Method for automatically adjusting and controlling spacing of Michelson shearing interference fringes

Abstract

The invention discloses a Michelson shearing interference fringe spacing automatic adjustment control method comprising the following steps: using a fast reflecting mirror as an adjusting element to control a Michelson interference light path, and generating shearing interference fringes; acquiring an image of the cut interference fringes in real time, and calculating a current fringe interval; calculating an error between the target stripe spacing and the current stripe spacing; and judging whether the error meets a preset tolerance range or not: if not, generating a control signal based on the error, controlling the fast reflecting mirror to adjust the reflection angle, generating new shearing interference fringes, and recalculating the current fringe spacing. The invention aims to provide the automatic adjustment and control method for the spacing of the Michelson shearing interference fringes, so as to solve the problems of complicated operation, difficulty in keeping consistency, insufficient control precision and incapability of dynamic control in the prior art, and achieve the purposes of dynamically controlling the Michelson interference system and automatically adjusting the spacing of the fringes.

Description

Technical Field

[0001] The invention relates to the field of interference measurement control, and in particular to a method for automatically adjusting and controlling the spacing of Michelson shearing interference fringes. Background Art

[0002] Shearing interferometry is an optical nondestructive testing technology. It is widely used in the fields of composite material nondestructive testing and vibration measurement due to its advantages of full field, non-contact, high sensitivity and good stability. By using the interference pattern formed by coherent light sources, the tiny displacement or strain on the surface of the object can be accurately measured. Precise control of the fringe spacing is crucial to the accuracy of shearing interferometry. The fringe spacing directly affects the resolution and contrast of the interference pattern. The appropriate fringe spacing can ensure the clarity of the interference image, improve the signal-to-noise ratio of the image, and make the measurement results more reliable.

[0003] In interferometry technology, the formation and spacing control of interference fringes are key factors that directly affect the measurement accuracy. Existing interferometry technology usually relies on manual adjustment or mechanical adjustment of optical elements to control the fringe spacing; among them, the manual adjustment method is cumbersome and difficult to maintain consistency, and the mechanical adjustment method has limited accuracy; in addition, existing interferometry measurement technology, whether manual adjustment or mechanical adjustment, does not have dynamic control capabilities, and it is difficult to achieve real-time and precise adjustment of the fringe spacing. Summary of the invention

[0004] The purpose of the present invention is to provide a method for automatically adjusting the spacing of Michelson shearing interference fringes to solve the problems in the prior art of complicated operation, difficulty in maintaining consistency, insufficient control accuracy and inability to dynamically control, so as to achieve the purpose of dynamically controlling the Michelson interference system and automatically adjusting the fringe spacing.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for automatically adjusting and controlling the spacing of Michelson shearing interference fringes, comprising the following steps:

[0007] S1, using the fast mirror as an adjustment element to control the Michelson interference light path and generate shear interference fringes;

[0008] S2, collecting the image of the shearing interference fringes in real time to obtain the current fringe spacing;

[0009] S3, calculating the error between the target stripe spacing and the current stripe spacing;

[0010] S4, determine whether the error meets the preset tolerance range: if not, proceed to step S5; if yes, end;

[0011] S5. Generate a control signal based on the error to control the fast reflection mirror to adjust the reflection angle, generate new shear interference fringes, and return to step S2.

[0012] In view of the problems in the prior art that the operation is cumbersome, it is difficult to maintain consistency, the accuracy is limited and it is impossible to dynamically control, the present invention proposes a Michelson shearing interference fringe spacing automatic adjustment control method, which uses a fast mirror as an adjustment element in the Michelson interference optical path (such as a moving mirror in the Michelson interference optical path), and adjusts the Michelson interference optical path by controlling the action of the fast mirror. Specifically, the present application collects the image of the generated shearing interference fringe in real time, and obtains the current fringe spacing, and then calculates the error between the current fringe spacing and the target fringe spacing; if the error meets the preset tolerance range, the current adjustment can be ended; if the error does not meet the preset tolerance range, otherwise the fast mirror is controlled based on the error, the reflection angle of the fast mirror is adjusted, and then the Michelson interference optical path is adjusted to obtain new shearing interference fringes, and then the current fringe spacing corresponding to the new shearing interference fringes is obtained, and compared with the target fringe spacing, and the above steps are repeated until the error meets the preset tolerance range.

[0013] The specific control method of the fast mirror based on the error in the present application can be adaptively set according to the actual working conditions so that the error is gradually reduced, that is, the current fringe spacing gradually approaches the target fringe spacing; the adjustment method for increasing or decreasing the interference fringe spacing that can be obtained by technicians in this field based on the existing technology, or any control method that can be adopted based on the existing control technology can be used in this application.

[0014] This application solves the problems of cumbersome operation, low consistency, and insufficient control accuracy in the prior art. It can automatically adjust the optical path in Michelson interference, realize automatic adjustment and dynamic feedback control of the interference fringe spacing, significantly improve the adjustment speed and accuracy, and effectively avoid overshoot and oscillation of Michelson shear interference fringes, ensuring the stability and accuracy of the fringe spacing. This application is not only suitable for interference fringe spacing control in laboratory environments, but also for various high-precision optical measurement scenarios based on shear interference technology, such as stress analysis, material deformation monitoring, etc. It has important application value for improving the automation level and accuracy of optical interferometry measurement systems.

[0015] Furthermore, the method for obtaining the current stripe spacing includes:

[0016] S201, preprocessing the image of the sheared interference fringes to obtain a first image with clear fringes;

[0017] S202, performing morphological processing on the first image to extract a stripe skeleton to obtain a second image;

[0018] The purpose of morphological processing is to extract a clear fringe skeleton and optimize the interference fringe structure.

[0019] S203, performing spectrum analysis on the second image to determine the fringe normal;

[0020] S204, drawing the stripe normal on the second image, calculating the total pixel length of the intersection of the stripe normal and the stripe; then calculating the average stripe spacing pixel length based on the number of times the black and white stripes alternate, and using the average stripe spacing pixel length as the current stripe spacing.

[0021] This scheme first determines the direction of the stripe normal, and then draws a normal perpendicular to the stripe direction on the second image based on the obtained stripe normal direction, and then calculates the average stripe spacing pixel length, which can be used as the required current stripe spacing for subsequent calculations.

[0022] Preferably, the preprocessing may adopt any one or more of the following: image graying and binarization, boundary noise removal, and connected region analysis; the purpose of the preprocessing is to obtain a first image with clear stripes;

[0023] Preferably, the morphological processing may adopt any one or more of the following: corrosion operation, small area removal, small hole filling, stripe skeleton extraction, and burr removal.

[0024] Furthermore, the method for determining the stripe normal includes:

[0025] S2031, performing a two-dimensional Fourier transform on the second image to obtain a frequency domain representation, moving the low-frequency components of the spectrum to the center, calculating the amplitude of the spectrum, performing a logarithmic transform on the amplitude of the spectrum, and obtaining a spectrum graph;

[0026] S2032, defining the center point of the spectrum graph, generating a mask area within a specified radius of the spectrum center, and obtaining a masked spectrum;

[0027] S2033, taking the maximum amplitude of the spectrum after masking as the main peak, obtaining the coordinates of the main peak in the spectrum, calculating the offset between the main peak and the center of the spectrum, and determining the normal angle of the fringe;

[0028] S2034, draw a straight line through the center point of the spectrum diagram at the normal angle of the stripe to obtain a stripe normal.

[0029] In this solution, the normal direction of the stripes is determined by extracting the main peak in the spectrum. The spectrum is centered by moving the low-frequency components of the spectrum to the center, which is convenient for subsequent spectrum analysis. This solution reduces the impact and interference on the slope by excluding the mask generation of low-frequency interference; the specified radius can be adaptively set according to the actual mask requirements and is not specifically limited here.

[0030] Furthermore, the formula for calculating the average pixel length of the stripes is:

[0031]

[0032] Where: d is the average pixel length of the stripes; d1 is the current stripe spacing; p is the pixel size; L is the total pixel length where the stripe normal intersects the stripes; and N is the number of alternations between black and white stripes.

[0033] By calculating the average stripe spacing pixel length d through this formula, the required current stripe spacing d1 can be obtained.

[0034] Furthermore, the target stripe spacing satisfies the following range:

[0035]

[0036] Where: d0 is the target fringe spacing; D is the size of the deformed surface element; L is the distance between the reflector and the detector in the Michelson interference light path; λ is the laser wavelength in the Michelson interference light path.

[0037] The inventors have found through research that interference fringes with a spacing within this range are clearer and have smaller measurement errors. Therefore, using the range of this solution as the control target for the fringe spacing is beneficial to ensuring the accuracy of the optical interferometry measurement system.

[0038] Further, the method of generating a control signal based on the error to control the fast reflection mirror to adjust the reflection angle includes:

[0039] S501, inputting the error into a PID controller;

[0040] S502, a PID controller generates a voltage control increment based on the error;

[0041] S503, adding the voltage control increment to the current control voltage of the fast mirror to obtain a new control voltage;

[0042] S504: The PID controller inputs the new control voltage to the fast mirror controller, and the fast mirror controller drives the fast mirror to adjust the reflection angle.

[0043] The input voltage of the fast mirror is related to the rotation angle of the fast mirror. Therefore, this scheme performs PID control on the fast mirror through the fringe spacing error fed back by the optical system. This feedback control mechanism can effectively avoid overshoot and oscillation of the optical system and ensure the stability and control accuracy of the fringe spacing.

[0044] Those skilled in the art should understand that the current control voltage of the fast reflex mirror in this solution refers to the voltage corresponding to the last control of the fast reflex mirror, and for the first power-on startup, it refers to the initial voltage of the fast reflex mirror.

[0045] Furthermore, the voltage control increment is generated by the following formula:

[0046]

[0047] Where: Δu is the voltage control increment; e is the error; K p is the proportional gain of the PID controller; K i is the integral gain of the PID controller; K d is the differential gain of the PID controller.

[0048] In this preferred solution, the PID controller combines the error of the stripe spacing with the proportional gain, integral gain and differential gain of the PID controller to generate a voltage control increment Δu, and generates a new control voltage with Δu to drive the fast mirror to adjust the angle, thereby realizing precise adjustment of the optical path. The new control voltage is obtained by the following formula:

[0049] u=u p +Δu;

[0050] Where: u is the new control voltage; u p is the current control voltage of the fast mirror.

[0051] Furthermore, before generating the voltage control increment, the proportional gain of the PID controller is optimized based on the current stripe spacing. The formula for optimizing the proportional gain of the PID controller is:

[0052]

[0053] Where: δ is the optimization parameter; d1 is the current fringe spacing; λ is the laser wavelength in the Michelson interference light path.

[0054] In this scheme, the PID controller dynamically adjusts its proportional gain based on the current fringe spacing, so that the proportional gain automatically tracks and adapts according to the changes in the interference fringes, and uses the optimized proportional gain to calculate the voltage control increment, thereby more accurately controlling the fast mirror angle, which is more conducive to achieving high-precision control of the interference fringe spacing.

[0055] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0056] 1. The present invention discloses a method for automatically adjusting and controlling the spacing of Michelson shearing interference fringes, which solves the problems of complicated operation, low consistency, insufficient control accuracy, etc. in the prior art. It can automatically adjust the optical path in Michelson interference, realize automatic adjustment and dynamic feedback control of the spacing of interference fringes, significantly improve the adjustment speed and accuracy, effectively avoid overshoot and oscillation of Michelson shearing interference fringes, and ensure the stability and accuracy of the fringe spacing.

[0057] 2. The automatic adjustment and control method of the spacing of Michelson shearing interference fringes of the present invention is not only suitable for the control of the spacing of interference fringes in laboratory environments, but also suitable for various high-precision optical measurement scenarios based on shearing interference technology, such as stress analysis, material deformation monitoring and other fields. It has important application value for improving the automation level and accuracy of optical interference measurement systems.

[0058] 3. The present invention provides a method for automatically adjusting the spacing of Michelson shearing interference fringes. The method performs PID control on the fast mirror through the fringing spacing error fed back by the optical system, generates a voltage control increment Δu, generates a new control voltage with Δu, drives the fast mirror to adjust the angle, and realizes precise adjustment of the optical path.

[0059] 4. The present invention provides a method for automatically adjusting the spacing of Michelson shearing interference fringes, which can dynamically adjust the proportional gain of the PID controller so that the proportional gain automatically tracks and adapts according to the changes in the interference fringes, and calculates the voltage control increment with the optimized proportional gain, thereby more accurately controlling the fast mirror angle and being more conducive to achieving high-precision control of the spacing of the interference fringes. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0061] Figure 1 It is a schematic diagram of the overall process of a specific embodiment of the present invention;

[0062] Figure 2 A schematic diagram of a process for obtaining the current stripe spacing in a specific embodiment of the present invention;

[0063] Figure 3 An image of sheared interference fringes captured by a CCD camera in a specific embodiment of the present invention;

[0064] Figure 4 It is a schematic diagram of drawing stripe normals on the second image in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0065] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0066] Embodiment 1:

[0067] like Figure 1 A Michelson shearing interference fringe spacing automatic adjustment control method shown includes the following steps:

[0068] S1, using the fast mirror as an adjustment element to control the Michelson interference light path and generate shear interference fringes;

[0069] S2, using a CCD camera to collect images of the shear interference fringes in real time, such as Figure 3 As shown; the current stripe spacing d1 is obtained by the stripe spacing recognition algorithm;

[0070] S3, calculating the error e between the target fringe spacing d0 and the current fringe spacing d1, e=d0-d1;

[0071] The target stripe spacing meets the following range:

[0072]

[0073] Where: d0 is the target fringe spacing; D is the size of the deformed surface element; L is the distance between the reflector and the detector in the Michelson interference light path; λ is the laser wavelength in the Michelson interference light path.

[0074] S4, determine whether the error e meets the preset tolerance range: if not, proceed to step S5; if yes, end; the preset tolerance range can be adaptively set according to specific needs;

[0075] S5, input the error e into the PID controller, the PID controller generates a control signal based on the error e, controls the fast reflection mirror to adjust the reflection angle, changes the light path, generates new shear interference fringes, and returns to step S2.

[0076] In this embodiment, due to the adjustment of the fast mirror angle, the interference fringe image in the Michelson shearing interference optical system changes accordingly, and the CCD camera collects a new fringe image again, analyzes the new fringe image using the fringe recognition algorithm, identifies the new current fringe spacing, recalculates the error e and feeds the data back to the PID controller to form a negative feedback closed-loop control system. In this closed-loop control system, the PID controller dynamically adjusts the fast mirror angle according to the error between the current fringe spacing and the target fringe spacing, ensuring that the spacing of the interference fringes gradually approaches the set range of the target fringe spacing.

[0077] Embodiment 2:

[0078] A method for automatically adjusting and controlling the spacing of Michelson shearing interference fringes. Based on Example 1, this embodiment identifies the current fringe spacing d1 by combining image processing and spectrum analysis. The process is as follows: Figure 2 As shown, specifically including:

[0079] S201, preprocessing the image of the sheared interference fringes collected by the CCD camera to obtain a first image with clear fringes. The specific steps include sequentially executing: image grayscale and binarization, removing boundary noise, and connected area analysis; through the above steps, a target binarized area with clear fringes is obtained as the required first image.

[0080] S202, performing morphological processing on the first image to extract a clear fringe skeleton and optimize the interference fringe structure, and using the obtained fringe skeleton image as the second image. The specific steps include:

[0081] (1) Corrosion operation:

[0082] Use the imerode function to erode the second image, using the diamond structure element strel('diamond',1) and an erosion degree of 1 pixel. This step is used to remove stripe edge noise and separate adjacent stripes to improve the independence of stripes.

[0083] (2) Small area removal:

[0084] Use the bwareaopen function to delete connected areas with an area less than 1000 pixels. This step removes isolated noise points and small areas and retains the main stripe structure.

[0085] (3) Small hole filling:

[0086] The limitedFill function is used to fill small holes, and the filling threshold is set to 20 pixels to ensure that the tiny holes inside the stripes are effectively filled, further improving the integrity of the stripes.

[0087] (4) Stripe skeleton extraction:

[0088] Use the 'skel' operation of the bwmorph function to refine the stripe area into skeleton lines with a width of 1 pixel, extract the structural framework of the stripes, and make the geometric information of the stripes more prominent for subsequent analysis.

[0089] (5) Deburring:

[0090] Deburring is performed on the refined skeleton image, using the 'spur' operation of the bwmorph function to remove hanging line segments less than 10 pixels in length. This step is used to eliminate redundant burrs on the edges and optimize the continuity and smoothness of the stripes.

[0091] S203, performing spectrum analysis on the second image to determine the fringe normal; the specific method includes:

[0092] (1) Perform a two-dimensional Fourier transform on the second image to obtain a frequency domain representation, and calculate the frequency spectrum information of the image by using the fft2 function.

[0093] Spectrum centering is achieved by moving the low-frequency components of the spectrum to the center.

[0094] Calculate the amplitude of the spectrum and obtain the frequency distribution intensity.

[0095] The spectrum amplitude is logarithmically transformed to enhance the display effect and obtain a spectrum diagram. The logarithmic transformation is used to compress the amplitude range and make the spectrum details more obvious.

[0096] (2) Define the center point of the spectrum graph, that is, the center position of the spectrum:

[0097]

[0098] Where: (u c ,v c ) is the coordinate of the center of the spectrum; W p , H p are the width and length of the spectrum graph respectively.

[0099] Generate a mask area within the specified radius R of the spectrum center. Its purpose is to exclude the low-frequency components of the spectrum radius R pixels, and remove the central low-frequency area through the mask to highlight the spatial frequency characteristics of the stripes and reduce the impact and interference on the slope. The mask area is expressed as:

[0100]

[0101] Where: mask(u,v) represents the mask area; (u,v) represents the coordinates within the mask area;

[0102] Preferably, the radius R is specified to be within a range of 30 to 100 pixels.

[0103] Generate a masked spectrum:

[0104] F filtered (u,v)=F magnitude (u,v)·mask(u,v) ；

[0105] Where: F filtered(u,v) is the spectrum after masking; F magnitude (u,v) is the spectrum before masking.

[0106] Search the maximum amplitude after masking in the spectrum as the main peak, and obtain the coordinates of the main peak in the spectrum (u p ,v p ). The normal angle θ of the fringe is determined by calculating the offset between the main peak and the center of the spectrum:

[0107]

[0108] (3) Draw a straight line through the center point of the spectrum diagram at the normal angle of the stripe to obtain the stripe normal.

[0109] S204, drawing the stripe normal on the second image, such as Figure 4 As shown; calculate the total pixel length of the intersection of the stripe normal and the stripe; then calculate the average stripe spacing pixel length based on the number of alternations of black and white stripes, and use the average stripe spacing pixel length as the current stripe spacing. The calculation formula is:

[0110]

[0111] Where: d is the average pixel length of the stripes; d1 is the current stripe spacing; p is the pixel size; L is the total pixel length where the stripe normal intersects the stripes; and N is the number of alternations between black and white stripes.

[0112] In a more preferred embodiment, the Michelson contrast formula is used in step S201 to define the clarity of the stripes:

[0113]

[0114] Where: C is Michelson contrast; I max ,I min are the maximum grayscale value and the minimum grayscale value of the stripe area, respectively. If C>0.5, the stripes are clear and the current image can be used as the first image with clear stripes; if C≤0.5, the current image cannot be used as the first image with clear stripes and further preprocessing is required.

[0115] Embodiment 3:

[0116] A method for automatically adjusting and controlling the spacing of Michelson shearing interference fringes, based on Embodiment 1 or 2, generates a control signal based on the error, and controls the fast reflection mirror to adjust the reflection angle, comprising:

[0117] S501 , input the error e and the current stripe spacing d1 into a PID controller.

[0118] S502, PID controller optimizes proportional gain K based on current stripe spacing p :

[0119]

[0120] Where: δ is the optimization parameter; d1 is the current fringe spacing; λ is the laser wavelength in the Michelson interference light path.

[0121] The optimization parameter δ can be adaptively set according to specific working conditions and is not specifically limited here.

[0122] The PID controller generates a voltage control increment Δu based on the error:

[0123]

[0124] Where: Δu is the voltage control increment; e is the error; K p is the proportional gain of the PID controller; K i is the integral gain of the PID controller; K d is the differential gain of the PID controller.

[0125] S503, adding the voltage control increment to the current control voltage of the fast mirror to obtain a new control voltage u;

[0126] u=u p +Δu;

[0127] Where: u is the new control voltage; u p is the current control voltage of the fast mirror.

[0128] S504: The PID controller inputs the new control voltage to the fast mirror controller, and the fast mirror controller drives the fast mirror to adjust the reflection angle.

[0129] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0130] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for automatically adjusting and controlling the spacing of Michelson shearing interference fringes, characterized in that: The following steps are involved: S1, using the fast mirror as an adjustment element to control the Michelson interference light path and generate shear interference fringes; S2, collecting the image of the shearing interference fringes in real time to obtain the current fringe spacing; S3, calculating the error between the target stripe spacing and the current stripe spacing; S4, determine whether the error meets the preset tolerance range: if not, proceed to step S5; if yes, end; S5. Generate a control signal based on the error to control the fast reflection mirror to adjust the reflection angle, generate new shear interference fringes, and return to step S2.

2. The method for automatically adjusting the spacing of Michelson shearing interference fringes according to claim 1, characterized in that: The method for obtaining the current stripe spacing comprises: S201, preprocessing the image of the sheared interference fringes to obtain a first image with clear fringes; S202, performing morphological processing on the first image to extract a stripe skeleton to obtain a second image; S203, performing spectrum analysis on the second image to determine the fringe normal; S204, drawing the stripe normal on the second image, calculating the total pixel length of the intersection of the stripe normal and the stripe; then calculating the average stripe spacing pixel length based on the number of times the black and white stripes alternate, and using the average stripe spacing pixel length as the current stripe spacing.

3. The method for automatically adjusting the spacing of Michelson shearing interference fringes according to claim 2, characterized in that: The method for determining the stripe normal comprises: S2031, performing a two-dimensional Fourier transform on the second image to obtain a frequency domain representation, moving the low-frequency components of the spectrum to the center, calculating the amplitude of the spectrum, performing a logarithmic transform on the amplitude of the spectrum, and obtaining a spectrum graph; S2032, defining the center point of the spectrum graph, generating a mask area within a specified radius of the spectrum center, and obtaining a masked spectrum; S2033, taking the maximum amplitude of the spectrum after masking as the main peak, obtaining the coordinates of the main peak in the spectrum, calculating the offset between the main peak and the center of the spectrum, and determining the normal angle of the fringe; S2034, drawing a straight line through the center point of the spectrum diagram at the normal angle of the stripe to obtain a stripe normal.

4. The method for automatically adjusting the spacing of Michelson shearing interference fringes according to claim 2, characterized in that: The formula for calculating the average pixel length of the stripes is: Where: d is the average stripe spacing pixel length; d1 is the current stripe spacing; p is the pixel size; L is the total pixel length where the stripe normal intersects the stripe, and N is the number of alternations between black and white stripes.

5. The method for automatically adjusting the spacing of Michelson shearing interference fringes according to claim 1, characterized in that: The target stripe spacing meets the following range: Where: d0 is the target fringe spacing; D is the size of the deformed surface element; L is the distance between the reflector and the detector in the Michelson interference light path; λ is the laser wavelength in the Michelson interference light path.

6. The method for automatically adjusting the spacing of Michelson shearing interference fringes according to claim 1, characterized in that: The method for generating a control signal based on the error and controlling the fast reflection mirror to adjust the reflection angle includes: S501, inputting the error into a PID controller; S502, a PID controller generates a voltage control increment based on the error; S503, adding the voltage control increment to the current control voltage of the fast mirror to obtain a new control voltage; S504: The PID controller inputs the new control voltage to the fast mirror controller, and the fast mirror controller drives the fast mirror to adjust the reflection angle.

7. The method for automatically adjusting and controlling the spacing of Michelson shearing interference fringes according to claim 6, characterized in that: The voltage control increment is generated by the following formula: Where: Δu is the voltage control increment; e is the error; K p is the proportional gain of the PID controller; K i is the integral gain of the PID controller; K d is the differential gain of the PID controller.

8. The method for automatically adjusting and controlling the spacing of Michelson shearing interference fringes according to claim 7, characterized in that: The new control voltage is obtained by the following formula: u=u p +Δu; Where: u is the new control voltage; u p is the current control voltage of the fast mirror.

9. The method for automatically adjusting and controlling the spacing of Michelson shearing interference fringes according to claim 7, characterized in that: Before generating the voltage control increments, the proportional gain of the PID controller is optimized based on the current fringe spacing.

10. The method for automatically adjusting and controlling the spacing of Michelson shearing interference fringes according to claim 9, characterized in that: The formula for optimizing the proportional gain of the PID controller is: Where: δ is the optimization parameter; d1 is the current fringe spacing; λ is the laser wavelength in the Michelson interference light path.

Images