A method for correcting primary mirror type error based on multimodal interferometric data fusion

Abstract

This application relates to the technical field of primary mirror profile error correction, and discloses a method for primary mirror profile error correction based on multimodal interferometric data fusion. The method includes: acquiring the interference fringe pattern of the primary mirror and constructing the interference phase pattern and interference amplitude pattern of the primary mirror; selecting a phase reference region in the interference phase pattern and constructing a central phase sequence for each phase reference region; constructing a phase drift model based on the central phase sequence of each phase reference region, and performing drift correction on the interference phase pattern based on the phase drift model; identifying response defect regions in the interference phase pattern; calculating the response confidence of pixels in the interference phase pattern, and performing defect correction on the response defect regions based on the response confidence of different pixels; generating a wavefront image of the primary mirror based on the interference phase pattern, and performing error analysis and correction of the primary mirror profile based on the wavefront image. This application can improve the accuracy of primary mirror profile error correction for large-aperture primary mirrors.

Description

Technical Field

[0001] This application relates to the technical field of primary mirror shape error correction, specifically to a primary mirror shape error correction method based on multimodal interferometric data fusion. Background Technology

[0002] Interferometry, with its advantages of being non-contact and highly sensitive, has become the mainstream technique for detecting primary mirror shape errors. However, in practical applications, due to factors such as the structural characteristics of the primary mirror itself, interference from the measurement environment, and limitations of data processing algorithms, the technique of calculating primary mirror shape errors based on interferometry has some shortcomings.

[0003] In interferometry, phase information is the core basis for retrieving the principal mirror shape error, and it is easily affected by external environmental disturbances and the characteristics of the equipment itself, resulting in drift. Existing technologies for suppressing phase drift mostly employ hardware compensation or simple software correction methods, which are difficult to completely eliminate the influence of minute environmental disturbances;

[0004] The quality of the interference fringe pattern directly determines the accuracy of phase extraction. However, in actual measurements, the interference fringe pattern often suffers from poor local data quality due to the influence of the primary mirror structure, illumination conditions, and optical system characteristics. For example, the edge region of the primary mirror is prone to fringe blurring and reduced contrast due to boundary effects; minor contamination on the primary mirror surface can cause breaks or jumps in the interference fringes in local areas; furthermore, uneven illumination of the interferometer and aberrations of optical components can also reduce the clarity of fringes in some areas, forming low-contrast or blurred regions. Existing phase extraction algorithms mostly assume that the overall data quality of the interference fringe pattern is consistent and do not perform special processing for low-quality data areas, affecting the accuracy of the overall surface shape accuracy assessment.

[0005] For example, patent application CN117213358A discloses an active compensation method for interferometer wavefront systematic errors, providing active compensation for wavefront errors introduced by the second collimating lens in large-aperture interferometers. First, an interferometric reference optical path system model is established in the optical design software Zemax; a polynomial is used to characterize the wavefront introduced by the second collimating lens; a custom surface shape in Zemax is used to model and simulate the systematic errors of the second collimating lens, such as surface shape error, material homogeneity error, residual stress, clamping deformation, and gravity deformation, and analyze the impact of these systematic errors on the reference wavefront. Based on the accurate modeling of the interferometric system, the systematic errors caused by the aforementioned error sources in the reference wavefront of the large-aperture interferometer are compensated by controlling the surface shape parameters of the deformable mirror. This scheme accurately models the systematic errors introduced by the second collimating lens in the reference wavefront and compensates for wavefront errors by controlling the surface sag of the deformable mirror, achieving high accuracy and good practicality. However, this scheme still suffers from the problem mentioned in the background of this application: it does not perform special processing for low-quality data areas, affecting the accuracy of the overall surface shape accuracy assessment.

[0006] The information disclosed in this background section is intended only to enhance the understanding of the overall background of this application and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0007] The technical problem to be solved by this application is to overcome the defects of the prior art and provide a primary mirror shape error correction method based on multimodal interferometric data fusion to improve the accuracy of primary mirror shape error correction for large apertures.

[0008] To solve the above-mentioned technical problems, this application provides the following technical solution:

[0009] A primary mirror type error correction method based on multimodal interferometric data fusion includes the following steps:

[0010] Obtain the interference fringe pattern of the primary mirror, and construct the interference phase pattern and interference amplitude pattern of the primary mirror based on the interference fringe pattern;

[0011] A phase reference region is selected in the interferometric phase diagram, and a central phase sequence for each phase reference region is constructed based on the interferometric amplitude diagram;

[0012] A phase drift model is constructed based on the central phase sequence of each phase reference region, and the interferometric phase map is drift corrected based on the phase drift model.

[0013] Identify the response defect region in the interference phase diagram;

[0014] Calculate the response confidence of each pixel in the interferometric phase image, and correct defects in the response defect area based on the response confidence of different pixels;

[0015] The wavefront diagram of the primary mirror is generated based on the interferometric phase diagram, and the error analysis and correction of the primary mirror surface shape are performed based on the wavefront diagram.

[0016] As a preferred embodiment of the primary mirror surface error correction method based on multimodal interferometric data fusion described in this application, the primary mirror is subjected to interference detection by an interferometer to obtain an interference fringe pattern; the pixel value of each pixel in the interference fringe pattern represents the interference fringe brightness of the reference light and the test light at the corresponding position on the primary mirror.

[0017] The pixel value of each pixel in the interference phase diagram represents the phase difference between the reference light and the test light for interference detection at the corresponding position of the primary mirror.

[0018] Constructing the interference phase map of the primary mirror based on the interference fringe map includes: performing phase extraction and phase unpacking on the pixel value of each pixel in the interference fringe map to obtain the pixel value of each pixel in the interference phase map;

[0019] The pixel value of each pixel in the interference amplitude diagram represents the relative value of the superimposed amplitude of the reference light and the test light at the corresponding position of the primary mirror.

[0020] Constructing the interference amplitude map of the primary mirror based on the interference fringe map includes: calculating the square root of the pixel value of each pixel in the interference fringe map and performing standardization processing to obtain the pixel value of each pixel in the interference amplitude map.

[0021] As a preferred embodiment of the primary mirror type error correction method based on multimodal interferometric data fusion described in this application, the method for selecting the phase reference region is as follows:

[0022] Set a first sliding window; based on the first sliding window, simultaneously extract pixels in the interference phase map and the interference amplitude map, and each sliding operation extracts a set of candidate regions; any set of candidate regions includes the phase candidate region extracted in the interference phase map and the amplitude candidate region extracted in the interference amplitude map.

[0023] Calculate the comprehensive score for each group of candidate regions; select the N groups of candidate regions with the highest comprehensive scores and extract the corresponding N phase candidate regions as N phase reference regions; extract the corresponding N amplitude candidate regions as N amplitude reference regions; N is a positive integer.

[0024] As a preferred embodiment of the primary mirror error correction method based on multimodal interferometric data fusion described in this application, the method for calculating the comprehensive score of any group of candidate regions is as follows:

[0025] The gradient magnitude of the pixel value of each pixel in the phase candidate region is calculated using the Sobel operator; the standard deviation of the gradient magnitude of the pixel value of each pixel in the phase candidate region is calculated and used as the first score of the corresponding group of candidate regions;

[0026] Calculate the first-order gradient of the pixel value of each pixel in the amplitude candidate region and extract the gradient magnitude; calculate the mean of the gradient magnitude of the pixel value of each pixel in the amplitude candidate region, and use it as the second score of the corresponding candidate region.

[0027] Calculate the minimum distance between the phase candidate region and the edge of the interferometric phase map, and use it as the third score for the corresponding group of candidate regions;

[0028] The comprehensive score of the candidate region for the corresponding group is calculated based on the first score, the second score, and the third score. The first score is negatively correlated with the comprehensive score, and the second or third score is positively correlated with the comprehensive score.

[0029] As a preferred embodiment of the primary mirror error correction method based on multimodal interferometric data fusion described in this application, the method for constructing the center phase sequence of any phase reference region is as follows:

[0030] In the amplitude reference region corresponding to the phase reference region, the fringe direction is identified, and the direction perpendicular to the fringe direction is marked as the reference direction.

[0031] Continuous pixels are extracted along the reference direction as amplitude reference points;

[0032] Calculate the pixel value gradient along the reference direction for each amplitude reference point and form a gradient sequence for the amplitude reference points;

[0033] Identify the local maxima of the pixel value gradient in the gradient sequence, and mark the amplitude reference point corresponding to each local maximum as the stripe rhythm center;

[0034] The phase value corresponding to the center position of each stripe rhythm is queried in the phase reference area and arranged into the center phase sequence of the phase reference area.

[0035] As a preferred embodiment of the primary mirror error correction method based on multimodal interferometric data fusion described in this application, the phase drift model is used to calculate the phase drift amount of each pixel in the interferometric phase image; the method for constructing the phase drift model is as follows:

[0036] Calculate the phase drift reference for each phase reference region based on the corresponding center phase sequence;

[0037] A phase drift model is constructed based on the phase drift reference of each phase reference region; specifically including:

[0038] Mark the phase drift value corresponding to the center coordinates of each phase reference area as the corresponding phase drift reference;

[0039] Based on the phase drift values ​​corresponding to the center coordinates of different phase reference regions, a surface equation of the phase drift value is fitted within the coordinate range of the interferometric phase diagram, which serves as the model equation for the phase drift model.

[0040] The drift correction of the interferometric phase image based on the phase drift model includes: calculating the phase drift amount of each pixel in the phase interferometric image based on the phase drift model; and subtracting the corresponding phase drift amount from the phase value of each pixel in the interferometric phase image to achieve drift correction of the interferometric phase image.

[0041] As a preferred embodiment of the primary mirror type error correction method based on multimodal interferometric data fusion described in this application, the method for calculating the phase drift reference of any phase reference region is as follows:

[0042] Fitting a reference phase sequence to the corresponding center phase sequence specifically includes:

[0043] The first phase value in the central phase sequence is extracted as the fitting starting point, and the phase value corresponding to the fitting starting point is used as the first reference phase value in the reference phase sequence and filled into the reference phase sequence;

[0044] The reference phase sequence is filled with reference phase values ​​based on the phase values ​​in the central phase sequence. Specifically, if the i-th phase value in the central phase sequence is greater than the (i-1)-th phase value, then the i-th reference phase value in the reference phase sequence is the (i-1)-th phase value plus 2π; otherwise, the i-th reference phase value in the reference phase sequence is the (i-1)-th phase value minus 2π. The value of i is in the range of 2, 3, ..., M; M is the number of phase values ​​in the central phase sequence.

[0045] Calculate the difference between each phase value in the central phase sequence and the corresponding reference phase value in the reference phase sequence, and use it as the residual of each phase value in the central phase sequence; calculate the mean of the residuals of each phase value in the central phase sequence, and use it as the phase drift reference for the corresponding phase reference area.

[0046] As a preferred embodiment of the primary mirror type error correction method based on multimodal interferometric data fusion described in this application, the method for identifying response defect regions in the interferometric phase map specifically includes:

[0047] Set a second sliding window; use the second sliding window to slide and select the observation area in the interference amplitude diagram; for any sliding selection, extract the maximum and minimum pixel values ​​of all pixels in the observation area; calculate the sharpness index of the observation area, which is the difference between the maximum and minimum pixel values ​​divided by the sum of the maximum and minimum pixel values;

[0048] Set a sharpness threshold; mark each observation area with a sharpness index lower than the sharpness threshold as a defect window;

[0049] Different defect windows are aggregated into potential defect regions through connected component analysis;

[0050] Set a first area threshold; mark potential defect areas with an area greater than the first area threshold as response defect areas in the interference amplitude diagram;

[0051] In the interferometric phase diagram, the region corresponding to any response defect region in the interferometric amplitude diagram is marked as a response defect region.

[0052] As a preferred embodiment of the primary mirror error correction method based on multimodal interferometric data fusion described in this application, the method further includes: identifying the response defect region in the interferometric phase map.

[0053] In the interferometric phase map, the gradient magnitude of the pixel value of each pixel is calculated using the Sobel operator, which serves as a continuity index for each pixel.

[0054] Set a continuity threshold, and mark pixels with a continuity index greater than the continuity threshold as phase defect points;

[0055] Phase defect points are aggregated into phase defect regions through connected component analysis;

[0056] A second area threshold is set, and phase defect regions with an area greater than the second area threshold are marked as response defect regions.

[0057] As a preferred embodiment of the primary mirror error correction method based on multimodal interferometric data fusion described in this application, the calculation of the response confidence of pixels in the interferometric phase image includes: setting a correction reference area for each response defect area in the interferometric phase image, and calculating the response confidence of each pixel in each correction reference area; wherein, the method for setting a correction reference area for any response defect area is as follows: setting the size and shape of the correction reference area; uniformly cutting m correction reference areas around the response defect area in the interferometric phase image; m is a positive integer; assigning a value to the response confidence of each pixel in each correction reference area based on the corresponding continuity index, and the larger the continuity index, the smaller the response confidence of the corresponding pixel.

[0058] As a preferred embodiment of the primary mirror type error correction method based on multimodal interferometric data fusion described in this application, the method for correcting defects in any response defect region is as follows:

[0059] In each correction reference area corresponding to the response defect area, the n pixels with the highest response confidence are extracted as correction reference points; n is a positive integer.

[0060] A phase surface equation is fitted based on the phase value and response confidence of each corrected reference point; when fitting the phase surface equation, the response confidence of each corrected reference point is used as the corresponding fitting weight.

[0061] The phase correction value of each pixel in the response defect area is calculated based on the phase surface equation, and the phase value of each pixel in the response defect area is replaced with the corresponding phase correction value.

[0062] As a preferred embodiment of the primary mirror surface error correction method based on multimodal interferometric data fusion described in this application, the step of generating the wavefront map of the primary mirror based on the interferometric phase map specifically includes:

[0063] Obtain the reference wavelength; calculate the wavefront value of each pixel based on the phase value of each pixel in the interference phase diagram and the reference wavelength, and construct the wavefront diagram of the primary mirror;

[0064] Error analysis and correction of the primary mirror shape are performed based on the wavefront diagram, specifically including:

[0065] The PV and RMS values ​​of the primary mirror are calculated based on the wavefront diagram. Thresholds are set for the PV and RMS values ​​respectively. If the PV and RMS values ​​of the primary mirror are both less than the corresponding thresholds, the primary mirror meets the processing standard. Otherwise, the primary mirror has processing errors and is reworked for correction.

[0066] Compared with the prior art, the beneficial effects achieved by this application are as follows:

[0067] This application integrates the interferometric phase map and the interferometric amplitude map. The interferometric amplitude map identifies information such as fringe contrast, edge occlusion, and fringe transitions, providing a data quality basis for the selection of the phase reference area and avoiding phase errors introduced by low-quality data. A phase drift model is used to calculate the phase drift of each pixel, effectively offsetting global or local phase shifts caused by light source wavelength drift, optical path differences, and environmental disturbances during interferometer measurement, thus eliminating key interference factors for subsequent surface error inversion.

[0068] To address common defects in primary mirror surface shape measurement, a targeted identification scheme was developed. A surrounding correction reference area was set up for each response defect area, and the confidence weight of the reference area pixels was assigned in combination with the continuity index. This effectively repaired defects such as edge ghosting and oversaturation points, avoiding false errors or data loss caused by traditional interpolation or elimination methods, and ensuring the integrity and authenticity of the surface shape data. Attached Figure Description

[0069] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0070] Figure 1 A flowchart of a primary mirror type error correction method based on multimodal interferometric data fusion provided in this application;

[0071] Figure 2 A flowchart illustrating the method for selecting the phase reference region and amplitude reference region provided in this application. Detailed Implementation

[0072] The technical solution of this application will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments and specific features in the embodiments are detailed descriptions of the technical solution of this application, rather than limitations thereof. In the absence of conflict, the embodiments and technical features in the embodiments can be combined with each other.

[0073] This embodiment introduces a primary mirror shape error correction method based on multimodal interferometric data fusion, referring to... Figure 1 The method includes the following steps:

[0074] Obtain the interference fringe pattern of the primary mirror, and construct the interference phase pattern and interference amplitude pattern of the primary mirror based on the interference fringe pattern;

[0075] Interference detection is performed on the primary mirror using an interferometer to obtain an interference fringe pattern. The pixel value of each pixel in the interference fringe pattern represents the brightness of the interference fringes between the reference and test beams at the corresponding position on the primary mirror. The brightness of the interference fringes is determined by the superposition effect of the amplitudes of the test and reference beams. The interference fringe pattern appears macroscopically as alternating bright and dark fringes. Bright areas correspond to enhanced superposition of the amplitudes of the two beams, while dark areas correspond to weakened superposition of the amplitudes.

[0076] The pixel value of each pixel in the interference phase diagram represents the phase difference between the reference light and the test light for interference detection at the corresponding position of the primary mirror.

[0077] Constructing the interference phase map of the primary mirror based on the interference fringe map includes: performing phase extraction and phase unpacking on the pixel value of each pixel in the interference fringe map to obtain the pixel value of each pixel in the interference phase map;

[0078] If there is a slight height difference between the primary mirror surface and the reference surface at a certain position (i.e., an error in the primary mirror surface), then there will be an optical path deviation between the test light and the reference light at the corresponding position. This optical path deviation is recorded in the interference fringes in the form of phase. The phase value of each pixel is obtained by phase extraction and phase unpacking, and the specific error of each position of the primary mirror surface can be further calculated based on the phase value.

[0079] The pixel value of each pixel in the interference amplitude diagram represents the relative value of the superimposed amplitude of the reference light and the test light at the corresponding position of the primary mirror. The relative value of the superimposed amplitude indicates that the pixel value is not the actual value of the superimposed amplitude, but a relative value calculated based on the interference fringe diagram. The proportional relationship between the relative values ​​of the superimposed amplitude of different pixels is the same as the proportional relationship between the actual values. Therefore, this application only needs to focus on the relative magnitude of the superimposed amplitude at different positions, without the need to calculate the actual value, thus avoiding the introduction of unnecessary calculation errors.

[0080] Constructing the interference amplitude map of the primary mirror based on the interference fringe pattern includes: calculating the square root of the pixel value of each pixel in the interference fringe pattern and performing standardization to obtain the pixel value of each pixel in the interference amplitude map. Standardization involves scaling the corresponding values ​​to a specified range to characterize the relative magnitude of the superimposed amplitude. The brightness of the interference fringe pattern is proportional to the square of the superimposed amplitude; therefore, the relative magnitude of the superimposed amplitude can be calculated from the interference fringe pattern. The pixel values ​​in the interference amplitude map can be used to identify information such as the contrast of the interference fringes, edge occlusion, and fringe transitions.

[0081] A phase reference region is selected in the interferometric phase diagram, and an amplitude reference region is selected in the interferometric amplitude diagram. A central phase sequence for each phase reference region is constructed based on the amplitude reference regions.

[0082] Reference Figure 2 The method for selecting the phase reference region and the amplitude reference region is as follows:

[0083] Set a first sliding window; based on the first sliding window, simultaneously extract pixels in the interference phase map and the interference amplitude map, and each sliding operation extracts a set of candidate regions; any set of candidate regions includes the phase candidate region extracted in the interference phase map and the amplitude candidate region extracted in the interference amplitude map.

[0084] Calculate the comprehensive score for each group of candidate regions; select the N groups of candidate regions with the highest comprehensive scores and extract the corresponding N phase candidate regions as N phase reference regions; extract the corresponding N amplitude candidate regions as N amplitude reference regions; N is a positive integer.

[0085] Those skilled in the art can set the size of the first sliding window based on actual needs, such that the size of the first sliding window is sufficient to span several interference fringes. If the interference phase map is aligned with the interference amplitude map, the positions of the phase candidate region and the amplitude candidate region in any set of candidate regions will completely coincide.

[0086] The method for calculating the comprehensive score of any group of candidate regions is as follows:

[0087] The gradient magnitude of the pixel value of each pixel in the phase candidate region is calculated using the Sobel operator; the standard deviation of the gradient magnitude of the pixel value of each pixel in the phase candidate region is calculated as the first score of the corresponding candidate region; the smaller the first score, the smoother the phase change in the phase candidate region and the better the stability.

[0088] Calculate the first-order gradient of the pixel value of each pixel in the amplitude candidate region and extract the gradient magnitude; calculate the mean of the gradient magnitude of the pixel value of each pixel in the amplitude candidate region as the second score of the corresponding candidate region; the larger the second score, the clearer the stripes and the stronger the contrast in the region.

[0089] The minimum distance between the phase candidate region and the edge of the interferometric phase map is calculated as the third score of the corresponding candidate region. The larger the third score, the farther the primary mirror position corresponding to the phase candidate region is from the edge of the primary mirror, and the lower the risk of phase distortion due to boundary effects.

[0090] The comprehensive score of the candidate region for the corresponding group is calculated based on the first score, the second score, and the third score. The first score is negatively correlated with the comprehensive score, and the second or third score is positively correlated with the comprehensive score.

[0091] Interferometric phase diagrams can directly reflect the error of the primary mirror shape, but their phase values ​​are often less accurate at the edges, in low-contrast areas, and in blurred areas, and there are problems such as phase jumps and background drift. Phase amplitude diagrams reflect the contrast or clarity of the interference fringes and can indicate the quality of the data. By selecting multiple regions with strong phase continuity in the interferometric phase diagram and good fringe clarity in the corresponding amplitude diagram as phase reference areas, it is possible to ensure that the phase reference areas are easy to identify the fringe rhythm center and that the phase drift reference calculated based on the phase reference areas has high accuracy.

[0092] The method for constructing the center phase sequence of any phase reference region is as follows:

[0093] In the amplitude reference region corresponding to the phase reference region, the fringe direction is identified, and the direction perpendicular to the fringe direction is marked as the reference direction. In this embodiment, the interference amplitude pattern is similar to the interference fringe pattern, and visually it mainly appears as a series of alternating bright and dark interference fringes. The fringe direction is the direction of the interference fringes themselves, that is, the tangent direction, which is also the direction of the phase contour lines. The principal direction angle of the local fringes can be estimated by Fourier transform or structural tensor analysis, thereby obtaining the fringe direction.

[0094] Continuous pixels are extracted along the reference direction as amplitude reference points;

[0095] Calculate the pixel value gradient along the reference direction for each amplitude reference point and form a gradient sequence for the amplitude reference points;

[0096] Local maxima of pixel value gradients in the gradient sequence are identified, and the amplitude reference point corresponding to each local maximum is marked as the fringe rhythm center. In this embodiment, the local maximum is the peak value. If the gradient sequence of amplitude reference points is plotted as a visual curve, multiple peaks exist on the curve, and the peak value of each peak is the local maximum extracted in this embodiment. The fringe rhythm center is the extreme point of pixel value in the interference amplitude diagram perpendicular to the fringe direction. Each fringe rhythm center corresponds to an interference fringe; for bright fringe, the fringe rhythm center corresponds to its brightest point, and for dark fringe, the fringe rhythm center corresponds to its darkest point.

[0097] The phase value corresponding to the center position of each stripe rhythm is queried in the phase reference area and arranged into the center phase sequence of the phase reference area.

[0098] A phase drift model is constructed based on the central phase sequence of each phase reference region, and the interferometric phase map is drift corrected based on the phase drift model.

[0099] The phase drift model is used to calculate the phase drift amount of each pixel in the interferometric phase image; the method for constructing the phase drift model is as follows.

[0100] The phase drift reference for each phase reference region is calculated based on the corresponding center phase sequence; the method for calculating the phase drift reference for any phase reference region is as follows:

[0101] Fitting a reference phase sequence to the corresponding center phase sequence specifically includes:

[0102] The first phase value in the central phase sequence is extracted as the fitting starting point, and the phase value corresponding to the fitting starting point is used as the first reference phase value in the reference phase sequence and filled into the reference phase sequence;

[0103] The reference phase sequence is filled with reference phase values ​​based on the phase values ​​in the central phase sequence. Specifically, if the i-th phase value in the central phase sequence is greater than the (i-1)-th phase value, then the i-th reference phase value in the reference phase sequence is the (i-1)-th phase value plus 2π; otherwise, the i-th reference phase value in the reference phase sequence is the (i-1)-th phase value minus 2π. The value of i is in the range of 2, 3, ..., M; M is the number of phase values ​​in the central phase sequence.

[0104] Calculate the difference between each phase value in the central phase sequence and the corresponding reference phase value in the reference phase sequence, and use it as the residual of each phase value in the central phase sequence; calculate the mean of the residuals of each phase value in the central phase sequence, and use it as the phase drift reference for the corresponding phase reference area.

[0105] In an interference fringe pattern, the difference in optical path length between any two adjacent fringes is one wavelength λ; when the optical path length changes by λ, the phase changes by 2π. By fitting a reference phase sequence to the central phase sequence based on this pattern and calculating the residual point by point, the overall phase drift level of the corresponding fringe rhythm center can be measured.

[0106] A phase drift model is constructed based on the phase drift reference of each phase reference region; specifically including:

[0107] Mark the phase drift value corresponding to the center coordinates of each phase reference area as the corresponding phase drift reference;

[0108] Based on the phase drift values ​​corresponding to the center coordinates of different phase reference regions, a surface equation of the phase drift value is fitted within the coordinate range of the interferometric phase map, which serves as the model equation for the phase drift model.

[0109] In this embodiment, the surface equation for the phase drift value is used to calculate the phase drift value at each position in the interferometric phase diagram. Optionally, the surface equation is fitted using B-spline interpolation or the Laplace equation boundary value method.

[0110] The phase drift correction of the interferometric phase image based on the phase drift model includes: calculating the phase drift amount of each pixel in the phase interferometric image based on the phase drift model; and subtracting the corresponding phase drift amount from the phase value of each pixel in the interferometric phase image to achieve drift correction of the interferometric phase image. By correcting the phase drift globally in the interferometric phase image, phase drift errors caused by light source wavelength drift, optical path differences, environmental disturbances, etc., during the measurement process of the interferometer can be suppressed.

[0111] Identifying response defect regions in the interference phase diagram; specifically including:

[0112] Set a second sliding window; use the second sliding window to slide and select the observation area in the interference amplitude diagram; for any sliding selection, extract the maximum and minimum pixel values ​​of all pixels in the observation area; calculate the sharpness index of the observation area, which is the difference between the maximum and minimum pixel values ​​divided by the sum of the maximum and minimum pixel values;

[0113] Set a sharpness threshold; mark each observation area with a sharpness index lower than the sharpness threshold as a defect window;

[0114] Different defect windows are aggregated into potential defect regions through connected component analysis;

[0115] Set a first area threshold; mark potential defect areas with an area greater than the first area threshold as response defect areas in the interference amplitude diagram;

[0116] Optionally, the second sliding window can be smaller, such as 8×8 pixels, to improve detection resolution while preventing an excessively large window from failing to accurately locate the boundary of the response defect area. Those skilled in the art can set the sharpness threshold and the first area threshold based on actual needs. Areas with excessively small sharpness indices exhibit blurred fringes, making phase extraction difficult, and often appear at edges, in areas of non-uniform illumination, or in areas of device contamination. Through connected component analysis, smaller false alarm areas are filtered out, ultimately outputting a larger, continuous anomaly response defect area.

[0117] In the interferometric phase diagram, the region corresponding to any response defect region in the interferometric amplitude diagram is marked as a response defect region.

[0118] In the interferometric phase map, the gradient magnitude of the pixel value of each pixel is calculated using the Sobel operator, which serves as a continuity index for each pixel.

[0119] Set a continuity threshold, and mark pixels with a continuity index greater than the continuity threshold as phase defect points;

[0120] Phase defect points are aggregated into phase defect regions through connected component analysis;

[0121] A second area threshold is set, and phase defect areas with an area larger than the second area threshold are marked as response defect areas. Those skilled in the art can set specific values ​​for the continuity threshold and the second area threshold based on actual needs. The continuity index can be used to identify phase error anomalies caused by phase jumps, tomography, phase unpacking errors, etc.

[0122] Calculate the response confidence of each pixel in the interferometric phase image, and correct defects in the response defect area based on the response confidence of different pixels;

[0123] Calculating the response confidence of pixels in the interferometric phase image includes: setting a correction reference region for each response defect region in the interferometric phase image, and calculating the response confidence of each pixel in each correction reference region; wherein, the method for setting a correction reference region for any response defect region is as follows: setting the size and shape of the correction reference region; for example, setting the correction reference region as a 7×7 window; uniformly cutting m correction reference regions around the response defect region in the interferometric phase image; m is a positive integer; assigning a value to the response confidence of each pixel in each correction reference region based on the corresponding continuity index, and the larger the continuity index, the smaller the response confidence of the corresponding pixel.

[0124] The method for defect correction of any response defect area is as follows:

[0125] In each correction reference area corresponding to the response defect area, the n pixels with the highest response confidence are extracted as correction reference points; n is a positive integer.

[0126] A phase surface equation is fitted based on the phase value and response confidence of each corrected reference point. When fitting the phase surface equation, the response confidence of each corrected reference point is used as the corresponding fitting weight. For example, the phase surface equation is fitted using the weighted least squares method. During the fitting process, when calculating the sum of squared residuals, the fitting residual of each corrected reference point is multiplied by the corresponding fitting weight.

[0127] The phase correction value of each pixel in the response defect area is calculated based on the phase surface equation, and the phase value of each pixel in the response defect area is replaced with the corresponding phase correction value.

[0128] By correcting the response defect area, response defects such as ghosting or oversaturation points that appear at the edge of the mirror can be corrected, ensuring the overall surface correction accuracy.

[0129] The wavefront diagram of the primary mirror is generated based on the interferometric phase diagram, and the error analysis and correction of the primary mirror surface shape are performed based on the wavefront diagram.

[0130] The generation of the wavefront image of the primary mirror based on the interferometric phase image specifically includes:

[0131] Obtain the reference wavelength; calculate the wavefront value of each pixel based on the phase value of each pixel in the interference phase diagram and the reference wavelength, and construct the wavefront diagram of the primary mirror;

[0132] In the wavefront image, the wavefront value of any pixel represents the optical path deviation between the primary mirror profile and the reference profile at the corresponding position, i.e., the contour error of the primary mirror profile at that position. The reference profile is the target profile designed for the primary mirror, such as a parabola.

[0133] The reference wavelength is the reference wavelength of the interferometer used when acquiring the interference fringe pattern of the primary mirror. For example, the wavelength of He-Ne laser is 632.8 nanometers. The wavefront value of any pixel is proportional to the reference wavelength and the phase value. Given the reference wavelength, the corresponding wavefront value can be calculated based on the phase value.

[0134] Error analysis and correction of the primary mirror shape are performed based on the wavefront diagram, specifically including:

[0135] The PV and RMS values ​​of the primary mirror are calculated based on the wavefront diagram. Thresholds are set for the PV and RMS values ​​respectively. If the PV and RMS values ​​of the primary mirror are both less than the corresponding thresholds, the primary mirror meets the processing standard. Otherwise, the primary mirror has processing errors and is reworked for correction.

[0136] The PV value, or peak-to-valley value, is calculated by subtracting the maximum and minimum values ​​of each pixel in the wavefront image. In primary mirror shape detection, the PV value represents the height difference between the maximum and minimum deviation points on the surface shape, reflecting the maximum fluctuation range of the surface shape deviation. The PMS value is the root mean square error of the pixel values ​​of all pixels in the wavefront image, reflecting the overall dispersion of the surface shape deviation.

[0137] The specific method for rework correction can be determined based on the type and magnitude of the error. For example, if the error is a localized minor bump or depression, such as only the PV value slightly exceeding the threshold and the wavefront value being unevenly distributed only locally, then localized fine polishing can be used to gradually reduce the local deviation. After correction, interferometer testing is required again to recalculate the PV and RMS values ​​and verify whether the main mirror surface meets the processing standards.

[0138] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0139] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of protection of this application, and these forms are all within the protection scope of this application.

Claims

1. A method for correcting primary mirror shape error based on multimodal interferometric data fusion, characterized in that: Includes the following steps: Obtain the interference fringe pattern of the primary mirror, and construct the interference phase pattern and interference amplitude pattern of the primary mirror based on the interference fringe pattern; A phase reference region is selected in the interferometric phase diagram, and a central phase sequence for each phase reference region is constructed based on the interferometric amplitude diagram; A phase drift model is constructed based on the central phase sequence of each phase reference region, and the interferometric phase map is drift corrected based on the phase drift model. Identify the response defect region in the interference phase diagram; Calculate the response confidence of each pixel in the interferometric phase image, and correct defects in the response defect area based on the response confidence of different pixels; The wavefront diagram of the primary mirror is generated based on the interferometric phase diagram, and the error analysis and correction of the primary mirror surface shape are performed based on the wavefront diagram. The method for selecting the phase reference region is as follows: Set a first sliding window; based on the first sliding window, simultaneously extract pixels in the interference phase map and the interference amplitude map, and each sliding operation extracts a set of candidate regions; any set of candidate regions includes the phase candidate region extracted in the interference phase map and the amplitude candidate region extracted in the interference amplitude map. Calculate the overall score for each group of candidate regions; Select the N candidate regions with the highest comprehensive scores and extract the corresponding N phase candidate regions as N phase reference regions; extract the corresponding N amplitude candidate regions as N amplitude reference regions; N is a positive integer; The method for calculating the comprehensive score of any group of candidate regions is as follows: The gradient magnitude of the pixel value of each pixel in the phase candidate region is calculated using the Sobel operator; the standard deviation of the gradient magnitude of the pixel value of each pixel in the phase candidate region is calculated and used as the first score of the corresponding group of candidate regions; Calculate the first-order gradient of the pixel value of each pixel in the amplitude candidate region and extract the gradient magnitude; Calculate the mean gradient magnitude of the pixel value of each pixel in the amplitude candidate region, and use it as the second score of the corresponding candidate region. Calculate the minimum distance between the phase candidate region and the edge of the interferometric phase map, and use it as the third score for the corresponding group of candidate regions; The comprehensive score of the candidate region for the corresponding group is calculated based on the first score, the second score, and the third score. The first score is negatively correlated with the comprehensive score, and the second or third score is positively correlated with the comprehensive score.

2. The method for correcting primary mirror shape error based on multimodal interferometric data fusion as described in claim 1, characterized in that: Interference detection is performed on the primary mirror using an interferometer to obtain an interference fringe pattern; the pixel value of each pixel in the interference fringe pattern represents the brightness of the interference fringes of the reference light and the test light at the corresponding position on the primary mirror. The pixel value of each pixel in the interference phase diagram represents the phase difference between the reference light and the test light for interference detection at the corresponding position of the primary mirror. Constructing the interference phase map of the primary mirror based on the interference fringe map includes: performing phase extraction and phase unpacking on the pixel value of each pixel in the interference fringe map to obtain the pixel value of each pixel in the interference phase map; The pixel value of each pixel in the interference amplitude diagram represents the relative value of the superimposed amplitude of the reference light and the test light at the corresponding position of the primary mirror. Constructing the interference amplitude map of the primary mirror based on the interference fringe map includes: calculating the square root of the pixel value of each pixel in the interference fringe map and performing standardization processing to obtain the pixel value of each pixel in the interference amplitude map.

3. The method for correcting primary mirror shape error based on multimodal interferometric data fusion as described in claim 2, characterized in that: The method for constructing the center phase sequence of any phase reference region is as follows: In the amplitude reference region corresponding to the phase reference region, the fringe direction is identified, and the direction perpendicular to the fringe direction is marked as the reference direction. Continuous pixels are extracted along the reference direction as amplitude reference points; Calculate the pixel value gradient along the reference direction for each amplitude reference point and form a gradient sequence for the amplitude reference points; Identify the local maxima of the pixel value gradient in the gradient sequence, and mark the amplitude reference point corresponding to each local maximum as the stripe rhythm center; The phase value corresponding to the center position of each stripe rhythm is queried in the phase reference area and arranged into the center phase sequence of the phase reference area.

4. The primary mirror type error correction method based on multimodal interferometric data fusion as described in claim 3, characterized in that: The phase drift model is used to calculate the phase drift amount of each pixel in the interferometric phase image; the method for constructing the phase drift model is as follows. Calculate the phase drift reference for each phase reference region based on the corresponding center phase sequence; A phase drift model is constructed based on the phase drift reference of each phase reference region; specifically including: Mark the phase drift value corresponding to the center coordinates of each phase reference area as the corresponding phase drift reference; Based on the phase drift values ​​corresponding to the center coordinates of different phase reference regions, a surface equation of the phase drift value is fitted within the coordinate range of the interferometric phase diagram, which serves as the model equation for the phase drift model. The drift correction of the interferometric phase image based on the phase drift model includes: calculating the phase drift amount of each pixel in the phase interferometric image based on the phase drift model; and subtracting the corresponding phase drift amount from the phase value of each pixel in the interferometric phase image to achieve drift correction of the interferometric phase image.

5. The method for correcting the primary mirror shape error based on multimodal interferometric data fusion as described in claim 4, characterized in that: The method for calculating the phase drift reference for any phase reference region is as follows: Fitting a reference phase sequence to the corresponding center phase sequence specifically includes: The first phase value in the central phase sequence is extracted as the fitting starting point, and the phase value corresponding to the fitting starting point is used as the first reference phase value in the reference phase sequence and filled into the reference phase sequence; The reference phase sequence is filled with reference phase values ​​based on the phase values ​​in the central phase sequence. Specifically, if the i-th phase value in the central phase sequence is greater than the (i-1)-th phase value, then the i-th reference phase value in the reference phase sequence is the (i-1)-th phase value plus 2π; otherwise, the i-th reference phase value in the reference phase sequence is the (i-1)-th phase value minus 2π. The value of i ranges from 2, 3, ..., M, where M is the number of phase values ​​in the central phase sequence. Calculate the difference between each phase value in the central phase sequence and the corresponding reference phase value in the reference phase sequence, and use it as the residual of each phase value in the central phase sequence; calculate the mean of the residuals of each phase value in the central phase sequence, and use it as the phase drift reference for the corresponding phase reference area.

6. The primary mirror type error correction method based on multimodal interferometric data fusion as described in claim 5, characterized in that: Identifying response defect regions in the interference phase diagram specifically includes: Set a second sliding window; use the second sliding window to slide and select the observation area in the interference amplitude diagram; for any sliding selection, extract the maximum and minimum pixel values ​​of all pixels in the observation area; calculate the sharpness index of the observation area, which is the difference between the maximum and minimum pixel values ​​divided by the sum of the maximum and minimum pixel values; Set a sharpness threshold; mark each observation area with a sharpness index lower than the sharpness threshold as a defect window; Different defect windows are aggregated into potential defect regions through connected component analysis; Set a first area threshold; mark potential defect areas with an area greater than the first area threshold as response defect areas in the interference amplitude diagram; In the interferometric phase diagram, the region corresponding to any response defect region in the interferometric amplitude diagram is marked as a response defect region.

7. The method for correcting the primary mirror shape error based on multimodal interferometric data fusion as described in claim 6, characterized in that: Identifying response defect regions in the interference phase diagram further includes: In the interferometric phase map, the gradient magnitude of the pixel value of each pixel is calculated using the Sobel operator, which serves as a continuity index for each pixel. Set a continuity threshold, and mark pixels with a continuity index greater than the continuity threshold as phase defect points; Phase defect points are aggregated into phase defect regions through connected component analysis; A second area threshold is set, and phase defect regions with an area greater than the second area threshold are marked as response defect regions.

8. The method for correcting the primary mirror shape error based on multimodal interferometric data fusion as described in claim 7, characterized in that: Calculating the response confidence of pixels in the interferometric phase image includes: setting a correction reference region for each response defect region in the interferometric phase image, and calculating the response confidence of each pixel in each correction reference region; wherein, the method for setting a correction reference region for any response defect region is as follows: setting the size and shape of the correction reference region; uniformly cutting m correction reference regions around the response defect region in the interferometric phase image; m is a positive integer; assigning a value to the response confidence of each pixel in each correction reference region based on the corresponding continuity index, and the larger the continuity index, the smaller the response confidence of the corresponding pixel.

9. The method for correcting the primary mirror shape error based on multimodal interferometric data fusion as described in claim 8, characterized in that: The method for defect correction of any response defect area is as follows: In each correction reference area corresponding to the response defect area, the n pixels with the highest response confidence are extracted as correction reference points; n is a positive integer. A phase surface equation is fitted based on the phase value and response confidence of each corrected reference point; When fitting the phase surface equation, the response confidence of each corrected reference point is used as the corresponding fitting weight; The phase correction value of each pixel in the response defect area is calculated based on the phase surface equation, and the phase value of each pixel in the response defect area is replaced with the corresponding phase correction value.

10. The method for correcting primary mirror surface error based on multimodal interferometric data fusion as described in claim 9, characterized in that: The generation of the wavefront image of the primary mirror based on the interferometric phase image specifically includes: Obtain the reference wavelength; calculate the wavefront value of each pixel based on the phase value of each pixel in the interference phase diagram and the reference wavelength, and construct the wavefront diagram of the primary mirror; Error analysis and correction of the primary mirror shape are performed based on the wavefront diagram, specifically including: The PV and RMS values ​​of the primary mirror are calculated based on the wavefront diagram. Thresholds are set for the PV and RMS values ​​respectively. If the PV and RMS values ​​of the primary mirror are both less than the corresponding thresholds, the primary mirror meets the processing standard. Otherwise, the primary mirror has processing errors and is reworked for correction.

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