringe. The fringe information entropy is selected as the fringe gradient loss function f(x) and the fringe gradient loss value is output. The Newton iteration algorithm is used as the gradient descent optimizer to find the loss c j The loss quickly reaches 0.

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

[0072]

[0073] The light intensity information after polarization shift is:

[0074]

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

[0076]

[0077] The initial random phase surface is input through the SLM to obtain the initial interference pattern, and the optical wavefront phase function information is obtained through polarization shift. Perform zernike fitting on the phase surface and define the weighted fitting coefficients

[0078] Loss function:

[0079]

[0080] q j The new phase function is loaded onto the SLM as the weighting coefficient to obtain new fringes and a new phase function.

[0081] Based on the phase function of Newton iteration:

[0082]

[0083] The loss function is defined to descend along the derivative direction, and finally an ideal wave surface is obtained where the evaluation function approaches 0.

[0084] Step 4: remove the standard spherical reflector, place it in the surface to be measured 12, turn on the laser 1 light source, use the spatial light modulator 9 and the imaging lens 11 to generate a dynamic point source array to perform interference detection on the surface shape of the surface to be measured.

[0085] During interference detection, the overlapping area where the outgoing light beams from the two most edge point light sources of the dynamic point source array illuminate the surface to be measured 12 is larger than the free-form surface aperture of the surface to be measured 1.

[0086] Step 5: Collect four interference patterns of each point source corresponding to the sub-aperture of the surface to be measured.

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

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

[0089] The mathematical model of the stitching algorithm planning restores the surface shape of the surface to be measured:

[0090] For two sub-apertures with overlapping areas, the surface data of the sub-apertures are represented by w1(x, y) and w2(x, y) respectively. Theoretically, the values ​​of the two in the overlapping area should be consistent. Since there is an error in the two measurements, there is a certain deviation in the overlapping area. Therefore, it is necessary to eliminate the error by coordinate transformation. The transformation relationship is:

[0091]

[0092] In the formula, w 10 (x,y) and w 20 (x, y) represent the theoretical surface 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 data of the two sub-apertures in the overlapping area remain unchanged, that is, w 10 (x,y)=w 20 (x, y), so for any two sub-apertures with overlapping areas, 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, ΔD=D1-D2. It can be seen that in order to know the deviation between the two surface shapes, it is only necessary to solve the splicing coefficients ΔA, ΔB, ΔC, and ΔD. Theoretically, four unknowns can be calculated based on the four equations. Therefore, by randomly selecting four points in the overlapping area that are not on the same straight line, the specific values ​​of the four splicing coefficients ΔA, ΔB, ΔC, and ΔD can be obtained. In order to reduce the error caused by the small amount of calculation data and improve the accuracy of the calculation results, a certain number of sampling points are selected and quantified, and then the least squares method is used to fit the corresponding splicing parameters when the residual sum of squares G is minimized. Among them, 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] Calculate the partial derivatives of the splicing coefficients in the above formula respectively and set them to 0. The specific formula is as follows:

[0098]

[0099] Solving each of the above equations, we can get 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). Each stitching coefficient can be obtained. For more than two sub-apertures, each sub-aperture is stitched and coordinate transformed in turn, and then the measurement data of the full-aperture surface is obtained by adding each surface shape, and finally the surface shape error of the surface to be measured is obtained.

[0102] In view of the shortcomings of traditional inclined wavefront interference and sub-aperture splicing interference, the present invention proposes for the first time an inclined wavefront sub-aperture splicing interference detection device based on a spatial light modulator, and innovatively proposes to generate a dynamic point source array with high position accuracy and good wavefront quality by combining the weighted Gerchberg and Saxton algorithm (GSW) with the Newton iterative interference fringe feedback algorithm in view of the modulation characteristics of the spatial light modulator. The 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 to be measured, and the spatial light modulator is used as a phase compensation element to dynamically generate a point source array, which can generate the required ideal inclined spherical waves for different parameters of the measured object, and has strong versatility compared to traditional point source generators. In addition, for large-caliber complex curved surfaces, sub-aperture splicing can be achieved without moving the interference device, reducing the error introduced by mechanical movement.

[0103] The above is only a specific implementation scheme of the present invention, and not a limitation thereof. Although referring to this implementation scheme, ordinary researchers in the field should be able to easily understand that they can still make equivalent substitutions for some technical features in the aforementioned scheme. These modifications and substitutions do not change the essence of the scheme and should be included in the protection scope of the present invention.

Claims

1. A tilted wave surface sub-aperture stitching interferometry detection method based on a spatial light modulator, characterized in that: Here are the steps: Step 1: Build the measurement optical path: The measuring optical path comprises a laser (1), a first lens (2), a second lens (3), an aperture (4), a polarizer (5), a polarization beam splitter (6), a first quarter wave plate (7), a reflector (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); A laser (1), a first lens (2), a second lens (3), an aperture (4), a polarizer (5), a polarization beam splitter prism (6), and a spatial light modulator (9) are sequentially arranged along a common first optical axis; a second optical axis perpendicular to the first optical axis also exists through the polarization beam splitter prism (6); a reflector (8), a first 1 / 4 wave plate (7), a polarization beam splitter prism (6), a third 1 / 4 wave plate (13), a third lens (14), a fourth lens (15), and a polarization camera (16) are sequentially arranged along the second optical axis; a second 1 / 4 wave plate (10), an imaging lens (11), and a surface to be measured (12) are sequentially arranged on the reflected light path of the spatial light modulator (9); the spatial light modulator (9) and the polarization camera (16) are respectively connected to a PC control terminal (17); The linearly polarized light emitted by the laser (1) passes through a first lens (2) and a second lens (3) to become a beam-expanding parallel light, and then passes through an aperture (4) to limit the aperture of the light beam, thus becoming a parallel light beam with high light intensity uniformity; passes through a polarizer (5) to be divided into two parallel light beams with polarization directions perpendicular to each other, and then passes through a polarization beam splitter prism (6) to be divided into a test light path and a reference light path; the test light path is on a first optical axis, and after being reflected by a spatial light modulator (9), passes through a second 1 / 4 wave plate (10) and an imaging lens (11) to reach a surface to be tested (12), records the surface type information of the surface to be tested, and then returns to the polarization beam splitter prism (6) along the imaging lens (11), the second 1 / 4 wave plate (10), and the spatial light modulator (9); since the test light beam passes through the 1 / 4 wave plate twice, the polarization direction of the test light beam is rotated. When the reference beam is rotated 90° and reaches the polarization beam splitter prism (6) again, it will be reflected and will pass through the third 1 / 4 wave plate (13), the third lens (14) and the fourth lens (15) along the second optical axis to reach the polarization camera (16); on the second optical axis, the reference beam passes through the first 1 / 4 wave plate (7) and reaches the reflector (8), where it will be reflected and will pass through the first 1 / 4 wave plate (7) again to reach the polarization beam splitter prism (6); because the reference beam passes through the 1 / 4 wave plate twice and the polarization direction is rotated 90°, when it reaches the polarization beam splitter prism (6) again, it will be transmitted and will pass through the third 1 / 4 wave plate (13), the third lens (14) and the fourth lens (15) along the second optical axis to reach the polarization camera (16); finally, an interference fringe pattern recording the surface information of the surface to be measured is captured at the polarization camera; Step 2: dividing the detection area of ​​the surface to be measured (12) according to the lens parameters of the surface to be measured (12), and determining the position parameters and ideal spherical wave modulation amount required for the spatial light modulator (9) and the imaging lens (11) to generate the dynamic point source array during the interference surface type detection according to the parameters of the divided detection area; Step 3, replacing the surface to be measured (12) with a standard spherical reflector, and using an iterative generation algorithm and a wavefront iteration algorithm to calibrate the position parameters of the dynamic point source array generated by the spatial light modulator (9) and the imaging lens (11) and the modulation amount of the ideal spherical wave; Step 4, remove the standard spherical reflector, place the surface to be measured (12), turn on the laser (1), and use the dynamic point source array of the spatial light modulator (9) and the imaging lens (11) generated in step 3 to perform interference detection on the surface shape of the surface to be measured (12); Step 5, the polarization camera (16) collects four sub-aperture interference patterns of each point source corresponding to the surface to be measured (12); Step 6, performing four-step phase shifting on the above sub-aperture interference pattern to obtain the wrapped phase; Step 7: splice the wrapped phases through a splicing algorithm to obtain surface information, compare the surface information with the lens parameters of the surface to be measured (12), and complete the detection of the surface error of the surface to be measured.

2. The tilted wave surface sub-aperture stitching interferometry detection method based on spatial light modulator according to claim 1, characterized in that: In step 1, the polarization direction of the linear polarized light emitted by the laser (1) is at an angle of 45° to the polarization direction of the polarizer (5); the angle between the splitting surface of the polarization splitting prism (6) and the main optical axis is 45°, and the angle between the normal line of the reflection surface of the spatial light modulator (9) and the first optical axis is 3 to 10°.

3. The tilted wave surface sub-aperture stitching interferometry detection method based on spatial light modulator according to claim 1, characterized in that: In step 3, the surface to be measured (12) is replaced with a standard spherical reflector, 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: According to the dynamic point source position parameters to be generated, based on the GSW weighted iteration algorithm, a point source array with accurate position is generated through a spatial light modulator (9) and an imaging lens (11); The GSW algorithm introduces weight factors to improve the brightness distribution of the image, reduce errors, and optimize the iterative process, thereby achieving holographic image reconstruction; When a dynamic point source array is generated by cooperating with a spatial light modulator (9) and an imaging lens (11), the GSW calculates the point array intensity distribution 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 a weight correction coefficient, thereby finally completing the accurate compensation of the required tilt amount and generating a dynamic point source with a precise position.

4. The tilted wave surface sub-aperture stitching interferometry detection method based on spatial light modulator according to claim 3, characterized in that: In step 3, the wavefront iteration algorithm is used to calibrate the modulation amount of the ideal spherical wave 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 the imaging lens (11) is obtained by the interference fringe feedback algorithm based on Newton iteration: The standard spherical mirror is used as the calibration surface, and the wavefront feedback calibration is performed on point sources with different tilt angles to generate the ideal spherical wavefront phase diagram; n+1 zernike coefficients Z are selected n As input, the interference fringe processing algorithm is used to extract the fringe, the fringe information entropy is selected as the fringe gradient loss function f(x) and the fringe gradient loss value is output, and the Newton iteration algorithm is used as the gradient descent optimizer loss to find the loss value c n The collection of , so that the loss quickly reaches 0; Use c n The phase indicated Written as: Among them, Z n represents the nth zernike coefficient; After polarization shift, the pixel information relationship of the four frames of images is solved, where the light intensity is I i , image number i=0,1,2,3: in, Represents the light wavefront phase function information; An initial random phase surface is input through a spatial light modulator (9) to obtain an initial interference pattern, and light wavefront phase function information is obtained through polarization shifting. Perform a zernike fit on the phase surface and weight the fitting coefficients to define the loss function f(x): q n The new phase function is loaded onto the spatial light modulator (9) as the weighting coefficient to obtain new fringes and a new phase function. The new phase function is iterated based on Newton: Among them, f'(x j ) represents the phase function after the jth iteration; x j represents the j-th phase function variable, j = 1, 2, 3, ...; The loss function is defined to descend along the derivative direction, and finally an ideal wave surface is obtained where the evaluation function approaches 0.

5. The tilted wave surface sub-aperture stitching interferometry detection method based on spatial light modulator according to claim 1, characterized in that: In step 7, the wrapped phases are spliced ​​by a splicing algorithm to obtain the surface information, as follows: A central sub-aperture is selected as a reference sub-aperture, and the reference sub-aperture is spliced ​​with other sub-apertures in turn. The divided sub-apertures are subjected to four-step phase shifting and unwrapping, and the phase information is converted into the phase information in the global coordinate system. The surface information is obtained by splicing the sub-apertures through the splicing algorithm.

6. The tilted wave surface sub-aperture stitching interferometry detection method based on spatial light modulator according to claim 1, characterized in that: In step 4, during interference detection, the overlapping area of ​​the emitted light from the two most edge point light sources of the dynamic point source array irradiating the surface to be measured (12) is larger than the free-form surface aperture of the surface to be measured (12).

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