A microscopic imaging device and phase reconstruction method thereof

Abstract

The present invention discloses a microscopic imaging device and a phase reconstruction method thereof, which relate to the field of digital holographic microscopic measurement. It is used to solve the problems of positioning errors caused by multiple movements of the existing microscopic imaging device, complex operation, and low reconstruction accuracy of the surface morphology of the sample to be measured. The device includes: a first beam splitter prism, which is located on the light-emitting side of the light source module and is used to split the laser beam into reference light and object light; an object light splitting module, which is used to make the object light carrying the surface information of the sample to be measured form four beams of diffracted light; a vortex reference module, which is used to convert the reference light into a vortex reference light with a spiral phase distribution and including four regions; a second beam splitter prism, which is used to combine the four diffracted lights and the vortex reference lights of the four regions, so that the four diffracted lights and the vortex reference lights of the four regions form interference fringes on the imaging target surface; an image acquisition system, which is used to perform single-frame acquisition of the interference fringes to obtain a single-frame four-frame phase-shifted hologram, thereby realizing real-time imaging measurement.

Description

Technical Field

[0001] The present invention relates to the field of digital holographic microscopy, and more particularly to a microscopy imaging device and a phase reconstruction method thereof. Background Art

[0002] By combining phase-shifting technology with digital holographic microscopy, phase-shifting digital holographic microscopy can effectively address the interference between zero-order and conjugate images during holographic reconstruction under coaxial recording conditions, resulting in higher-resolution holographic reconstructions. Currently, phase-shifting digital holography can be categorized into two types: temporal phase shifting and spatial phase shifting, based on the different ways in which phase shift is generated. Temporal phase shifting involves changing the phase of a reference beam through the mechanical movement of a phase shifter in a time sequence, thereby recording the corresponding hologram. This method can only observe static samples or slowly changing processes, resulting in low imaging accuracy and slow speed. Spatial phase shifting, on the other hand, utilizes multiple synchronized CCD cameras or divides the recording surface of a single CCD camera into multiple portions, allowing for the simultaneous recording of multiple holograms with different phase shifts in a single exposure. This enables real-time observation of dynamic samples and their changing processes. Digital holographic systems incorporating spatial phase shifting technology require a spectrometer to separate the object and reference beams. Phase shifts are then introduced between the two beams using a phase shifter, ultimately producing holograms with varying phase shifts.

[0003] Currently, spatial phase-shifting digital holography is divided into two methods, multi-camera recording and single-camera recording (pixel mask method), depending on the number of imaging receiving devices. The multi-CCD recording method uses multiple independent and separate beam paths, each of which is synchronously exposed by a separate CCD, thereby recording phase-shifted interference patterns with different phase shift amounts. For example, in the paper "Phase-shifting digital holographic microscopy by using a multi-camera setup," Carlos T et al. employed a multi-camera setup to achieve single-shot capture and obtain the desired phase-shifted interference image. This setup, by setting different output channels, can simultaneously obtain the desired phase-shifted interference image. The patent "Method for Measuring Optical Phase Using Synchronous Phase-Shifting Interference and Implementing an Optical Path" employs a conventional beam splitter and a polarization beam splitter to perform six-way beam splitting of the incident light source. Combined with polarization phase shifting technology, six phase-shifted interference patterns are simultaneously recorded, achieving efficient spatial separation and synchronous recording. The size of the interference pattern obtained by the multi-CCD recording method is consistent with the photosensitive area of a single CCD, which can obtain a larger observation field of view. However, the system structure is relatively complex, requiring precise synchronization control of the camera, and has extremely high requirements for the simultaneity of signal acquisition. The single-camera recording method is to cover the specially made micro-polarizer array on the recording target surface of the CCD, so that each pixel can record a different phase shift. By resampling and combining the entire recorded interference pattern, multiple interference patterns with different phase shifts are formed. For example: In the paper "Dynamic Fizeau Interferometer Using Short Coherence Light Source", a pair of short coherence orthogonal polarization beams were obtained by using a short coherence diode-pumped solid-state laser. Combined with a polarization camera, short coherence Fizeau-type spatial phase shift interferometry was realized.

[0004] Compared with temporal phase-shifting technology, spatial phase-shifting technology can capture multiple phase-shifted holograms at the same time, solving the problems of slow imaging speed and the inability to achieve real-time online imaging. However, spatial phase-shifting technology also has some limitations. For example, the multi-CCD recording method requires that the exposure of all cameras must be precisely synchronized, which places strict demands on the simultaneity of acquisition; the single-camera recording method relies on a polarization phase-shifting scheme, which is easily affected by deviations in the azimuth angle and delay of the polarization optical element. In addition, during the phase reconstruction process, a fixed-step phase-shifting algorithm is usually used, which reduces the flexibility of the system. Summary of the Invention

[0005] The embodiment of the present invention provides a microscopic imaging device and a phase reconstruction method thereof, which are used to solve the problems of positioning errors caused by multiple movements of the device in existing microscopic imaging, complex operation, and low accuracy in reconstructing the surface morphology of the measured sample.

[0006] An embodiment of the present invention provides a microscopic imaging device, comprising:

[0007] a first beam splitter prism, located on the light-emitting side of the light source module, for splitting the laser beam into reference light and object light;

[0008] An object light splitting module, which is used to form the object light carrying the surface information of the sample to be measured into four beams of diffracted light;

[0009] a vortex reference module, configured to convert the reference light into a vortex reference light having a spiral phase distribution and including four regions;

[0010] a second beam splitter prism, which is used to combine the four diffracted lights and the vortex reference lights in four regions, so that the four diffracted lights and the vortex reference lights in four regions form interference fringes on an imaging target surface;

[0011] An image acquisition system is used to perform single-frame acquisition of the interference fringes to obtain four phase-shifted holograms in a single frame, thereby realizing real-time imaging measurement.

[0012] Preferably, the objective light splitting module includes a second microscope objective lens, an aperture and a two-dimensional grating splitting system;

[0013] The second microscope objective lens is used to make the object light carrying the surface information of the sample to be measured into parallel light;

[0014] An aperture, which is used to limit the beam aperture angle of the parallel object light carrying the surface information of the sample to be measured;

[0015] A two-dimensional grating spectroscopic system is used to diffract parallel object light carrying surface information of a sample to be measured to obtain four beams of diffracted light.

[0016] 3. The device according to claim 1, wherein the vortex reference module comprises a spiral phase plate and a first microscope objective lens;

[0017] The spiral phase plate is used to modulate the reference light to form a vortex reference light with a spiral phase distribution and including four regions;

[0018] The first microscope objective lens is used to form parallel light from the vortex reference light in the four regions.

[0019] An embodiment of the present invention provides a phase reconstruction method, including:

[0020] Acquire four single-frame phase-shifted holograms of the sample to be tested and an intensity map of a vortex reference light using a microscopic imaging device, perform binarization on the intensity map of the vortex reference light, determine the intensity minimum point in the obtained vortex light intensity map as the coordinate of a vortex phase singular point, and determine the angle of each pixel point in each sub-phase-shifted hologram relative to the vortex phase singular point based on the coordinates of each pixel point in the four phase-shifted holograms and the coordinates of the vortex phase singular point;

[0021] When the phase shift value of each pixel point in the first sub-phase-shift hologram is zero, the phase shift value of each pixel point in the second sub-phase-shift hologram, the third sub-phase-shift hologram, and the fourth sub-phase-shift hologram relative to each pixel point in the first sub-phase-shift hologram is determined in sequence according to the geometric relationship between the four phase-shift holograms;

[0022] When the phase shift value of each pixel in the four phase-shift holograms does not change with the change of pixels, the least squares error between the actual light intensity and the theoretical light intensity of each pixel is determined according to the least squares theory, and the phase corresponding to each pixel is obtained according to the least squares error. The phase of the sample to be tested is reconstructed according to the phase corresponding to each pixel.

[0023] Preferably, the angle of each pixel point in each sub-phase-shifted hologram relative to the vortex phase singular point is expressed by the following formula:

[0024]

[0025] Among them, o(x0,y0) represents the coordinates of the vortex phase singular point, p m (x m,n ,y m,n ) represents the coordinates of each pixel in the hologram, θ m,n represents the angle of the nth pixel in the mth sub-phase shift hologram relative to the vortex phase singularity, y m,n represents the coordinate of the nth pixel in the mth sub-phase shift hologram on the y-axis, xm ,n represents the coordinate of the nth pixel point in the mth sub-phase shift hologram on the x-axis, y0 represents the coordinate of the vortex phase singular point on the y-axis, x0 represents the coordinate of the vortex phase singular point on the x-axis, m=1,2,3,4, n=1,2,....N, N represents a positive integer.

[0026] Preferably, the phase shift values of each pixel point in the second sub-phase-shift hologram, the third sub-phase-shift hologram and the fourth sub-phase-shift hologram relative to each pixel point in the first sub-phase-shift hologram are as follows:

[0027]

[0028] Among them, δ 2,nrepresents the phase shift value of the nth pixel in the second sub-phase-shift hologram, δ 3,n represents the phase shift value of the nth pixel in the third sub-phase-shift hologram, δ 4,n represents the phase shift value of the nth pixel in the fourth sub-phase shift hologram, θ 1,n represents the angle of the nth pixel of the first sub-phase-shifted hologram relative to the vortex phase singularity, θ 2,n represents the angle of the nth pixel of the second sub-phase-shifted hologram relative to the vortex phase singularity, θ 3,n represents the angle of the nth pixel of the third sub-phase-shifted hologram relative to the vortex phase singularity, θ 4,n Represents the angle of the nth pixel of the fourth sub-phase-shifted hologram relative to the vortex phase singularity.

[0029] Preferably, the least square error between the actual light intensity of each pixel and the theoretical light intensity is determined by the following formula:

[0030]

[0031] Among them, L(x,y) represents the least square error between the actual light intensity of each pixel and the theoretical light intensity. It represents the actual light intensity of four phase-shifted holograms in a single frame, I m,n (x,y) represents the theoretical light intensity of four phase-shifted holograms in a single frame, I m,n (x,y)=A+B cos[δ m,n (x,y)]+C sin[δ m,n (x,y)], A represents the background light intensity of the hologram, A=I m,0 (x,y), B represents the product of the modulation depth of the hologram and the phase cosine, C represents the product of the modulation depth of the hologram and the sine of the phase, cos[δ m,n (x,y)] represents the phase shift cosine value of all measurement frames m at the nth pixel; sin[δ m,n (x,y)] represents the phase shift sine value of all measurement frames m at the nth pixel, ΔI m (x,y) represents the modulation degree of the hologram; Indicates the phase cosine value of the nth pixel; Indicates the phase sine value of the n-th pixel.

[0032] Preferably, the phase corresponding to each pixel is determined by the following formula:

[0033]

[0034] in, Indicates the phase corresponding to each pixel, {Xn}=[ABC] T =[H n ] -1 [K n ],{X n} represents a set of linear equations, H n Represents a system of linear equations containing sine and cosine terms of phase shift values, K n represents a vector containing the actual light intensity of four phase-shifted holograms in a single frame; represents the sum of the phase shift cosine values of all measurement frames m at the nth pixel point, represents the sum of the squared cosine values of the phase shift of all measurement frames m at the nth pixel point, represents the sum of the products of the sine and cosine values of the phase shift of all measurement frames m at the nth pixel point, represents the sum of the phase shift sine values of all measurement frames m at the nth pixel point, represents the sum of the squared sine values of the phase shift of all measurement frames m at the nth pixel point, It means summing the light intensity values of all measurement frames m at the nth pixel point. It is the sum of the total light intensity of the nth pixel and the cosine value of the phase shift. It is the sum of the total light intensity of the nth pixel and the sine value of the phase shift.

[0035] An embodiment of the present invention provides a computer device, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes any one of the above-mentioned phase reconstruction methods.

[0036] An embodiment of the present invention provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the processor executes any one of the above-mentioned phase reconstruction methods.

[0037] An embodiment of the present invention provides a microscopic imaging device and a phase reconstruction method thereof, the device comprising: a first beam splitter prism, located on the light-emitting side of a light source module, for splitting a laser beam into a reference beam and an object beam; an object beam splitter module, for forming the object beam carrying surface information of a sample to be measured into four beams of diffracted light; a vortex reference module, for converting the reference light into vortex reference light having a spiral phase distribution and including four regions; a second beam splitter prism, for combining the four diffracted lights and the vortex reference lights of the four regions, so that the four diffracted lights and the vortex reference lights of the four regions form interference fringes on an imaging target surface; and an image acquisition system, for performing single-frame acquisition of the interference fringes to obtain a single-frame four-frame phase-shifted hologram, thereby realizing real-time imaging measurement. The vortex reference module in the device uses a vortex phase plate to modulate the vortex reference light, and uses the special spiral phase distribution of the vortex light to obtain a vortex reference light with a vortex phase distribution and including four regions. The vortex reference light with a vortex phase distribution and including four regions interferes with the four diffracted lights from the object light splitting module, and obtains four phase-shifted holograms of the object to be measured through single-frame imaging, effectively avoiding the positioning error caused by multiple movements of the phase shifter and the singularity of the vortex light. It has the advantages of simple operation and the ability to realize real-time imaging measurement, and can be widely used in fields such as surface morphology detection of micro-optical components. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0039] Figure 1 A schematic diagram of the module structure of a microscopic imaging device provided by an embodiment of the present invention;

[0040] Figure 2 A schematic diagram of the specific structure of a microscopic imaging device provided by an embodiment of the present invention;

[0041] Figure 3 A schematic flow chart of a phase reconstruction method provided by an embodiment of the present invention;

[0042] Figure 4 A schematic diagram of a vortex reference beam provided by an embodiment of the present invention;

[0043] Figure 5 A schematic diagram of calculating each pixel point in a phase-shift hologram provided by an embodiment of the present invention;

[0044] Among them, there are a light source module ~10, an objective light spectrometer module ~20, a vortex reference module ~30, an image acquisition system ~40, a He-Ne laser ~101, a beam expander collimator ~102, a first spectrometer prism ~501, a device to be measured ~201, a second microscope objective lens ~202, a second plane reflector ~203, an aperture ~204, a two-dimensional grating spectrometer system ~205, a first plane reflector ~301, a spiral phase plate ~302, a first microscope objective lens ~303, a second spectrometer prism ~502, an imaging tube lens ~401, a CMOS ~402, and a computer ~403. DETAILED DESCRIPTION

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0046] Figure 1 A schematic diagram of the module structure of a microscopic imaging device provided by an embodiment of the present invention; Figure 2 A schematic diagram of the specific structure of a microscopic imaging device provided by an embodiment of the present invention; Figure 1 and Figure 2 , a microscopic imaging device provided by an embodiment of the present invention is described in detail, such as Figure 1 As shown, the microscopic imaging device provided by the embodiment of the present invention mainly includes: a light source module 10, a first spectroscopic prism 501, an object light spectroscopic module 20, a vortex reference module 30, a second spectroscopic module 502 and an image acquisition system 40.

[0047] Specifically, the light source module is used to provide a laser light source. In an embodiment of the present invention, the light source module 10 includes a He-Ne laser 101 and a beam expander collimator 102, wherein the He-Ne laser is connected to the beam expander collimator, and the beam expander collimator is composed of a microscope objective lens and a lens. The beam expander collimator is arranged at a position close to the He-Ne laser. In the light source module, the light beam emitted by the He-Ne laser is adjusted to a suitable spot size through the microscope objective lens and the lens.

[0048] Furthermore, the first beam splitter prism is arranged opposite to the light source module and located on the light output side of the light source module. The first beam splitter prism is used to split the laser beam from the light source module into object light and reference light.

[0049] Furthermore, an objective light splitting module is located on the object light exit side, and a sample 201 to be tested is disposed between the objective light exit side and the objective light splitting module. After the object light from the first beam splitting prism passes through the sample to be tested, it carries information about the sample's surface and enters the objective light splitting module. The objective light splitting module splits the incoming object light carrying information about the sample's surface into four diffracted beams.

[0050] Furthermore, the vortex reference module located at the light-emitting side of the reference light is used to convert the reference light from the first beam splitter prism into a vortex reference light having a spiral phase distribution and including four regions.

[0051] The second spectroscopic prism is located on the light-emitting side of the object light spectroscopic module and the reference light spectroscopic module, and is used to combine the four diffracted light beams from the object light spectroscopic module and the vortex reference light beams including four regions from the reference light spectroscopic module, so that the combined four diffracted light beams and the vortex reference light beams including four regions form interference fringes on the imaging target surface.

[0052] In an embodiment of the present invention, the image acquisition system is located on the light-emitting side of the second beam splitter prism, and the combined four beams of diffracted light and the vortex reference light including four regions can form an interference pattern on the imaging target surface of the image acquisition system. The image acquisition system performs single-frame acquisition of the above-mentioned interference fringes to obtain a single-frame four-frame phase-shifted hologram, thereby realizing real-time imaging measurement.

[0053] In the microscopic imaging device provided by an embodiment of the present invention, a vortex reference module utilizes a vortex phase plate to modulate vortex reference light, and utilizes the special spiral phase distribution of vortex light to obtain vortex reference light with a vortex phase distribution and including four regions. The vortex reference light with a vortex phase distribution and including four regions interferes with the four beams of diffracted light from the object light splitting module, and four phase-shifted holograms of the object to be measured are obtained through single-frame imaging, effectively avoiding the positioning error caused by multiple movements of the phase shifter and the singularity problem of vortex light. The device has the advantages of simple operation and the ability to realize real-time imaging measurement, and can be widely used in fields such as surface morphology detection of micro-optical elements.

[0054] For example, in the microscopic imaging device provided by an embodiment of the present invention, the objective light splitting module includes a second microscope objective lens 202 , an aperture 204 and a two-dimensional grating splitting system 205 .

[0055] Among them, the second microscope objective lens can make the object light carrying the surface information of the sample to be measured form parallel light, that is, form parallel object light carrying the surface information of the sample to be measured; the aperture located on the light-exiting side of the second microscope is used to limit the beam aperture angle of the parallel object light carrying the surface information of the sample to be measured, and the two-dimensional grating spectrometer system is located on the light-exiting side of the aperture, and the two-dimensional grating spectrometer system is used to diffract the parallel object light with limited beam aperture angle, thereby forming four beams of diffracted light.

[0056] In an embodiment of the present invention, a two-dimensional grating spectroscopic system includes a two-dimensional grating, a positive lens, and a pinhole stop. The two-dimensional grating is used to disperse parallel object light that limits the aperture angle of the beam into multiple diffraction orders, each of which carries information about the surface of the sample to be measured. The positive lens, located on the light-exiting side of the two-dimensional grating, is used to focus the four diffracted lights to ensure that the focused four diffracted light beams have consistent light intensity and coherence during the subsequent interference process. The pinhole stop, located on the light-exiting side of the positive lens, is used to limit the diameter of the four focused diffracted light beams to prevent interference from stray light.

[0057] It should be noted that, in actual applications, the object light spectrometer module also includes a second plane reflector 203, wherein the second plane reflector is arranged between the second microscope objective lens and the aperture, and is used to reflect the parallel object light carrying the surface information of the sample to be measured from the second microscope objective lens, so that the reflected parallel object light carrying the surface information of the sample to be measured enters the aperture.

[0058] For example, in the microscopic imaging device provided by an embodiment of the present invention, the vortex reference module includes a spiral phase plate 302 and a first microscope objective lens 303;

[0059] Among them, the spiral phase plate is used to modulate the reference light to form a vortex reference light with a spiral phase distribution and including four areas; the spiral phase plate can introduce high-precision phase shift, thereby effectively avoiding the phase shift error introduced by multiple movements of the phase shifter; the first microscope objective lens is used to make the vortex reference light in the four areas form parallel light, and the parallel light beam can form a clear image after passing through the first microscope objective lens while maintaining the phase information of the parallel light.

[0060] It should be noted that, in actual applications, the vortex reference module also includes a first plane mirror 301, wherein the first plane mirror is arranged between the spiral phase plate and the first beam splitter prism, and is used to reflect the reference light from the first beam splitter prism so that the reflected reference light enters the spiral phase plate.

[0061] In the microscopic imaging device provided by the embodiment of the present invention, the image acquisition module includes an imaging tube lens 401 , a CMOS 402 and a computer 403 .

[0062] In order to more clearly introduce the microscopic imaging device provided by the embodiment of the present invention, the following describes the processing process of the single-frame four-phase-shifted hologram obtained by the microscopic imaging device, that is, the phase reconstruction method. Figure 3 A flow chart of a phase reconstruction method according to an embodiment of the present invention is shown in FIG. Figure 3 As shown, the method includes the following steps:

[0063] Step 101: acquiring four single-frame phase-shifted holograms of a sample to be tested and an intensity map of a vortex reference light using a microscopic imaging device, binarizing the intensity map of the vortex reference light, determining the intensity minimum point in the obtained vortex light intensity map as the coordinate of a vortex phase singular point, and determining the angle of each pixel point in each sub-phase-shifted hologram relative to the vortex phase singular point based on the coordinates of each pixel point in the four phase-shifted holograms and the coordinates of the vortex phase singular point;

[0064] Step 102: When the phase shift value of each pixel point in the first phase-shifted sub-hologram is zero, the phase shift value of each pixel point in the second phase-shifted sub-hologram, the third phase-shifted sub-hologram, and the fourth phase-shifted sub-hologram relative to each pixel point in the first phase-shifted sub-hologram is determined in sequence according to the geometric relationship between the four phase-shifted holograms.

[0065] Step 103: When the phase shift value of each pixel in the four phase-shift holograms does not change with the change of pixels, the least squares error between the actual light intensity and the theoretical light intensity of each pixel is determined according to the least squares theory, the phase corresponding to each pixel is obtained according to the least squares error, and the phase of the sample to be tested is reconstructed according to the phase corresponding to each pixel.

[0066] Before step 101, the microscopic imaging device is first put into working state, specifically including: the laser beam emitted by the He-Ne laser passes through the microscope objective lens and lens in the beam expansion and collimation system in sequence to obtain a suitable spot size, the laser beam enters the first beam splitter prism and is divided into object light and reference light, wherein the object light carries the surface information of the sample to be measured after passing through the second microscope objective lens and the plane mirror, and after passing through the aperture, reaches the spectroscopic system composed of a two-dimensional grating, a positive lens and a pinhole aperture, and then generates four diffracted lights; after passing through the plane mirror, the reference light is incident on the spiral phase plate (SpiralPhasePlate, also called vortex phase plate) and converted into a vortex beam, which is divided into four areas, such as Figure 4 As shown in (b), the four diffracted lights pass through the first microscope objective lens and reach the second beam splitter prism; the four diffracted lights are matched and combined with the vortex reference lights consisting of four regions and then pass through the tube lens to form stable interference on the imaging target surface of the CMOS camera, realizing the acquisition of a single digital hologram.

[0067] In step 101, a single-frame four-frame phase-shift hologram of the sample to be tested and an intensity map of the vortex reference light are obtained based on a microscopic imaging device. When the microscopic imaging device works normally, a single-frame four-frame phase-shift hologram can be obtained, such as Figure 4 As shown in (c), when the microscopic imaging device is working normally, the light path diagram of the obstruction light can be used to collect the intensity diagram of the vortex reference light.

[0068] like Figure 4According to this characteristic, as shown in (a), it can be determined that the four diffracted beams carrying the surface information of the sample to be measured interfere with the vortex reference light respectively, and the interference light intensity distribution can be expressed as follows:

[0069]

[0070] Where I0(x,y) represents the background light intensity of the interference pattern; ΔI(x,y) represents the modulation degree of the interference pattern; and ΔI(x,y) is the phase of the sample to be measured.

[0071] Furthermore, the intensity map of the collected vortex reference light is grayscaled and binarized, and the minimum intensity value in the obtained vortex light intensity map is determined as the coordinate of the vortex phase singularity. In an embodiment of the present invention, the coordinate of the vortex phase singularity is determined to be o(x0, y0).

[0072] Furthermore, according to the coordinates of each pixel point in the four phase-shifted holograms and the coordinates of the vortex phase singular point, the angle of each pixel point in each sub-phase-shifted hologram relative to the vortex phase singular point is determined. Among them, the coordinates of each pixel point in the four phase-shifted holograms can be expressed as p m (x m,n ,y m,n ), where m is the ordinal number of the four holograms, m = 1, 2, 3, 4; n is the ordinal number of the pixels in the four holograms, n = 1, 2, .... N, where N is a positive integer.

[0073] Furthermore, the angle of each pixel point in each sub-phase-shifted hologram relative to the vortex phase singularity can be determined by the following formula:

[0074]

[0075] Among them, o(x0,y0) represents the coordinates of the vortex phase singular point, p m (x m,n ,y m,n ) represents the coordinates of each pixel in the hologram, θ m,n represents the angle of the nth pixel in the mth sub-phase shift hologram relative to the vortex phase singularity, y m,n represents the coordinate of the nth pixel in the mth sub-phase shift hologram on the y-axis, x m,n represents the coordinate of the nth pixel point in the mth sub-phase shift hologram on the x-axis, y0 represents the coordinate of the vortex phase singular point on the y-axis, x0 represents the coordinate of the vortex phase singular point on the x-axis, m=1,2,3,4, n=1,2,....N, N represents a positive integer.

[0076] In step 102, the four phase-shifted holograms are named as the first sub-phase-shifted hologram, the second sub-phase-shifted hologram, the third sub-phase-shifted hologram, and the fourth sub-phase-shifted hologram. In the embodiment of the present invention, when the corresponding values of the pixels in the first sub-phase-shifted hologram are set to zero, the geometric relationship between the four corresponding holograms can be calculated, such as Figure 5 As shown, the phase shift values of each pixel point in the second sub-phase-shift hologram, the third sub-phase-shift hologram and the fourth sub-phase-shift hologram relative to each pixel point in the first sub-phase-shift hologram are determined in sequence.

[0077] Specifically, let the corresponding value δ of each pixel point in the first sub-phase shift hologram be 1,n If the phase shift value of each pixel point in the second sub-phase-shift hologram, the third sub-phase-shift hologram, and the fourth sub-phase-shift hologram relative to each pixel point in the first sub-phase-shift hologram is 0, the phase shift value of each pixel point in the second sub-phase-shift hologram, the third sub-phase-shift hologram, and the fourth sub-phase-shift hologram relative to each pixel point in the first sub-phase-shift hologram can be determined by the following formula:

[0078]

[0079] Among them, δ 2,n represents the phase shift value of the nth pixel in the second sub-phase-shift hologram, δ 3,n represents the phase shift value of the nth pixel in the third sub-phase-shift hologram, δ 4,n represents the phase shift value of the nth pixel in the fourth sub-phase shift hologram, θ 1,n represents the angle of the nth pixel of the first sub-phase-shifted hologram relative to the vortex phase singularity, θ 2,n represents the angle of the nth pixel of the second sub-phase-shifted hologram relative to the vortex phase singularity, θ 3,n represents the angle of the nth pixel of the third sub-phase-shifted hologram relative to the vortex phase singularity, θ 4,n Represents the angle of the nth pixel of the fourth sub-phase-shifted hologram relative to the vortex phase singularity.

[0080] In step 103, the least square method may be performed on each pixel of the four phase-shifted holograms according to the phase shift value of each sub-phase-shifted hologram obtained in the above steps, and then the phase distribution of each pixel may be calculated.

[0081] Specifically, when the phase shift value of each pixel in the four phase-shift holograms does not change with the change of pixels, that is, the background light intensity and modulation degree of each pixel in the phase-shift hologram are consistent and do not change with the change of pixels, formula (1) can be rewritten as follows:

[0082]

[0083] Furthermore, if the following variables exist in the formula, formula (4) can be further rewritten as:

[0084] I m,n=A+B cos[δ m,n (x,y)]+C sin[δ m,n (x,y)] (5)

[0085] The variables include: A=I m,0 (x,y),

[0086] Furthermore, A represents the background light intensity of the hologram, B represents the product of the modulation of the hologram and the phase cosine, and C represents the product of the modulation of the hologram and the phase sine; cos[δ m,n (x,y)] represents the phase shift cosine value of all measurement frames m at the nth pixel; sin[δ m,n (x,y)] represents the phase shift sine value of all measurement frames m at the nth pixel, ΔI m (x,y) represents the modulation of the hologram (the degree of variation of light intensity in the hologram); Indicates the phase cosine value of the nth pixel; Indicates the phase sine value of the n-th pixel.

[0087] Furthermore, according to the least squares theory, if the actual light intensity is That is, the actual light intensity of four phase-shifted holograms in a single frame is Then the least squares error between the actual light intensity and the theoretical light intensity can be expressed by the following formula:

[0088]

[0089] Among them, L(x,y) represents the least square error between the actual light intensity of each pixel and the theoretical light intensity. It represents the actual light intensity of four phase-shifted holograms in a single frame, I m,n (x,y) represents the theoretical light intensity of four phase-shifted holograms in a single frame.

[0090] In practical applications, when When , L(x,y) has a minimum value, and the linear equation system is:

[0091] {X n}=[H n ] -1 [K n ] (7)

[0092] It should be noted that formula (6) defines the least square error between the actual light intensity of each pixel and the theoretical light intensity. When the partial derivative of L(x, y) with respect to A, B, and C is zero, L(x, u) reaches its minimum value. n}=[H n ] -1[K n ], can be used to find the optimal solution of A, B, and C. Formula (7) can also be written as:

[0093] {X n}=[ABC] T (8)

[0094] in,

[0095]

[0096] Among them, {X n} represents a set of linear equations, including A, B and C; H n Represents a system of linear equations containing sine and cosine terms of phase shift values, K n A vector representing the actual light intensity of four phase-shifted holograms in a single frame. represents the sum of the cosine values of the phase shift of all measurement frames m at the n-th pixel, representing the sum of the cosine components of the phase shift change; represents the sum of the squares of the cosine values of the phase shift of all measurement frames m at the n-th pixel, representing the sum of the squares of the cosine components of the phase shift changes; represents the sum of the products of the sine and cosine values of the phase shift of all measurement frames m at the n-th pixel point, representing the cross term of the sine and cosine components of the phase shift change; represents the sum of the sinusoidal values of the phase shift of all measurement frames m at the nth pixel, representing the sum of the sinusoidal components of the phase shift change; It represents the sum of the squares of the sinusoidal values of the phase shift of all measurement frames m for the n-th pixel point, and represents the sum of the squares of the sinusoidal components of the phase shift change. is the sum of the light intensity values of all measurement frames m at the n-th pixel, which represents the total light intensity at the n-th pixel; It is the sum of the total light intensity of the n-th pixel and the product of the cosine value of the phase shift, which represents the part of the light intensity that changes with the cosine component of the phase shift; It is the sum of the total light intensity of the nth pixel and the product of the sine value of the phase shift, which represents the part of the light intensity that changes with the sine component of the phase shift.

[0097] After obtaining the unknown quantities A, B, and C according to the above formula, the phase corresponding to each pixel can be determined by the following formula:

[0098]

[0099] In an embodiment of the present invention, after the phase corresponding to each pixel point is determined, a loop is used to traverse all pixel points, and the above step 104 is repeated to obtain the pixel phase, and the calculated phase value is stored in the corresponding position of the phase diagram until all pixel points are processed. The calculated phases of all pixel points are combined to complete the reconstruction of the phase of the device under test.

[0100] It should be noted that the loop start condition is: the loop starts from the first pixel point of the four phase-shifted holograms (the pixel point in the upper left corner of the image), and the loop end condition is: the loop ends after traversing all the pixel points of the four phase-shifted holograms.

[0101] In summary, an embodiment of the present invention provides a microscopic imaging device and a phase reconstruction method thereof, wherein the vortex reference module in the device utilizes a vortex phase plate to modulate a vortex reference light, and utilizes the special spiral phase distribution of the vortex light to obtain a vortex reference light with a vortex distribution in phase and including four regions, wherein the vortex reference light with a vortex distribution in phase and including four regions interferes with the four beams of diffracted light from the object light splitting module, and obtains four phase-shifted holograms of the object to be measured through single-frame imaging, effectively avoiding the positioning error caused by multiple movements of the phase shifter and the singularity problem of the vortex light, and has the advantages of simple operation and the ability to realize real-time imaging measurement, and can be widely used in fields such as surface morphology detection of micro-optical elements. This method utilizes the acquired phase-shifted hologram single and vortex reference light image, effectively avoiding the problem that the multi-CCD recording method requires that the exposure of all cameras must be precisely synchronized; and utilizes the least squares generalized phase shift algorithm to obtain the reconstruction of the pixel phase, eliminating the restriction that the phase shift amount must be equal, and improving the system's adaptability to environmental changes.

[0102] Another embodiment of the present invention also provides a computer device, which includes: a processor and a memory; the memory is used to store computer program code, and the computer program code includes computer instructions; when the processor executes the computer instructions, the electronic device performs each step of the phase reconstruction method shown in the above method embodiment.

[0103] Another embodiment of the present invention further provides a computer-readable storage medium, which stores computer instructions. When the computer instructions are executed on a computer device, the computer device executes the steps of the phase reconstruction method shown in the above method embodiment.

[0104] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0105] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A microscopic imaging device, characterized in that: include: a first beam splitter prism, located on the light-emitting side of the light source module, for splitting the laser beam into reference light and object light; An object light splitting module, which is used to form the object light carrying the surface information of the sample to be measured into four beams of diffracted light; a vortex reference module, configured to convert the reference light into a vortex reference light having a spiral phase distribution and including four regions; a second beam splitter prism, which is used to combine the four diffracted lights and the vortex reference lights in four regions, so that the four diffracted lights and the vortex reference lights in four regions form interference fringes on an imaging target surface; An image acquisition system is used to acquire the interference fringes in a single frame to obtain four phase-shifted holograms in a single frame, thereby realizing real-time imaging measurement; Wherein, the objective light splitting module includes a second microscope objective lens, an aperture and a two-dimensional grating splitting system; The second microscope objective lens is used to make the object light carrying the surface information of the sample to be measured into parallel light; An aperture, which is used to limit the beam aperture angle of the parallel object light carrying the surface information of the sample to be measured; A two-dimensional grating spectroscopic system, which is used to diffract parallel object light carrying surface information of the sample to be measured to obtain four beams of diffracted light; The vortex reference module includes a spiral phase plate and a first microscope objective lens; The spiral phase plate is used to modulate the reference light to form a vortex reference light with a spiral phase distribution and including four regions; The first microscope objective lens is used to form parallel light from the vortex reference light in the four regions.

2. A phase reconstruction method, characterized in that: include: Based on the microscopic imaging device described in claim 1, a single-frame four-phase-shifted hologram of the sample to be tested and an intensity map of the vortex reference light are obtained, the intensity map of the vortex reference light is binarized, the intensity minimum point in the obtained vortex light intensity map is determined as the coordinate of the vortex phase singular point, and the angle of each pixel point in each sub-phase-shifted hologram relative to the vortex phase singular point is determined based on the coordinates of each pixel point in the four-phase-shifted hologram and the coordinates of the vortex phase singular point; When the phase shift value of each pixel point in the first sub-phase-shift hologram is zero, the phase shift value of each pixel point in the second sub-phase-shift hologram, the third sub-phase-shift hologram, and the fourth sub-phase-shift hologram relative to each pixel point in the first sub-phase-shift hologram is determined in sequence according to the geometric relationship between the four phase-shift holograms; When the phase shift value of each pixel in the four phase-shift holograms does not change with the change of pixels, the least squares error between the actual light intensity and the theoretical light intensity of each pixel is determined according to the least squares theory, and the phase corresponding to each pixel is obtained according to the least squares error. The phase of the sample to be tested is reconstructed according to the phase corresponding to each pixel.

3. The phase reconstruction method according to claim 2, characterized in that: The angle of each pixel point in each sub-phase-shifted hologram relative to the vortex phase singular point is expressed by the following formula: Among them, o(x0,y0) represents the coordinates of the vortex phase singular point, p m (x m,n ,y m,n ) represents the coordinates of each pixel in the hologram, θ m,n represents the angle of the nth pixel in the mth sub-phase shift hologram relative to the vortex phase singularity, y m,n represents the coordinate of the nth pixel in the mth sub-phase shift hologram on the y-axis, x m,n represents the coordinate of the nth pixel point in the mth sub-phase shift hologram on the x-axis, y0 represents the coordinate of the vortex phase singular point on the y-axis, x0 represents the coordinate of the vortex phase singular point on the x-axis, m=1,2,3,4, n=1,2,....N, N represents a positive integer.

4. The phase reconstruction method according to claim 2, wherein: The phase shift values of each pixel point in the second sub-phase-shifted hologram, the third sub-phase-shifted hologram, and the fourth sub-phase-shifted hologram relative to each pixel point in the first sub-phase-shifted hologram are as follows: Among them, δ 2,n represents the phase shift value of the nth pixel in the second sub-phase-shift hologram, δ 3,n represents the phase shift value of the nth pixel in the third sub-phase-shift hologram, δ 4,n represents the phase shift value of the nth pixel in the fourth sub-phase shift hologram, θ 1,n represents the angle of the nth pixel of the first sub-phase-shifted hologram relative to the vortex phase singularity, θ 2,n represents the angle of the nth pixel of the second sub-phase-shifted hologram relative to the vortex phase singularity, θ 3,n represents the angle of the nth pixel of the third sub-phase-shifted hologram relative to the vortex phase singularity, θ 4,n Represents the angle of the nth pixel of the fourth sub-phase-shifted hologram relative to the vortex phase singularity.

5. The phase reconstruction method according to claim 2, wherein: The least square error between the actual light intensity of each pixel and the theoretical light intensity is determined by the following formula: Among them, L(x,y) represents the least square error between the actual light intensity of each pixel and the theoretical light intensity. It represents the actual light intensity of four phase-shifted holograms in a single frame, I m,n (x,y) represents the theoretical light intensity of four phase-shifted holograms in a single frame, I m,n (x,y)=A+B cos[δ m,n (x,y)]+C sin[δ m,n (x,y)], A represents the background light intensity of the hologram, A=I m,0 (x,y), B represents the product of the modulation depth of the hologram and the phase cosine, C represents the product of the modulation depth of the hologram and the sine of the phase, cos[δ m,n (x,y)] represents the phase shift cosine value of all measurement frames m at the nth pixel; sin[δ m,n (x,y)] represents the phase shift sine value of all measurement frames m at the nth pixel, ΔI m (x,y) represents the modulation degree of the hologram; Indicates the phase cosine value of the nth pixel; Indicates the phase sine value of the n-th pixel.

6. The phase reconstruction method according to claim 2, wherein: The phase corresponding to each pixel is determined by the following formula: in, Indicates the phase corresponding to each pixel, {X n }=[ABC] T =[H n ] -1 [K n ],{X n } represents a set of linear equations, H n Represents a system of linear equations containing sine and cosine terms of phase shift values, K n represents a vector containing the actual light intensity of four phase-shifted holograms in a single frame; represents the sum of the phase shift cosine values of all measurement frames m at the nth pixel point, represents the sum of the squared cosine values of the phase shift of all measurement frames m at the nth pixel point, represents the sum of the products of the sine and cosine values of the phase shift of all measurement frames m at the nth pixel point, represents the sum of the phase shift sine values of all measurement frames m at the nth pixel point, represents the sum of the squared sine values of the phase shift of all measurement frames m at the nth pixel point, It means summing the light intensity values of all measurement frames m at the nth pixel point. It is the sum of the total light intensity of the nth pixel and the cosine value of the phase shift. It is the sum of the total light intensity of the nth pixel and the sine value of the phase shift.

7. A computer device, characterized in that: The computer device includes a memory and a processor, the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the phase reconstruction method according to any one of claims 2 to 6.

8. A computer-readable storage medium, characterized in that A computer program is stored, and when the computer program is executed by a processor, the processor is caused to perform the phase reconstruction method according to any one of claims 2 to 6.

Images