High-contrast and high-precision phase delay visualization method and system

Abstract

The present invention discloses a high-contrast and high-precision phase delay visualization method and system, which can improve the measurement accuracy and contrast of phase delay. By splitting the full interference spectrum to obtain multiple groups of Jones matrix diagrams, and converting the multiple groups of Jones matrix diagrams into multiple Mueller matrix diagrams, a Mueller matrix containing depolarization information caused by noise is finally obtained by summing and averaging. The depolarization introduced by noise is removed by polar decomposition, leaving only the Mueller matrix containing phase delay information, and then the horizontal line phase delay and 45° line phase delay that can be achieved with high precision in low signal-to-noise ratio areas are obtained. These are displayed in color, and the brightness of the vector phase delay true color diagram is adjusted using the color space principle to achieve high-contrast phase delay visualization. This solution not only avoids the influence of the system signal-to-noise ratio, can achieve high-precision phase delay measurement in low signal-to-noise ratio areas, but also can achieve high-contrast anisotropic microstructure imaging.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical imaging, and in particular relates to a high-contrast and high-precision phase delay visualization method and system. Background Art

[0002] When light is incident on a sample with optical anisotropy, it is typically decomposed into two orthogonal polarized lights, whose propagation speeds and refractive indices are generally different, an effect known as birefringence. Birefringence is an important physical quantity that characterizes optically anisotropic structures. It is closely related to the physical properties of the sample's microstructure, such as tissues such as collagen, muscle, and nerves. In clinical practice, birefringence has been successfully demonstrated as an effective indicator for biological diagnosis. For example, birefringence has been used to quantitatively distinguish different degrees of cervical precancerous lesions; the degree of liver cirrhosis can also be determined by measuring changes in birefringence.

[0003] Many polarization techniques have been developed to measure the birefringence properties of samples, including field-based Jones algebra and intensity-based Mueller algebra. Polarization-sensitive OCT (PS-OCT) based on the Jones matrix can not only obtain the deep structural information of the sample, but also obtain birefringence information that can reflect the microscopic and even ultramicroscopic structure of the sample, and has received widespread attention. The Mueller matrix-based polarization imaging system (MMIP) is more popular in obtaining all the polarization properties of the sample (such as scattering, dichroism, and birefringence). The above technologies can provide more accurate anisotropic structural information by detecting the birefringence parameters of the sample, and have been widely used to characterize the microstructural characteristics of the sample at the tissue level (nerve bundles, blood vessels, muscles, etc.) and the cellular level (cell nucleus, chromosomes, etc.).

[0004] As a functional extension of optical coherence tomography (OCT), polarization-sensitive OCT (PS-OCT) usually uses the Jones matrix eigenvalue method to detect the birefringence characteristics of the sample. Traditionally, the Jones matrix eigenvalue method is a widely used and accepted method for solving polarization information. First, the similarity matrix of the measured Jones matrix is obtained, and then the eigenvalue decomposition of the similarity matrix is performed to obtain the phase delay information. However, the measurement accuracy of the phase delay is highly dependent on the signal-to-noise ratio of the system. In low signal-to-noise ratio areas, especially in deep imaging areas, the measured value of the phase delay will deviate seriously from the true value and vary randomly, which greatly reduces the image contrast and the measurement accuracy of the phase delay.

[0005] In addition, as a basic functional indicator of birefringence, in most polarization imaging techniques, phase delay parameters related to birefringence characteristics are usually detected and analyzed. Analyzing changes in phase delay can help understand the physical properties and structural changes of the sample, and can greatly improve the specific contrast of the sample. Especially in the biomedical field, changes in phase delay can reflect the state of the disease, which helps to better clinical diagnosis and classification. Currently, scalar phase delay parameters are widely used, benefiting from their ability to visualize ultrastructural density (for example, the density of collagen fibers). However, due to its inherent limitations, scalar phase delay cannot fully describe the characteristics of birefringence and shows relatively low contrast for internal anisotropic structures, which seriously hinders the application of advanced polarization imaging technology in related fields. Therefore, vector phase delay, including horizontal, 45°-linear and circular phase delay components, has received increasing attention. However, it is currently difficult and time-consuming for researchers to read and analyze these three components simultaneously.

[0006] The above-mentioned problems of low-precision and low-contrast phase delay measurement methods have seriously restricted the application and promotion of advanced polarization imaging systems in important fields. Summary of the Invention

[0007] In view of this, the present invention provides a high-contrast and high-precision phase delay visualization method and system, which can improve the measurement accuracy and contrast of the sample phase delay.

[0008] To achieve the above object, the present invention provides a high-contrast and high-precision phase delay visualization method, comprising the following steps:

[0009] Step 1: The PS-OCT system measures two mutually orthogonal full interference spectra.

[0010] Step 2: Split the two full interference spectrum signals respectively through m narrow-band window functions to obtain m independent narrow-band sub-interference spectra of size n.

[0011] Step 3: Zero-padded each of the m discrete narrow-band interference spectra of size n to obtain an interference spectrum of size N, and then performed Fourier transform to obtain m groups of Jones maps. The Jones map is composed of Jones matrices. Each pixel in the Jones map represents a Jones matrix, and the elements in the Jones matrix are Jones elements.

[0012] Step 4: The sub-pixel cross-correlation method is used to achieve spatial alignment between each Jones element in the Jones matrix; the adaptive averaging method is used to eliminate the global phase of the spatially adjacent Jones elements after position alignment; the obtained Jones matrix is calibrated with the surface of the sample to be tested or the surface of the upper layer of the sample to be tested as the reference surface to obtain m groups of similar Jones maps; finally, the m groups of similar Jones maps are converted into corresponding m groups of Mueller maps by mathematical methods.

[0013] Step 5: Average the m groups of Mueller plots to obtain the averaged Mueller matrix. Perform polar decomposition on the averaged Mueller matrix to obtain a Mueller matrix containing only phase delay information, and then obtain the horizontal line phase delay, 45° line phase delay, and circular phase delay.

[0014] Step 6: Map the obtained horizontal line phase delay, 45° line phase delay, and circular phase delay to the green, red, and blue channels, respectively. Then, use the true color image processing algorithm to synthesize the vector phase delay true color image. In addition, use the color space principle to adjust the brightness of the vector phase delay true color image to achieve high-contrast phase delay visualization.

[0015] Furthermore, in step 1, the PS-OCT system measures two mutually orthogonal full interference spectra, and then also includes removing the DC term and compensating for dispersion on the two full interference spectra.

[0016] Preferably, in step 4, the surface of the sample to be tested or the surface of the upper layer of the sample to be tested is used as a reference surface to calibrate the obtained Jones matrix to obtain m groups of similar Jones graphs, specifically:

[0017]

[0018] Among them J C is the similar Jones matrix; η H η V are the detection efficiencies of the horizontal and vertical detection channels, respectively; are the horizontal polarization component and the vertical polarization component of the reference light, * is the conjugation operation; J out J is the Jones matrix of the path from sample to detector; sample,T is the Jones matrix of the sample; z i is the depth of the Jones graph at layer i; J sample,T (z i ) refers to the sample at a depth of z i The Jones matrix below.

[0019] Preferably, in step 4, the m groups of similar Jones graphs are converted into corresponding m groups of Mueller graphs by mathematical means, specifically:

[0020]

[0021] Where M is the Mueller matrix; U is the Pauli matrix; and J is the calibrated Jones matrix.

[0022] Preferably, step five is specifically as follows:

[0023] The obtained m groups of Mueller diagrams are averaged to obtain the mean Mueller matrix diagram M;

[0024] Perform polar decomposition on the averaged Mueller matrix to remove the depolarization and double attenuation characteristics to obtain the Mueller matrix M containing only phase delay information R ;

[0025] Then, the obtained phase delay matrix M R By finding the trace, we can get the scalar phase delay value R:

[0026] Where tr(M R ) is the pair matrix M R Seeking traces;

[0027] Vector Phase Delay The three components are: horizontal line phase delay R H , 45° line phase delay R 45 , circular phase delay R C .

[0028] Another embodiment of the present invention further provides a high-contrast and high-precision phase delay visualization system, a full interference spectrum processing module, a spectrum segmentation module, a sub-interference spectrum processing module, a matrix processing module and a visualization module.

[0029] The full interference spectrum processing module receives the two mutually orthogonal full interference spectra measured by the PS-OCT system, removes the DC term and compensates for the dispersion of the two full interference spectra, and then outputs them to the spectrum segmentation module.

[0030] The spectrum segmentation module is used to split the two full interference spectrum signals respectively through m narrowband window functions, thereby obtaining m independent narrowband sub-interference spectrum outputs of size n, which are sent to the sub-interference spectrum processing module.

[0031] The sub-interference spectrum processing module is used to zero-fill each of the m discrete narrow-band sub-interference spectra of size n in each channel to obtain an interference spectrum of size N, and then perform Fourier transform to obtain m groups of Jones maps. The Jones map is composed of a Jones matrix. Each pixel in the Jones map represents a Jones matrix, and the elements in the Jones matrix are Jones elements. The output of the sub-interference spectrum processing module is m groups of Jones maps, which are sent to the matrix processing module.

[0032] The matrix processing module is used to achieve spatial position alignment between each Jones element in the Jones matrix through the sub-pixel cross-correlation method; the spatially adjacent Jones elements after position alignment are respectively subjected to the adaptive averaging method to eliminate the global phase; the obtained Jones matrix is calibrated with the surface of the sample to be tested or the surface of the upper layer of the sample to be tested as the reference surface to obtain m groups of similar Jones maps; finally, the m groups of similar Jones maps are respectively converted into corresponding m groups of Mueller maps through mathematical methods.

[0033] The matrix processing module is also used to average the m groups of Mueller diagrams to obtain the averaged Mueller matrix diagram; the averaged Mueller matrix is subjected to polar decomposition to obtain a Mueller matrix containing only phase delay information, and then the horizontal line phase delay, 45° line phase delay, and circular phase delay are obtained as the output of the matrix processing module and sent to the visualization module.

[0034] The visualization module is used to map the obtained horizontal line phase delay, 45° line phase delay, and circular phase delay into green, red, and blue channels, respectively, and then use a true color image processing algorithm to synthesize a true color image of the vector phase delay. In addition, the brightness of the true color image of the vector phase delay is adjusted using the color space principle to achieve high-contrast phase delay visualization.

[0035] Preferably, in the matrix processing module, the surface of the sample to be tested or the surface of the upper layer of the sample to be tested is used as a reference surface to calibrate the obtained Jones matrix to obtain m groups of similar Jones graphs, specifically:

[0036]

[0037] Among them J C is the similar Jones matrix; η H η V are the detection efficiencies of the horizontal and vertical detection channels, respectively; are the horizontal polarization component and the vertical polarization component of the reference light, * is the conjugation operation; J out J is the Jones matrix of the path from sample to detector; sample,T is the Jones matrix of the sample; zi is the depth of the Jones graph at layer i; J sample,T (z i ) refers to the sample at a depth of z i The Jones matrix below.

[0038] The obtained m groups of Mueller diagrams are averaged to obtain the averaged Mueller matrix diagram; the averaged Mueller matrix is subjected to polar decomposition to obtain a Mueller matrix containing only phase delay information, and then the horizontal line phase delay, 45° line phase delay and circular phase delay are obtained, specifically:

[0039]

[0040] Where M is the Mueller matrix; U is the Pauli matrix; J is the calibrated Jones matrix;

[0041] The obtained m groups of Mueller diagrams are averaged to obtain the Mueller matrix diagram M after the mean.

[0042] Perform polar decomposition on the averaged Mueller matrix to remove the depolarization and double attenuation characteristics to obtain the Mueller matrix M containing only phase delay information R .

[0043] Then, the obtained phase delay matrix M R By finding the trace, we can get the scalar phase delay value R:

[0044] Where tr(M R ) is the pair matrix M R Seeking traces.

[0045] Vector Phase Delay The three components are: horizontal line phase delay R H , 45° line phase delay R 45 , circular phase delay R C .

[0046] Beneficial effects:

[0047] 1. The present invention provides a method for calculating high phase delay measurement accuracy in low signal-to-noise ratio areas. The full interference spectrum is split to obtain multiple groups of Jones matrix diagrams, and the multiple groups of Jones matrix diagrams are converted into multiple Mueller matrix diagrams. Finally, the Mueller matrix containing the depolarization information caused by noise is obtained by the addition and averaging method. The depolarization introduced by noise is removed by the polar decomposition method, leaving only the Mueller matrix containing phase delay information, and then the horizontal line phase delay and 45° line phase delay that can be achieved with high precision in low signal-to-noise ratio areas are obtained. It is displayed in color, and the brightness of the vector phase delay true color diagram is adjusted using the color space principle to achieve high-contrast phase delay visualization. This solution not only avoids the influence of the system signal-to-noise ratio, can achieve high-precision phase delay measurement in low signal-to-noise ratio areas, but also can achieve high-contrast anisotropic microstructure imaging. This method greatly improves the contrast and measurement accuracy of polarization images, and strongly promotes the application of polarization imaging systems.

[0048] 2. This invention provides a method for improving the imaging depth of phase delay maps. Because the proposed method improves the accuracy of phase delay measurements in low signal-to-noise ratio regions, it enhances image contrast in deep imaging regions, thereby improving the effective imaging depth of the phase delay map.

[0049] 3. This invention provides a true-color vector computational imaging method that improves the contrast of phase-delay images. Compared to traditional images, it can provide more microstructural details of tissue samples. Secondly, observing true-color images allows for more comprehensive qualitative analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Shown is a flow chart of a high contrast / high precision phase delay visualization method;

[0051] Figure 2 The graph shows the cumulative phase delay value of the quarter-wave plate as a function of the signal-to-noise ratio. DETAILED DESCRIPTION

[0052] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0053] This invention provides a high-contrast / high-precision phase delay visualization method, comprising full interferometric spectroscopy processing, spectral segmentation, sub-interferometric spectroscopy processing, Jones matrix processing, Mueller matrix processing, and phase delay image processing. The full interferometric spectroscopy processing involves removing the DC term and compensating for dispersion in two mutually orthogonal full interferometric spectra measured by a PS-OCT system. This is a complete workflow.

[0054] Spectral segmentation involves dividing the processed two full interferometer spectrum signals using m narrowband window functions (of size n, where the value of n affects the value of m), thereby obtaining m independent narrowband sub-interferometer spectra of size n. Narrowband spectra can be shaped by window functions, which can be Gaussian, Hanning, Hamming, triangular, or rectangular. A narrowband spectrum is defined as having a bandwidth greater than that of the full interferometer spectrum.

[0055] Sub-interference spectrum processing refers to padding the m discrete narrow-band interference spectra of size n in each channel with zeros to obtain an interference spectrum of size N, and then performing Fourier transform to obtain m groups of Jones diagrams. Each pixel in a diagram represents a Jones matrix, and the elements in the Jones matrix are Jones elements.

[0056] Jones matrix processing involves spatially aligning each Jones element in the Jones matrix using sub-pixel cross-correlation. Adaptive averaging is then performed on adjacent Jones elements after alignment to eliminate global phase. The resulting Jones matrix is calibrated using the surface of the sample under test or the surface above it as a reference surface to obtain m sets of similar Jones maps. Finally, each of these m sets of similar Jones maps is mathematically converted into m corresponding Mueller maps.

[0057] Mueller matrix processing involves averaging the m sets of Mueller plots to obtain the mean Mueller matrix. Polar decomposition is then performed on the mean Mueller matrix to obtain a Mueller matrix containing only phase delay information, which in turn determines the horizontal and 45° line phase delays. This step achieves high precision and eliminates the effects of noise on phase delay. By using polar decomposition, noise is converted into another optical parameter, eliminating its influence on phase delay measurement.

[0058] Phase delay image processing involves mapping the obtained horizontal line phase delay and 45° line phase delay to the green and red channels, respectively, setting the blue channel to a constant value a, and then using a true color image processing algorithm to synthesize a true color image of the vector phase delay. In addition, the brightness of the true color image of the vector phase delay is adjusted using the color space principle to achieve high-contrast phase delay visualization.

[0059] Example 1:

[0060] Figure 1This is a flowchart of the high-contrast / high-precision phase lag visualization method. It includes full interferometry spectroscopy processing, spectral segmentation, sub-interferometry spectroscopy processing, Jones matrix processing, Mueller matrix processing, and phase lag image processing. Full interferometry spectroscopy processing involves removing the DC term and performing dispersion compensation on the two mutually orthogonal full interferometry spectra measured by the PS-OCT system.

[0061] Spectral segmentation refers to the process of splitting the two processed full interference spectrum signals by three narrowband window functions (size of 350 pixels), thereby obtaining three independent narrowband sub-interference spectra of 350 pixels in size. Among them, the narrowband spectrum can be shaped by the window function, and the window function adopts the Gaussian window function;

[0062] Sub-interference spectrum processing refers to padding the three discrete narrow-band interference spectra of 350 pixels in each channel with zeros to obtain interference spectra of 1024 pixels in size, and then performing Fourier transform to obtain three sets of Jones diagrams.

[0063] Jones matrix processing involves spatially aligning each Jones element in the Jones matrix using sub-pixel cross-correlation. Adaptive averaging is then performed on adjacent Jones elements after alignment to eliminate global phase. The resulting Jones matrix is calibrated using the surface of the sample under test as a reference. Three sets of similar Jones maps are obtained using the following equation.

[0064]

[0065] Among them J C Similar Jones matrix, η H η V Detection efficiency of horizontal and vertical detection channels The horizontal polarization component and the vertical polarization component of the reference light, *conjugate, J out is the Jones matrix of the path from sample to detector, J sample,T Jones matrix of the sample, z i is the depth of the Jones graph at layer i; J sample,T (z i ) refers to the sample at a depth of z i Jones matrix below;

[0066] The three calibrated Jones graphs are converted into three Mueller graphs using the following formula:

[0067]

[0068] Among them, M is the Mueller matrix; U is the Pauli matrix, J is the calibrated Jones matrix;

[0069] Mueller matrix processing refers to adding and averaging the three converted Mueller matrices.

[0070]

[0071] Where N is the number of measurements, M (n) Mueller matrix of the nth measurement;

[0072] The Mueller matrix containing (1) depolarization information caused by system instability and speckle noise; (2) double attenuation characteristics caused by the system itself and the sample; and (3) birefringence caused by the system and the sample is obtained. It is shown as follows

[0073]

[0074] Among them, m 00 ~m 33 are the 16 subgraphs in the Mueller matrix, M Δ is the depolarization matrix, M R is the phase delay matrix, M D is a double attenuation matrix.

[0075] The scalar bidirectional attenuation value D can be first obtained through the Mueller matrix:

[0076]

[0077] Bidirectional attenuation matrix M D Expressed as:

[0078]

[0079]

[0080] Among them, T represents transpose, T u represents the transmittance of unpolarized light, is the vector bidirectional attenuation, m D M D The lower right triangular matrix of .

[0081] Vector bidirectional attenuation The three components are horizontal bidirectional attenuation D H , 45° bidirectional attenuation D 45 , circular bidirectional attenuation D C , specifically expressed as follows:

[0082]

[0083] in is the bidirectional attenuation direction vector, and we continue to obtain the depolarization matrix. First, we obtain the intermediate matrix:

[0084] M'=M Δ M R =MM D -1

[0085] Where m' is the 3×3 matrix under M', det(M') determines the sign of the following equation, and λ1, λ2, and λ3 are m'(m') T Characteristic roots of:

[0086]

[0087] Then we can get the depolarized Mueller matrix M Δ :

[0088]

[0089] The scalar debiasing value Δ is:

[0090]

[0091] Vector polarization degree The three components of horizontal linear polarization P H , 45° linear polarization degree P 45 , circular polarization degree P C The calculation formula is as follows:

[0092]

[0093] Finally, the phase delay matrix M is obtained R :

[0094]

[0095] m R is the phase delay matrix M R The lower right triangular matrix, scalar phase delay value R:

[0096]

[0097] Vector Phase Delay The three components of the horizontal line phase delay R H , 45° line phase delay R 45 , circular phase delay R C The calculation formula is as follows:

[0098]

[0099] Among them, (a1, a2, a3) is the fast axis direction vector, i=1, 2, 3, ε ijk It is the Levi-Civita symbol. Unit vector.

[0100] Phase delay image processing refers to delaying the vector phase The horizontal line phase delay component P H 、R H , 45° line phase delay R 45 , and circular phase delay R C They are mapped into three channels: green, red and blue respectively, and then the three channels are synthesized into a true color map of vector polarization degree using true color image processing algorithm.

[0101] Example 2:

[0102] Another embodiment of the present invention further provides a high-contrast and high-precision phase delay visualization system, characterized by a full interference spectrum processing module, a spectrum segmentation module, a sub-interference spectrum processing module, a matrix processing module and a visualization module.

[0103] The full interference spectrum processing module receives the two mutually orthogonal full interference spectra measured by the PS-OCT system, removes the DC term and compensates for the dispersion of the two full interference spectra, and then outputs them to the spectrum segmentation module.

[0104] The spectrum segmentation module is used to split the two full interference spectrum signals respectively through m narrowband window functions, thereby obtaining m independent narrowband sub-interference spectrum outputs of size n, which are sent to the sub-interference spectrum processing module.

[0105] The sub-interference spectrum processing module is used to zero-fill each of the m discrete narrow-band sub-interference spectra of size n in each channel to obtain an interference spectrum of size N, and then perform Fourier transform to obtain m groups of Jones maps. The Jones map is composed of a Jones matrix. Each pixel in the Jones map represents a Jones matrix, and the elements in the Jones matrix are Jones elements. The output of the sub-interference spectrum processing module is m groups of Jones maps, which are sent to the matrix processing module.

[0106] The matrix processing module is used to achieve spatial position alignment between each Jones element in the Jones matrix through the sub-pixel cross-correlation method; the spatially adjacent Jones elements after position alignment are respectively subjected to the adaptive averaging method to eliminate the global phase; the obtained Jones matrix is calibrated with the surface of the sample to be tested or the surface of the upper layer of the sample to be tested as the reference surface to obtain m groups of similar Jones maps; finally, the m groups of similar Jones maps are respectively converted into corresponding m groups of Mueller maps through mathematical methods.

[0107] The matrix processing module is also used to average the m groups of Mueller diagrams to obtain the averaged Mueller matrix diagram; the averaged Mueller matrix is subjected to polar decomposition to obtain a Mueller matrix containing only phase delay information, and then the horizontal line phase delay, 45° line phase delay, and circular phase delay are obtained as the output of the matrix processing module and sent to the visualization module.

[0108] The visualization module is used to map the obtained horizontal line phase delay, 45° line phase delay, and circular phase delay into green, red, and blue channels, respectively, and then use a true color image processing algorithm to synthesize a true color image of the vector phase delay. In addition, the brightness of the true color image of the vector phase delay is adjusted using the color space principle to achieve high-contrast phase delay visualization.

[0109] In the matrix processing module, the surface of the sample to be tested or the surface above the sample to be tested is used as the reference surface to calibrate the obtained Jones matrix to obtain m groups of similar Jones graphs, specifically:

[0110]

[0111] Among them J C is the similar Jones matrix; η H η V are the detection efficiencies of the horizontal and vertical detection channels, respectively; are the horizontal polarization component and the vertical polarization component of the reference light, * is the conjugation operation; J out J is the Jones matrix of the path from sample to detector; sample,T is the Jones matrix of the sample; z i is the depth of the Jones graph at layer i; J sample,T (z i ) refers to the sample at a depth of z i Jones matrix below;

[0112] The obtained m groups of Mueller diagrams are averaged to obtain the averaged Mueller matrix diagram; the averaged Mueller matrix is subjected to polar decomposition to obtain a Mueller matrix containing only phase delay information, and then the horizontal line phase delay, 45° line phase delay and circular phase delay are obtained, specifically:

[0113]

[0114] Where M is the Mueller matrix; U is the Pauli matrix; J is the calibrated Jones matrix;

[0115] The obtained m groups of Mueller diagrams are averaged to obtain the mean Mueller matrix diagram M;

[0116] Perform polar decomposition on the averaged Mueller matrix to remove the depolarization and double attenuation characteristics to obtain the Mueller matrix M containing only phase delay information R ;

[0117] Then, the obtained phase delay matrix M R By finding the trace, we can get the scalar phase delay value R:

[0118] Where tr(M R ) is the pair matrix M R Seeking traces;

[0119] Vector Phase Delay The three components are: horizontal line phase delay R H , 45° line phase delay R 45 , circular phase delay R C .

[0120] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high-contrast and high-precision phase delay visualization method, characterized in that The steps include: Step 1: The PS-OCT system measures two mutually orthogonal full-interference spectra; Step 2: Split the two full interference spectrum signals respectively by m narrowband window functions, thereby obtaining m independent narrowband sub-interference spectra of size n; Step 3: Zero-padded each of the m discrete narrowband sub-interference spectra of size n to obtain an interference spectrum of size N, and then Fourier transformed to obtain m groups of Jones maps. The Jones map is composed of Jones matrices. Each pixel in the Jones map represents a Jones matrix, and the elements in the Jones matrix are Jones elements. Step 4: Use the sub-pixel cross-correlation method to achieve spatial alignment between each Jones element in the Jones matrix; use the adaptive averaging method to eliminate the global phase of the spatially adjacent Jones elements after position alignment; The surface of the sample to be tested or the surface above the sample to be tested is used as a reference surface, and the obtained Jones matrix is calibrated to obtain m groups of similar Jones graphs; finally, the m groups of similar Jones graphs are respectively converted into corresponding m groups of Mueller graphs by mathematical methods; Step 5: Average the m groups of Mueller graphs to obtain the averaged Mueller matrix; perform polar decomposition on the averaged Mueller matrix to obtain a Mueller matrix containing only phase delay information, and then obtain the horizontal line phase delay, 45° line phase delay, and circular phase delay; Step 6: Map the obtained horizontal line phase delay, 45° line phase delay, and circular phase delay to the green, red, and blue channels, respectively. Then, use the true color image processing algorithm to synthesize the vector phase delay true color image. In addition, use the color space principle to adjust the brightness of the vector phase delay true color image to achieve high-contrast phase delay visualization.

2. A high-contrast and high-precision phase delay visualization method according to claim 1, characterized in that: The step 1 includes measuring two mutually orthogonal full interference spectra obtained by the PS-OCT system, and then performing a process of removing DC terms and compensating for dispersion on the two full interference spectra.

3. A high-contrast and high-precision phase delay visualization method according to claim 1, characterized in that: In the fourth step, the surface of the sample to be tested or the surface of the upper layer of the sample to be tested is used as a reference surface to calibrate the obtained Jones matrix to obtain m groups of similar Jones graphs, specifically: Among them J C is the similar Jones matrix; η H η V are the detection efficiencies of the horizontal and vertical detection channels, respectively; are the horizontal polarization component and the vertical polarization component of the reference light, * is the conjugation operation; J out J is the Jones matrix of the path from sample to detector; sample,T is the Jones matrix of the sample; z i is the depth of the Jones graph at layer i; J sample,T (z i ) refers to the sample at a depth of z i The Jones matrix below.

4. A high-contrast and high-precision phase delay visualization method according to claim 3, characterized in that: In the fourth step, m groups of similar Jones graphs are converted into corresponding m groups of Mueller graphs by mathematical methods, specifically: Where M is the Mueller matrix; U is the Pauli matrix; and J is the calibrated Jones matrix.

5. A high-contrast and high-precision phase delay visualization method according to claim 3, characterized in that: The step five is specifically as follows: The obtained m groups of Mueller diagrams are averaged to obtain the mean Mueller matrix diagram M; Perform polar decomposition on the averaged Mueller matrix to remove the depolarization and double attenuation characteristics to obtain the Mueller matrix M containing only phase delay information R ; Then, the obtained phase delay matrix M R By finding the trace, we can get the scalar phase delay value R: Where tr(M R ) is the pair matrix M R Seeking traces; Vector Phase Delay The three components are: horizontal line phase delay R H , 45° line phase delay R 45 , circular phase delay R C .

6. High contrast and high precision phase delay visualization system, characterized by, Full interference spectrum processing module, spectrum segmentation module, sub-interference spectrum processing module, matrix processing module and visualization module; The full-interference spectrum processing module receives the two mutually orthogonal full-interference spectra measured by the PS-OCT system, removes the DC term and compensates for the dispersion of the two full-interference spectra, and then outputs them to the spectrum segmentation module; The spectrum segmentation module is used to split the two full interference spectrum signals respectively through m narrowband window functions, thereby obtaining m independent narrowband sub-interference spectrum outputs of size n, which are sent to the sub-interference spectrum processing module; The sub-interference spectrum processing module is used to zero-fill each of the m discrete narrow-band sub-interference spectra of size n in each channel to obtain an interference spectrum of size N, and then perform Fourier transform to obtain m groups of Jones maps. The Jones map is composed of Jones matrices. Each pixel in the Jones map represents a Jones matrix, and the elements in the Jones matrix are Jones elements. The output of the sub-interference spectrum processing module is m groups of Jones diagrams, which are sent to the matrix processing module; The matrix processing module is used to achieve spatial position alignment between each Jones element in the Jones matrix by using a sub-pixel cross-correlation method; and to eliminate the global phase by using an adaptive averaging method for the spatially adjacent Jones elements after position alignment; The surface of the sample to be tested or the surface above the sample to be tested is used as a reference surface, and the obtained Jones matrix is calibrated to obtain m groups of similar Jones graphs; finally, the m groups of similar Jones graphs are respectively converted into corresponding m groups of Mueller graphs by mathematical methods; The matrix processing module is further configured to average the m groups of Mueller diagrams to obtain a mean Mueller matrix diagram; perform polar decomposition on the mean Mueller matrix to obtain a Mueller matrix containing only phase delay information, and then obtain horizontal line phase delay, 45° line phase delay, and circular phase delay as outputs of the matrix processing module, which are fed into the visualization module; The visualization module is used to map the obtained horizontal line phase delay, 45° line phase delay, and circular phase delay into green, red, and blue channels, respectively, and then use a true color image processing algorithm to synthesize a true color map of the vector phase delay. In addition, the brightness of the true color map of the vector phase delay is adjusted using the color space principle to achieve high-contrast phase delay visualization.

7. The high contrast and high precision phase delay visualization system according to claim 6, characterized in that In the matrix processing module, the surface of the sample to be tested or the surface of the upper layer of the sample to be tested is used as a reference surface to calibrate the obtained Jones matrix to obtain m groups of similar Jones graphs, specifically: Among them J C is the similar Jones matrix; η H η V are the detection efficiencies of the horizontal and vertical detection channels, respectively; are the horizontal polarization component and the vertical polarization component of the reference light, * is the conjugation operation; J out J is the Jones matrix of the path from sample to detector; sample,T is the Jones matrix of the sample; z i is the depth of the Jones graph at layer i; J sample,T (z i ) refers to the sample at a depth of z i Jones matrix below; The m groups of Mueller diagrams are averaged to obtain a Mueller matrix diagram after the mean; the Mueller matrix after the mean is polar decomposed to obtain a Mueller matrix containing only phase delay information, and then the horizontal line phase delay, the 45° line phase delay and the circular phase delay are obtained, specifically: Where M is the Mueller matrix; U is the Pauli matrix; J is the calibrated Jones matrix; The obtained m groups of Mueller diagrams are averaged to obtain the mean Mueller matrix diagram M; Perform polar decomposition on the averaged Mueller matrix to remove the depolarization and double attenuation characteristics to obtain the Mueller matrix M containing only phase delay information R ; Then, the obtained phase delay matrix M R By finding the trace, we can get the scalar phase delay value R: Where tr(M R ) is the pair matrix M R Seeking traces; Vector Phase Delay The three components are: horizontal line phase delay R H , 45° line phase delay R 45 , circular phase delay R C .

Images