Device and method for measuring distance between wavefront sensor microlens array and detector

Abstract

The invention discloses a device and a method for measuring the distance between a wavefront sensor microlens array and a detector, belongs to the field of sensors, and aims to solve the problem of difficulty in accurate measurement in a Shack-Hartmann wavefront sensor distance value calibration method. The device comprises a point light source, a sliding table, a linear guide rail, a data transmission line and a processor, the point light source comprises a laser light source, an optical fiber coupler, an optical fiber and an adjusting seat, the head end of the optical fiber is connected with the laser light source through the optical fiber coupler, and the tail end of the optical fiber is erected at the center of the adjusting seat; the wavefront sensor moves back and forth along the linear guide rail through the sliding table. The light incident side of the wavefront sensor is right opposite to the tail end of the optical fiber, a light beam emitted by the point light source enters the wavefront sensor to generate a light spot matrix grey-scale map, and the light spot matrix grey-scale maps generated when the wavefront sensor moves to different positions are sent to the processor through the data transmission line. And the processor obtains the distance between the wavefront sensor microlens array and the detector according to the light spot matrix grey-scale maps at different positions.

Description

Technical Field

[0001] The invention relates to a method for measuring the distance between a microlens array and a detector of a shipped wavefront sensor, and belongs to the field of sensors. Background Art

[0002] The wavefront is a surface composed of points with the same phase in a propagating light beam, and light beam propagation is actually the process of continuous reproduction of the wavefront, which contains a lot of important information in the process of light beam propagation. Therefore, the study of the wavefront has great application value.

[0003] Wavefront sensing technology is an optical wavefront measurement method that has developed rapidly with the emergence of adaptive optics, active optics and other technologies. It is one of the important research directions in the field of modern photoelectric detection. Based on different detection principles, wavefront sensing technology measures the wavefront of the beam by modulating and sampling the measured beam, providing key technical support for the development of large-aperture astronomical observations, laser beam purification, free-space optical communications, biological imaging and other fields.

[0004] At present, the commonly used advanced optical wavefront sensing technologies mainly include wavefront overall tilt sensing technology, Shack-Hartmann optical wavefront sensing technology, pyramid optical wavefront sensing technology, lateral shearing interference optical wavefront sensing technology, curvature optical wavefront sensing technology and holographic optical wavefront sensing technology.

[0005] Among them, the Shack-Hartmann wavefront sensor (SHWS) is widely used in astronomy, high-energy laser, fundus imaging, optical communication and optical detection due to its clear physical principles, high light energy utilization, fast detection speed and stable performance.

[0006] See also Figure 1 As shown, the common Shack-Hartmann wavefront sensor is mainly composed of a microlens array 5-1 and a detector 5-2, and the supporting components also include a calibration light source 1 and a lens 2. The detector 5-2 uses a CCD or CMOS camera. The measurement principle of the wavefront sensor is based on the measurement of the tilt of the incident wavefront in each microlens sub-aperture, and the tilt of the incident wavefront in each sub-aperture is used to splice the wave aberration of the entire incident wavefront. Usually, the distance from the microlens to the photodetector is the focal length of the microlens, but there are certain errors in the processing and installation of the microlens. The error sources of the Shack-Hartmann wavefront sensor are mainly three aspects: the inaccuracy of the center of mass position of the light beam, the inaccuracy of the spacing d between the microlens array surface and the detector, and the imperfection of the wavefront reconstruction algorithm.

[0007] The error introduced by the position of the beam center of mass is Figure 1,,When the beam centroid is at two different positions, two different wavefronts 3 and 4 will be generated. The error introduced by the position of the beam centroid and the error introduced by the wavefront reconstruction algorithm depend on the processing accuracy and size of the hardware, the background noise processing of the software, the algorithm selection and optimization, etc. These errors can only be reduced by the reasonable selection of hardware parameters and the improvement of software algorithms, and cannot be corrected by calibration. The spacing value d between the microlens array surface and the detector is a value that can be accurately corrected by calibration.

[0008] Currently, the common calibration method in the industry is to change the propagation angle of parallel light to calculate the spacing value. This method relies on the collimation accuracy of the laser and the measurement accuracy of the light deviation angle. The high-precision collimation of the laser itself is quite difficult and time-consuming and equipment-intensive to operate, and the optical fiber deviation angle is also difficult to measure accurately. Summary of the invention

[0009] Aiming at the problem that the existing Shack-Hartmann wavefront sensor spacing value calibration method is difficult to measure accurately, the present invention provides a device and method for measuring the spacing between a wavefront sensor microlens array and a detector.

[0010] In one aspect, the present invention provides a device for measuring the distance between a wavefront sensor microlens array and a detector, comprising a point light source 1, a slide table 6, a linear guide rail 7, a data transmission line 8 and a processor 9.

[0011] The point light source 1 includes a laser light source 1-1, a fiber coupler 1-2, an optical fiber 1-3 and an adjustment seat 1-4. The head end of the optical fiber 1-3 is connected to the laser light source 1-1 through the fiber coupler 1-2, and the tail end of the optical fiber 1-3 is mounted at the center of the adjustment seat 1-4.

[0012] The wavefront sensor 5 moves forward and backward along the linear guide rail 7 via the slide 6;

[0013] The light incident side of the wavefront sensor 5 is directly opposite to the tail end of the optical fiber 1-3. The light beam emitted by the point light source 1 is incident on the wavefront sensor 5 to generate a spot matrix grayscale image. The spot matrix grayscale images of the wavefront sensor 5 when it moves to different positions are sent to the processor 9 through the data transmission line 8. The processor 9 obtains the spacing between the wavefront sensor microlens array and the detector based on the spot matrix grayscale images at different positions.

[0014] In another aspect, the present invention provides a method for measuring the distance between a wavefront sensor microlens array and a detector, the method comprising the following steps:

[0015] Step 1: The wavefront sensor 5 moves along the linear guide rail 7 to obtain n light spot matrix grayscale images at different positions;

[0016] Step 2: The processor performs the following processing on the n light spot matrix grayscale images to obtain the centroid distances Q1, Q2, ..., Q of all light spot matrix grayscale images. n :

[0017] Step 21: Perform Fourier transform FFT on the grayscale image of the i-th light spot matrix to obtain a frequency domain image, i = 1, 2, ..., n, and then perform Fourier transform shift FFT Shift to delete the frequencies near the 0 frequency to achieve center frequency alignment;

[0018] Step 22: Filter the frequency domain image processed in step 21 using the ruv mask, wherein the ruv mask is formed by superimposing the r mask and the uv mask, wherein the r mask filters the spot frequency in the X direction of the image, and the uv mask filters the spot frequency in the Y direction of the image; obtain the spot frequency after filtering, and intercept the circular frequency domain near the spot frequency;

[0019] Step 2 and 3, perform inverse fast Fourier transform (iFFT) on the circular frequency domain near the spot frequency to obtain the wrapped phase in the u direction and the wrapped phase in the v direction;

[0020] Step 24: perform an unwrapping operation to obtain an unwrapping phase in the u direction and an unwrapping phase in the v direction;

[0021] Step 25, obtain the fringe order in the u direction and the fringe order in the v direction, wherein the fringe order in the u direction = the unwrapped phase in the u direction - the wrapped phase in the u direction, and the fringe order in the v direction = the unwrapped phase in the v direction - the wrapped phase in the v direction;

[0022] Step 26: Superimpose the fringe order in the u direction and the fringe order in the v direction to generate a contour map;

[0023] Step 27: Use parallel computing to extract the brightness centroid coordinates of all light spots in the contour map, and then obtain the centroid spacing Q of the grayscale map of the i-th light spot matrix i ;

[0024] Step 3: Obtain the position reading error ΔR according to the following formula:

[0025]

[0026] The position reading error ΔR is used to characterize the distance between the front end of the housing of the wavefront sensor 5 and the microlens array 5 - 1 ;

[0027] Step 4: The processor 9 obtains the distance d between the wavefront sensor microlens array and the detector according to the following formula based on the spot matrix grayscale image generated by any wavefront sensor 5:

[0028]

[0029] In the formula, Ri represents the position of the wavefront sensor 5 read when generating the i-th light spot matrix grayscale image, which is the distance between the point light source 1 and the front end of the housing of the wavefront sensor 5; R i +ΔR is used to represent the distance between the point light source 1 and the microlens array 5 - 1 of the wavefront sensor 5 ; and P represents the lens period of the microlens array 5 - 1 .

[0030] Preferably, the process of obtaining the center frequency in step 22 is:

[0031] Use the ruv mask to filter the image processed in step 2.1 to obtain the highest grayscale value amplitude H in the spot matrix grayscale image. max The corresponding frequency f in the frequency domain image max , and obtain the frequency in the frequency domain image The corresponding gray value amplitude H in the spot matrix grayscale image re ;

[0032] Determine whether the relationship is satisfied: 3H re >H max , if satisfied, As the spot frequency f0, otherwise f max As the spot frequency f0.

[0033] Preferably, the process of intercepting the circular frequency domain near the spot frequency in step 22 is:

[0034] With the spot frequency f0 as the center, the frequency range is kept within the radius circular area.

[0035] Preferably, in step 27, the centroid distance Q of the i-th light spot matrix grayscale image is obtained. i The process is:

[0036] Parallel computing is used to traverse and record all pixel information in the contour map. The pixel information is pixel coordinates × pixel brightness. All pixel information is saved in the array corresponding to the area to which it belongs. Brightness weighted calculation is performed to obtain the brightness centroid coordinates of the light spot. The distance between the brightness centroid coordinates of two adjacent light spots is the centroid distance.

[0037] Beneficial effects of the present invention:

[0038] The present invention directly uses a point light source for calibration. This method does not rely on the collimation of light, does not require the measurement of the angle of light, and does not even require that the center of the point light source and the center of the sensor be on the same optical axis. This greatly reduces the requirements for equipment installation and the requirements for measuring instruments. Using the device provided by this patent, the sensor spacing value can be easily calibrated without any additional optical instruments. The operation process only includes installing the sensor to be tested, and starting the program prepared by the method of the present invention on the computer to obtain accurate results. This makes the device in this patent suitable for various laboratories and wavefront sensor manufacturers to quickly perform field testing and calibration of wavefront sensors without worrying about the lack of external experimental equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of the general structure of the Shack-Hartmann wavefront sensor;

[0040] Figure 2 It is a schematic structural diagram of a device for measuring the distance between a wavefront sensor microlens array and a detector according to the present invention;

[0041] Figure 3 It is a diagram of the image processing process in the method for measuring the distance between the wavefront sensor microlens array and the detector of the present invention;

[0042] Figure 4 It is a principle diagram of a method for measuring the distance between a wavefront sensor microlens array and a detector according to the present invention;

[0043] Figure 5 It is a flow chart of a method for measuring the distance between a wavefront sensor microlens array and a detector according to the present invention. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0046] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0047] Specific implementation method 1: The following is combined Figure 2The present embodiment is described. The device for measuring the distance between the wavefront sensor microlens array and the detector in the present embodiment comprises a point light source 1, a slide table 6, a linear guide rail 7, a data transmission line 8 and a processor 9.

[0048] The point light source 1 includes a laser light source 1-1, a fiber coupler 1-2, an optical fiber 1-3 and an adjustment seat 1-4. The head end of the optical fiber 1-3 is connected to the laser light source 1-1 through the fiber coupler 1-2, and the tail end of the optical fiber 1-3 is mounted at the center of the adjustment seat 1-4.

[0049] The wavefront sensor 5 moves forward and backward along the linear guide rail 7 via the slide 6;

[0050] The light incident side of the wavefront sensor 5 is directly opposite to the tail end of the optical fiber 1-3. The light beam emitted by the point light source 1 is incident on the wavefront sensor 5 to generate a spot matrix grayscale image. The spot matrix grayscale images of the wavefront sensor 5 when it moves to different positions are sent to the processor 9 through the data transmission line 8. The processor 9 obtains the spacing between the wavefront sensor microlens array and the detector based on the spot matrix grayscale images at different positions.

[0051] The device of this embodiment is used to re-measure the distance d between the microlens array 5 - 1 and the detector 5 - 2 of the wavefront sensor 5 after leaving the factory, so as to provide more accurate data support in application.

[0052] The adjustment seat 1-4 in this embodiment is used to adjust the position of the tail end of the optical fiber 1-3 so that the light beam can face the wavefront sensor 5 when it is output.

[0053] During measurement, the wavefront sensor 5 moves back and forth along the linear guide rail 7 through the slide 6. The detector 5-2 of the wavefront sensor 5 at each position generates a light spot matrix grayscale image, and a large amount of data is sent to the processor 9 through the data transmission line 8 to complete the measurement of d.

[0054] Specific implementation method 2: The following is combined Figures 1 to 5 This embodiment is described. The method for measuring the distance between the wavefront sensor microlens array and the detector described in this embodiment is implemented based on the measuring device for the distance between the wavefront sensor microlens array and the detector described in the first embodiment. The method includes the following steps:

[0055] Step 1: The wavefront sensor 5 moves along the linear guide rail 7 to obtain n light spot matrix grayscale images at different positions;

[0056] Step 2: The processor performs the following processing on the n light spot matrix grayscale images to obtain the centroid distances Q1, Q2, ..., Q of all light spot matrix grayscale images. n :

[0057] Step 21: Perform Fourier transform FFT on the grayscale image of the i-th light spot matrix to obtain a frequency domain image, i = 1, 2, ..., n, and then perform Fourier transform shift FFT Shift to delete the frequencies near the 0 frequency to achieve center frequency alignment;

[0058] The position described in this step refers to the distance between the front end of the wavefront sensor 5 housing and the point light source 1. Due to the influence of the housing, there is a slight deviation between the distance and the distance to the microlens array 5-1 and the read distance, which will be measured in subsequent steps.

[0059] Step 22: Filter the frequency domain image processed in step 21 using the ruv mask, wherein the ruv mask is formed by superimposing the r mask and the uv mask, wherein the r mask filters the spot frequency in the X direction of the image, and the uv mask filters the spot frequency in the Y direction of the image; obtain the spot frequency after filtering, and intercept the circular frequency domain near the spot frequency;

[0060] At present, the common method for selecting the spot search area in the industry is to directly use grid selection. This method relies on the known microlens array parameter values ​​and detector parameter values, and also relies on manual adjustment of the grid to the extent that the spot can be framed. This method is more suitable for the situation where the parameters are known and the number of spots is small, but when the parameters are unknown and the number of spots is large, such as 64x64=4096 spots, and the number of pictures reaches thousands, manual selection of the search area becomes difficult to achieve. In addition, the use of grid selection sometimes causes part of the spot or the center of the spot to leave the grid, which affects the calculation of the centroid of the spot for this grid and its neighboring grids, reducing the accuracy of the centroid search.

[0061] Therefore, in order to realize the large-scale automatic selection of spot search areas, the present invention adopts an improved directional filtering method for the spot matrix. This method does not rely on parameters, does not rely on manual selection, and is adaptable to spot matrices in various situations. It also has a good recognition effect for high-noise and low-signal-to-noise ratio spot matrices. And the identified spot search area boundary will avoid the spot highlight area, and automatically select the low-brightness area between adjacent spots as the area boundary, which can avoid the centroid search error caused by the spot partially or completely leaving the area.

[0062] In this step, the frequency domain image is filtered using the RUV mask. The light spot matrix grayscale image generated by the wavefront sensor 5 is periodically arranged in the x and y directions in the spatial domain, so we can perform filtering operations on it in the x and y directions respectively to extract the arrangement pattern of the light spots.

[0063] The process of obtaining the center frequency is:

[0064] Use the ruv mask to filter the image processed in step 2.1 to obtain the highest grayscale value amplitude H in the spot matrix grayscale image. max The corresponding frequency f in the frequency domain image max , and obtain the frequency in the frequency domain image The corresponding gray value amplitude H in the spot matrix grayscale image re ;

[0065] Determine whether the relationship is satisfied: 3H re >H max , if satisfied, As the spot frequency f0, otherwise f max As the spot frequency f0.

[0066] After finding the frequency f0 of the light spot, we filter out the frequency of the light spot and retain the frequency domain exceeding one quarter of the frequency of the light spot. Specifically, the process of intercepting the circular frequency domain near the frequency of the light spot is:

[0067] With the spot frequency f0 as the center, the frequency range is kept within the radius circular area.

[0068] For example, if f0 = 1 / 200 cycle / pixel, a circular frequency domain with 1 / 200 cycle / pixel as the center and 1 / 800 cycle / pixel as the radius is cut out, and then iFFT is performed on the circular frequency domain near the spot frequency to obtain an image containing only the spot frequency.

[0069] Step 2 and 3: Perform inverse fast Fourier transform (iFFT) on the circular frequency domain near the spot frequency to obtain the wrapped phase in the u direction and the wrapped phase in the v direction; see Figure 3 shown.

[0070] Step 24: perform an unwrapping operation to obtain an unwrapping phase in the u direction and an unwrapping phase in the v direction;

[0071] Step 25, obtain the fringe order in the u direction and the fringe order in the v direction, wherein the fringe order in the u direction = the unwrapped phase in the u direction - the wrapped phase in the u direction, and the fringe order in the v direction = the unwrapped phase in the v direction - the wrapped phase in the v direction;

[0072] The obtained phase order is the distribution order of the light spot.

[0073] Step 26: Superimpose the fringe order in the u direction and the fringe order in the v direction to generate a contour map;

[0074] Step 27: Use parallel computing to extract the brightness centroid coordinates of all light spots in the contour map, and then obtain the centroid spacing Q of the grayscale map of the i-th light spot matrix i ;

[0075] Currently, the common method for extracting centroid coordinates is to crop the search area of ​​a single light spot from the image and then calculate its brightness-weighted centroid. However, this method is only suitable for cases with fewer light spots. When the number of light spots is as high as 4096, this method takes 10 minutes to analyze an image. When faced with two thousand images, the calibration time of a single sensor is extended to 13 days, which is almost unacceptable.

[0076] To this end, the present invention proposes a method for extracting the center of mass coordinates using parallel computing. By encoding the CUDA program, the analysis time for a single image is only 1 second, which is 600 times faster. For two thousand images, the analysis process can be completed in only half an hour, which greatly improves the usability of the entire method.

[0077] Get the centroid distance Q of the i-th spot matrix grayscale image i The process is:

[0078] Parallel computing is used to traverse and record all pixel information in the contour map. The pixel information is pixel coordinates × pixel brightness. All pixel information is saved in the array corresponding to the area to which it belongs. Brightness weighted calculation is performed to obtain the brightness centroid coordinates of the light spot. The distance between the brightness centroid coordinates of two adjacent light spots is the centroid distance.

[0079] Step 3: Obtain the position reading error ΔR according to the following formula:

[0080]

[0081] The position reading error ΔR is used to characterize the distance between the front end of the housing of the wavefront sensor 5 and the microlens array 5 - 1 ;

[0082] Step 4: The processor 9 obtains the distance d between the wavefront sensor microlens array and the detector according to the following formula based on the spot matrix grayscale image generated by any wavefront sensor 5:

[0083]

[0084] In the formula, R i represents the position of the wavefront sensor 5 read when generating the i-th light spot matrix grayscale image, which is the distance between the point light source 1 and the front end of the housing of the wavefront sensor 5; R i +ΔR is used to characterize the distance between the point light source 1 and the microlens array 5 - 1 of the wavefront sensor 5 ; P represents the lens period of the microlens array 5 - 1 , which can be obtained from the parameter table provided by the microlens manufacturer.

[0085] If multiple movements generate multiple spacings d, theoretically, these values ​​are consistent, but in practice there may be a certain deviation, so the present invention can take the average value of n d as the final result.

[0086] The position recorded in step 21 during the movement of the wavefront sensor 5 refers to the distance between the front end of the wavefront sensor 5 housing and the point light source 1. Due to the influence of the housing, there is a slight deviation between this distance and the distance of the microlens array 5-1 and the read distance, that is, the position reading error ΔR. When calculating the spacing d later, the distance between the point light source 1 and the microlens array 5-1 should be substituted instead of the distance between the point light source 1 and the front end of the wavefront sensor 5 housing. Therefore, the purpose of multiple movements is to calculate ΔR.

[0087] See also Figure 4 , build a measurement model The goal of the least squares method is to find ΔR to minimize the following sum of squared errors S:

[0088]

[0089] For the determination of the distance d between the wavefront sensor microlens array and the detector, the industry's commonly used method is to change the angle of parallel light to obtain the wavefront slope, which is equal to the ratio of the spot spacing to the MLA-CMOS spacing value. The spot spacing is obtained through image analysis, and the spacing value is finally calculated. This method relies on the collimation effect of the point light source. The processing technology of the collimating lens will cause the parallel light to not be completely collimated, and there are extremely high requirements for the calibration of the parallel light after collimation. In addition, it is necessary to measure the angle of the parallel light while moving the light source, which further increases the operational requirements. Each link will increase the error value of the measurement result.

[0090] In order to reduce the measurement cost, reduce the operation links, and reduce the measurement error, the present invention proposes a method of directly using a point light source for calibration. This method does not rely on the collimation of light, does not require the measurement of the angle of light, and does not even require the center of the point light source and the center of the sensor to be on the same optical axis. This greatly reduces the requirements for equipment installation and the requirements for measuring instruments. Using the device provided by the present invention, the sensor spacing value can be easily calibrated without any additional optical instruments. The operation process only includes installing the sensor to be tested, starting the supporting software on the computer, and then just waiting for the measurement report. This makes the device in the present invention suitable for various laboratories and wavefront sensor manufacturers, and can quickly perform field testing and calibration of wavefront sensors without worrying about the lack of external experimental equipment.

[0091] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in conjunction with a single embodiment may be used in other described embodiments.

Claims

1. A device for measuring the distance between a wavefront sensor microlens array and a detector, characterized in that: It includes a point light source (1), a slide table (6), a linear guide rail (7), a data transmission line (8) and a processor (9), The point light source (1) comprises a laser light source (1-1), a fiber coupler (1-2), an optical fiber (1-3) and an adjustment seat (1-4); the head end of the optical fiber (1-3) is connected to the laser light source (1-1) via the fiber coupler (1-2), and the tail end of the optical fiber (1-3) is mounted at the center of the adjustment seat (1-4); The wavefront sensor (5) moves forward and backward along the linear guide rail (7) via the slide table (6); The light incident side of the wavefront sensor (5) is directly opposite to the tail end of the optical fiber (1-3), and the light beam emitted by the point light source (1) is incident on the wavefront sensor (5) to generate a light spot matrix grayscale image. The light spot matrix grayscale images obtained when the wavefront sensor (5) moves to different positions are sent to the processor (9) through the data transmission line (8), and the processor (9) obtains the distance between the wavefront sensor microlens array and the detector according to the light spot matrix grayscale images at different positions.

2. A method for measuring the distance between a wavefront sensor microlens array and a detector, the method being implemented based on the device for measuring the distance between a wavefront sensor microlens array and a detector as claimed in claim 1, characterized in that: The method comprises the following steps: Step 1: The wavefront sensor (5) moves along the linear guide rail (7) to obtain n light spot matrix grayscale images at different positions; Step 2: The processor performs the following processing on the n light spot matrix grayscale images to obtain the centroid distances Q1, Q2, ..., Q of all light spot matrix grayscale images. n : Step 21: Perform Fourier transform FFT on the grayscale image of the i-th light spot matrix to obtain a frequency domain image, i = 1, 2, ..., n, and then perform Fourier transform shift FFT Shift to delete the frequencies near the 0 frequency to achieve center frequency alignment; Step 22: Filter the frequency domain image processed in step 21 using the ruv mask, wherein the ruv mask is formed by superimposing the r mask and the uv mask, wherein the r mask filters the spot frequency in the X direction of the image, and the uv mask filters the spot frequency in the Y direction of the image; obtain the spot frequency after filtering, and intercept the circular frequency domain near the spot frequency; Step 2 and 3, perform inverse fast Fourier transform (iFFT) on the circular frequency domain near the spot frequency to obtain the wrapped phase in the u direction and the wrapped phase in the v direction; Step 24: perform an unwrapping operation to obtain an unwrapping phase in the u direction and an unwrapping phase in the v direction; Step 25, obtain the fringe order in the u direction and the fringe order in the v direction, wherein the fringe order in the u direction = the unwrapped phase in the u direction - the wrapped phase in the u direction, and the fringe order in the v direction = the unwrapped phase in the v direction - the wrapped phase in the v direction; Step 26: Superimpose the fringe order in the u direction and the fringe order in the v direction to generate a contour map; Step 27: Use parallel computing to extract the brightness centroid coordinates of all light spots in the contour map, and then obtain the centroid spacing Q of the grayscale map of the i-th light spot matrix i ; Step 3: Obtain the position reading error ΔR according to the following formula: The position reading error ΔR is used to characterize the distance between the front end of the housing of the wavefront sensor (5) and the microlens array (5-1); Step 4: The processor (9) obtains the distance d between the wavefront sensor microlens array and the detector according to the following formula based on the spot matrix grayscale image generated by any wavefront sensor (5): In the formula, R i represents the position of the wavefront sensor (5) read when generating the i-th light spot matrix grayscale image, which is the distance between the point light source (1) and the front end of the housing of the wavefront sensor (5); R i +ΔR is used to characterize the distance between the point light source (1) and the microlens array (5-1) of the wavefront sensor (5); P represents the lens period of the microlens array (5-1).

3. The method for measuring the distance between the wavefront sensor microlens array and the detector according to claim 2, characterized in that: Step 22 The process of obtaining the center frequency is: Use the ruv mask to filter the image processed in step 2.1 to obtain the highest grayscale value amplitude H in the spot matrix grayscale image. max The corresponding frequency f in the frequency domain image max , and obtain the frequency in the frequency domain image The corresponding gray value amplitude H in the spot matrix grayscale image re ; Determine whether the relationship is satisfied: 3H re >H max , if satisfied, As the spot frequency f0, otherwise f max As the spot frequency f0.

4. The method for measuring the distance between the wavefront sensor microlens array and the detector according to claim 3, characterized in that: The process of intercepting the circular frequency domain near the spot frequency in step 22 is: With the spot frequency f0 as the center, the frequency range is kept within the radius circular area.

5. The method for measuring the distance between the wavefront sensor microlens array and the detector according to claim 4, characterized in that: In step 27, the centroid distance Q of the grayscale image of the i-th light spot matrix is ​​obtained. i The process is: Parallel computing is used to traverse and record all pixel information in the contour map. The pixel information is pixel coordinates × pixel brightness. All pixel information is saved in the array corresponding to the area to which it belongs. Brightness weighted calculation is performed to obtain the brightness centroid coordinates of the light spot. The distance between the brightness centroid coordinates of two adjacent light spots is the centroid distance.

Images