CN-116626888-B - Full-depth dispersion compensation method and system for polarization sensitive optical coherence tomography

CN116626888BCN 116626888 BCN116626888 BCN 116626888BCN-116626888-B

Abstract

The application discloses a full-depth dispersion compensation method and a full-depth dispersion compensation system for polarization sensitive optical coherence tomography, comprising the following steps of imaging a reflector, reducing the background to obtain a signal as a real part, performing Hilbert transformation as an imaginary part, performing inverse Fourier transformation, filtering out information of polarization artifacts, and extracting phase information, wherein the optical path difference of two arms of an original interference signal is delta z Step five, moving the reference arm to the symmetrical position of the zero optical path to obtain an original interference signal with the optical path difference of-delta z, repeating the step two to the step four, and extracting phase information According to the formula: and obtaining a dispersion function, and performing dispersion compensation on the image.

Inventors

LIANG YANMEI
XU SONGWEN
YANG DI
CHEN WENGUANG

Assignees

上海美沃精密仪器股份有限公司

Dates

Publication Date: 20260505
Application Date: 20230510

Claims (3)

1. A full-depth dispersion compensation method of polarization sensitive optical coherence tomography (PS-OCT), comprising the steps of: step one, imaging a reflecting mirror by using a PS-OCT system to obtain an original interference signal, wherein the optical path difference of two arms is ; Step two, background reduction is carried out on the interference signals in the horizontal direction in the signals with the two paths of polarization directions perpendicular to each other, and signals are obtained As the real part, pair Performing Hilbert transform as imaginary part to obtain amplitude and phase information of signal ; Step three, pair Performing inverse Fourier transform, filtering the result, and filtering out information of polarization artifact; Step four, filtering Extracting phase information of the reflector ; Step five, moving a reference arm, and moving the imaging position of the reflecting mirror to a symmetrical position of the imaging position about a zero optical path, wherein the optical path difference of the two arms at the symmetrical position is obtained as follows Repeating the second step and the fourth step to obtain phase information ; According to the formula: Calculating to obtain dispersion function Multiplying the two interference signals with mutually perpendicular polarization directions by the dispersion function Performing dispersion compensation, and finally calculating to obtain a PS-OCT image by using the intensity signals after the two paths of dispersion compensation; Signal signal Can be expressed as: ; Wherein, the , The reflected signal intensities of the sample arm and the reference arm respectively, A dispersion function to be obtained is obtained; the two mirror signal phases that are symmetrical about the zero optical path can be expressed as: ; ; Thus calculated dispersion function The method comprises the following steps: ; and multiplying the acquired interference signals with the two mutually perpendicular polarization directions by the dispersion function respectively, performing dispersion compensation to obtain two dispersion-eliminated OCT intensity signals, and finally calculating and obtaining the PS-OCT image by using the two intensity signals.
2. A PS-OCT system for implementing the full-depth dispersion compensation method as claimed in claim 1 is characterized by comprising a wide-spectrum light source, wherein light output by the wide-spectrum light source is output into linearly polarized light along the vertical direction after passing through a polarization controller, the linearly polarized light enters an annular device, light emitted from the annular device is uniformly divided into a reference beam and a sample beam after passing through a polarization beam splitter and a 50:50 polarization maintaining coupler a end, the reference beam is reflected back to a polarization maintaining coupler c end by a reflector through a collimator, a quarter wave plate with an included angle of 22.5 DEG between a fast axis direction and the vertical direction, the sample beam is converted into a circular polarization state by a collimator and a quarter wave plate with an included angle of 45 DEG between the fast axis direction and the vertical direction, then the sample beam is irradiated to a sample to be detected after passing through a scanning vibrating mirror and a focusing mirror, the light scattered back from the sample returns to a polarization maintaining coupler d end along the original path, the reference beam enters the polarization maintaining coupler c end and the sample beam enters the polarization maintaining coupler d end, the light after passing through a collimator and a fast axis direction enters a polarization maintaining coupler b, the sample beam enters a second balanced detector and a second balanced light detector, the sample beam enters a second balanced light detector and a second balanced light detector, the sample beam enters a second balanced light receiving end and a balanced light detector, and a second balanced light detector enters a balanced light receiving end, and a balanced light receiving device is calculated, and obtaining a sample polarization image after dispersion compensation by a full-depth dispersion compensation method and data processing of PS-OCT.
3. An electronic device comprising a processor, a memory coupled to the processor, the memory storing instructions for execution by the processor, the processor configured to execute the instructions stored by the memory to perform the steps of the full depth dispersion compensation method of claim 1.

Description

Full-depth dispersion compensation method and system for polarization sensitive optical coherence tomography Technical Field The application relates to a full-depth dispersion compensation method and a full-depth dispersion compensation system for polarization sensitive optical coherence tomography, which are applied to polarization sensitive optical coherence tomography (Polarization-SENSITIVE OPTICAL COHERENCE TOMOGRAPHY is called PS-OCT for short) and are used for compensating the dispersion existing in a polarization sensitive optical coherence tomography system, and belong to the technical field of polarization sensitive optical coherence tomography. Background OCT is an important imaging technique in biomedical optical imaging field, and has advantages of non-invasiveness, no damage, high resolution, etc. Since being invented in 1991, the imaging device becomes a hot spot of biomedical nondestructive optical imaging research, and is currently applied to clinical diagnosis and pathological research in the fields of ophthalmology, cardiovascular department and the like. Along with the development of technology, the functions of OCT are gradually expanded, and various functional OCT types, such as angiography OCT, polarization sensitive OCT, and the like, appear. OCT is based on partially coherent light interference, axial resolution is one of the key factors of OCT imaging quality, and OCT requires the use of a broad spectrum light source in order to achieve high axial resolution, so any index mismatch between the sample arm and the reference arm can cause dispersion in the system, widening the axial Point Spread Function (PSF), resulting in reduced resolution and reduced signal-to-noise ratio. For the PS-OCT system, two interference signals with mutually perpendicular polarization directions need to be obtained, and an OCT functional image is obtained through calculation, so that the image quality is seriously affected by the axial resolution degradation caused by chromatic dispersion. Currently, methods for compensating chromatic dispersion mainly include a hardware method and a software method. Hardware is to compensate for dispersion by adding a dispersion compensating element to the optical path, but this increases the cost and complexity of the system. The software method is mainly characterized in that the collected interference signals are subjected to data processing, and dispersion compensation is performed by a numerical calculation method. One common method is an iterative method, which evaluates the dispersion compensation result using an index such as image sharpness, and calculates the second-order and third-order dispersion coefficients, so as to eliminate the dispersion (reference ：M.Wojtkowski,V.J.Srinivasan,T.H.Ko,J.G.Fujimoto,A.Kowalczyk,and J.S.Duker,"Ultrahigh-resolution,high-speed,Fourier domain optical coherence tomography and methods for dispersion compensation,"Opt.Express,12,2404-2422(2004)),, but such a method can only correct the third-order dispersion, can not correct the higher-order dispersion, and has a large calculation amount, and reduces the imaging speed of the system, another method is a symmetrical phase measurement method (reference ：K.Singh,G.Sharma and G.J.Tearney,"Estimation and compensation of dispersion for a high-resolution optical coherence tomography system",J.Opt.,20,025301(2018))., which calculates the dispersion compensation curve by measuring the phase of a symmetrical position mirror, so as to eliminate the dispersion). Disclosure of Invention The technical problem to be solved by the application is how to effectively compensate the chromatic dispersion existing in the PS-OCT system. In order to solve the technical problems, the technical scheme of the application provides a full-depth dispersion compensation method applied to a PS-OCT system, which comprises the following steps: imaging a reflector by using a PS-OCT system to obtain an original interference signal, wherein the optical path difference of two arms is delta z; Subtracting the background of the interference signal in the horizontal direction in the two paths of signals with mutually perpendicular polarization directions to obtain a signal S (k, delta z) as a real part, and performing Hilbert transformation on the signal S (k, delta z) as an imaginary part to obtain amplitude and phase information of the signal Step three, pairAnd performing inverse Fourier transform, filtering the result, and filtering out information of polarization artifacts. Specifically, firstly, finding the position of a reflector signal, and windowing the signal by taking the position as the center to eliminate the influence of polarization artifact; Step four, filtering Extracting phase information of the reflector Step five, moving a reference arm, moving the imaging position of the reflecting mirror to a symmetrical position of the imaging position of the step about zero optical path, obtaining an original inter