Chessboard grating light splitting vortex beam four-step phase shift interference microscopic imaging system and method

Abstract

The present application relates to a kind of chessboard grating spectrometer vortex light beam four-step phase shift interference microscopic imaging system and method, belong to optical imaging field, including laser light source, beam expander, collimating mirror A, beam splitter A, chessboard grating A, collimating mirror B, vortex wave plate group, beam splitter B, beam splitter C, sample to be measured, microscopic objective A, small hole, microscopic objective B, chessboard grating B, mirror B, beam splitter D, camera and computer terminal;The present application uses chessboard grating spectrometer and vortex light phase shift interference in optical microscopic imaging, avoids the use of polarization camera, and can complete single collection interference pattern imaging, and measurement speed is fast, imaging precision is high, real-time is good, principle is simple, etc., provides a novel effective idea for optical microscopic imaging.

Description

TECHNICAL FIELD

[0001] The application provides a chessboard grating splitting vortex beam four-step phase shift interference microscopic imaging system and method, and belongs to the field of optical imaging. BACKGROUND

[0002] The past interference measurement technology is measured by recognizing the change of interference fringes, and the stability of the measurement result is difficult to guarantee. Modern interference measurement technology combines electronic technology, computer technology, photoelectric image processing technology and the like, and has greatly improved in precision. Among them, the phase shift interference technology is to change the optical path difference of the reference light path and the measurement light path by controlling the piezoelectric ceramic driver to move the reference mirror or changing the wavelength of the laser, causing the movement of the interference fringes. By controlling the phase change difference to be 90° to collect the interference group, combining with specific mathematical algorithm and model for calculation, the topographic information of the measured sample is reconstructed.

[0003] The basis of laser interference measurement is to convert the mechanical displacement into the change of the electrical signal of the interference fringes by using the traditional interference structure, and the corresponding information is obtained by counting and analyzing the interference fringes. The interference fringes are stripes with light and dark alternation, and the fringes move in the camera field of view with the change of the optical path difference. The number of fringe movement is usually a non-integer, and the decimal part needs to be estimated, which limits the measurement accuracy.

[0004] The vortex beam is a kind of beam with annular intensity distribution and spiral wavefront structure, carrying orbital angular momentum (OAM), and the orbital angular momentum state carried by the Laguerre-Gaussian mode is also called topological charge. The vortex beam has unique interference characteristics. The interference fringes obtained by the interference of vortex light and plane wave or the self-conjugate interference of vortex light are petal-shaped interference fringes. When the optical path difference changes, the whole interference pattern rotates, which changes the change of the number of fringes into the identification of the angle, solving the problem faced by the traditional fringe counting.

[0005] The phase shift interference measurement can be divided into time phase shift interference and space phase shift interference. For time phase shift interference, the interference pattern at different phase differences must be collected multiple times for data processing. For space phase shift interference, there is a space phase shift mode based on a polarization camera. The phase difference of the vortex beam can be controlled by controlling the rotation angle within a period, and it does not depend on the polarization camera. Therefore, the phase shift interference technology based on the vortex beam can realize fast and accurate imaging using a common camera, and is a novel imaging method. However, the imaging rate needs to be improved. SUMMARY

[0006] The present application comprehensively analyzes the existing vortex beam interference mode and optical microscopic imaging mode, and proposes a chessboard grating splitting vortex beam four-step phase shift interference microscopic imaging system and method, aiming to further improve the imaging rate of the microscopic imaging system.

[0007] The technical scheme of the present application is:

[0008] A chessboard grating light splitting vortex beam four-step phase shift interference microscopic imaging system, comprising a laser light source, a beam expander, a collimator A, a beam splitter A, a chessboard grating A, a collimator B, a vortex wave plate set, a beam splitter B, a beam splitter C, a microscope objective A, a sample to be measured, a pinhole, a microscope objective B, a chessboard grating B, a collimator C, a beam splitter D, a camera and a computer terminal;

[0009] The plane wave emitted by the laser light source is shaped after passing through the beam expander and the collimator A, and the shaped beam is incident on the beam splitter A, which divides the plane wave passing through the beam splitter A into two paths of test light T and reference light R, wherein the test light T is used to carry sample information, and the reference light R is used to generate a phase difference;

[0010] The reference light R is incident on the chessboard grating A and is evenly divided into four by the chessboard grating A, and the beam is collimated back to the parallel direction of the optical axis after passing through the collimator B, obtaining four parallel propagating plane waves R1, R2, R3, R4; The plane waves R1, R2, R3, R4 pass through the vortex wave plate set to generate four vortex lights R1', R2', R3', R4' carrying different phase differences; The reference light is reflected by the beam splitter B and then reflected by the beam splitter D and enters the camera;

[0011] The test light T is reflected by the beam splitter C and carries sample information after passing through the sample to be measured; The test light carrying sample information passes through the microscope objective A, the pinhole and the microscope objective B in turn to complete pinhole filtering; The test light is incident on the chessboard grating B and is evenly divided into four by the chessboard grating B, and the beam is collimated back to the parallel direction of the optical axis after passing through the collimator C, obtaining four parallel propagating plane waves T1, T2, T3, T4; The test light passes through the beam splitter D and enters the camera to interfere with the reference light, and R1'-T1, R2'-T2, R3'-T3, R4'-T4 correspond one by one at the interference position;

[0012] The computer terminal is connected with the camera and is used for four-step phase shift phase recovery.

[0013] Preferably, the laser light source emits a 633nm wavelength beam.

[0014] An imaging method based on the above-mentioned chessboard grating light splitting vortex beam four-step phase shift interference microscopic imaging system, comprising the following steps:

[0015] (1) Emit a 633nm wavelength beam from the laser light source;

[0016] (2) The beam is shaped to a suitable size after passing through the beam expander and the collimator A;

[0017] (3) The light beam is incident on a beam splitter A, and the 633 nm plane wave passing through the beam splitter A is divided into two paths, i.e., a test light T and a reference light R, wherein the test light T is used to carry sample information, and the reference light R is used to generate a phase difference;

[0018] (4) The reference light R is incident on a chessboard grating A and is evenly divided into four by the chessboard grating A. After passing through a collimating mirror B, the light beam is collimated back to the parallel direction of the optical axis, and four parallel propagating plane waves R1, R2, R3 and R4 are obtained;

[0019] (5) The plane waves R1, R2, R3 and R4 pass through a vortex wave plate set to generate four vortex lights R1', R2', R3' and R4' carrying different phase differences;

[0020] (6) The reference light R is reflected by the beam splitter B and then reflected by the beam splitter D to enter a camera;

[0021] (7) The test light T is reflected by the beam splitter C and carries sample information after passing through a sample to be measured;

[0022] (8) The test light carrying sample information passes through a microscope objective A, a pinhole and a microscope objective B in sequence to complete pinhole filtering;

[0023] (9) The test light is incident on a chessboard grating B and is evenly divided into four by the chessboard grating B. After passing through a collimating mirror C, the light beam is collimated back to the parallel direction of the optical axis, and four parallel propagating plane waves T1, T2, T3 and T4 are obtained;

[0024] (10) The test light passes through the beam splitter D and enters the camera to interfere with the reference light beam. R1'-T1, R2'-T2, R3'-T3 and R4'-T4 correspond to each other at the interference position (in space, R1' corresponds to T1, R2' corresponds to T2, R3' corresponds to T3, and R4' corresponds to T4, and they do not interfere with each other);

[0025] (11) The camera collects data and imports it into a computer terminal for four-step phase shift phase reconstruction.

[0026] Preferably, in step (7), the sample to be measured is a paramecium cell sample.

[0027] Preferably, in steps (4) and (9), the chessboard gratings A and B have the same structure and are made of N-BK7 glass substrate and liquid crystal polymer birefringent material, and have a sandwich structure of "front and rear glass substrates + middle LCP functional film layer";

[0028] In the LCP functional film layer, liquid crystal molecules are arranged in a checkerboard-like structure, with consistent orientation angles within each pixel grid and a phase difference of π between adjacent pixel grids. The device has a retardation of λ / 2 across the entire device plane, where λ represents the wavelength of light. A single checkerboard grating can achieve uniform 2×2 beam splitting. Cascaded gratings are composed of orthogonally combined one-dimensional beam splitting elements, resulting in a multi-layer structure. The checkerboard grating of this invention has only one layer in its design, serving as a two-dimensional beam splitting element. Its complexity is less than that of cascaded gratings, making the checkerboard grating thinner and easier to integrate.

[0029] Preferably, in step (5), the vortex waveplate group consists of four first-order vortex waveplates. Each first-order vortex waveplate has the function of converting the incident plane wave into a vortex beam. They are arranged in a 2×2 pattern in space, and are placed at rotation angles of 0°, 90°, 180° and 270° respectively. This produces four beams of vortex light R1', R2', R3' and R4' with the same output direction and carrying different phase differences.

[0030] Preferably, in step (3), when the beam is incident on beam splitter A, the intensity of the plane wave is expressed as:

[0031] E=E0·exp(ik·z)(1)

[0032] E0 is the amplitude of the beam, k = 2π / λ is the wave number, and z is the optical path length of the beam in the propagation direction.

[0033] For the reference beam, after the plane wave is split by the checkerboard grating A, and then its direction is corrected by the collimating lens B, four plane waves E with their propagation directions parallel to the optical axis are obtained. r1 E r2 E r3 E r4 :

[0034]

[0035] Among them, z r It is the optical path length in the reference light. It is the phase of the reference light;

[0036] After passing through the vortex waveplate assembly, the four plane waves become four vortex beams carrying OAM phase, with additional phases of 0, π / 2, π, and 3π / 2 respectively:

[0037]

[0038] Where l is the topological charge of the vortex beam and θ is the rotation angle.

[0039] Preferably, for the test optical path, the plane wave carries the phase information of the sample after passing through it, and then passes through a pinhole filter to remove stray light:

[0040]

[0041] wherein z t is the optical path in the test light path, δ is the phase information of the measured sample, is the phase of the test light path;

[0042] After the chessboard grating B splits the light, and after the collimating mirror C corrects the direction, four beams of plane waves carrying sample information are obtained, which have a propagation direction parallel to the optical axis:

[0043]

[0044] Correspondingly, after the beam splitter D, the light of the reference light and the test light interferes at the camera, and the interference pattern is generally the superposition of the spatial distribution of four parts of light intensity, and the light intensity of each part is:

[0045]

[0046] I1, I2, I3, I4 respectively represent the light intensity of R1'-T1 interference, the light intensity of R2'-T2 interference, the light intensity of R3'-T3, and the light intensity of R4'-T4.

[0047] Preferably, the four-step phase shift phase reconstruction process in step (11) is:

[0048] Firstly, the obtained interference pattern is segmented, that is, a 2x2 square picture is divided into four equal 1x1 squares, to obtain four pairs of decomposed interference patterns A, B, C and D.

[0049] Then, the four-step phase shift method is used for phase reconstruction, and the phase is expressed as the arctangent of the ratio of the difference between interference pattern D and interference pattern B, and the difference between interference pattern C and interference pattern A:

[0050]

[0051] The phase of the measured sample is obtained, and the optical microscopic imaging is completed.

[0052] The details of the present application can be referred to the prior art.

[0053] The beneficial effects of the present application are:

[0054] 1. The vortex beam four-step phase shift interference microscopic imaging system using the chessboard grating splitting can perform four-step phase shift demodulation according to a single collected interference pattern, which can greatly improve the processing rate of optical microscopic imaging.

[0055] 2、The vortex wave plate set used in the application can introduce vortex beams with fixed phase difference, and a new idea is introduced for four-step phase shift interference, and phase reconstruction can be efficiently and accurately completed by using an ordinary camera.

[0056] 3、Compared with the three-piece structure of the chessboard grating and the cascade grating, the chessboard grating single piece can realize 2*2 beam splitting, and is more easily integrated.

[0057] 4、The chessboard grating splitting and vortex light phase shift interference are used in optical microscopic imaging in the application, single collection interference imaging can be completed without using a polarization camera, and the measurement speed is fast, the imaging precision is high, the real-time performance is good, the principle is simple, and the like, thereby providing a novel and effective idea for optical microscopic imaging. BRIEF DESCRIPTION OF DRAWINGS

[0058] The drawings accompanying the specification of this application form a part of this application and serve to further understand the application, the illustrative embodiments of the application and the description thereof are used to explain the application, and do not constitute an improper limitation on the application.

[0059] Fig. 1 It is a schematic diagram of the chessboard grating, wherein (a) is a schematic diagram of uniform splitting of the chessboard grating, and (b) is a phase schematic diagram of the chessboard grating;

[0060] Fig. 2 It is a schematic diagram of the beam after customizing the vortex wave plate set for plane wave incidence, wherein (a) is a first-order vortex phase in the direction of 0°, and an additional phase difference is 0; (b) is a first-order vortex phase in the direction of 90°, and an additional phase difference is π / 2; (c) is a first-order vortex phase in the direction of 180°, and an additional phase difference is π; (d) is a first-order vortex phase in the direction of 270°, and an additional phase difference is 3π / 2;

[0061] Fig. 3 It is an interference result of the vortex beam carrying sample information and the plane wave, wherein (a) is an R1'-T1 interference result, (b) is an R2'-T2 interference result, (c) is an R3'-T3 interference result, and (d) is an R4'-T4 interference result;

[0062] Fig. 4 It is a sample imaging result recovered by four-step phase shift;

[0063] Fig. 5 It is a schematic diagram of a vortex beam four-step phase shift interference microscopic imaging system for chessboard grating splitting;

[0064] Fig. 6 It is a schematic diagram of a vortex beam four-step phase shift interference microscopic imaging system structure for chessboard grating splitting;

[0065] Fig. 7A schematic diagram of working steps of a chessboard grating light-splitting vortex beam four-step phase shift interference microscopic imaging system;

[0066] Wherein, 1-laser light source, 2-beam expander, 3-collimator A, 4-beam splitter A, 5-chessboard grating A, 6-collimator B, 7-vortex wave plate set, 8-beam splitter B, 9-beam splitter C, 10-sample to be measured, 11-40X microscope objective A, 12-small hole, 13-40X microscope objective B, 14-chessboard grating B, 15-collimator C, 16-beam splitter D, 17-camera, 18-computer terminal. DETAILED DESCRIPTION

[0067] In order for those skilled in the art to better understand the technical solutions in the specification, the technical solutions in the embodiments of the specification will be described clearly and completely below in combination with the drawings in the embodiments of the specification, but not limited to this, the embodiments of the application not described in detail are all according to the conventional technology in the art.

[0068] Embodiment 1

[0069] A chessboard grating light-splitting vortex beam four-step phase shift interference microscopic imaging system, as shown in Figs. 1-7 laser light source 1, beam expander 2, collimator A 3, beam splitter A 4, chessboard grating A 5, collimator B 6, vortex wave plate set 7, beam splitter B 8, beam splitter C 9, 40X microscope objective A 11, sample to be measured 10, small hole 12, 40X microscope objective B 13, chessboard grating B 14, collimator C 15, beam splitter D 16, camera 17 and computer terminal 18;

[0070] The plane wave emitted by the laser light source 1 with a wavelength of 633 nm passes through the beam expander 2 and the collimator A 3 after shaping, and the shaped light beam is incident on the beam splitter A 4, which divides the plane wave passing through the beam splitter A 4 into two paths of test light T and reference light R, wherein the test light T is used to carry sample information, and the reference light R is used to generate a phase difference;

[0071] The reference light R is incident on the chessboard grating A 5 and is evenly divided into four by the chessboard grating A 5, and the light beam is collimated back to the optical axis parallel direction after passing through the collimator B 6, obtaining four parallel propagating plane waves R1, R2, R3, R4; The plane waves R1, R2, R3, R4 pass through the vortex wave plate set 7 to generate four vortex lights R1', R2', R3', R4' carrying different phase differences; The reference light is reflected by the beam splitter B 8 and then reflected by the beam splitter D 16 and enters the camera 17;

[0072] The test light T is reflected by the beam splitter C 9, passes through the sample to be tested to carry sample information, and then passes through the 40X microscope objective A 11, the pinhole 12 and the 40X microscope objective B 13 to complete the pinhole filtering. The test light is incident on the chessboard grating B 14 and is evenly divided into four by the chessboard grating B 14. The light beams are collimated by the collimating mirror C 15 to be parallel to the optical axis, and four parallel propagating plane waves T1, T2, T3 and T4 are obtained. The test light passes through the beam splitter D 16 and enters the camera 17 to interfere with the reference light. R1'-T1, R2'-T2, R3'-T3 and R4'-T4 correspond to each other at the interference position.

[0073] The computer terminal 18 is connected with the camera and is used for four-step phase shift phase recovery.

[0074] Embodiment 2

[0075] A vortex beam four-step phase shift interference microscopic imaging method based on a chessboard grating, comprising the following steps:

[0076] (1) A 633 nm wavelength light beam is emitted by a laser light source;

[0077] (2) The light beam is shaped to a suitable size by a beam expander and a collimating mirror A;

[0078] The 633 nm laser is incident on the beam splitter A in the form of a plane wave after passing through the beam expander and the collimating mirror. The light intensity of the plane wave is expressed as:

[0079] E=E0·exp(ik·z) (1)

[0080] (3) The light beam is incident on the beam splitter A, and the 633 nm plane wave passing through the beam splitter A is divided into test light T and reference light R. The test light T is used to carry sample information, and the reference light R is used to generate a phase difference;

[0081] (4) The reference light R is incident on the chessboard grating A and is evenly divided into four by the chessboard grating A. The light beams are collimated by the collimating mirror B to be parallel to the optical axis, and four parallel propagating plane waves E r1 r2 r3 r4 are obtained.

[0082]

[0083] wherein z r is the optical path in the reference light path, is the phase of the reference light path.

[0084] ​​​(5) Plane waves R1, R2, R3, R4 pass through the vortex wave plate set, generating four vortex beams R1', R2', R3', R4' carrying different phase differences;

[0085] After passing through the vortex wave plate set, the four plane waves become four vortex beams carrying OAM phase, and the additional phases are 0, π / 2, π, 3π / 2 respectively:

[0086]

[0087] Wherein, l is the topological charge number of the vortex beam, and θ is the rotation angle.

[0088] (6) The reference light R is reflected by the beam splitter B and then reflected by the beam splitter D to enter the camera;

[0089] (7) After the test light T is reflected by the beam splitter C, it carries sample information through the paramecium cell sample;

[0090]

[0091] Wherein, z t is the optical path in the test light path, δ is the information of the measured sample, is the phase of the test light path.

[0092] (8) The test light carrying sample information passes through the microscope objective A, the pinhole, and the microscope objective B in turn to complete the pinhole filtering;

[0093] (9) The test light is incident on the chessboard grating B and is evenly divided into four by the chessboard grating B. The light beams are collimated by the collimating mirror C to be parallel to the optical axis direction, obtaining four parallel plane waves T1, T2, T3, T4;

[0094]

[0095] (10) The test light passes through the beam splitter D and enters the camera to interfere with the reference beam. R1'-T1, R2'-T2, R3'-T3, R4'-T4 correspond one by one at the interference position (in space, R1' corresponds to T1, R2' corresponds to T2, R3' corresponds to T3, and R4' corresponds to T4, and they do not interfere with each other);

[0096]

[0097] I1, I2, I3, I4 respectively represent the light intensity of R1'-T1 interference, the light intensity of R2'-T2 interference, the light intensity of R3'-T3, and the light intensity of R4'-T4.

[0098] (11) The camera collects data and imports into the computer terminal to perform four-step phase shift phase reconstruction.

[0099]

[0100] The above describes the preferred embodiments of the present application. It should be noted that, for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which should also be considered as the protection scope of the present application.

Claims

1. A four-step phase-shifting interferometric microscopy imaging system for vortex beams split by a checkerboard grating, characterized in that, The laser light source, the beam expander, the collimator A, the beam splitter A, the chessboard grating A, the collimator B, the vortex wave plate set, the beam splitter B, the beam splitter C, the microscope A, the sample to be measured, the pinhole, the microscope B, the chessboard grating B, the collimator C, the beam splitter D, the camera and the computer terminal are included. The plane wave emitted by the laser light source is shaped after passing through the beam expander and the collimator A, and the shaped light beam is incident on the beam splitter A, which divides the 633nm plane wave passing through the beam splitter A into two paths of test light T and reference light R, wherein the test light T is used to carry sample information, and the reference light R is used to generate a phase difference. The reference light R is incident on the chessboard grating A and is evenly divided into four, and the light beam is collimated back to the parallel direction of the optical axis after passing through the collimator B, obtaining four parallel plane waves R1, R2, R3 and R4; the plane waves R1, R2, R3 and R4 pass through the vortex wave plate set to generate four vortex lights R1', R2', R3' and R4' carrying different phase differences; the reference light is reflected by the beam splitter B and then reflected by the beam splitter D and enters the camera. The test light T is reflected by the beam splitter C, passes through the sample to be measured to carry sample information; the test light carrying sample information passes through the microscope A, the pinhole and the microscope B in sequence to complete pinhole filtering; the test light is incident on the chessboard grating B and is evenly divided into four, and the light beam is collimated back to the parallel direction of the optical axis after passing through the collimator C, obtaining four parallel plane waves T1, T2, T3 and T4; the test light passes through the beam splitter D and enters the camera to interfere with the reference light, and R1'-T1, R2'-T2, R3'-T3 and R4'-T4 correspond one by one at the interference position. The computer terminal is connected with the camera and is used for four-step phase shift phase recovery.

2. The chessboard-raster, spectrally resolved, vortex-beam, four-step phase- shifting interferometric microscopy system of claim 1, wherein, The laser light source emits a 633nm wavelength light beam.

3. An imaging method of a four-step phase-shifting interferometric microscopy system based on the chessboard optical raster beam splitting of claim 1, characterized in that, The method comprises the following steps: (1) emitting a 633nm wavelength light beam from a laser light source; (2) shaping the light beam after passing through the beam expander and the collimator A; (3) the light beam is incident on the beam splitter A, which divides the 633nm plane wave passing through the beam splitter A into two paths of test light T and reference light R, wherein the test light T is used to carry sample information, and the reference light R is used to generate a phase difference; (4) the reference light R is incident on the chessboard grating A and is evenly divided into four, and the light beam is collimated back to the parallel direction of the optical axis after passing through the collimator B, obtaining four parallel plane waves R1, R2, R3 and R4; (5) the plane waves R1, R2, R3 and R4 pass through the vortex wave plate set to generate four vortex lights R1', R2', R3' and R4' carrying different phase differences; (6) the reference light R is reflected by the beam splitter B and then reflected by the beam splitter D and enters the camera; (7) the test light T is reflected by the beam splitter C, passes through the sample to be measured to carry sample information; (8) the test light carrying sample information passes through the microscope A, the pinhole and the microscope B in sequence to complete pinhole filtering; (9) the test light is incident on the chessboard grating B and is evenly divided into four, and the light beam is collimated back to the parallel direction of the optical axis after passing through the collimator C, obtaining four parallel plane waves T1, T2, T3 and T4; (10) After the test light passes through the beam splitter D, it enters the camera and interferes with the reference beam. R1'-T1, R2'-T2, R3'-T3, and R4'-T4 correspond one-to-one in the interference position. (11) The camera data is imported into the computer terminal for four-step phase-shifting reconstruction.

4. The imaging method of claim 3, wherein, In step (7), the sample to be tested is a Paramecium cell sample.

5. The imaging method of claim 3, wherein, In steps (4) and (9), the checkerboard grating A and checkerboard grating B have the same structure. They are both made of N-BK7 glass substrate and liquid crystal polymer birefringent material, presenting a sandwich structure of "front and back glass substrates + middle LCP functional film layer". In the LCP functional film layer, liquid crystal molecules are arranged in a checkerboard structure, with the orientation angle of each pixel cell being consistent and the phase difference between adjacent pixel cells being π. The entire device plane has a retardation of λ / 2, where λ represents the wavelength of light.

6. The imaging method of claim 5, wherein, In step (5), the vortex waveplate group consists of four first-order vortex waveplates. Each first-order vortex waveplate has the function of converting the incident plane wave into a vortex beam. They are arranged in a 2×2 pattern in space, and are placed at rotation angles of 0°, 90°, 180° and 270° respectively. This produces four beams of vortex light R1', R2', R3' and R4' with the same output direction and different phase differences.

7. The imaging method of claim 6, wherein, In step (3), the beam is incident on beam splitter A, and the intensity of the plane wave is expressed as: E=E0·exp(ik·z)(1) E0 is the amplitude of the beam, k = 2π / λ is the wave number, and z is the optical path length of the beam in the propagation direction. For the reference light, the plane wave passes through the chessboard grating A for splitting, and then passes through the collimating mirror B for correcting the direction to obtain four plane waves E with parallel propagation direction and optical axis r1 、 E r2 、 E r3 、 E r4 : wherein z r is an optical path in the reference light, is a phase of the reference light; After passing through the vortex waveplate assembly, the four plane waves become four vortex beams carrying OAM phase, with additional phases of 0, π / 2, π, and 3π / 2 respectively: Where l is the topological charge of the vortex beam and θ is the rotation angle.

8. The imaging method of claim 7, wherein, For the test optical path, the plane wave carries the phase information of the sample after passing through it, and then passes through a pinhole filter to remove stray light: Among them, z t δ represents the optical path length in the test optical path, and δ represents the phase information of the sample being measured. It tests the phase of the optical path; After being split by the checkerboard grating B and then oriented by the collimating lens C, four plane waves carrying sample information are obtained, with their propagation directions parallel to the optical axis. Correspondingly, after passing through beam splitter D, the reference light and the test light interfere at the camera. The interference pattern is generally represented by the superposition of four parts of light intensity in spatial distribution, and the light intensity of each part is as follows: I1, I2, I3, and I4 represent the light intensities of the interferences in R1'-T1, R2'-T2, R3'-T3, and R4'-T4, respectively.

9. The imaging method of claim 8, wherein, The four-step phase-shifting reconstruction process in step (11) is as follows: First, the captured interferograms are segmented to obtain four decomposed interferograms: A, B, C, and D. Then, the phase is reconstructed using a four-step phase-shifting method. The phase is expressed as the arctangent of the ratio of interferogram D minus interferogram B to interferogram C minus interferogram A: The phase of the sample is obtained, and optical microscopic imaging is completed.

Images