PS-OCT polarization artifact suppression method based on cross coupling coefficient

Abstract

The invention discloses a PS-OCT polarization artifact suppression method based on a cross coupling coefficient. Comprising two parts of pre-measurement based on matrix calculation and PS-OCT data processing based on a cross coupling coefficient, according to the pre-measurement, a dual-channel interference signal is obtained by scanning a wave plate through a PS-OCT system, and then a ghosting artifact displacement set and the cross coupling coefficient are obtained; in the data processing step, a PS-OCT data processing method based on a cross coupling coefficient is used for detecting a sample and processing a dual-channel interference signal, and finally a PS-OCT image without polarization artifacts is obtained. Through the cross coupling coefficient, the cross coupling effect generated by various polarization elements can be quantified, and accurate suppression of polarization artifacts is achieved; the cross coupling coefficient is obtained in advance through the detection wave plate, in actual imaging, the cross coupling coefficient does not need to be measured any more, and the speed of suppressing polarization artifacts is increased; on the premise that the original configuration of the system is not changed, the polarization artifacts are comprehensively suppressed.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical imaging, and particularly relates to a polarization artifact suppression method based on cross-coupling coefficients for polarization sensitive optical coherence tomography (PS-OCT). BACKGROUND

[0002] Optical coherence tomography (OCT) is a non-invasive, high-resolution, high-sensitivity and real-time imaging technology, which has been widely used in clinical diagnosis of ophthalmology and cardiology. Polarization sensitive OCT (PS-OCT) as a functional extension of OCT can characterize the composition and microstructure of biological tissues by detecting the polarization information of biological tissues. In order to meet the needs of different application scenarios, researchers have developed a variety of PS-OCT systems. Among them, the PS-OCT system based on polarization maintaining optical fiber shows excellent flexibility and anti-interference, which can meet more stringent clinical needs, and is an important development direction to realize the practicality of PS-OCT.

[0003] Polarization artifact is a key factor affecting the imaging quality of the PS-OCT system based on polarization maintaining optical fiber, mainly including horizontal artifact and ghost artifact. The difference between horizontal artifact and ghost artifact is that horizontal artifact is mainly affected by the Fresnel reflection of optical elements, which will produce multiple horizontal lines across the width of the B-scan image in the image, interfering with the identification of the actual structure of the sample; ghost artifact is mainly affected by the backscattered light of the sample, which produces a pseudo-artifact similar to the sample structure but with different depths in the image. This artifact covers the sample image, not only affecting the clarity of the image, but also reducing the measurement accuracy of the polarization information of the sample. At present, the background spectrum removal method is the main method to suppress horizontal artifact, which can effectively reduce the generation of horizontal artifact by averaging the collected data. Compared with horizontal artifact, ghost artifact is more difficult to suppress due to its diverse presentation form and complex generation mechanism, which is the main problem in the current research of polarization artifact suppression method.

[0004] Currently, researchers mainly use two methods to suppress polarization artifacts including ghost artifacts. One is a hardware method based on long polarization-maintaining optical fiber, for example, in 2008, M.K. Al-Qaisi et al. inserted a long polarization-maintaining optical fiber at the light source end to move the polarization artifacts out of the imaging range, thereby suppressing the influence of polarization artifacts on imaging. However, this method usually needs to insert tens of meters of polarization-maintaining optical fiber, which not only increases the system cost but also introduces a large amount of dispersion, resulting in a decline in imaging quality (M.K. Al-Qaisi, T. Akkin, "Polarization-sensitive optical coherence tomography based on polarization-maintaining fibers and frequency multiplexing," Optics Express, 2008, 16, 13032-13041.). Another method for suppressing polarization artifacts is a software method based on wavelet transform proposed by R. Byers et al. in 2019, which does not need to change the optical system, but is mainly aimed at the polarization artifacts generated on the surface of the sample, and has limited effect on the polarization artifacts generated by the internal structure of the sample (R. Byers, S. Matcher, "Attenuation of stripe artifacts in optical coherence tomography images through wavelet-FFT filtering," Biomedical Optics Express, 2019, 10, 4179-4189.). Therefore, although the existing polarization artifact suppression methods of PS-OCT can reduce the influence of artifacts to some extent, there are still many deficiencies, which are difficult to meet the imaging needs of PS-OCT in practical applications. Therefore, there is still an urgent need for an efficient and comprehensive PS-OCT polarization artifact suppression method to optimize the image quality of PS-OCT. SUMMARY

[0005] The purpose of the present application is to overcome the deficiencies of the prior art method, and to provide a PS-OCT polarization artifact suppression method based on cross-coupling coefficients, which can quickly and comprehensively suppress the influence of polarization artifacts on the image quality of PS-OCT without changing the system settings.

[0006] To achieve the above purpose, the technical scheme provided by the present application is:

[0007] A polarization artifact suppression method for PS-OCT based on cross-coupling coefficient, comprising two parts of a matrix calculation-based prediction and PS-OCT data processing based on cross-coupling coefficient, the matrix calculation-based prediction is used to obtain a polarization artifact displacement set and cross-coupling coefficients (including cross-coupling contrast coefficient and cross-coupling vector coefficient); the PS-OCT data processing based on cross-coupling coefficient is used to perform data processing according to the polarization artifact displacement set and cross-coupling coefficients obtained by the prediction, so as to obtain a PS-OCT image without polarization artifact; the specific steps comprise:

[0008] The first part, the matrix calculation-based prediction

[0009] Step 1: scanning a quarter-wave plate using a PS-OCT system, and collecting a two-channel interference signal S H (k) and S V (k) of a horizontal detection channel and a vertical detection channel, wherein k is a wave number domain coordinate, and H and V represent the horizontal detection channel and the vertical detection channel respectively;

[0010] Step 2: based on the two-channel interference signal S H (k) and S V (k) in step 1, calculating amplitude signals A H (z) and A V (z) of the two channels and an intensity signal I(z) of the PS-OCT, wherein z is a spatial domain coordinate, and the calculation formula is as follows:

[0011] A H (z)=|FT -1 (S H (k))|

[0012] A V (z)=|FT -1 (S V (k))|

[0013] I(z)=|A H (z) 2 +A V (z) 2 |

[0014] Wherein, FT -1 (·) represents an inverse Fourier transform;

[0015] Step 3: based on the intensity signal I(z) in step 2, selecting an upper edge position z Uc and a lower edge position z Dc of the wave plate by using a manual or automatic peak searching method, wherein Uc represents the upper edge, and Dc represents the lower edge; and selecting a polarization artifact position set {z Ui} n and {z Di} n where U corresponds to the upper edge, D corresponds to the lower edge, i represents the artifact serial number, and n represents the total number of artifacts;

[0016] Step 4: Based on the upper and lower edge positions of the wave plate and the set of polarization artifact positions described in Step 3, a set of ghost artifact displacement {Δz i} n where i represents the artifact serial number, n represents the total number of artifacts, and the calculation formula is as follows:

[0017] Δz i = z Uc - z Ui ;

[0018] Step 5: Based on the dual-channel amplitude signals described in Step 2, the set of polarization artifact positions of the upper and lower edges described in Step 3, and the set of polarization artifact displacements described in Step 4, a cross-coupling contrast coefficient calculation method is used to calculate and output the set of cross-coupling contrast coefficients of the horizontal detection channel H and the vertical detection channel V and and the de-artifact amplitude signals A Ha (z) and A Va (z);

[0019] Step 6: Based on the set of cross-coupling contrast coefficients of the horizontal detection channel H and the vertical detection channel V described in Step 5 and and the de-artifact amplitude signals A Ha (z) and A Va (z), a cross-coupling vector coefficient calculation method is used to calculate the set of cross-coupling vector coefficients of the horizontal detection channel H and the vertical detection channel V and

[0020] Second part, PS-OCT data processing based on cross-coupling coefficients

[0021] Step 7: Using the PS-OCT system to detect the sample, collecting the dual-channel interference signals of the sample and where k is the wave number domain coordinate, H and V represent the horizontal detection channel and the vertical detection channel, respectively;

[0022] Step 8: Based on the dual-channel interference signals described in Step 7 and performing inverse Fourier transform to obtain the complex amplitudes of the horizontal detection channel H and the vertical detection channel V interference signals and are represented as:

[0023]

[0024]

[0025] where FT -1 (·) denotes inverse Fourier transform, and denote the amplitude and phase of the complex amplitude of the horizontal probe channel H interference signal after inverse Fourier transform, respectively, and denote the amplitude and phase of the complex amplitude of the vertical probe channel V interference signal after inverse Fourier transform, respectively;

[0026] Step 9: Based on the polarization artifact displacement set {Δz i} n and the cross-coupling vector coefficient set obtained in step 5 and A reference amplitude signal calculation method is used to calculate the reference amplitude signals of the horizontal probe channel H and the vertical probe channel V and

[0027] Step 10: Based on the polarization artifact displacement set {Δz i} n and the cross-coupling vector coefficient set and The reference amplitude signals of the horizontal probe channel H and the vertical probe channel V are used to calculate the de-artifact amplitude signals of the horizontal probe channel H and the vertical probe channel V and A de-artifact amplitude signal calculation method is used to calculate the de-artifact amplitude signals of the horizontal probe channel H and the vertical probe channel V

[0028] Step 11: Obtain the de-artifact complex amplitude of the dual-channel interference signal and is expressed as:

[0029]

[0030]

[0031] Step 12: Based on the de-artifact complex amplitude of the dual-channel interference signal in step 11, calculate and output the de-polarization artifact PS-OCT image including but not limited to: intensity image, phase delay image, optical axis image and polarization uniformity image. The specific calculation steps are as follows:

[0032]

[0033]

[0034]

[0035] where I represents intensity, δ represents phase delay, θ represents optical axis, and DOPU represents degree of polarization uniformity (DOPU).

[0036] Further, the cross-coupling contrast coefficient calculation method in step 5 is as follows:

[0037] Step 5-1: initialize artifact serial number i = 1 and de-artifact amplitude signal A Ha (z) and A Va (z), the calculation formula is as follows:

[0038] A Ha (z) = A H (z)

[0039] A Va (z) = A V (z);

[0040] Step 5-2: set the judgment condition, if i is less than or equal to n, execute the next loop body, otherwise exit the loop and execute step 5-7;

[0041] Step 5-3: in the loop body, calculate the cross-coupling contrast coefficient of the horizontal detection channel H and the vertical detection channel V of the artifact serial number i, the calculation formula is as follows:

[0042]

[0043] Step 5-4: in the loop body, update the de-artifact amplitude signal A Ha (z) and A Va (z), the calculation formula is as follows:

[0044]

[0045] A Ha = A Ha '

[0046] A Va = A Va '

[0047] Where “=” represents assignment operation, that is, assigning the calculation result on the right side to the variable on the left side, A Ha (z)' and A Va (z)' are the intermediate variables required for updating A Ha (z) and A Va (z);

[0048] Step 5-5: increase i by 1;

[0049] Step 5-6: return to Step 5-2, rejudge the condition and execute the loop until i is greater than n;

[0050] Step 5-7: after the loop ends, output the cross-coupling coefficient set of the horizontal detection channel H and the vertical detection channel V and and the de-artifact amplitude signal A Ha (z) and A Va (z).

[0051] Further, the cross-coupling vector coefficient calculation method in Step 6 is as follows:

[0052] Step 6-1: initialize the artifact serial number i = 1;

[0053] Step 6-2: set the judgment condition, if i is less than or equal to n, execute the loop body, otherwise exit the loop and execute Step 6-6;

[0054] Step 6-3: in the loop body, calculate the cross-coupling vector coefficient of the horizontal detection channel H and the vertical detection channel V of the artifact serial number i, the calculation formula is as follows:

[0055]

[0056] Step 6-4: increase i by 1;

[0057] Step 6-5: return to Step 6-2, rejudge the condition and execute the loop until i is greater than n;

[0058] Step 6-6: after the loop ends, obtain the cross-coupling vector coefficient set of the horizontal detection channel H and the vertical detection channel V and

[0059] Further, the reference amplitude signal calculation method in Step 9 is as follows:

[0060] Step 9-1: initialize the artifact serial number i = 1 and the reference amplitude signal and The calculation formula is as follows:

[0061]

[0062] wherein, and are the amplitude signals of the horizontal detection channel H and the vertical detection channel V interference signals;

[0063] Step 9-2: Set the judgment condition, if i is less than or equal to n, execute the loop body, otherwise exit the loop, execute step 9-6;

[0064] Step 9-3: In the loop body, update the reference amplitude signal and The calculation formula is as follows:

[0065]

[0066] A Hb = A Hb '

[0067] A Vb = A Vb '

[0068] Where "=" represents assignment operation, that is, the right calculation result is assigned to the left variable, A Hb (z)' and A Vb (z)' are intermediate variables required to update A Hb (z) and A Vb (z).

[0069] Step 9-4: Increase i by 1;

[0070] Step 9-5: Return to step 9-2, rejudge the condition and execute the loop until i is greater than n;

[0071] Step 9-6: After the loop ends, the reference amplitude signals of the horizontal detection channel H and the vertical detection channel V are obtained and

[0072] Further, the artifact-removed amplitude signal calculation method of step 10 is as follows:

[0073] Step 10-1: Initialize artifact number i = 1 and artifact-removed amplitude signal and The calculation formula is as follows:

[0074]

[0075] Step 10-2: Set the judgment condition, if i is less than or equal to n, execute the loop body, otherwise exit the loop, execute step 10-6;

[0076] Step 10-3: In the loop body, update the artifact-removed amplitude signal and The calculation formula is as follows:

[0077]

[0078] AHc = A Hc '

[0079] A Vc = A Vc '

[0080] wherein the "=" represents an assignment operation, that is, the result of the right side is assigned to the left variable, A Hc (z)' and A Vc (z)' is an intermediate variable required for updating A Hc (z) and A Vc (z);

[0081] Step 10-4: increase i by 1;

[0082] Step 10-5: return to step 10-2, rejudge the condition and execute the loop until i is greater than n;

[0083] Step 10-6: after the loop ends, the deartifact amplitude signals of the horizontal detection channel H and the vertical detection channel V are obtained and

[0084] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0085] (1) The cross-coupling coefficient proposed in the method of the present application can quantify the cross-coupling effect generated by various polarization elements, and accurately suppress the polarization artifact.

[0086] (2) The method of the present application proposes a prediction method, which obtains the cross-coupling coefficient in advance by detecting the wave plate. In actual imaging, it is no longer necessary to measure the cross-coupling coefficient, thereby improving the speed of suppressing the polarization artifact.

[0087] (3) The PS-OCT polarization artifact suppression method based on the cross-coupling coefficient proposed in the present application combines the prediction method and the actual imaging method. By measuring and using the cross-coupling coefficient, the polarization artifact can be comprehensively suppressed without changing the original configuration of the system. BRIEF DESCRIPTION OF DRAWINGS

[0088] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope.

[0089] Figure 1 A flow chart of the PS-OCT polarization artifact suppression method based on the cross-coupling coefficient described in the embodiments of the present application;

[0090] Figure 2A flow chart of a cross-coupling contrast coefficient calculation method according to an embodiment of the present application;

[0091] Figure 3 A flow chart of a cross-coupling vector coefficient calculation method according to an embodiment of the present application;

[0092] Figure 4 A flow chart of a reference amplitude signal calculation method according to an embodiment of the present application;

[0093] Figure 5 A flow chart of a de-artifact amplitude signal calculation method according to an embodiment of the present application;

[0094] Figure 6 A data table of cross-coupling contrast coefficients obtained according to an embodiment of the present application;

[0095] Figure 7 A data table of cross-coupling vector coefficients obtained according to an embodiment of the present application;

[0096] Figure 8 Reference amplitude signal images of a horizontal detection channel H and a vertical detection channel V obtained according to an embodiment of the present application;

[0097] Figure 9 De-artifact amplitude signal images of a horizontal detection channel H and a vertical detection channel V obtained according to an embodiment of the present application;

[0098] Figure 10 PS-OCT intensity images before and after quarter-wave plate artifact suppression obtained according to an embodiment of the present application;

[0099] Figure 11 Chicken PS-OCT images before and after artifact suppression obtained according to an embodiment of the present application. DETAILED DESCRIPTION

[0100] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0101] Therefore, the detailed description of the embodiments of the present application provided in the drawings below is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art without making creative efforts based on the embodiments in the present application are within the scope of protection of the present application.

[0102] In order to make the above objectives, characteristics and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0103] The present application provides a PS-OCT polarization artifact suppression method based on cross-coupling coefficient, which comprises two parts of a matrix calculation-based prediction and PS-OCT data processing based on cross-coupling coefficient, the matrix calculation-based prediction is used to obtain a polarization artifact displacement set and a cross-coupling coefficient; and the PS-OCT data processing based on cross-coupling coefficient is used to obtain a PS-OCT image without polarization artifact. Figure 1 The present application provides a PS-OCT polarization artifact suppression method based on cross-coupling coefficient, which comprises two parts of a matrix calculation-based prediction and PS-OCT data processing based on cross-coupling coefficient, the matrix calculation-based prediction is used to obtain a polarization artifact displacement set and a cross-coupling coefficient; and the PS-OCT data processing based on cross-coupling coefficient is used to obtain a PS-OCT image without polarization artifact.

[0104] The first part is a matrix calculation-based prediction

[0105] The flow chart of the matrix calculation-based prediction method according to the present application is shown in the left side of FIG. 1, and the specific steps include: Figure 1

[0106] Step 100: scanning a quarter-wave plate using a PS-OCT system, and collecting double-channel interference signals S H (k) and S V (k) of a horizontal detection channel and a vertical detection channel, wherein k is a wave number domain coordinate, and H and V represent the horizontal detection channel and the vertical detection channel, respectively.

[0107] Step 200: based on the double-channel interference signals S H (k) and S V (k) described in step 100, calculating amplitude signals A H (z) and A V (z) of the double channels and an intensity signal I(z) of the PS-OCT, wherein z is a spatial domain coordinate, and the calculation formula is as follows:

[0108] A H (z) = |FT -1 (S H (k))|

[0109] A V (z) = |FT -1 (S V (k))|

[0110] I(z) = |A​H (z) 2 +A V (z) 2 |

[0111] where FT -1 denotes inverse Fourier transform; the inverse Fourier transform method used in this embodiment is fast inverse Fourier transform, and the transform point number is 4096.

[0112] Step 300: Based on the intensity signal I(z) described in step 2, the upper edge and lower edge positions z Uc and z Dc of the wave plate are selected by using artificial or automatic peak searching method Ui , where Uc denotes the upper edge, Dc denotes the lower edge, and the polarized artifact position set {z n} and {z Di} of the upper edge and lower edge are selected n , where U corresponds to the upper edge, D corresponds to the lower edge, i represents the artifact serial number, and n represents the total number of artifacts. In this embodiment, the upper edge position z Uc = 7.66 and the lower edge position z Dc = 10.48, which are in units of millimeters, as shown in Figure 10 . In this embodiment, i is from 1 to 6, n is 6, which indicates that there are 6 artifacts in the PS-OCT system used in this embodiment, and the polarized artifact position set {z Ui} of the upper edge and lower edge is {7.23, 8.09, 7.37, 7.95, 7.52, 7.80} n

[0113] and {z Di} n = {10.05, 10.91, 10.19, 10.77, 10.34, 10.62}, which are in units of millimeters.

[0114] Step 400: Based on the upper and lower edge positions of the wave plate and the polarized artifact position set described in step 3, the ghost artifact displacement set {Δz i} n is calculated, and the calculation formula is as follows:

[0115] Δz i = z Uc -z Ui

[0116] In this embodiment, the ghost artifact displacement set is {Δz i} n = {0.43, -0.43, 0.29, -0.29, 0.14, -0.14}, which are in units of millimeters.

[0117] ​Step 500: Based on the dual-channel amplitude signals described in step 200, the polarized artifact position set of the upper edge and the lower edge described in step 300, and the polarized artifact displacement set described in step 400, a cross-coupling contrast coefficient set of the horizontal detection channel H and the vertical detection channel V is calculated and output using a cross-coupling contrast coefficient calculation method and and the de-artifact amplitude signal A Ha (z) and A Va (z). Figure 6 The cross-coupling contrast coefficient set obtained in step 500 of the embodiment.

[0118] Step 600: Based on the cross-coupling contrast coefficient set of the horizontal detection channel H and the vertical detection channel V described in step 500 and and the de-artifact amplitude signal A Ha (z) and A Va (z), a cross-coupling vector coefficient set of the horizontal detection channel H and the vertical detection channel V is calculated using a cross-coupling vector coefficient calculation method and Figure 7 The cross-coupling vector coefficient set obtained in step 600 of the embodiment.

[0119] Second part, PS-OCT data processing based on cross-coupling coefficients

[0120] The flowchart of the PS-OCT data processing based on cross-coupling coefficients described in the embodiment of the application is shown in Figure 1 on the right side, and the specific steps include:

[0121] Step 700: Using a PS-OCT system to detect a sample and collect a dual-channel interference signal of the sample and wherein k is a wave number domain coordinate, H and V represent the horizontal detection channel and the vertical detection channel respectively. The sample detected in the embodiment is an ex vivo chicken; the number of single collection points of the dual-channel interference signal is 4096 points.

[0122] Step 800: Based on the dual-channel interference signal described in step 700 and inverse Fourier transform is performed to obtain the complex amplitude of the horizontal detection channel H and the vertical detection channel V interference signals and is expressed as:

[0123]

[0124] wherein FT -1(·) represents inverse Fourier transform, and respectively represent the amplitude and phase of the complex amplitude of the horizontal detection channel H interference signal after inverse Fourier transform, and respectively represent the amplitude and phase of the complex amplitude of the vertical detection channel V interference signal after inverse Fourier transform. The inverse Fourier transform method used in this embodiment is fast inverse Fourier transform, and the transform point number is 4096.

[0125] Step 900: based on the polarization artifact displacement set {Δz i} n and the cross-coupling contrast coefficient set obtained in step 5 and A reference amplitude signal calculation method is used to calculate the reference amplitude signals of the horizontal detection channel H and the vertical detection channel V and Figure 8 The reference amplitude signal images of the horizontal detection channel H and the vertical detection channel V obtained in this embodiment of the application.

[0126] Step 1000: based on the polarization artifact displacement set {Δz i} n and the cross-coupling vector coefficient set and The reference amplitude signals of the horizontal detection channel H and the vertical detection channel V are used and A de-artifact amplitude signal calculation method is used to calculate the de-artifact amplitude signals of the horizontal detection channel H and the vertical detection channel V and Figure 9 The de-artifact amplitude signal images of the horizontal detection channel H and the vertical detection channel V obtained in this embodiment of the application.

[0127] Step 1100: obtain the de-artifact complex amplitude of the dual-channel interference signal and are represented as:

[0128]

[0129]

[0130] This embodiment uses the phase obtained in step 800 and the de-artifact amplitude signal obtained in step 1000 to obtain the de-artifact complex amplitude according to the formula in this step 1100.

[0131] Step 1200: Based on the de-artifact complex amplitude of the dual-channel interference signal in step 1100, calculate and output the de-polarization artifact PS-OCT images including but not limited to: intensity image, phase retardation image, optical axis image and polarization uniformity image, and the specific calculation steps are as follows:

[0132]

[0133]

[0134] Wherein, I represents intensity, δ represents phase retardation, θ represents optical axis, and DOPU represents degree of polarization uniformity (DOPU). Figure 11 Intensity images, phase retardation images, optical axis images and polarization uniformity images before and after chicken artifact suppression obtained by the embodiment of the application.

[0135] Figure 2 In the PS-OCT polarization artifact suppression method based on cross-coupling coefficient, the cross-coupling contrast coefficient calculation method in step 500 is as follows:

[0136] Step 501: Initialize artifact serial number i = 1 and de-artifact amplitude signal A Ha (z) and A Va (z), the calculation formula is as follows:

[0137] A Ha (z) = A H (z)

[0138] A Va (z) = A V (z)

[0139] Step 502: Set the judgment condition, if i is less than or equal to n, execute the next loop body, otherwise exit the loop and execute step 507.

[0140] Step 503: In the loop body, calculate the cross-coupling contrast coefficient of horizontal detection channel H and vertical detection channel V of artifact serial number i, and the calculation formula is as follows:

[0141]

[0142] Step 504: In the loop body, update the de-artifact amplitude signal A Ha (z) and A Va (z), the calculation formula is as follows:

[0143]

[0144] A Ha = A Ha '

[0145] A Va = A Va '

[0146] wherein "=" represents assignment operation, i.e. the result of the right side is assigned to the left variable, A Ha (z)' and A Va (z)' is an intermediate variable required for updating A Ha (z) and A Va (z).

[0147] Step 505: increase i by 1.

[0148] Step 506: return to step 502, rejudge the condition and execute the loop until i is greater than n. In this embodiment, if i is less than or equal to 6, execute the loop body, otherwise, exit the loop.

[0149] Step 507: after the loop ends, output the cross-coupling contrast coefficient set of horizontal detection channel H and vertical detection channel V and and the de-artifact amplitude signal A Ha (z) and A Va (z).

[0150] Figure 3 is a cross-coupling coefficient-based PS-OCT polarization artifact suppression method, the cross-coupling vector coefficient calculation method of step 600, the calculation steps are as follows:

[0151] Step 601: initialize artifact serial number i = 1.

[0152] Step 602: set the judgment condition, if i is less than or equal to n, execute the loop body, otherwise, exit the loop and execute step 606.

[0153] Step 603: in the loop body, calculate the cross-coupling contrast coefficient of horizontal detection channel H and vertical detection channel V of artifact serial number i, the calculation formula is as follows:

[0154]

[0155] Step 604: increase i by 1.

[0156] Step 605: return to step 602, rejudge the condition and execute the loop until i is greater than n. In this embodiment, if i is less than or equal to 6, execute the loop body, otherwise, exit the loop.

[0157] Step 606: After the loop, the cross-coupling vector coefficient set of the horizontal detection channel H and the vertical detection channel V is obtained and

[0158] Figure 4 In the PS-OCT polarization artifact suppression method based on cross-coupling coefficients described in the embodiment of the application, the reference amplitude signal calculation method in step 900, the calculation steps are as follows:

[0159] Step 901: initialize the artifact serial number i = 1 and the reference amplitude signal and The calculation formula is as follows:

[0160]

[0161] Among them, and are the amplitude signals of the horizontal detection channel H and the vertical detection channel V interference signals.

[0162] Step 902: set the judgment condition, if i is less than or equal to n, execute the loop body, otherwise exit the loop and execute step 906.

[0163] Step 903: in the loop body, update the reference amplitude signal and The calculation formula is as follows:

[0164]

[0165] A Hb = A Hb '

[0166] A Vb = A Vb '

[0167] The "=" in it represents the assignment operation, that is, the calculation result on the right side is assigned to the variable on the left side, A Hb (z)' and A Vb (z)' are intermediate variables required to update A Hb (z) and A Vb (z);

[0168] Step 904: increase i by 1.

[0169] Step 905: return to step 902, rejudge the condition and execute the loop until i is greater than n. In this embodiment, if i is less than or equal to 6, execute the loop body, otherwise exit the loop.

[0170] Step 906: after the loop, the reference amplitude signals of the horizontal detection channel H and the vertical detection channel V are obtained and

[0171] Figure 5 In the PS-OCT polarization artifact suppression method based on cross-coupling coefficient, the calculation method of the artifact-removed amplitude signal in step 1000 is as follows:

[0172] Step 1001: initialize the artifact serial number i = 1 and the artifact-removed amplitude signal and The calculation formula is as follows:

[0173]

[0174] Step 1002: set the judgment condition, if i is less than or equal to n, execute the loop body, otherwise exit the loop and execute step 1006;

[0175] Step 1003: in the loop body, update the artifact-removed amplitude signal and The calculation formula is as follows:

[0176]

[0177] A Hc = A Hc '

[0178] A Vc = A Vc '

[0179] Where “=” represents assignment operation, that is, the calculation result on the right side is assigned to the variable on the left side, A Hc (z)' and A Vc (z)' are intermediate variables required for updating A Hc (z) and A Vc (z);

[0180] Step 1004: increase i by 1.

[0181] Step 1005: return to step 1002, rejudge the condition and execute the loop until i is greater than n. In this embodiment, if i is less than or equal to 6, execute the loop body, otherwise exit the loop.

[0182] Step 1006: after the loop ends, the artifact-removed amplitude signals of the horizontal detection channel H and the vertical detection channel V are obtained and

[0183] Figure 10The PS-OCT intensity images before and after the quarter-wave plate artifact suppression obtained by the embodiment of the present application can see that the polarization artifacts existing in the upper and lower edges of the quarter-wave plate are effectively suppressed.

[0184] Figure 11 The PS-OCT images of chicken meat before and after the artifact suppression obtained by the embodiment of the present application can see that there are obvious polarization artifacts near the surface of the chicken meat, and the polarization artifacts inside and outside the chicken meat in the PS-OCT image can be comprehensively suppressed by using the method provided by the present application.

[0185] The above embodiments are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable the personnel familiar with the art to understand the content of the present application and implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A method for suppressing polarization artifacts in PS-OCT based on cross-coupling coefficient, characterized in that, The method comprises two parts: a matrix-based prediction and a PS-OCT data processing method based on cross-coupling coefficients. The matrix-based prediction is used to obtain the polarization artifact displacement set, cross-coupling contrast coefficient, and cross-coupling vector coefficient. The PS-OCT data processing method based on cross-coupling coefficients performs data processing based on the polarization artifact displacement set and cross-coupling coefficients obtained from the prediction to obtain a PS-OCT image without polarization artifacts. The specific steps include: Part 1: Predictions Based on Matrix Calculation Step 1: Use a PS-OCT system to scan the quarter-wave plate and acquire the dual-channel interference signal S from the horizontal and vertical probe channels. H (k) and S V (k), where k is the wavenumber domain coordinate, and H and V represent the horizontal and vertical detection channels, respectively; Step 2: Based on the dual-channel interference signal S described in Step 1 H (k) and S V (k), calculate the amplitude signal A of the two channels. H (z) and A V (z) and the intensity signal I(z) of PS-OCT, where z is the spatial domain coordinate, are calculated as follows: A H (z)=|FT -1 (S H (k))| A V (z)=|FT -1 (S V (k))| I(z)=|A H (z) 2 +A V (z) 2 | Among them, FT -1 (·) indicates the inverse Fourier transform; Step 3: Based on the intensity signal I(z) described in Step 2, select the upper and lower edge positions z of the waveplate using manual or automatic peak-finding methods. Uc and z Dc Where Uc represents the upper edge and Dc represents the lower edge; and the set of polarization artifact positions of the upper and lower edges {z} is selected. Ui } n and {z Di } n Where U corresponds to the top edge, D corresponds to the bottom edge, i represents the artifact number, and n represents the total number of artifacts; Step 4: Based on the waveplate upper and lower edge positions and polarization artifact position sets described in Step 3, calculate the ghost artifact displacement set {Δz}. i } n Where i represents the artifact index and n represents the total number of artifacts, the calculation formula is as follows: Δz i =with Uc -with Ui ; Step 5: Based on the dual-channel amplitude signal described in Step 2, the polarization artifact position sets of the upper and lower edges described in Step 3, and the polarization artifact displacement sets described in Step 4, a cross-coupling contrast coefficient calculation method is used to calculate and output the cross-coupling contrast coefficient sets of the horizontal detection channel H and the vertical detection channel V. and and artifact removal amplitude signal A Ha (z) and A Va (z); Step 6: Based on the cross-coupling comparison coefficient set of the horizontal detection channel H and the vertical detection channel V described in Step 5. and and artifact removal amplitude signal A Ha (z) and A Va (z) A cross-coupling vector coefficient calculation method is used to calculate the set of cross-coupling vector coefficients for the horizontal detection channel H and the vertical detection channel V. and Part Two: PS-OCT Data Processing Based on Cross-Coupling Coefficient Step 7: Use a PS-OCT system to probe the sample and acquire the sample's dual-channel interference signal. and Where k is the wavenumber domain coordinate, and H and V represent the horizontal and vertical detection channels, respectively; Step 8: Based on the dual-channel interference signal described in Step 7 and Performing an inverse Fourier transform yields the complex amplitudes of the interference signals from the horizontal detection channel H and the vertical detection channel V. and Represented as: Among them, FT -1 (·) represents the inverse Fourier transform. and Let A and B represent the amplitude and phase of the complex amplitude of the horizontal probe channel H interference signal after inverse Fourier transform, respectively. and These represent the amplitude and phase of the complex amplitude of the vertical probe channel V interference signal after inverse Fourier transform, respectively; Step 9: Based on the polarization artifact displacement set {Δz} obtained in Step 4 i } n The set of cross-coupling comparison coefficients obtained in step 5 and A reference amplitude signal calculation method is used to calculate the reference amplitude signals of the horizontal detection channel H and the vertical detection channel V. and Step 10: Based on the polarization artifact displacement set {Δz} i } n and cross-coupled vector coefficient set and Using reference amplitude signals from the horizontal detection channel H and the vertical detection channel V and An artifact-free amplitude signal calculation method is employed to calculate the artifact-free amplitude signals of the horizontal detection channel H and the vertical detection channel V. and Step 11: Obtain the artifact-free complex amplitude of the dual-channel interference signal and Represented as: Step 12: Based on the artifact-free complex amplitude of the dual-channel interference signal described in Step 11, calculate and output the PS-OCT image with depolarization artifacts, including but not limited to: intensity image, phase retardation image, optical axis image, and polarization uniformity image. The specific calculation steps are as follows: Where I represents intensity, δ represents phase delay, θ represents optical axis, and DOPU represents polarization uniformity (DOPU).

2. The method according to claim 1, characterized in that, The method for calculating the cross-coupling comparison coefficient in step 5 is as follows: Step 5-1: Initialize the artifact sequence number i = 1 and the artifact removal amplitude signal A of the horizontal probe channel H and the vertical probe channel V. Ha (z) and A Va (z), the calculation formula is as follows: And Ha (from)=A H (from) And Va (from)=A V (of); Step 5-2: Set a condition: if i is less than or equal to n, execute the next loop body; otherwise, exit the loop and execute step 5-7. Step 5-3: Within the loop, calculate the cross-coupling contrast coefficient between the horizontal detection channel H and the vertical detection channel V of artifact number i. The calculation formula is as follows: Step 5-4: Within the loop, update the artifact removal amplitude signal A. Ha (z) and A Va (z), the calculation formula is as follows: A Ha =A Ha ' A Va =A Va ' The "=" sign indicates an assignment operation, which assigns the result of the calculation on the right to the variable on the left. A Ha (z)' and A Va (z)' is for updating A Ha (z) and A Va (z) The intermediate variables required; Step 5-5: Increment i by 1; Step 5-6: Return to step 5-2, re-evaluate the conditions and execute the loop until i is greater than n; Steps 5-7: After the loop ends, output the set of cross-coupling comparison coefficients for the horizontal detection channel H and the vertical detection channel V. and and artifact removal amplitude signal A Ha (z) and A Va (z).

3. The method according to claim 1, characterized in that, The method for calculating the cross-coupling vector coefficients in step 6 is as follows: Step 6-1: Initialize the artifact index i = 1; Step 6-2: Set a condition: if i is less than or equal to n, execute the loop body; otherwise, exit the loop and execute step 6-6. Step 6-3: Within the loop, calculate the cross-coupling vector coefficients of the horizontal detection channel H and the vertical detection channel V for artifact number i. The calculation formula is as follows: Step 6-4: Increment i by 1; Step 6-5: Return to step 6-2, re-evaluate the conditions and execute the loop until i is greater than n; Step 6-6: After the loop is completed, obtain the set of cross-coupling vector coefficients for the horizontal detection channel H and the vertical detection channel V. and 4. The method according to claim 1, characterized in that, The method for calculating the reference amplitude signal in step 9 is as follows: Step 9-1: Initialize the artifact index i = 1 and the reference amplitude signal and The calculation formula is as follows: in, and It is the amplitude signal of the interference signal between the horizontal detection channel H and the vertical detection channel V; Step 9-2: Set a condition: if i is less than or equal to n, execute the loop body; otherwise, exit the loop and execute step 9-6. Step 9-3: Within the loop, update the reference amplitude signal. and The calculation formula is as follows: A Hb =A Hb ' A Vb =A Vb ' The "=" sign indicates an assignment operation, which assigns the result of the calculation on the right to the variable on the left. A Hb (z)' and A Vb (z)' is for updating A Hb (z) and A Vb (z) The intermediate variables required; Step 9-4: Increment i by 1; Step 9-5: Return to step 9-2, re-evaluate the condition and execute the loop until i is greater than n; Step 9-6: After the loop is completed, obtain the reference amplitude signals for the horizontal detection channel H and the vertical detection channel V. and 5. The method according to claim 1, characterized in that, The method for calculating the artifact removal amplitude signal in step 10 is as follows: Step 10-1: Initialize the artifact index i = 1 and the artifact removal amplitude signal and The calculation formula is as follows: Step 10-2: Set a condition: if i is less than or equal to n, execute the loop body; otherwise, exit the loop and execute step 10-6. Step 10-3: Within the loop, update the artifact removal amplitude signal. and The calculation formula is as follows: A Hc =A Hc ' A Vc =A Vc ' The "=" sign indicates an assignment operation, which assigns the result of the calculation on the right to the variable on the left. A Hc (z)' and A Vc (z)' is for updating A Hc (z) and A Vc (z) The intermediate variables required; Step 10-4: Increment i by 1; Step 10-5: Return to step 10-2, re-evaluate the conditions and execute the loop until i is greater than n; Step 10-6: After the loop ends, obtain the artifact-free amplitude signals of the horizontal detection channel H and the vertical detection channel V. and

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