A polarization characteristic parameter measurement system and method

Abstract

The present invention belongs to the field of optical measurement technology, and discloses a polarization characteristic parameter measurement system and method. The present invention first builds a polarization characteristic parameter measurement system, collects and obtains a number of original sample images, then after replacing the sample with a blackboard, collects and obtains a laser spot image while the parameters of the polarization characteristic parameter measurement system remain unchanged, and then uses a calculation control module to reconstruct the laser elliptical light intensity distribution according to the laser spot image to obtain an elliptical Gaussian light intensity distribution diagram, and maps the elliptical Gaussian light intensity distribution diagram to a number of original sample images to obtain a number of light intensity corrected sample images; and then calculates and obtains the Mueller matrix element image and polarization characteristic parameter image corresponding to the sample. The present invention performs light intensity correction on the original sample image, which can quickly eliminate the influence of the laser light intensity Gaussian distribution and realize high-precision polarization characteristic parameter measurement.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical measurement, and more specifically, relates to a polarization characteristic parameter measurement system and method. Background Art

[0002] There are two main ways to obtain sample polarization information (i.e. polarization characteristic parameters): amplitude division method and double rotating wave plate method. Among them, the amplitude division method sets four polarization mirrors with different polarization directions and collects polarization images in four directions at the same time. The operation is simple, but the polarization information dimension is less; the double rotating wave plate method needs to rotate two wave plates for multiple image collections, and the polarization information obtained is more and more accurate, but the operation is more complicated.

[0003] The traditional double-rotating wave plate method uses LED light sources for illumination, and the LED spectrum is relatively wide, which will lead to errors in the wave plate delay. At present, some studies use lasers for illumination, but in actual operation, after the laser beam is expanded, it is found that the intensity of the laser spot irradiated on the sample is Gaussian distributed. Although the light intensity is normalized when calculating the Mueller matrix, the normalization process can only avoid the error caused by the fluctuation of the system light intensity at different times, but cannot avoid the error caused by different illumination of different areas of the sample at the same time.

[0004] In terms of the application of medical testing, during traditional tumor resection surgery, doctors will remove the tumor and surrounding tissue that may be cancerous as much as possible. The resected tissue samples will be sent to the pathology department for pathological diagnosis. After fixation, dehydration, wax immersion, embedding, slicing, staining and other steps, the type, grade and stage of the tumor will be evaluated. However, this step has a long cycle. The polarization characteristic parameter measurement system can realize real-time sampling of resected tissue samples, and can quickly detect tumor boundaries during surgery, assist doctors in making surgical decisions, minimize patient damage and achieve better treatment effects.

[0005] When using the double rotating wave plate method for polarization measurement, how to effectively solve the problem of uneven distribution of laser Gaussian light intensity and improve the measurement accuracy of polarization characteristic parameters, thereby assisting doctors in more accurately diagnosing the pathological state of tissue samples, is a technical problem that this field is concerned about and needs to solve. Summary of the invention

[0006] The present invention provides a polarization characteristic parameter measurement system and method, thereby solving the problem in the prior art that when a double rotating wave plate method is used to perform polarization measurement, the uneven distribution of laser Gaussian light intensity affects the measurement accuracy of polarization characteristic parameters.

[0007] The present invention provides a method for measuring polarization characteristic parameters, comprising the following steps:

[0008] Step 1, building a polarization characteristic parameter measurement system, wherein the polarization characteristic parameter measurement system includes a light source module, a polarization modulation module, a stage, a polarization analyzer demodulation module, an image acquisition module and a calculation control module;

[0009] Step 2, placing the sample in the first area of ​​the stage; the laser light emitted by the light source module is incident obliquely onto the stage after passing through the polarization modulation module, and the reflected light is emitted vertically and passes through the polarization analysis demodulation module and the image acquisition module in sequence;

[0010] Using the calculation control module to control the rotation angles of the first rotating stage in the polarization modulation module and the second rotating stage in the polarization detection and demodulation module, and using the calculation control module to control the image acquisition module to perform image acquisition to obtain a plurality of original sample images;

[0011] Step 3, replacing the sample with a blackboard, and placing the blackboard in the first area of ​​the stage; acquiring a laser spot image while keeping the parameters of the polarization characteristic parameter measurement system unchanged;

[0012] Step 4: using the calculation control module to reconstruct the laser elliptical intensity distribution according to the laser spot image to obtain an elliptical Gaussian intensity distribution map, and mapping the elliptical Gaussian intensity distribution map to a number of original sample images to obtain a number of intensity-corrected sample images;

[0013] Step 5, using the calculation control module to calculate the Mueller matrix element image corresponding to the sample according to a plurality of light intensity corrected sample images;

[0014] Step 6: Using the calculation control module, calculate the polarization characteristic parameter image corresponding to the sample according to the Mueller matrix element image corresponding to the sample.

[0015] Preferably, the initial state of the polarization characteristic parameter measurement system is: the polarization direction of the laser emitted by the light source module is consistent with the light transmission direction of the first polarizer in the polarization modulation module, the fast axis direction of the first phase retarder in the polarization modulation module, and the light transmission direction of the second polarizer in the polarization analyzer and demodulator module, and the fast axis direction of the second phase retarder in the polarization analyzer and demodulator module;

[0016] The computing control module controls the first rotating stage and the second rotating stage to rotate according to preset angles respectively, and then controls the image acquisition module to acquire images. The first rotating stage and the second rotating stage rotate in the same direction along the light propagation direction.

[0017] Preferably, step 4 includes the following sub-steps:

[0018] Take the elliptical short axis intensity sequence I corresponding to the laser spot image sn , I sn =[i s1 ,i s2 ,i s3 , ..., i sn ], where n = 1, 2, 3, ..., N, N is the ellipse minor axis intensity sequence I sn Length;

[0019] For the elliptical minor axis intensity sequence I sn Perform Fourier transform to obtain the sequence F after Fourier transform sn ;

[0020] The Fourier transformed sequence F sn Denoise and obtain the denoised sequence F sdnn ;

[0021] For the denoised sequence F sdnn Perform inverse Fourier transform to obtain the elliptical short-axis Gaussian light intensity sequence I corresponding to the laser spot image gaosin ;

[0022] Based on the elliptical minor axis Gaussian light intensity sequence I gaosin The elliptical Gaussian light intensity distribution diagram is obtained.

[0023] Preferably, by converting the Fourier transformed sequence F sn After a low-pass filter H n , to realize the Fourier transformed sequence F sn De-noising; the low-pass filter H n Only the DC component and the fundamental frequency signal are retained.

[0024] Preferably, the method for obtaining the elliptical Gaussian light intensity distribution diagram comprises:

[0025] Obtain the number of pixels a occupied by the major axis of the ellipse, the number of pixels b occupied by the minor axis of the ellipse, and the number of pixels c occupied by the focal length of the laser spot image, and generate a black image with a length of 2a and a width of 2b; perform M cycles of judgment to determine whether each point (x i ,y i ) is on the circumference of the ellipse, where M = N / 2 = b, i = 0, 1, 2, ..., 2a, j = 0, 1, 2, ..., 2b; when a point is judged on the circumference of the ellipse in the mth cycle, if the point is judged to be on the circumference of the ellipse, the light intensity value of the point is replaced by the Gaussian light intensity value corresponding to n = N / 2 + m, recorded as I(i, j) = = i gaosi(N / 2+m); Otherwise, keep the light intensity value of the point unchanged; after completing the loop judgment, an elliptical Gaussian light intensity distribution diagram with a length of 2a and a width of 2b is obtained.

[0026] Preferably, it is determined that each point (x i ,y j ) is on the circumference of an ellipse:

[0027] Generate long axis sequence A m =[ab 1 / M,ab 2 / M,ab 3 / M,...,ab m / M Short axis sequence B m = [1, 2, ..., M] and focal length sequence C m =[cb 1 / M,cb 2 / M,cb 3 / M,...,cb m / M] Among them, b m For short axis sequence B m Elements in

[0028] In the mth cycle, determine whether a certain point is close to the first focus F 1 (a m -c m , M), the second focus F 2 (a m +c m , M) Is ​​the sum of the distances 2a, where a m A is the long axis sequence m The elements in c m is the focal length sequence C m The elements in If the sum is 2a, the point is judged to be on the circumference of the ellipse.

[0029] Preferably, in step 6, a Mueller matrix decomposition method and a Mueller matrix transformation method are used to calculate the polarization characteristic parameter image corresponding to the sample based on the Mueller matrix element image corresponding to the sample.

[0030] Preferably, the sample is a living tissue sample, and the living tissue sample is obtained by: cutting the living tissue into thin slices with a first thickness, placing the thin slices on a glass slide, covering with a cover glass and accumulating air bubbles to obtain the living tissue sample.

[0031] On the other hand, the present invention provides a polarization characteristic parameter measurement system, including: a light source module, a polarization modulation module, a stage, a polarization analyzer demodulation module, an image acquisition module and a calculation control module;

[0032] The polarization characteristic parameter measurement system is used to execute the steps in the above-mentioned polarization characteristic parameter measurement method.

[0033] Preferably, the light source module comprises a laser and a beam expander arranged in sequence along the light path;

[0034] The polarization modulation module comprises a first polarizer and a first phase retarder arranged in sequence along the optical path, and the first phase retarder is embedded in the first rotating platform;

[0035] The loading platform comprises a storage plate clamp and a support frame, and the storage plate clamp is fixed by the support frame;

[0036] The polarization analyzer and demodulator module comprises a second phase retarder and a second polarizer which are sequentially arranged along the optical path, and the second phase retarder is embedded in the second rotating platform;

[0037] The image acquisition module adopts a CCD camera;

[0038] The computing control module is connected to the first rotating stage, the second rotating stage and the CCD camera respectively.

[0039] One or more technical solutions provided in the present invention have at least the following technical effects or advantages:

[0040] (1) In view of the problem that the intensity of the parameter map is uneven due to the Gaussian distribution of the laser spot intensity when the double rotating wave plate method is used for polarization measurement, thereby affecting the measurement accuracy of the polarization characteristic parameters, the present invention first builds a polarization characteristic parameter measurement system, collects and obtains a number of original sample images, then after replacing the sample with a blackboard, collects and obtains the laser spot image while the parameters of the polarization characteristic parameter measurement system remain unchanged, and then uses the calculation control module to reconstruct the laser elliptical intensity distribution according to the laser spot image to obtain an elliptical Gaussian intensity distribution map, and maps the elliptical Gaussian intensity distribution map to a number of original sample images to obtain a number of intensity corrected sample images; then calculates and obtains the Mueller matrix element image and polarization characteristic parameter image corresponding to the sample, thereby realizing high-precision polarization characteristic parameter measurement. The present invention performs light intensity correction on the original sample image, and uses the Fourier filtering method to quickly eliminate the influence of the Gaussian distribution of the laser intensity, thereby improving the measurement accuracy.

[0041] (2) The polarization characteristic parameter measurement method provided by the present invention can be specifically applied to the measurement of polarization characteristic parameters of living tissues, and can realize instant, non-contact, and high-precision measurement of polarization optical characteristic parameters of living tissues, thereby assisting doctors in diagnosing tissue pathological conditions and greatly shortening the diagnosis time compared to traditional pathological detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic diagram of the structure of a polarization characteristic parameter measurement system provided in Example 1 of the present invention.

[0043] Among them, 1-laser, 2-beam expander, 3-first polarizer, 4-first phase delay, 5-first rotating table, 6-plate clamp, 7-second phase delay, 8-second rotating table, 9-second polarizer, 10-image acquisition module, 11-computing control module. DETAILED DESCRIPTION

[0044] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0045] Embodiment 1:

[0046] Embodiment 1 provides a polarization characteristic parameter measurement system, see Figure 1 , including: a light source module, a polarization modulation module, a stage, a polarization demodulation module, an image acquisition module 10 (also understood as a light intensity acquisition module) and a calculation control module 11.

[0047] The light source module includes a laser 1 and a beam expander 2 arranged in sequence along the optical path; the laser 1 can use a helium-neon laser as an illumination light source, which has the advantage of good monochromaticity and can provide a spectrum output with a narrower line width, thereby avoiding the error of wave plate delay caused by a wide spectrum line. If this system is used for medical auxiliary detection, a 5-7mW helium-neon laser can be specifically used to ensure safety and avoid unnecessary damage to tissue samples.

[0048] The polarization modulation module includes a first polarizer 3 and a first phase retarder 4 (for example, a quarter wave plate can be used) arranged in sequence along the optical path, and the first phase retarder 4 is embedded in a first rotating platform 5. The stage includes a plate clamp 6 and a support frame, and the plate clamp 6 is fixed by the support frame. The polarization analysis demodulation module includes a second phase retarder 7 (for example, a quarter wave plate can be used) and a second polarizer 9 arranged in sequence along the optical path, and the second phase retarder 7 is embedded in a second rotating platform 8.

[0049] The image acquisition module 10 may be a CCD camera; the calculation control module 11 is connected to the first rotating stage 5, the second rotating stage 8 and the CCD camera respectively.

[0050] The expanded collimated laser light emitted by the light source module passes through the polarization modulation module and is incident obliquely on the sample of the mounting plate clamp 6 of the stage, and the reflected light is emitted vertically and passes through the polarization analysis demodulation module and the image acquisition module 10 in sequence.

[0051] The initial state of the polarization characteristic parameter measurement system is: the polarization direction of the laser emitted by the light source module is consistent with the light transmission direction of the first polarizer 3 in the polarization modulation module, the fast axis direction of the first phase retarder 4 in the polarization modulation module, and the light transmission direction of the second polarizer 9 in the polarization analyzer and demodulator module, and the fast axis direction of the second phase retarder 7 in the polarization analyzer and demodulator module.

[0052] The computing control module 11 is used to control the first rotating table 5 and the second rotating table 8 to rotate according to a preset angle respectively, and then control the image acquisition module 10 to acquire images. The first rotating table 5 and the second rotating table 8 rotate in the same direction along the light propagation direction. For example, the computing control module 11 controls the first rotating table 5 and the second rotating table 8 to rotate according to a specific angle with an angle ratio of 1:5, and then controls the CCD camera to acquire images, and repeats this cycle several times (generally 16 times or 32 times). In a preferred solution, the first rotating table 5 can be controlled to rotate 5.625° and the second rotating table 8 can be controlled to rotate 28.125° before acquiring images. The above rotation angles can achieve a better balance between accuracy and time cost. For example, the first rotating table 5 and the second rotating table 8 can both rotate clockwise along the direction of the incident light.

[0053] The calculation control module 11 is also used to receive the acquired image, and process the image to calculate the Mueller matrix and sample polarization characteristic parameters.

[0054] Specifically, the calculation control module is also used to reconstruct the laser elliptical intensity distribution according to the laser spot image to obtain an elliptical Gaussian intensity distribution map, and map the elliptical Gaussian intensity distribution map to several original sample images to obtain several intensity-corrected sample images.

[0055] The computing control module can perform the following operations:

[0056] Take the elliptical short axis intensity sequence I corresponding to the laser spot image sn , I sn =[i s1 ,i s2 ,i s3 ,...,i sn ], where n = 1, 2, 3, ..., N, N is the ellipse minor axis intensity sequence I sn The length of the ellipse minor axis intensity sequence I sn Perform Fourier transform to obtain the sequence F after Fourier transform sn ; The Fourier transformed sequence F sn Denoise and obtain the denoised sequence F sdnn ; For the denoised sequence F sdnnPerform inverse Fourier transform to obtain the elliptical short-axis Gaussian light intensity sequence I corresponding to the laser spot image gaosin ; Based on the elliptical minor axis Gaussian light intensity sequence I gaosin The elliptical Gaussian light intensity distribution diagram is obtained.

[0057] The calculation control module is also used to calculate the Mueller matrix element image corresponding to the sample according to a plurality of light intensity corrected sample images; the calculation control module is also used to calculate the polarization characteristic parameter image corresponding to the sample according to the Mueller matrix element image corresponding to the sample.

[0058] The polarization characteristic parameter measurement system provided in Example 1 performs polarization measurement based on the double rotating wave plate method. The system can solve the problem in the prior art that when the double rotating wave plate method is used for polarization measurement, the uneven distribution of laser Gaussian light intensity affects the measurement accuracy of the polarization characteristic parameters. The system can effectively improve the measurement accuracy of the polarization characteristic parameters and assist doctors in more accurately diagnosing the pathological state of tissue samples.

[0059] Using the above system, the present invention also proposes a method for measuring polarization characteristic parameters, which is described below with reference to Example 2.

[0060] Embodiment 2:

[0061] Embodiment 2 provides a method for measuring polarization characteristic parameters, comprising the following steps:

[0062] Step 1: construct a polarization characteristic parameter measurement system, which includes a light source module, a polarization modulation module, a stage, a polarization analyzer and demodulator module, an image acquisition module and a calculation control module.

[0063] Specifically, the polarization characteristic parameter measurement system is described in the description of Example 1, which will not be described again here.

[0064] Step 2, placing the sample in the first area of ​​the stage; the laser emitted by the light source module is obliquely incident on the stage after passing through the polarization modulation module, and the reflected light is vertically emitted and passes through the polarization analyzer demodulation module and the image acquisition module in sequence; the calculation control module is used to control the rotation angle of the first rotating table in the polarization modulation module and the second rotating table in the polarization analyzer demodulation module, and the calculation control module is used to control the image acquisition module to perform image acquisition to obtain a plurality of original sample images.

[0065] Step 3, replace the sample with a blackboard, and place the blackboard in the first area of ​​the stage (i.e., place the blackboard at the same position as the plate holder); while keeping the parameters of the polarization characteristic parameter measurement system unchanged, collect a laser spot image.

[0066] Step 4: using the calculation control module to reconstruct the laser elliptical intensity distribution according to the laser spot image to obtain an elliptical Gaussian intensity distribution map, and mapping the elliptical Gaussian intensity distribution map to a number of original sample images to obtain a number of intensity-corrected sample images.

[0067] The step 4 is described in detail below, which mainly includes the following main steps:

[0068] (1) Since the laser irradiates the sample at an oblique incidence, the light spot captured by the camera is elliptical. The elliptical short axis intensity sequence I corresponding to the laser spot image is taken. sn , denoted as I ss =[i s1 ,i s2 ,i s3 , ..., i sn ] Where n = 1, 2, 3, ..., N, N is the ellipse minor axis intensity sequence I sn The length of the ellipse minor axis intensity sequence I sn Perform Fourier transform to obtain the sequence F after Fourier transform sn .

[0069] In addition, based on the Fourier transformed sequence F sn We can also get the real coefficient sequence A sn 、Fourier imaginary coefficient sequence B sn 、MOD sn Generate a standard Gaussian distribution sequence and perform Fourier transform on it to obtain the standard Gaussian distribution sequence Fourier real number coefficient sequence A gn 、Fourier imaginary coefficient sequence B gn 、MOD gn By comparing A sn and A gn , B sn and B gn 、MOD sn and MOD gn , we can find the Fourier coefficient A of the elliptical short axis intensity sequence of the laser spot image sn , B sn 、MOD sn There is noise, but the profile is similar to the Fourier coefficient A of the standard Gaussian distribution sequence gn , B gn 、MOD gn Therefore, the next step is to perform denoising.

[0070] (2) The Fourier transformed sequence F sn Denoise and obtain the denoised sequence F sdnn .

[0071] For example, the Fourier transformed sequence F sn After a low-pass filter H n , to realize the Fourier transformed sequence F sn De-noising; the low-pass filter H n Only the DC component and the fundamental frequency signal are retained.

[0072] (3) The denoised sequence F sdnn Perform inverse Fourier transform to obtain the elliptical short-axis Gaussian light intensity sequence I corresponding to the laser spot image gaosin Based on the ellipse minor axis Gaussian intensity sequence I gaosin The elliptical Gaussian light intensity distribution diagram is obtained.

[0073] Specifically, the method for obtaining the elliptical Gaussian light intensity distribution diagram includes:

[0074] Obtain the number of pixels a occupied by the major axis of the ellipse of the laser spot image (which can also be considered as the length of the major axis), the number of pixels b occupied by the minor axis of the ellipse (which can also be considered as the length of the minor axis), and the number of pixels c occupied by the focal length (which can also be considered as the focal length) to generate a black image with a length of 2a and a width of 2b, that is, the grayscale value of each pixel is 0.

[0075] Generate long axis sequence A m =[ab 1 / M,ab 2 / M,ab 3 / M,...,ab m / M], short axis sequence B m =[1, 2, ..., M] (where m = 1, 2, 3 ... b, M = N / 2 = b), focal length sequence C m =[cb 1 / M,cb 2 / M,cb 3 / M,...,cb m / M]; where b m For short axis sequence B m The elements in .

[0076] That is, the short axis sequence is a natural number starting from 1 to b (b corresponds to the short axis length), the long axis sequence is a sequence obtained based on the long axis length a, the short axis sequence element, and the short axis length b, and the focal length sequence is a sequence obtained based on the focal length c, the short axis sequence element, and the short axis length b.

[0077] Perform M cycles of judgment to determine whether each point (x i ,y j) is on the circumference of the current ellipse, where M=N / 2=b, i=0,1,2,...,2a, j=0,1,2,...,2b.

[0078] When a point is judged in the mth cycle, if it is judged that the point is on the circumference of the ellipse, the light intensity value of the point is replaced by the Gaussian light intensity value corresponding to n = N / 2 + m, recorded as I(i,j) = i gaosi(N / 2+m) , corresponding to I gaosin The value of the element with subscript n=N / 2+m in the sequence. Otherwise (i.e., it is determined that the point is not on the circumference of the ellipse), the light intensity value of the point is kept unchanged (i.e., the original pixel value of 0 is kept unchanged).

[0079] In the mth cycle, determine whether a certain point is close to the first focus F 1 (a m -c m ,M), the second focus F 2 (a m +c m ,M) Whether the sum of the distances is 2a, where a m A is the long axis sequence m The elements in c m is the focal length sequence C m The elements in If the sum is 2a, the point is judged to be on the circumference of the ellipse.

[0080] After completing the cyclic judgment, an elliptical Gaussian light intensity distribution diagram with a length of 2a and a width of 2b is obtained.

[0081] An elliptical Gaussian light intensity distribution diagram with a length of 2a and a width of 2b is mapped to a number of original sample images to obtain a number of light intensity corrected sample images.

[0082] Step 5: Utilizing the calculation control module, the Mueller matrix element image corresponding to the sample is calculated based on a plurality of light intensity corrected sample images.

[0083] The method for calculating the Mueller matrix element image may adopt an existing algorithm, and specifically refer to the Mueller matrix calculation algorithm proposed by RMAAzzam or algorithms proposed by other patents, such as the algorithm described in patent CN 111366536 A.

[0084] Step 6: Using the calculation control module, calculate the polarization characteristic parameter image corresponding to the sample according to the Mueller matrix element image corresponding to the sample.

[0085] Specifically, the polarization characteristic parameter image corresponding to the sample is obtained by calculating the Mueller matrix element image corresponding to the sample using the Mueller matrix decomposition method and the Mueller matrix transformation method.

[0086] The present invention aims at the problem of uneven intensity of parameter graph introduced by Gaussian distribution of laser spot light intensity, and proposes a Fourier filtering method, which can quickly eliminate the influence of Gaussian distribution of laser light intensity. In addition, the polarized laser light source also has higher energy density and spatial coherence, which can effectively improve the measurement accuracy.

[0087] The polarization characteristic parameter measurement method provided by the present invention can be specifically applied to the measurement of polarization characteristic parameters of living tissues, and can realize instant, non-contact, and high-precision measurement of polarization optical characteristic parameters of living tissues, assisting doctors in diagnosing tissue pathological conditions, and can greatly shorten the diagnosis time compared with traditional pathological detection.

[0088] When specifically applied to the measurement of polarization characteristic parameters of living tissue, the sample is a living tissue sample, and the living tissue sample is obtained in the following manner: the living tissue is cut into a thin slice having a first thickness (for example, a thickness within 5 mm), the thin slice is placed on a glass slide, covered with a cover glass and air bubbles are accumulated to obtain the living tissue sample. During the operation, the glass slide is placed on the object holder clamp of the stage. The plane of the glass slide is parallel to the plane of the object holder clamp of the stage, which can ensure that the laser is obliquely incident on the surface of the biopsy tissue sample, and the CCD camera collects the scattered light reflected from the surface of the biopsy sample vertically, avoiding the collection of high-intensity laser spots in the direction of the laser mirror reflection. Then, a number of tissue images (for example, 32 liver tissue images) and a laser spot image are obtained in the manner described in Example 2, and then a number of light intensity corrected tissue images, Mueller matrix element images of tissue samples, and polarization characteristic parameter images of tissue samples are obtained.

[0089] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for measuring polarization characteristic parameters, characterized in that: The following steps are involved: Step 1, building a polarization characteristic parameter measurement system, wherein the polarization characteristic parameter measurement system includes a light source module, a polarization modulation module, a stage, a polarization analyzer demodulation module, an image acquisition module and a calculation control module; Step 2, placing the sample in the first area of ​​the stage; the laser light emitted by the light source module is incident obliquely onto the stage after passing through the polarization modulation module, and the reflected light is emitted vertically and passes through the polarization analysis demodulation module and the image acquisition module in sequence; Using the calculation control module to control the rotation angles of the first rotating stage in the polarization modulation module and the second rotating stage in the polarization detection and demodulation module, and using the calculation control module to control the image acquisition module to perform image acquisition to obtain a plurality of original sample images; Step 3, replacing the sample with a blackboard, and placing the blackboard in the first area of ​​the stage; acquiring a laser spot image while keeping the parameters of the polarization characteristic parameter measurement system unchanged; Step 4: using the calculation control module to reconstruct the laser elliptical intensity distribution according to the laser spot image to obtain an elliptical Gaussian intensity distribution map, and mapping the elliptical Gaussian intensity distribution map to a number of original sample images to obtain a number of intensity-corrected sample images; The step 4 includes the following sub-steps: Take the elliptical short axis intensity sequence I corresponding to the laser spot image sn , I sn =[i s1 ,i s2 ,i s3 , ..., i sn ], where n = 1, 2, 3, ..., N, N is the ellipse minor axis intensity sequence I sn Length; For the elliptical minor axis intensity sequence I sn Perform Fourier transform to obtain the sequence F after Fourier transform sn ; The Fourier transformed sequence F sn Denoise and obtain the denoised sequence F sdnn ; For the denoised sequence F sdnn Perform inverse Fourier transform to obtain the elliptical short-axis Gaussian light intensity sequence I corresponding to the laser spot image gaosin ; Based on the elliptical minor axis Gaussian light intensity sequence I gaosin Obtaining the elliptical Gaussian light intensity distribution diagram; The method for obtaining the elliptical Gaussian light intensity distribution diagram comprises: Obtain the number of pixels a occupied by the major axis of the ellipse, the number of pixels b occupied by the minor axis of the ellipse, and the number of pixels c occupied by the focal length of the laser spot image, and generate a black image with a length of 2a and a width of 2b; perform M cycles of judgment to determine whether each point (x i ,y j ) is on the circumference of the ellipse, where M = N / 2 = b, i = 0, 1, 2, ..., 2a, j = 0, 1, 2, ..., 2b; when a point is judged on the circumference of the ellipse in the mth cycle, if the point is judged to be on the circumference of the ellipse, the light intensity value of the point is replaced by the Gaussian light intensity value corresponding to n = N / 2 + m, recorded as I(i, j) = i gaosi(N / 2+m) ; Otherwise, keep the light intensity value of the point unchanged; After completing the loop judgment, an elliptical Gaussian light intensity distribution diagram with a length of 2a and a width of 2b is obtained; Determine each point (x i ,y j ) is on the circumference of an ellipse: Generate long axis sequence A m =[ab1 / M,ab2 / M,ab3 / M,…,ab m / M], short axis sequence B m = [1, 2, ..., M] and focal length sequence C m =[cb1 / M,cb2 / M,cb3 / M,...,cb m / M]; where b m For short axis sequence B m Elements in In the mth cycle, determine whether a certain point is close to the first focus F1 (a m -c m , M), the second focus F2 (a m +c m , M) Is ​​the sum of the distances 2a, where a m A is the long axis sequence m The elements in c m is the focal length sequence C m The elements in If the sum is 2a, the point is judged to be on the circumference of the ellipse; Step 5, using the calculation control module to calculate the Mueller matrix element image corresponding to the sample according to a plurality of light intensity corrected sample images; Step 6: Using the calculation control module, calculate the polarization characteristic parameter image corresponding to the sample according to the Mueller matrix element image corresponding to the sample.

2. The polarization characteristic parameter measurement method according to claim 1, characterized in that: The initial state of the polarization characteristic parameter measurement system is that the polarization direction of the laser emitted by the light source module is consistent with the light transmission direction of the first polarizer in the polarization modulation module, the fast axis direction of the first phase retarder in the polarization modulation module, and the light transmission direction of the second polarizer in the polarization analyzer and demodulator module, and the fast axis direction of the second phase retarder in the polarization analyzer and demodulator module; The computing control module controls the first rotating stage and the second rotating stage to rotate according to preset angles respectively, and then controls the image acquisition module to acquire images. The first rotating stage and the second rotating stage rotate in the same direction along the light propagation direction.

3. The polarization characteristic parameter measurement method according to claim 1, characterized in that: By taking the Fourier transformed sequence F sn After a low-pass filter H n , to realize the Fourier transformed sequence F sn Denoising; the low-pass filter H n Only the DC component and the fundamental frequency signal are retained.

4. The polarization characteristic parameter measurement method according to claim 1, characterized in that: In the step 6, the polarization characteristic parameter image corresponding to the sample is obtained by calculating the Mueller matrix element image corresponding to the sample using the Mueller matrix decomposition method and the Mueller matrix transformation method.

5. The polarization characteristic parameter measurement method according to claim 1, characterized in that: The sample is a living tissue sample, which is obtained by the following method: cutting the living tissue into thin slices with a first thickness, placing the thin slices on a glass slide, covering them with a cover glass, and squeezing out air bubbles to obtain the living tissue sample.

6. A polarization characteristic parameter measurement system, characterized in that: include: Light source module, polarization modulation module, stage, polarization analysis and demodulation module, image acquisition module and calculation control module; The polarization characteristic parameter measurement system is used to execute the steps in the polarization characteristic parameter measurement method according to any one of claims 1 to 5.

7. The polarization characteristic parameter measurement system according to claim 6, characterized in that: The light source module includes a laser and a beam expander arranged in sequence along the light path; The polarization modulation module comprises a first polarizer and a first phase retarder arranged in sequence along the optical path, and the first phase retarder is embedded in the first rotating platform; The loading platform comprises a storage plate clamp and a support frame, and the storage plate clamp is fixed by the support frame; The polarization analyzer and demodulator module comprises a second phase retarder and a second polarizer which are sequentially arranged along the optical path, and the second phase retarder is embedded in the second rotating platform; The image acquisition module adopts a CCD camera; The computing control module is connected to the first rotating stage, the second rotating stage and the CCD camera respectively.

Images