Micro-displacement measurement device and method based on laguerre-gaussian beam conjugate interference

Abstract

The present application relates to a kind of micro-displacement measurement device and method based on Laguerre-Gaussian beam conjugate interference, belong to laser interference measurement technical field, including conjugate interference component, imaging component and processor.Conjugate interference component is based on LG light and Mach-Zehnder interferometer to carry out conjugate interference, imaging component respectively before and after the displacement of the object to be measured, interference process is photographed, obtains interference image before displacement and interference image after displacement, processor processes interference image before displacement and interference image after displacement, obtains the displacement size and direction of the object to be measured, whether the object can be observed in real time simple and convenient displacement change, and can realize the micro-displacement measurement of picometer level.

Description

Technical Field

[0001] This invention relates to the field of laser interferometry technology, and in particular to a micro-displacement measurement device and method based on Laguerre-Gaussian beam conjugate interference. Background Technology

[0002] Laser interferometry plays an important role in micro-displacement measurement research due to its high-precision optical standard scale. Although the geometry of interferometers is different, their basic functions are similar. The wavefront from the reference surface is compared and interfered with the wavefront from the lens or surface being measured. By analyzing the obtained interferogram, a quantitative and qualitative result of the parameter to be measured can be obtained.

[0003] Laguerre-Gaussian (LG) beams possess the physical properties of helical phase and annular intensity, making them widely applicable in optical manipulation, high-resolution microscopy, optical communication, quantum communication, and optical measurement. Mach-Zehnder interferometers offer simple testing principles and low noise, and specific measurements can be achieved through flexible modifications to the optical path. However, currently, there is no micro-displacement measurement technique based on LG beams with adjustable topological charge and Mach-Zehnder interferometers. Summary of the Invention

[0004] The purpose of this invention is to provide a micro-displacement measurement device and method based on Laguerre-Gaussian beam conjugate interference, which can realize the measurement of micro-displacement by performing conjugate interference based on Laguerre-Gaussian beam and Machzed interferometer.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A micro-displacement measurement device based on Laguerre-Gaussian beam conjugate interferometry, the micro-displacement measurement device comprising: a conjugate interferometer component, an imaging component, and a processor;

[0007] The conjugate interference component includes: an LG light generating component and a Mach-Zehnder interferometer; the LG light generating component and the Mach-Zehnder interferometer are optically connected; the LG light generating component is used to generate a first LG light with arbitrarily adjustable topological charge number and transmit the first LG light to the Mach-Zehnder interferometer; the Mach-Zehnder interferometer is used to transmit the first LG light to the object under test and receive a second LG light conjugate to the first LG light reflected by the object under test, and cause the first LG light and the second LG light to interfere;

[0008] The imaging component is used to capture the interference process of the first LG light and the second LG light before the object under test is displaced, to obtain an interference image before displacement; it is also used to capture the interference process of the first LG light and the second LG light after the object under test is displaced, to obtain an interference image after displacement.

[0009] The processor is communicatively connected to the imaging component; the processor is used to process the pre-displacement interferometric image and the post-displacement interferometric image to obtain the displacement magnitude and direction of the object under test.

[0010] In some embodiments, the LG light generating component includes a laser and a first beam splitter and a spatial light modulator arranged sequentially along the laser transmission direction; the laser is used to emit laser light; the first beam splitter is used to transmit the laser light to the spatial light modulator; the spatial light modulator is used to perform phase modulation on the laser light to generate a first LG light with arbitrarily adjustable topological charge, and to return the first LG light to the first beam splitter; the first beam splitter is also used to reflect the first LG light to the Mach-Zehnder interferometer.

[0011] In some embodiments, a polarizer is arranged between the laser and the first beam splitter; the polarizer is used to adjust the polarization angle of the laser to adapt to the spatial light modulator.

[0012] In some embodiments, a collimating and beam-expanding device is arranged between the laser and the first beam-splitting prism; the collimating and beam-expanding device is used to collimate and expand the laser beam.

[0013] In some embodiments, the Mach-Zehnder interferometer includes a second beam splitter, a first standard mirror, a second standard mirror, and a third beam splitter; the second beam splitter transmits the first LG light to the first standard mirror and the second standard mirror respectively; the first standard mirror reflects the first LG light to the third beam splitter; the third beam splitter transmits the first LG light to the object under test and receives the second LG light, which is conjugate to the first LG light, reflected by the object under test; the second standard mirror reflects the first LG light to the third beam splitter; the third beam splitter combines the first LG light and the second LG light, causing interference between them.

[0014] A micro-displacement measurement method based on Laguerre-Gaussian beam conjugate interference, controlling the operation of the aforementioned micro-displacement measurement device, the micro-displacement measurement method comprising:

[0015] The receiving imaging unit captures a pre-displacement interferometric image before the object under test is displaced and a post-displacement interferometric image after the object under test is displaced.

[0016] The magnitude and direction of the displacement of the object under test are obtained by processing the pre-displacement and post-displacement interference images.

[0017] In some embodiments, processing the pre-displacement interferometric image and the post-displacement interferometric image to obtain the magnitude and direction of the displacement of the object under test specifically includes:

[0018] The pre-displacement interference image is processed to obtain the pre-displacement light intensity curve;

[0019] The displacement-adjusted interference image is processed to obtain the displacement-adjusted light intensity curve;

[0020] The magnitude and direction of the displacement of the object under test are determined based on the light intensity curve before displacement and the light intensity curve after displacement.

[0021] In some embodiments, processing the pre-displacement interferometric image to obtain the pre-displacement light intensity curve specifically includes:

[0022] The pre-displacement interferometric image is enhanced to obtain the enhanced image;

[0023] The enhanced image is subjected to connected component identification and centroid calibration to determine the centroid of each connected component;

[0024] Based on all the centroids, perform a circular fit to obtain the fitted circle center and the centroid radius;

[0025] The interference image before displacement is scanned based on the fitted circle center and the centroid radius to obtain the light intensity curve before displacement; the light intensity curve is the curve of light intensity value changing with angle.

[0026] In some embodiments, the step of image enhancement of the pre-displacement interferometric image to obtain the enhanced image specifically includes:

[0027] The interference image before displacement is denoised to obtain the denoised image;

[0028] The denoised image is thresholded to obtain a binarized image;

[0029] Morphological operations are performed on the binarized image to obtain an enhanced image; the morphological operations include dilation and erosion.

[0030] In some embodiments, determining the magnitude and direction of the displacement of the object under test based on the light intensity curve before displacement and the light intensity curve after displacement specifically includes:

[0031] Record the first angle of the peak point in the light intensity curve before the displacement, and record the second angle of the peak point in the light intensity curve after the displacement;

[0032] Calculate the difference between the second angle and the first angle, use the absolute value of the difference as the rotation angle, and use the sign of the difference as the rotation direction;

[0033] The magnitude of the displacement of the object under test is calculated based on the rotation angle, and the direction of the displacement of the object under test is determined based on the rotation direction.

[0034] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0035] This invention provides a micro-displacement measurement device and method based on Laguerre-Gaussian beam conjugate interferometry, comprising a conjugate interferometer component, an imaging component, and a processor. The conjugate interferometer component performs conjugate interferometry based on LG beams and a Mach-Zehnder interferometer. The imaging component captures images of the interference process before and after displacement of the object under test, obtaining an interference image before displacement and an interference image after displacement. The processor processes these images to obtain the magnitude and direction of the displacement of the object under test. This allows for real-time and convenient observation of whether the object has undergone displacement changes and enables picometer-level micro-displacement measurement. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the micro-displacement measuring device provided in Embodiment 1 of the present invention;

[0038] Figure 2 This is a flowchart of the micro-displacement measurement method provided in Embodiment 2 of the present invention;

[0039] Figure 3 This is a schematic diagram of the pre-displacement interferometric image provided in Embodiment 2 of the present invention;

[0040] Figure 4 This is a schematic diagram of the displacement interference image provided in Embodiment 2 of the present invention;

[0041] Figure 5 This is a flowchart of the image processing of the interference images before and after displacement provided in Embodiment 2 of the present invention;

[0042] Figure 6 This is a schematic diagram of the light intensity curve before displacement provided in Embodiment 2 of the present invention;

[0043] Figure 7 This is a schematic diagram of the light intensity curve after displacement provided in Embodiment 2 of the present invention;

[0044] Figure 8 This is a schematic diagram of the peak width of the interferometric images under different topological charge numbers provided in Embodiment 2 of the present invention.

[0045] Symbol explanation:

[0046] 1-Laser; 2-Polarizer; 3-Collimating and expanding device; 4-First beam splitter; 5-Spatial light modulator; 6-First computer; 7-Second beam splitter; 8-First standard mirror; 9-Second standard mirror; 10-Third beam splitter; 11-Two-dimensional photoelectric sensor; 12-Second computer; 13-Object under test. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] The purpose of this invention is to provide a micro-displacement measurement device and method based on Laguerre-Gaussian beam conjugate interference, which can realize the measurement of micro-displacement by performing conjugate interference based on Laguerre-Gaussian beam and Machzed interferometer.

[0049] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0050] Example 1:

[0051] This embodiment provides a micro-displacement measurement device based on Laguerre-Gaussian beam conjugate interferometry, such as... Figure 1 As shown, the micro-displacement measurement device includes: a conjugate interferometer, an imaging component, and a processor.

[0052] The conjugate interference component includes an LG light generating assembly and a Mach-Zehnder interferometer, with the LG light generating assembly and the Mach-Zehnder interferometer optically connected. The LG light generating assembly generates a first LG light with arbitrarily adjustable topological charge and transmits the first LG light to the Mach-Zehnder interferometer. The Mach-Zehnder interferometer transmits the first LG light to the object under test 13, receives a second LG light reflected from the object under test 13 that is conjugate with the first LG light, and causes the first LG light and the second LG light to interfere.

[0053] A planar reflector is fixed on the object under test 13, which can return the light path to its original path, thereby generating the second LG light and reflecting it to the Machzed interferometer.

[0054] The imaging component is used to capture the interference process of the first LG light and the second LG light before the object under test 13 is displaced, to obtain an interference image before displacement, and is also used to capture the interference process of the first LG light and the second LG light after the object under test 13 is displaced, to obtain an interference image after displacement.

[0055] In this embodiment, the object under test 13 can be displaced by piezoelectric ceramics, and the imaging component can be a two-dimensional photoelectric sensor 11, which can be a CCD, CMOS or a two-dimensional photoelectric detector array.

[0056] The processor is communicatively connected to the imaging component. The processor processes the pre-displacement and post-displacement interferometric images to obtain the magnitude and direction of the displacement of the object under test 13. In this embodiment, the processor can be a second computer 12.

[0057] As an optional implementation, the LG light generating component in this embodiment includes a laser 1 and a first beam splitter 4 and a spatial light modulator 5 arranged sequentially along the laser transmission direction. The laser 1 is used to emit laser light, the first beam splitter 4 is used to transmit the laser light to the spatial light modulator 5, the spatial light modulator 5 is used to perform phase modulation on the laser light to generate a first LG light with arbitrarily adjustable topological charge, and returns the first LG light to the first beam splitter 4. The first beam splitter 4 is also used to reflect the first LG light to a Mach-Zehnder interferometer.

[0058] Specifically, the laser 1 in this embodiment can be a solid-state, liquid, or fiber laser. However, in order for the spatial light modulator 5 to generate a high-quality vortex light field, on the one hand, the wavelength of the laser 1 must match the operating wavelength range of the spatial light modulator 5, and on the other hand, the linewidth of the laser 1 must be narrow and the beam quality close to the diffraction limit. The splitting ratio of the first beam splitter prism 4 can be 50:50. The spatial light modulator 5 in this embodiment can be a reflective pure phase spatial light modulator or a transmissive pure phase spatial light modulator. The spatial light modulator 5 is controlled by the first computer 6 to load a phase diagram with a topological charge of l to modulate the laser and generate an LG beam with an arbitrarily adjustable topological charge. That is, the spatial light modulator 5 needs to be controlled by host computer software to perform phase modulation on the incident laser. The first computer 6 is equipped with control software that matches the spatial light modulator 5. Different phase diagrams can be generated by presetting the topological charge through the control software and loaded onto the spatial light modulator 5 to drive the spatial light modulator 5 to modulate the laser and obtain the first LG beam. A phase hologram encodes only the phase information of a light wave; essentially, it is a type of phase hologram that can be used to control phase changes and is a type of computational hologram. The first computer 6 can generate phase holograms in two ways: one is to directly generate the phase hologram by manipulating the control software of the spatial light modulator 5 on the first computer 6; the other is to use programming software to generate the phase hologram based on the phase formula of vortex light.

[0059] Preferably, the LG light generating component in this embodiment further includes a polarizer 2, which is arranged between the laser 1 and the first beam splitter 4. The polarizer 2 is used to adjust the polarization angle of the laser to adapt to the spatial light modulator 5.

[0060] Since the phase-modulated spatial light modulator 5 only modulates the incident beam whose polarization direction is parallel to the principal axis of the liquid crystal molecules, a polarizer 2 is needed to convert the polarization direction of the laser emitted from the laser 1 to the polarization direction required by the spatial light modulator 5. Therefore, the function of the polarizer 2 is to match the spatial light modulator 5; it only affects vertical polarization. Adjusting the angle of the polarizer 2 so that its polarization direction is parallel to the principal optical axis of the spatial light modulator 5 allows the spatial light modulator 5 to operate in pure phase mode. In other words, the polarizer 2 converts the emitted laser beam into a beam with a polarization direction parallel to the principal optical axis, enabling the spatial light modulator 5 to operate in pure phase mode. Only in pure phase mode can the spatial light modulator 5 generate a high-quality LG beam.

[0061] The LG light generating assembly in this embodiment also includes a collimating and beam expanding device 3, which is arranged between the laser 1 and the first beam splitter 4. The collimating and beam expanding device 3 is used to collimate and expand the laser beam. The collimating and beam expanding device 3 in this embodiment includes a first lens and a second lens arranged sequentially. The first lens and the second lens can be K9 plano-convex lenses.

[0062] When polarizer 2 and collimating beam expander 3 are arranged simultaneously, polarizer 2 can be located between laser 1 and collimating beam expander 3. Polarizer 2 is used to adjust the polarization angle of the laser to match the spatial light modulator 5. Collimating beam expander 3 is used to collimate and expand the laser after the polarization angle is adjusted.

[0063] As an optional implementation, the Mach-Zehnder interferometer in this embodiment includes a second beam splitter 7, a first standard mirror 8, a second standard mirror 9, and a third beam splitter 10. The second beam splitter 7 transmits the first LG light to the first standard mirror 8 and the second standard mirror 9 respectively. The first standard mirror 8 reflects the first LG light to the third beam splitter 10. The third beam splitter 10 transmits the first LG light to the object under test 13 and receives the second LG light, which is conjugate to the first LG light, reflected by the object under test 13. The second standard mirror 9 reflects the first LG light to the third beam splitter 10, and the third beam splitter 10 combines the first and second LG lights, causing them to interfere.

[0064] In this embodiment, the beam splitting ratio of the second beam splitter 7 and the third beam splitter 10 can be 50:50.

[0065] based on Figure 1 The structural setup and operation of the conjugate interference component are as follows: Laser 1 generates a laser beam, which is then polarized at the incident angle by polarizer 2, collimated and expanded by collimating and expanding device 3. The collimated and expanded laser beam is then incident on spatial light modulator 5 through first beam splitter 4, generating first LG light with arbitrarily adjustable topological charge, which returns to first beam splitter 4 and is reflected to second beam splitter 7. After being split by second beam splitter 7, one beam of first LG light is reflected by first standard mirror 8 and then passes through third beam splitter 10 to reach the object under test 13. After being reflected by the object under test 13, second LG light is generated and reflected and output by third beam splitter 10. The other beam of first LG light is reflected by second standard mirror 9 and then output by third beam splitter 10. The two beams are combined by third beam splitter 10 and interfere, which is imaged by two-dimensional photoelectric sensor 11, recording the interference image before and after displacement.

[0066] This embodiment provides a micro-displacement measurement device based on the conjugate interference principle of LG beams. The incident laser is modulated into an LG beam by the spatial light modulator 5 and then enters the structured optical path of the Mach-Zehnder interferometer. One of the LG beams is reflected by the object under test 13 and the third beam splitter 10 to become a conjugate LG beam. After the two beams interfere, the interference fringes are distributed in a petal shape. Since the displacement of the object will cause a change in the optical path difference of one of the paths, the petal-shaped interference fringes will rotate. The magnitude of the object's micro-displacement can be determined by the rotation angle, and the direction of the object's micro-displacement can be determined by the rotation direction. Therefore, an image processing algorithm is used to identify the changes in the rotation angle and rotation direction of the petal-shaped fringes of the conjugate interference, thereby measuring the object's micro-displacement. It can be used to observe whether the object has a displacement change in real time and can also achieve picometer-level micro-displacement measurement.

[0067] Example 2:

[0068] This embodiment provides a micro-displacement measurement method based on Laguerre-Gaussian beam conjugate interferometry, controlling... Figure 1 The micro-displacement measuring device shown works as follows: Figure 2 As shown, the micro-displacement measurement method includes:

[0069] S1: Receive the pre-displacement interferometric image captured by the imaging component before the object under test 13 is displaced and the post-displacement interferometric image captured after the object under test 13 is displaced.

[0070] S2: Process the pre-displacement interference image and the post-displacement interference image to obtain the displacement magnitude and direction of the object under test 13.

[0071] like Figure 3 As shown, it is a petal-shaped interference pattern of the conjugate interference of an LG beam with a topological charge of 2 before the displacement of the object 13 under test, captured by a two-dimensional photoelectric sensor 11. It is an interference image before displacement. Figure 3 Each petal in the diagram corresponds to a bright fringe in the interference pattern produced by two plane light waves; therefore, four petals are equivalent to four bright fringes. For example... Figure 4 As shown, it is a petal-shaped interference pattern of the conjugate interference of an LG beam with a topological charge of 2 after the object under test 13 is displaced, captured by a two-dimensional photoelectric sensor 11. It is an interference image after displacement.

[0072] like Figure 5 As shown, S2 may include:

[0073] (1) Process the interference image before displacement to obtain the light intensity curve before displacement;

[0074] (1) may include:

[0075] (1.1) Image enhancement is performed on the interferometric image before displacement to obtain the enhanced image;

[0076] This step may include: first, denoising the pre-displacement interference image to obtain a denoised image; then, thresholding the denoised image to obtain a binarized image; and finally, performing morphological operations on the binarized image to obtain an enhanced image, including dilation and erosion.

[0077] In this embodiment, median filtering is used for noise removal because it can effectively preserve image edge details while removing noise. An adaptive thresholding method can be used for thresholding, with the threshold calculated using this method. The purpose of morphological operations is to fill small holes within individual petals in the binarized image with solids and remove small connected components outside the individual petals.

[0078] (1.2) Perform connected region identification and centroid calibration on the enhanced image to determine the centroid of each connected region; a connected region refers to an individual petal.

[0079] The enhanced image after image enhancement is a petal-shaped image. The software algorithm is used to identify each individual petal as a connected region, and the centroid of each individual petal is extracted to obtain the centroid coordinates.

[0080] (1.3) Perform a circular fit based on all centroids to obtain the fitted circle center and centroid radius;

[0081] By combining the least squares method with a circular curve fitted from the centroid, the center of the fitted circle and the centroid radius are determined.

[0082] (1.4) Based on the fitted circle center and centroid radius, the light intensity of the interference image before displacement is scanned to obtain the light intensity curve before displacement. The light intensity curve is the curve of light intensity value changing with angle.

[0083] The scanning principle is to extract the light intensity on the circumference of the interference image before displacement counterclockwise by taking the fitted circle center as the origin and the centroid radius as the radius, so as to obtain the light intensity value at each angle and construct the light intensity curve before displacement.

[0084] like Figure 6 As shown, it is the intensity peak curve of the petal interference image of the test object 13 before displacement, which is drawn after image processing, i.e., the light intensity curve before displacement.

[0085] (2) Process the displacement interference image to obtain the displacement light intensity curve;

[0086] The process of processing the interferometric image after displacement is the same as that of processing the interferometric image before displacement, and will not be repeated here. Figure 7As shown, it is the intensity peak curve of the petal interference image of the object under test 13 after displacement, which is drawn after image processing, i.e., the light intensity curve after displacement.

[0087] (3) Determine the magnitude and direction of the displacement of the object to be measured 13 based on the light intensity curve before displacement and the light intensity curve after displacement.

[0088] Specifically, record the first angle of the peak point in the light intensity curve before displacement, and record the second angle of the peak point in the light intensity curve after displacement; calculate the difference between the second angle and the first angle, use the absolute value of the difference as the rotation angle, and use the sign of the difference as the rotation direction; calculate the displacement of the object 13 under test based on the rotation angle, and determine the displacement direction of the object 13 under test based on the rotation direction.

[0089] In this embodiment, the peak point can be either the highest point or the lowest point.

[0090] When the object under test 13 undergoes a displacement of length δ, the phase difference changes by 2kδ, where k = 2π / λ, k is the wave vector of light, a constant independent of the topological charge, and λ is the wavelength of the incident laser. According to the LG conjugate interference theory, the change in the interference phase difference causes the interference image to rotate by an angle θ = kδ / l, where l is the topological charge. For example, when l = 2, after the object is displaced by a length δ = λ / 4, the petal-shaped interference fringes will rotate by an angle of π / 4. Therefore, the magnitude of the displacement can be quickly determined using the rotation angle. By calculating the change in the peak position of the light intensity before and after the displacement, the rotation angle of the image produced by the displacement is obtained as θ = 45°. The displacement of the object, δ = λ / 4, can be obtained using the relationship between angle and displacement, θ = kδ / l.

[0091] For a given topological charge number, the rotation directions of the petal-shaped interference patterns for forward and reverse displacements are opposite. Therefore, the direction of displacement can be determined by the rotation direction of the petal patterns.

[0092] The process of determining the rotation angle is as follows: The peak points of the light intensity curve before displacement are numbered in sequence, and the peak points of the light intensity curve after displacement are also numbered in sequence. The difference between the peak positions with the same number before and after displacement is calculated, and the number of rotation angles equal to the number of peak points can be obtained. The average of these values ​​is taken as the final rotation angle.

[0093] The micro-displacement measurement method disclosed in this embodiment changes the optical path difference of the interference optical path by applying object displacement. The change in the interference optical path difference causes the petal-shaped interference fringes to rotate. Using LG beam conjugate interference, the rotation angle and direction of the petal interference fringes intuitively show the object displacement and direction. Based on image processing operations, the specific magnitude and direction value of the displacement can be accurately obtained.

[0094] As the topological charge number *l* increases, the number of petals in the interference image increases to 2*l*, thus increasing the number of intensity peaks. This provides more samples for data processing, helping to reduce the average error. Furthermore, an increase in the topological charge number *l* results in a narrower interference fringe, which aids in peak detection and improves the resolution of image processing. Figure 8 As shown. Since the topological charge number in this invention can be arbitrarily adjusted according to the physical quantity to be measured, this embodiment is also valuable for detecting other parameters such as refractive index, gas-liquid concentration, and thickness of transparent media.

[0095] Each embodiment in this specification focuses on the differences from other embodiments. For the same or similar parts between the embodiments, please refer to each other.

[0096] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A micro-displacement measurement device based on Laguerre-Gaussian beam conjugate interference, characterized in that, The micro-displacement measurement device includes: a conjugate interferometer component, an imaging component, and a processor; The conjugate interference component includes: an LG light generating component and a Mach-Zehnder interferometer; the LG light generating component and the Mach-Zehnder interferometer are optically connected; the LG light generating component is used to generate a first LG light with arbitrarily adjustable topological charge number and transmit the first LG light to the Mach-Zehnder interferometer; the Mach-Zehnder interferometer is used to transmit the first LG light to the object under test and receive a second LG light conjugate to the first LG light reflected by the object under test, and cause the first LG light and the second LG light to interfere; The LG light generating component includes a laser and a first beam splitter and a spatial light modulator arranged sequentially along the laser transmission direction; the laser is used to emit laser light; the first beam splitter is used to transmit the laser light to the spatial light modulator; the spatial light modulator is used to phase modulate the laser light to generate a first LG light with arbitrarily adjustable topological charge, and to return the first LG light to the first beam splitter; the first beam splitter is also used to reflect the first LG light to the Mach-Zehnder interferometer; the spatial light modulator is a phase modulation type. A polarizer is arranged between the laser and the first beam splitter; the polarizer is used to adjust the polarization angle of the laser to match the spatial light modulator, so that the spatial light modulator is in a pure phase operating mode. The imaging component is used to capture the interference process of the first LG light and the second LG light before the object under test is displaced, to obtain an interference image before displacement; it is also used to capture the interference process of the first LG light and the second LG light after the object under test is displaced, to obtain an interference image after displacement. The processor is communicatively connected to the imaging component; the processor is used to process the pre-displacement interferometric image and the post-displacement interferometric image to obtain the magnitude and direction of the displacement of the object under test; Processing the pre-displacement and post-displacement interferometric images to obtain the magnitude and direction of the displacement of the object under test specifically includes: The pre-displacement interferometric image is processed to obtain a pre-displacement light intensity curve. Specifically, this includes: image enhancement of the pre-displacement interferometric image to obtain an enhanced image; connected component identification and centroid calibration of the enhanced image to determine the centroid of each connected component, where each connected component is an independent petal; circular fitting based on all centroids to obtain the fitted circle center and centroid radius; and scanning the pre-displacement interferometric image based on the fitted circle center and centroid radius, specifically using the fitted circle center as the origin and the centroid radius as the radius, extracting the light intensity on the circumference of the pre-displacement interferometric image counterclockwise to obtain the pre-displacement light intensity curve; the light intensity curve is a curve showing the change in light intensity value with angle. The displacement-adjusted interference image is processed to obtain the displacement-adjusted light intensity curve; Determining the magnitude and direction of the displacement of the object under test based on the light intensity curve before displacement and the light intensity curve after displacement specifically includes: recording a first angle of the peak point in the light intensity curve before displacement, and recording a second angle of the peak point in the light intensity curve after displacement; calculating the difference between the second angle and the first angle, using the absolute value of the difference as the rotation angle, and using the sign of the difference as the rotation direction; calculating the magnitude of the displacement of the object under test based on the rotation angle, and determining the direction of the displacement of the object under test based on the rotation direction; θ= k / l ; k =2π / λ ； Where θ is the rotation angle; k The wave vector of light; The magnitude of the displacement; l The topological load number; λ λ is the wavelength of the incident laser.

2. The micro-displacement measuring device according to claim 1, characterized in that, A collimating and beam-expanding device is arranged between the laser and the first beam-splitting prism; the collimating and beam-expanding device is used to collimate and expand the laser beam.

3. The micro-displacement measuring device according to claim 1, characterized in that, The Mach-Zehnder interferometer includes a second beam splitter, a first standard mirror, a second standard mirror, and a third beam splitter; the second beam splitter is used to transmit the first LG light to the first standard mirror and the second standard mirror, respectively. The first standard reflector is used to reflect the first LG light to the third beam splitter; The third beam splitter is used to transmit the first LG light to the object under test and to receive the second LG light, which is conjugate with the first LG light, reflected by the object under test. The second standard reflector is used to reflect the first LG light to the third beam splitter; The third beam splitter is used to combine the first LG beam and the second LG beam, causing them to interfere with each other.

4. A micro-displacement measurement method based on Laguerre-Gaussian beam conjugate interference, controlling the operation of the micro-displacement measurement device according to any one of claims 1-3, characterized in that, The micro-displacement measurement method includes: The receiving imaging unit captures a pre-displacement interferometric image before the object under test is displaced and a post-displacement interferometric image after the object under test is displaced. The magnitude and direction of the displacement of the object under test are obtained by processing the pre-displacement and post-displacement interference images. Processing the pre-displacement and post-displacement interferometric images to obtain the magnitude and direction of the displacement of the object under test specifically includes: The pre-displacement interferometric image is processed to obtain a pre-displacement light intensity curve. Specifically, this includes: image enhancement of the pre-displacement interferometric image to obtain an enhanced image; connected component identification and centroid calibration of the enhanced image to determine the centroid of each connected component, where each connected component is an independent petal; circular fitting based on all centroids to obtain the fitted circle center and centroid radius; and scanning the pre-displacement interferometric image based on the fitted circle center and centroid radius, specifically using the fitted circle center as the origin and the centroid radius as the radius, extracting the light intensity on the circumference of the pre-displacement interferometric image counterclockwise to obtain the pre-displacement light intensity curve; the light intensity curve is a curve showing the change in light intensity value with angle. The displacement-adjusted interference image is processed to obtain the displacement-adjusted light intensity curve; Determining the magnitude and direction of the displacement of the object under test based on the light intensity curve before displacement and the light intensity curve after displacement specifically includes: recording a first angle of the peak point in the light intensity curve before displacement, and recording a second angle of the peak point in the light intensity curve after displacement; calculating the difference between the second angle and the first angle, using the absolute value of the difference as the rotation angle, and using the sign of the difference as the rotation direction; calculating the magnitude of the displacement of the object under test based on the rotation angle, and determining the direction of the displacement of the object under test based on the rotation direction; θ= k / l ; k =2π / λ ； Where θ is the rotation angle; k The wave vector of light; The magnitude of the displacement; l The topological load number; λ λ is the wavelength of the incident laser.

5. The micro-displacement measurement method according to claim 4, characterized in that, The process of enhancing the pre-displacement interferometric image to obtain the enhanced image specifically includes: The interference image before displacement is denoised to obtain the denoised image; The denoised image is thresholded to obtain a binarized image; Morphological operations are performed on the binarized image to obtain an enhanced image; the morphological operations include dilation and erosion.

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