Dual-wavelength vortex light interference displacement measurement system and method for compensating installation and adjustment errors through image recognition

Abstract

The invention relates to a dual-wavelength vortex light interference displacement measurement system and a dual-wavelength vortex light interference displacement measurement method for compensating installation and adjustment errors through image recognition, and belongs to the technical field of optical precision measurement of precision measurement. Comprising a laser light source A, a beam expander A, a collimating mirror A, a vortex wave plate A, a laser light source B, a beam expander B, a collimating mirror B, a vortex wave plate B, a beam splitter prism A, a reflector A, a reflector B, a beam splitter prism B, a reflector C, a displacement table and a camera. An image recognition method is used for processing a dual-wavelength vortex light interferogram, displacement calculation is carried out according to the overall intensity change distribution of the interferogram, and different from traditional angle recognition extraction, the method is used for solving the problem that a measurement result is affected by system errors existing in a measurement system. The traditional angle identification precision is reduced due to interference pattern distortion, so that the measurement precision is influenced, the error influence is effectively reduced, the accuracy of the measurement result is ensured, and the micro-displacement measurement method is novel, effective, high in precision and large in range.

Description

Technical Field

[0001] The present invention relates to a dual-wavelength vortex light interference displacement measurement system and method for image recognition and compensation of adjustment errors, belonging to the technical field of optical precision testing for precision measurement. Background Art

[0002] A vortex beam is a light beam with a ring-shaped intensity distribution and a spiral wavefront structure. It has not only spin angular momentum but also orbital angular momentum. Using vortex beams for interference can obtain unique interference characteristics. The fringes obtained by the interference of vortex light with plane waves or the self-conjugate interference of vortex light are petal-shaped interference fringes. The overall interference pattern rotates with the change of the optical path difference. Compared with traditional plane wave interference, the change in the number of interference fringes is converted into a change in the angle, which improves the accuracy of interference demodulation.

[0003] The micro-displacement measurement method based on vortex beam interferometry is a high-precision micro-displacement measurement method. By utilizing the interference characteristics of vortex beams, displacement changes in the test optical path are manifested as rotations in the interference pattern. Identifying the angle of the interference pattern effectively addresses the inaccurate fringe counting problem in traditional interferometry methods. The dual-wavelength interferometry method can effectively increase the measurement range of vortex interferometry displacement measurement systems. The linear relationship between the rotation angle and the fitting wavelength greatly increases the measurement range, which in turn amplifies existing system errors.

[0004] The measurement accuracy of the system places strict demands on the alignment of the measurement system. The tilt or offset of components in the optical path will be reflected in the interference pattern. The traditional processing method is to reduce the influence of errors by correcting the interference pattern. Interference patterns with distortion are difficult to apply directly. In the vortex interferometer system, systematic errors can cause distortion of the interference fringes. After the petal-shaped fringes are bent, it is difficult to accurately extract the angle. However, in the dual-wavelength vortex light interference pattern, the distribution of the bright and dark areas of the fringes shows periodic changes with the displacement and has a linear correspondence with the displacement. Even when there is an alignment error in the system, the change in the light and dark distribution of the distorted fringes remains unaffected. Therefore, the intensity ratio of the interference pattern can be calculated through image recognition methods, thereby calculating the displacement in the measurement optical path. This method is a novel, effective, high-precision, large-scale micro-displacement measurement method that reduces the influence of alignment errors. Summary of the Invention

[0005] In response to the shortcomings of the existing technology and in order to further solve the problem that the tilt error caused by system adjustment in traditional measurement methods is difficult to handle, the present invention comprehensively analyzes the existing vortex beam interferometer displacement measurement methods and proposes a dual-wavelength vortex light interferometer displacement measurement system based on image recognition to compensate for adjustment errors. The system includes a dual-wavelength vortex light interferometer displacement measurement system and an image recognition distorted dual-wavelength interferogram displacement demodulation method, aiming to solve the problem that adjustment errors affect measurement results in precision displacement measurement systems.

[0006] The technical solutions of the present invention are as follows: A dual-wavelength vortex optical interferometry displacement measurement system with image recognition and compensation for adjustment errors includes a laser light source A (wavelength λ1), a beam expander A, a collimator A, a vortex wave plate A (wavelength λ1), a laser light source B (wavelength λ2), a beam expander B, a collimator B, a vortex wave plate B (wavelength λ2), a beam splitter A, a reflector A, a reflector B, a beam splitter B, a reflector C, a translation stage, and a camera. Beam expander A, collimator A, and vortex wave plate A are placed in sequence on the output optical path of laser light source A. Beam expander B, collimator B, and vortex wave plate B are placed in sequence on the output optical path of laser light source B. Vortex wave plate A and vortex wave plate B are placed on the two incident surfaces of beam splitter prism A. Reflectors A and B are set on the optical paths of the two exiting surfaces of beam splitter prism A. The light paths reflected by reflectors A and B are incident on beam splitter prism B. A camera and reflector C are placed on the two exiting optical paths of beam splitter prism B, respectively. Reflector C is located on the translation stage.

[0007] Preferably, the emission wavelength of the laser light source A is λ1, and the emission wavelength of the laser light source B is λ2, where λ1 and λ2 are two different wavelengths.

[0008] Preferably, the topological charges of the vortex wave plate A and the vortex wave plate B are the same.

[0009] More preferably, the topological charge is 2. Using a topological charge of 2 provides better results. Compared to a topological charge of 1, a topological charge of 2 makes it easier to observe interference fringes. Compared to higher topological charges of 3, 4, 5, 6, etc., the central singularity area of the vortex light with a topological charge of 2 is smaller, and the effective data area of the interference pattern is larger.

[0010] Preferably, the beam splitter prism A and the beam splitter prism B are conventional cubic beam splitter prisms.

[0011] Laser light source A emits visible light of a wavelength (e.g., 633 nm). The plane wave of the emitted light beam passes through beam expander A and collimator A, then is shaped into a plane wave of appropriate size. After passing through vortex wave plate A with a topological charge of 2, it becomes a vortex beam carrying orbital angular momentum. The vortex beam with a wavelength of 633 nm and a topological charge of 2 is incident from the left side of beam splitter A and is split into two paths: test light and reference light. The transmitted light is the test light, and the reflected light is the reference light. Similarly, a different visible light wavelength (e.g., 532 nm) is emitted by laser light source B. The plane wave emitted by the wavelength beam is shaped into a plane wave of appropriate size after passing through beam expander B and collimator B. After passing through vortex wave plate B with a topological charge of 2, it becomes a vortex beam carrying orbital angular momentum. The vortex beam with a wavelength of 532 nm and a topological charge of 2 is incident from the upper side of beam splitter A and is divided into two paths: test light and reference light. The reflected light is the test light, and the transmitted light is the reference light. After being reflected by mirror A, the test beam passes through beam splitter B. The beam hits mirror C mounted on the translation stage, and after being reflected by beam splitter B again, it propagates to the camera. After being reflected by mirror B, the reference beam passes through beam splitter B and reaches the camera, where it interferes with the test beam. Since there are two beams of different wavelengths in the optical path, the interference pattern is the superposition of the interference results of the two beams of different wavelengths. After the interference pattern is captured by the camera, the computer processes the interference information and calculates the displacement generated in the test optical path.

[0012] A dual-wavelength vortex optical interferometry displacement measurement method with image recognition and compensation for adjustment errors comprises the following steps: (1) Laser light source A and laser light source B emit laser beams with different wavelengths of 633 nm and 532 nm, respectively, which are beam A and beam B; (2) The light beam is shaped into a plane wave of suitable size after passing through beam expander A, beam expander B and collimator A, collimator B respectively; (3) After passing through vortex wave plate A and vortex wave plate B, the beam becomes a vortex beam carrying orbital angular momentum, with wavelengths of 633 nm and 532 nm respectively; (4) The 633nm vortex beam A enters the beam splitter prism A from the left and is divided into two paths: test light and reference light after passing through the beam splitter prism A. The transmitted light is the test light and the reflected light is the reference light. The test light is transmitted through the beam splitter prism A, and the reference light is reflected through the beam splitter prism A. (5) The 532nm vortex beam B enters the beam splitter prism A from the top and is divided into two paths: test light and reference light after passing through the beam splitter prism A. The reflected light is the test light and the transmitted light is the reference light. The test light is reflected through the beam splitter prism A, and the reference light is transmitted through the beam splitter prism A. (6) After being reflected by the reflector A, the two test beams are transmitted through the beam splitter B and then illuminate the reflector C, which is mounted on the translation stage; (7) The linear motion of the control stage introduces a displacement difference between the reference light path and the test light path. The light beam reflects on the reflector C and carries the displacement information, which is then reflected again by the beam splitter B and enters the camera. (8) The two reference beams are reflected by the reflector B, transmitted through the beam splitter prism B and then enter the camera; (9) The test beam and the reference beam interfere with each other at the camera position. The interference pattern is a superposition of petal-shaped interference patterns. As the displacement changes, the petals periodically separate and overlap. The displacement value in the system is calculated by processing the interference pattern information.

[0013] Preferably, in step (3), after the laser beam passes through the beam expander and the collimator, it enters the vortex wave plate in the form of a plane wave. The light intensity of the plane wave is expressed as: E = E 0· exp ( ik·z ) (1) E 0 is the amplitude of the beam, k =2π / λ is the wave number of light, z is the optical path of the light beam in the direction of propagation, i is the plural symbol; After passing through the vortex wave plate group, the plane wave becomes a vortex beam carrying the OAM phase: E = E 0· exp ( ilθ ) (2) in, l is the topological charge of the vortex beam, θ is the azimuth.

[0014] Preferably, in the splitting of the vortex beam in step (4) and step (5), the test beam is expressed as: E t = E 0· exp( ilθ+ik · z t +φ t ) (3) The reference beam is expressed as: E r = E 0· exp( ilθ+ik · z r +φ r ) (4) in, z t is the optical length in the test light path, φ t is the phase of the test optical path, z r is the optical path length in the reference light path, φ r is the phase of the reference optical path.

[0015] Preferably, the change in displacement information carried by the test beam in step (7) is reflected in formula (3) z t In the term, the displacement change is calculated from the optical path difference: d =( z t - z r ) / 2 (5).

[0016] Preferably, the interference pattern in step (9) is obtained by superimposing the interference results of the two wavelength beams: I 1=( E t1 + E r1 )· ( E t1 + E r1 ) * (6) I 2=( E t2 + E r2 )· ( E t2 + E r2 ) * (7) I = I 1+ I 2 (8) in, E t1 、 E t2 The test beams have wavelengths of λ1633nm and λ2532nm respectively. E r1 、 E r2 The reference beams are of wavelengths λ1633nm and λ2532nm respectively. *represents the conjugation operator, I 1 and I 2 are the interference pattern intensity distributions of the self-conjugate interference of the vortex beam with a wavelength of λ1633nm and the vortex beam with a wavelength of λ2532nm, respectively. I is the intensity distribution of the interference pattern captured by the camera, which is the superposition result of the two.

[0017] Preferably, the interference pattern is processed in step (9) by extracting the number of pixels in the bright and dark areas of the interference pattern to calculate the light-dark ratio: (9) in, m is the total number of pixels in the interference pattern, n is the number of bright pixels in the interference pattern, t is the proportion of bright area; As the position value changes, calculate the change in the proportion of the bright area within an interference cycle and record the maximum value t max and minimum value t min , perform normalization processing; perform image processing on the interference graph before displacement and the interference graph after displacement to obtain the bright area ratio value t 1 and t 2. Calculate the displacement value as: (10).

[0018] The beneficial effects of the present invention are: 1. The present invention uses a dual-wavelength vortex light interferometry displacement measurement system with image recognition to compensate for assembly errors. The dual-wavelength vortex light measurement interference pattern is completely different from the interference pattern of a single wavelength. A vortex beam with orbital angular momentum is used as the test light and reference light. By controlling the number of reflections of the light beam, a pair of conjugate vortex beams is regulated. Micro-displacement measurement is performed based on the principle of self-conjugate interference of the vortex beam, and the resolution can reach sub-nanometer level.

[0019] 2. The dual-wavelength vortex beam interferometry micro-displacement measurement method used in the present invention can greatly improve the measurement range and solve the contradiction between measurement accuracy and measurement range in traditional measurements.

[0020] 3. The present invention processes the interference pattern in vortex light interferometry using an image recognition method, which performs displacement calculation based on the number of light and dark pixels recognized in the image. This method is capable of processing interference patterns with tilt errors, avoiding the rigid requirement of optical path alignment in existing methods. If there is a tilt error, the measurement result will also be biased. The method proposed in the present invention is resistant to such tilt errors and can effectively reduce measurement errors caused by deterioration of interference pattern quality due to adjustment errors in the measurement system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagrams comparing the introduction of adjustment errors into the interference system, where (a) is a schematic diagram without errors, and (b) is a schematic diagram with the introduction of tilt errors; Figure 2 Schematic diagram of the comparison of the self-conjugate interferogram of vortex light when an adjustment error is introduced into the interference system, where (a) is the schematic diagram without error, and (b) is the schematic diagram with the introduction of tilt error; Figure 3 Schematic diagram comparing the self-conjugate interference of single-wavelength vortex light and dual-wavelength vortex light after displacement, where (a) is the self-conjugate interference pattern of single-wavelength vortex light after displacement, and (b) is the self-conjugate interference pattern of dual-wavelength vortex light after displacement; Figure 4 Figure 2 is a schematic diagram comparing the interference patterns before and after the displacement when a tilt error is introduced into the dual-wavelength vortex light self-conjugate interferometry displacement measurement system. (a) shows the dual-wavelength vortex light self-conjugate interferometry pattern before the displacement when the tilt error exists, and (b) shows the dual-wavelength vortex light self-conjugate interferometry pattern after the displacement when the tilt error exists. Figure 5 Schematic diagram of the displacement measurement results of dual-wavelength vortex optical interferometry for compensating alignment errors for image recognition; Figure 6 Schematic diagram of a dual-wavelength vortex optical interferometry displacement measurement system for compensating for alignment errors in image recognition; Figure 7 Schematic diagram of the working structure of the dual-wavelength vortex optical interferometry displacement measurement system for compensating for alignment errors in image recognition; Figure 8 Schematic diagram of the working steps of the dual-wavelength vortex optical interferometry displacement measurement system for compensating for alignment errors in image recognition; Among them: 1-laser light source A, 2-beam expander A, 3-collimator A, 4-vortex wave plate A, 5-laser light source B, 6-beam expander B, 7-collimator B, 8-vortex wave plate B, 9-beam splitter A, 10-reflector A, 11-reflector B, 12-beam splitter B, 13-reflector C, 14-translation stage, 15-camera. DETAILED DESCRIPTION

[0022] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, they will be described in detail below with reference to the accompanying drawings and specific embodiments, but are not limited thereto. Matters not fully described in the present invention shall be based on conventional techniques in the art.

[0023] Example 1: A dual-wavelength vortex optical interferometry displacement measurement system with image recognition and compensation for adjustment errors, such as Figure 6As shown, it includes a laser light source A (wavelength λ1) (1), a beam expander A (2), a collimator A (3), a vortex wave plate A (wavelength λ1) (4), a laser light source B (wavelength λ2) (5), a beam expander B (6), a collimator B (7), a vortex wave plate B (wavelength λ2) (8), a beam splitter A (9), a reflector A (10), a reflector B (11), a beam splitter B (12), a reflector C (13), a translation stage (14), and a camera (15).

[0024] The emission wavelength of laser light source A is λ1, and the emission wavelength of laser light source B is λ2. λ1 and λ2 are two different wavelengths. In this embodiment, λ1 is 633 nm and λ2 is 532 nm. Figure 6 The white arrows in the figure represent the light beams of laser light source A, and the black arrows represent the light beams of laser light source B.

[0025] Beam expander A, collimator A, and vortex wave plate A are placed in sequence on the output optical path of laser light source A. Beam expander B, collimator B, and vortex wave plate B are placed in sequence on the output optical path of laser light source B. Vortex wave plate A and vortex wave plate B are placed on the two incident surfaces of beam splitter prism A. Reflectors A and B are set on the optical paths of the two exiting surfaces of beam splitter prism A. The light paths reflected by reflectors A and B are incident on beam splitter prism B. A camera and reflector C are placed on the two exiting optical paths of beam splitter prism B, respectively. Reflector C is located on the translation stage.

[0026] Vortex wave plates A and B have the same topological charge of 2. Using a topological charge of 2 yields better results. Compared to a topological charge of 1, a topological charge of 2 makes it easier to observe interference fringes. Compared to higher topological charges of 3, 4, 5, 6, and so on, a topological charge of 2 has a smaller central singularity and a larger effective data area in the interference pattern.

[0027] Beam splitter prisms A and B are conventional cubic beam splitter prisms.

[0028] Visible light with a wavelength of 633nm is emitted by laser light source A. The plane wave of the light beam is shaped into a plane wave of appropriate size after passing through beam expander A and collimator A, and then becomes a vortex beam carrying orbital angular momentum after passing through vortex wave plate A with a topological charge of 2. The vortex beam with a wavelength of 633nm and a topological charge of 2 is incident from the left side of the beam splitter A and is divided into test light and reference light. Among them, the transmitted light is the test light and the reflected light is the reference light.

[0029] Similarly, another different visible light wavelength of 532nm is emitted by the laser light source B. The plane wave emitted by the wavelength beam is shaped into a plane wave of appropriate size after passing through the beam expander B and the collimator B, and becomes a vortex beam carrying orbital angular momentum after passing through the vortex wave plate B with a topological charge of 2; the vortex beam with a wavelength of 532nm and a topological charge of 2 is incident from the upper side of the spectrometer A and is divided into two paths: test light and reference light, among which the reflected light is the test light and the transmitted light is the reference light.

[0030] After being reflected by the reflector A, the test beam passes through the dichroic prism B. The beam hits the reflector C mounted on the translation stage, and after being reflected by the dichroic prism B again, it propagates to the camera.

[0031] After being reflected by the reflector B, the reference beam is transmitted through the beam splitter prism B and then propagates to the camera, where it interferes with the test beam. Since there are two beams of different wavelengths in the optical path at the same time, the interference pattern is the superposition of the interference results of the two beams of different wavelengths. After the interference pattern is captured by the camera, the computer processes the interference information and calculates the displacement generated in the test optical path, such as Figure 7 .

[0032] Example 2 A dual-wavelength vortex optical interferometry displacement measurement method with image recognition and compensation for adjustment errors, such as Figure 8 As shown, the steps include: (1) Laser light source A and laser light source B emit laser beams with different wavelengths of 633 nm and 532 nm, respectively, which are beam A and beam B.

[0033] (2) The light beam is shaped into a plane wave of suitable size after passing through beam expander A, beam expander B and collimator A, collimator B respectively.

[0034] (3) After passing through vortex wave plate A and vortex wave plate B, the light beam becomes a vortex beam carrying orbital angular momentum with wavelengths of 633 nm and 532 nm, respectively.

[0035] After passing through the beam expander and collimator, the laser beam enters the vortex wave plate in the form of a plane wave. The light intensity of the plane wave is expressed as: E = E 0· exp ( ik·z ) (1) E 0 is the amplitude of the beam, k =2π / λ is the wave number of light, z is the optical path of the light beam in the direction of propagation, i is the plural symbol; After passing through the vortex wave plate group, the plane wave becomes a vortex beam carrying the OAM phase: E = E 0· exp ( ilθ ) (2) in, l is the topological charge of the vortex beam, θ is the azimuth.

[0036] (4) The 633nm vortex beam A enters the beam splitter prism A from the left and is divided into two paths: test light and reference light after passing through the beam splitter prism A. The transmitted light is the test light and the reflected light is the reference light. The test light is transmitted through the beam splitter prism A and the reference light is reflected through the beam splitter prism A.

[0037] (5) The 532nm vortex beam B enters the beam splitter A from the top and is divided into two paths: test light and reference light after passing through the beam splitter A. The reflected light is the test light and the transmitted light is the reference light. The test light is reflected through the beam splitter A, and the reference light is transmitted through the beam splitter A.

[0038] In step (4) and step (5), the vortex beam is split and the test beam is expressed as: E t = E 0· exp( ilθ+ik · z t +φ t ) (3) The reference beam is expressed as: E r = E 0· exp( ilθ+ik · z r +φ r ) (4) in, z t is the optical length in the test light path, φ t is the phase of the test optical path, z r is the optical path length in the reference light path, φ r is the phase of the reference optical path.

[0039] (6) After being reflected by reflector A, the two test beams pass through beam splitter B and then illuminate reflector C, which is mounted on a translation stage. The translation stage on which reflector C is mounted can be adjusted in angle, introducing a tilt error into the measurement system.

[0040] (7) The linear motion of the control stage introduces a displacement difference between the reference light path and the test light path. After the light beam is reflected on the reflector C, it carries the displacement information and is reflected again by the dichroic prism B before entering the camera.

[0041] The change of displacement information carried by the test beam is reflected in formula (3) z t In the term, the displacement change is calculated from the optical path difference: d =( z t - z r ) / 2 (5).

[0042] (8) The two reference beams are reflected by mirror B, transmitted through beam splitter prism B and enter the camera.

[0043] (9) The test beam carries the displacement information loaded on the reflector C and interferes with the reference beam at the target surface of the camera. The interference pattern is a superposition of petal-shaped interference patterns. As the displacement changes, the petals periodically separate and overlap. The displacement value in the system is calculated by interferogram information processing. Two light sources with different wavelengths are used to interfere separately in the same measurement system. The camera captures the interference pattern of the superposition of the two wavelengths. The loaded displacement is then demodulated through image recognition using a single interference pattern.

[0044] The interference pattern is obtained by superimposing the interference results of two wavelength beams: I 1=( E t1 + E r1 )· ( E t1 + E r1 ) * (6) I 2=( E t2 + E r2 )· ( E t2 + E r2 ) * (7) I = I 1+ I 2 (8) in, E t1 、 E t2 The test beams have wavelengths of λ1633nm and λ2532nm respectively.E r1 、 E r2 The reference beams are of wavelengths λ1633nm and λ2532nm respectively. * represents the conjugation operator, I 1 and I 2 are the interference pattern intensity distributions of the self-conjugate interference of the vortex beam with a wavelength of λ1633nm and the vortex beam with a wavelength of λ2532nm, respectively. I is the intensity distribution of the interference pattern captured by the camera, which is the superposition result of the two.

[0045] The interference pattern processing process is as follows: the interference results captured by the camera are imported into the computer for image processing. The interference pattern is processed based on conventional image recognition methods, and the number of pixels in the bright and dark areas of the interference pattern is extracted to calculate the brightness-darkness ratio: (9) in, m is the total number of pixels in the interference pattern, n is the number of bright pixels in the interference pattern, t is the proportion of bright area; As the position value changes, calculate the change in the proportion of the bright area within an interference cycle and record the maximum value t max and minimum value t min , perform normalization processing; perform image processing on the interference graph before displacement and the interference graph after displacement to obtain the bright area ratio value t 1 and t 2. Calculate the displacement value as: (10) Figure 5 Schematic diagram of the displacement measurement results of dual-wavelength vortex light interferometry for image recognition and compensation of alignment errors. The horizontal axis represents the change in displacement value, and the vertical axis represents the light-dark ratio of formula (9).

[0046] Experimental example Figure 1 Schematic diagrams comparing the introduction of adjustment errors into the interferometer system, where (a) is a schematic diagram without errors, and (b) is a schematic diagram with the introduction of tilt errors. Serial number 1 (indicated by the solid line) represents the propagation path of the reference light, and serial number 2 (indicated by the dotted line) represents the propagation path of the measurement light. Figure 2 Schematic comparison of the self-conjugate interferogram of vortex light when an adjustment error is introduced into the interference system. (a) is a schematic diagram without error, and (b) is a schematic diagram with a tilt error introduced. The comparison results show that the introduction of a tilt error in the system causes fringe distortion in the self-conjugate interferogram of vortex light. Figure 3Schematic diagram comparing the results of self-conjugate interference of single-wavelength vortex light and self-conjugate interference of dual-wavelength vortex light after displacement, where (a) is the self-conjugate interference pattern of single-wavelength vortex light after displacement, and (b) is the self-conjugate interference pattern of dual-wavelength vortex light after displacement. The comparison results show that the ratio of light and dark areas of the single-wavelength vortex light interference pattern does not change with displacement, while the ratio of light and dark areas of the dual-wavelength vortex light interference pattern changes linearly with displacement. Figure 4 This is a schematic diagram comparing the interference patterns before and after loading displacement when a tilt error is introduced into the dual-wavelength vortex light self-conjugate interferometer displacement measurement system. (a) is the dual-wavelength vortex light self-conjugate interferometer pattern before displacement when a tilt error exists, and (b) is the dual-wavelength vortex light self-conjugate interferometer pattern after displacement when a tilt error exists. The comparison results show that when a tilt error is introduced, there is still a good linear relationship between the light and dark area ratio of the dual-wavelength vortex light interference pattern and the displacement change.

Claims

1. A dual-wavelength vortex optical interferometry displacement measurement system with image recognition and compensation for adjustment errors, characterized in that: Including laser light source A, beam expander A, collimator A, vortex wave plate A, laser light source B, beam expander B, collimator B, vortex wave plate B, beam splitter A, reflector A, reflector B, beam splitter B, reflector C, translation stage, camera; Beam expander A, collimator A, and vortex wave plate A are placed in sequence on the output optical path of laser light source A. Beam expander B, collimator B, and vortex wave plate B are placed in sequence on the output optical path of laser light source B. Vortex wave plate A and vortex wave plate B are placed on the two incident surfaces of beam splitter prism A. Reflectors A and B are set on the optical paths of the two exiting surfaces of beam splitter prism A. The light paths reflected by reflectors A and B are incident on beam splitter prism B. A camera and reflector C are placed on the two exiting optical paths of beam splitter prism B, respectively. Reflector C is located on the translation stage.

2. The dual-wavelength vortex optical interferometry displacement measurement system with image recognition and compensation for adjustment error according to claim 1 is characterized in that: The emission wavelength of the laser light source A is λ1, and the emission wavelength of the laser light source B is λ2, where λ1 and λ2 are two different wavelengths.

3. The dual-wavelength vortex optical interferometry displacement measurement system with image recognition and compensation for adjustment error according to claim 1 is characterized in that: The topological charges of vortex wave plate A and vortex wave plate B are the same; More preferably, the topological charge is 2.

4. The dual-wavelength vortex optical interferometry displacement measurement system with image recognition and compensation for adjustment error according to claim 1 is characterized in that: Beamsplitter A and Beamsplitter B are cubic beamsplitter prisms.

5. A dual-wavelength vortex optical interferometry displacement measurement method with image recognition and compensation for adjustment errors, characterized in that: The steps are as follows: (1) Laser light source A and laser light source B emit laser beams of different wavelengths, which are beam A and beam B respectively; (2) The light beam is shaped into a plane wave of suitable size after passing through beam expander A, beam expander B and collimator A, collimator B respectively; (3) After the light beam passes through vortex wave plate A and vortex wave plate B respectively, it becomes a vortex beam carrying orbital angular momentum; (4) The vortex beam A enters the beam splitter prism A from the left and is divided into two paths: test light and reference light after passing through the beam splitter prism A. The transmitted light is the test light and the reflected light is the reference light. The test light is transmitted through the beam splitter prism A and the reference light is reflected through the beam splitter prism A. (5) The vortex beam B enters the beam splitter prism A from the top and is divided into two paths: test light and reference light after passing through the beam splitter prism A. The reflected light is the test light and the transmitted light is the reference light. The test light is reflected through the beam splitter prism A, and the reference light is transmitted through the beam splitter prism A. (6) After being reflected by the reflector A, the two test beams are transmitted through the beam splitter B and then illuminate the reflector C, which is mounted on the translation stage; (7) The linear motion of the control stage introduces a displacement difference between the reference light path and the test light path. The light beam reflects on the reflector C and carries the displacement information, which is then reflected again by the beam splitter B and enters the camera. (8) The two reference beams are reflected by the reflector B, transmitted through the beam splitter prism B and then enter the camera; (9) The test beam and the reference beam interfere with each other at the camera position. The interference pattern is a superposition of petal-shaped interference patterns. As the displacement changes, the petals periodically separate and overlap. The displacement value in the system is calculated by processing the interference pattern information.

6. The dual-wavelength vortex light interferometry displacement measurement method with image recognition and compensation for adjustment error according to claim 5 is characterized in that: In step (3), after the laser beam passes through the beam expander and collimator, it enters the vortex wave plate in the form of a plane wave. The light intensity of the plane wave is expressed as: E = E 0· exp ( ik· z ) （1） E 0 is the amplitude of the beam, k =2π / λ is the wave number of light, z is the optical path of the light beam in the direction of propagation, i is the plural symbol; After passing through the vortex wave plate group, the plane wave becomes a vortex beam carrying the OAM phase: E = E 0· exp ( ilθ ) （2） in, l is the topological charge of the vortex beam, θ is the azimuth.

7. The dual-wavelength vortex light interferometry displacement measurement method with image recognition and compensation for adjustment error according to claim 5 is characterized in that: In step (4) and step (5), the vortex beam is split and the test beam is expressed as: E t = E 0 · exp( ilθ + ik · z t +φ t ) (3) The reference beam is expressed as: E r = E 0 · exp( ilθ + ik · z r +φ r ) (4) in, z t is the optical length in the test light path, φ t is the phase of the test optical path, z r is the optical path length in the reference light path, φ r is the phase of the reference optical path.

8. The dual-wavelength vortex light interferometry displacement measurement method with image recognition and compensation for adjustment error according to claim 5 is characterized in that: The change in displacement information carried by the test beam in step (7) is reflected in formula (3) z t In the term, the displacement change is calculated from the optical path difference: d =( z t - z r ) / 2 （5）。 9. The dual-wavelength vortex light interferometry displacement measurement method with image recognition and compensation for adjustment error according to claim 5, characterized in that: The interference pattern in step (9) is obtained by superimposing the interference results of the two wavelength beams: I 1=( E t1 + E r1 )· ( E t1 + E r1 ) * （6） I 2=( E t2 + E r2 )· ( E t2 + E r2 ) * （7） I = I 1+ I 2 （8） in, E t1 、 E t2 are the test beams with wavelengths λ1 and λ2 respectively, E r1 、 E r2 are the reference beams with wavelengths λ1 and λ2, respectively. * represents the conjugation operator, I 1 and I 2 are the interference pattern intensity distributions of the self-conjugate interference of the vortex beam with wavelength λ1 and the vortex beam with wavelength λ2, I is the intensity distribution of the interference pattern captured by the camera, which is the superposition result of the two.

10. The dual-wavelength vortex optical interferometry displacement measurement method with image recognition and compensation for adjustment errors according to claim 5, characterized in that: The process of processing the interference pattern in step (9) is to extract the number of pixels in the bright and dark areas of the interference pattern and calculate the brightness-darkness ratio: （9） in, m is the total number of pixels in the interference pattern, n is the number of bright pixels in the interference pattern, t is the proportion of bright area; As the position value changes, calculate the change in the proportion of the bright area within an interference cycle and record the maximum value t max and minimum value t min , perform normalization processing; perform image processing on the interference graph before displacement and the interference graph after displacement to obtain the bright area ratio value t 1 and t 2. Calculate the displacement value as: （10）。

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