A full eye imaging method and system based on polarization sensitive optical coherence tomography

Abstract

The application discloses a full-eye imaging method and system based on polarization-sensitive optical coherence tomography. Two interference signals with horizontal and vertical polarization directions are obtained by scanning an eye by a polarization-sensitive optical coherence tomography system, a polarization state of light is represented by using Stokes vectors, and real-time image reconstruction is performed. The full-eye imaging is realized based on the polarization-sensitive optical coherence tomography, structure and polarization information of the full eye is provided without labeling, and the recognition efficiency and accuracy of ophthalmic disease examination can be effectively improved, and the doctor is assisted in diagnosis. The imaging system is simple, convenient to package, has the advantages of non-invasion, high resolution, and in-vivo real-time detection of internal structure and polarization characteristics of the full-eye tissue.

Description

Technical Field

[0001] This application relates to a whole-eye imaging method and system based on polarization-sensitive optical coherence tomography, belonging to the field of bioimaging technology. Background Technology

[0002] Ophthalmic diseases such as refractive errors, cataracts, glaucoma, and fundus lesions can affect the structure and function of the eye. To assess these diseases and the resulting visual physiological changes, techniques capable of real-time, high-resolution imaging of the eye are essential. Optical coherence tomography (OCT), as a non-invasive, high-resolution, non-contact, and real-time imaging technique, has gradually become a routine diagnostic technique in ophthalmology.

[0003] Whole-eye OCT imaging, capable of simultaneously measuring information from the anterior segment and fundus, holds significant value in clinical ophthalmology. For instance, some ophthalmic diseases involve physiological changes in both the anterior segment and fundus, and myopia screening requires measuring axial length. While whole-eye OCT imaging systems have matured in recent years, traditional OCT can only detect biological sample structures through intensity information, making it difficult to reveal detailed tissue features.

[0004] Polarization techniques, by detecting changes in the polarization state of light after reflection or scattering through biological tissues, can obtain more polarization information than structural information alone. Polarization-sensitive OCT (PS-OCT), combined with polarization techniques, can distinguish tissues that are indistinguishable in OCT structural images by analyzing the polarization characteristics of the sample, building upon the acquired tissue structural information. Many tissues in the eye affect the polarization state of light. For example, the retinal pigment epithelium and choroid containing melanin can disrupt the polarization state of light and can be identified as depolarized tissues; the sclera and retinal nerve fiber layer, with their fibrous structures, are birefringent. Therefore, PS-OCT can help doctors identify these tissues and make diagnoses.

[0005] In 2011, Yiheng Lim et al. proposed a PS-OCT system for imaging the cornea and anterior segment, and studied the polarization characteristics of follicles after keratoconus and trabeculectomy (Lim Y, Yamanari M, Fukuda S, et al. Birefringence measurement of cornea and anterior segment by office-based polarization-sensitive optical coherence tomography[J]. Biomedical opticsexpress,2011,2(8):2392-2402.). In 2014, Boy Braaf et al. developed a fundus PS-OCT system based on fiber optic structure, demonstrating the phase delay and optical axis orientation information of the human retina (Braaf B, Vermeer KA, de Groot M, et al. Fiber-based polarization-sensitive OCT of the human retina with correction of system polarization distortions[J]. Biomedical optics express,2014,5(8):2736-2758.). Most subsequent studies employed a similar dual-input configuration, illuminating the sample with two beams of orthogonally polarized light and obtaining the polarization states of the two reflected beams to determine the sample's polarization characteristics. This method does not require strict control over the polarization state of the incident light, is easy to operate and maintain, and exhibits good stability. However, dual-input PS-OCT incurs significant time and space costs, and its optical path and imaging process are complex. Furthermore, currently, there is no PS-OCT system that comprehensively measures and images the entire eye.

[0006] Therefore, there is an urgent need for a whole-eye imaging method and system based on PS-OCT that can achieve high-resolution, non-contact, and non-invasive real-time imaging of the whole eye, providing information on eye tissue structure and polarization. Summary of the Invention

[0007] The purpose of this application is to overcome the shortcomings of the existing technology and provide a whole-eye imaging method and system based on PS-OCT, which can provide structural and polarization function information of the whole eye without labeling.

[0008] The specific technical solution is to provide a whole-eye imaging method based on polarization-sensitive optical coherence tomography (PS-OCT). The PS-OCT imaging system scans the eye to obtain two interference signals with horizontal and vertical polarization directions. The Stokes vector is used to represent the polarization state of light to perform real-time image reconstruction.

[0009] The specific steps are as follows:

[0010] Step 1: Acquire data with the polarization direction horizontal (I) H (k) and vertical direction I V (k) two interference signals;

[0011] Step 2: After preprocessing the two interference signals by removing background light and zero-padding, I is obtained. H (k) and I V The wavenumber domain signal of (k) is used; the inverse Fourier transform of the wavenumber domain signal is performed to obtain the complex amplitudes of the two interference signals in the horizontal and vertical directions, which are expressed as:

[0012]

[0013]

[0014] Where, parameter z represents the depth coordinate along the axial direction, and A and The amplitude and phase of the interference signal are represented by H and V, respectively; the subscripts H and V represent the horizontal and vertical directions, respectively; based on the above formula, eye information related to depth z can be obtained from the interference signal measured by two orthogonal polarization channels.

[0015] Step 3: Calculate the Stokes vector Describing the polarization state of light: Calculating the polarization image, based on the PS-OCT imaging principle, firstly, the corresponding Stokes vector is calculated.

[0016]

[0017] Here, the Stokes vector is the expression describing polarization, and I, Q, U, and V are the parameters of the Stokes vector; phase difference It describes the phase difference of the interfering light measured in two orthogonal polarization channels;

[0018] Step 4: Further calculate the four parameters based on the Stokes vector: reflection intensity I, cumulative phase delay δ, cumulative optical axis θ, and polarization uniformity (DOPU), as shown below:

[0019] I(z)=|A H (z)2 |+|A V (z) 2

[0020]

[0021]

[0022]

[0023] The measurement ranges of δ and θ are [0, π / 2] and [-π / 2, π / 2], respectively, which are used to describe the cumulative polarization state change of the eye from the surface to the measurement depth. DOPU represents the overall polarization degree within the selected window, which is used to describe the depolarization characteristics of the eye.

[0024] In the above methods, the PS-OCT imaging system is either fiber optic OCT or spatial light OCT.

[0025] In the above methods, the PS-OCT imaging system is a time-domain OCT, a spectral-domain OCT, or a swept-frequency light source OCT.

[0026] Optionally, the PS-OCT imaging system can be a swept-frequency light source PS-OCT imaging system, including a broadband light source, a polarization controller, a circulator, a polarization beam splitter I, a polarization-maintaining coupler, a collimator I, a quarter-wave plate I, a dispersion compensator, an aperture, a mirror, a collimator II, a quarter-wave plate II, an eye scanning module, a polarization beam splitter II, a balanced detector I, a balanced detector II, and a signal processing device.

[0027] The light output from the broadband light source is linearly polarized vertically after passing through a polarization controller. This linearly polarized light enters a circulator, and the light exiting the circulator is split into a reference beam and a sample beam after passing through polarization beam splitter one and the 50:50 polarization-maintaining coupler (end a). The reference beam passes through collimator one, a quarter-wave plate one with a 22.5° angle between the fast axis and the vertical direction, a dispersion compensator, and an aperture, and is reflected back to the polarization-maintaining coupler (end c) by a mirror. The sample beam passes through collimator two and a quarter-wave plate two with a 45° angle between the fast axis and the vertical direction, converting the sample beam from linearly polarized to circularly polarized. The sample beam is then viewed through the eye. The scanning module illuminates the eye, and the light scattered from the eye returns along the original path to end d of the polarization-maintaining coupler. The reference light entering end c of the polarization-maintaining coupler and the sample light entering end d interfere, and the interfered light exits from the polarization-maintaining coupler. The light exiting end a of the polarization-maintaining coupler enters polarization beam splitter one, and the light along the vertical direction passes through a circulator to enter balanced detector one, while the light along the horizontal direction enters balanced detector two. The light exiting end b of the polarization-maintaining coupler passes through polarization beam splitter two, and the light along the vertical direction enters balanced detector one, while the light along the horizontal direction enters balanced detector two. Balanced detector one and balanced detector two receive the light and convert it into an electrical signal, which is then transmitted to the signal processing device.

[0028] Optionally, the PS-OCT imaging system can be a spectral domain PS-OCT imaging system, including: a broadband light source, a linear polarizer, a non-polarizing beam splitter, a first quarter-wave plate, a dispersion compensator, an aperture, a mirror, a second quarter-wave plate, an eye scanning module, a polarizing beam splitter, a signal detector one, a signal detector two, and a signal processing device.

[0029] The light output from the broadband light source is linearly polarized vertically after passing through a linear polarizer. This linearly polarized light then enters a 50:50 unpolarized beam splitter and is split into a reference beam and a sample beam. The reference beam passes through a first quarter-wave plate (22.5° angle between the fast axis and the vertical), a dispersion compensator, and an aperture, and is reflected back to the unpolarized beam splitter by a mirror. The sample beam passes through a second quarter-wave plate (45° angle between the fast axis and the vertical), converting it from linearly polarized to circularly polarized. The sample beam illuminates the eye through an eye scanning module, and the light scattered from the eye returns to the unpolarized beam splitter along its original path. The reference and sample beams entering the unpolarized beam splitter interfere with each other, and the polarized beam splitter splits the interfered light into two beams with vertical and horizontal polarization directions, which are received by signal detector one and signal detector two, respectively. Signal detector one and signal detector two convert the received light into electrical signals, which are then transmitted to a signal processing device.

[0030] In a spectral domain PS-OCT imaging system, the signal detectors include a spectrometer and a linear array camera. The spectrometer disperses the light, and the linear array camera receives it.

[0031] Optionally, the PS-OCT imaging system can be a time-domain PS-OCT imaging system, including: a broadband light source, a linear polarizer, a non-polarizing beam splitter, a first quarter-wave plate, a dispersion compensator, an aperture, a mirror, a second quarter-wave plate, an eye scanning module, a polarizing beam splitter, a first signal detector, a second signal detector, and a signal processing device.

[0032] The light output from the broadband light source is linearly polarized vertically after passing through a linear polarizer. This linearly polarized light then enters a 50:50 unpolarized beam splitter and is split into a reference beam and a sample beam. The reference beam passes through a first quarter-wave plate (22.5° angle between the fast axis and the vertical), a dispersion compensator, and an aperture, and is reflected back to the unpolarized beam splitter by a mirror. The sample beam passes through a second quarter-wave plate (45° angle between the fast axis and the vertical), converting it from linearly polarized to circularly polarized. The sample beam illuminates the eye through an eye scanning module, and the light scattered from the eye returns to the unpolarized beam splitter along its original path. The reference and sample beams entering the unpolarized beam splitter interfere, and the polarized beam splitter splits the interfered light into two beams with vertical and horizontal polarization directions, which are received by a first signal detector and a second signal detector, respectively. The first and second signal detectors convert the received light into electrical signals, which are then transmitted to a signal processing device.

[0033] In a time-domain PS-OCT imaging system, the signal detector is a point detector, and the reflector moves longitudinally to achieve depth scanning.

[0034] Preferably, the eye scanning module is used to focus and scan the sample beam at different positions throughout the eye, including fundus imaging mode and anterior segment imaging mode.

[0035] Furthermore, the eye scanning module switches between fundus and anterior segment imaging modes by switching lenses to achieve whole-eye imaging. When the eye scanning module executes fundus imaging mode, its structure along the optical path includes a scanning galvanometer, a first convex lens, a second convex lens, and then to the eye under test. The sample beam is focused onto the fundus after passing through the eye scanning module to achieve fundus imaging. When the eye scanning module executes anterior segment imaging mode, its structure along the optical path includes a scanning galvanometer, a first convex lens, a third concave lens, a fourth convex lens, a second convex lens, and then to the eye under test. The sample beam is focused onto the anterior segment after passing through the eye scanning module to achieve anterior segment imaging.

[0036] This application utilizes polarization-sensitive optical coherence tomography to achieve whole-eye imaging, providing label-free structural and polarization information for the entire eye. This effectively improves the efficiency and accuracy of ophthalmic disease examinations, assisting doctors in diagnosis. The underlying imaging system is simple, easy to package, and offers advantages such as non-invasiveness, high resolution, and real-time in vivo detection of the internal structure and polarization characteristics of the entire eye tissue. Attached Figure Description

[0037] Figure 1 A flowchart of the PS-OCT whole-eye imaging method provided in this application;

[0038] Figure 2 This is a schematic diagram of the structure of a swept-frequency light source PS-OCT imaging system provided in one embodiment of this application;

[0039] In the diagram, 101-Broadband light source, 102-Polarization controller, 103-Circulator, 104-Polarization beam splitter I, 105-Polarization maintaining coupler, 106-Collider I, 107-Quarter-wave plate I, 108-Dispersion compensator, 109-Aperture, 110-Mirror, 111-Collider II, 112-Quarter-wave plate II, 400-Eye scanning module, 113-Polarization beam splitter II, 114-Balanced detector I, 115-Balanced detector II, 116-Signal processing device;

[0040] Figure 3 This is a schematic diagram of the structure of a spectral domain PS-OCT imaging system provided in one embodiment of this application;

[0041] In the diagram, 201-broadband light source, 202-linear polarizer, 203-unpolarized beam splitter, 204-first quarter-wave plate, 205-dispersion compensator, 206-aperture, 207-mirror, 208-second quarter-wave plate, 400-eye scanning module, 209-polarized beam splitter, 210-signal detector one, 211-signal detector two, 212-signal processing device;

[0042] Figure 4 This is a schematic diagram of the structure of a time-domain PS-OCT imaging system provided in one embodiment of this application;

[0043] In the figure, 301-broadband light source, 302-linear polarizer, 303-unpolarized beam splitter, 304-first quarter-wave plate, 305-dispersion compensator, 306-aperture, 307-mirror, 308-second quarter-wave plate, 400-eye scanning module, 309-polarized beam splitter, 310-first signal detector, 311-second signal detector, 312-signal processing device;

[0044] Figure 5-1 and Figure 5-2 This is a schematic diagram of the eye scanning module; in which, Figure 5-1 This is a schematic diagram of the fundus imaging mode of the eye scanning module; Figure 5-2 This is a schematic diagram of the anterior segment imaging mode of the eye scanning module;

[0045] In the figure, 401-scanning galvanometer, 402-first convex lens, 403-second convex lens, 404-eye under test, 405-third concave lens, and 406-fourth convex lens. Detailed Implementation

[0046] To make this application more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0047] This application provides a whole-eye imaging method and system based on PS-OCT. The PS-OCT imaging system scans the eye to obtain two interference signals with horizontal and vertical polarization directions. The polarization state of light is represented by Stokes vectors, and real-time image reconstruction is performed.

[0048] The flowchart of the PS-OCT whole-eye imaging method provided in this application is as follows: Figure 1 As shown, the specific steps are as follows:

[0049] Step 1: Acquire data with the polarization direction horizontal (I) H (k) and vertical direction I V (k) two interference signals;

[0050] Step 2: After preprocessing the two interference signals by removing background light and zero-padding, I is obtained. H (k) and I V The wavenumber domain signal (k) is obtained by performing an inverse Fourier transform on the wavenumber domain signal to obtain the complex amplitudes of the two interference signals in the horizontal and vertical directions, which can be expressed as:

[0051]

[0052]

[0053] Where, parameter z represents the depth coordinate along the axial direction, and A and The amplitude and phase of the interference signal are represented by H and V, respectively; the subscripts H and V represent the horizontal and vertical directions, respectively; based on the above formula, eye information related to depth z can be obtained from the interference signal measured by two orthogonal polarization channels.

[0054] Step 3: Calculate the Stokes vector Describing the polarization state of light: Calculating the polarization image, based on the PS-OCT principle, firstly, the corresponding Stokes vector is calculated.

[0055]

[0056] Here, the Stokes vector is the expression describing polarization, and I, Q, U, and V are the parameters of the Stokes vector; phase difference It describes the phase difference of the interfering light measured in two orthogonal polarization channels;

[0057] Step 4: Further calculate the four parameters—reflection intensity I, cumulative phase delay δ, cumulative optical axis θ, and polarization uniformity DOPU—based on the Stokes vector, as shown below:

[0058] I(z)=|A H (z) 2 |+|A V (z) 2

[0059]

[0060]

[0061]

[0062] The measurement ranges of δ and θ are [0, π / 2] and [-π / 2, π / 2], respectively, which are used to describe the cumulative polarization state change of the eye from the surface to the measurement depth. DOPU represents the overall polarization degree within the selected window, which is used to describe the depolarization characteristics of the eye.

[0063] The PS-OCT-based whole-eye imaging method provided in this application takes as input two interference signals with horizontal and vertical polarization directions obtained by scanning the eye through a PS-OCT imaging system. The specific PS-OCT imaging system is not limited and can be either all-fiber transmission or spatial light transmission. The method is simple, the system is lightweight, and real-time image reconstruction can be achieved.

[0064] The eye is scanned using a PS-OCT imaging system, which can be a fiber optic OCT or a spatial light OCT; it can be a time-domain OCT, a spectral-domain OCT, or a swept-frequency light source OCT; see the following examples.

[0065] Example 1

[0066] In one embodiment, a swept-frequency light source PS-OCT system is used, see [link to relevant documentation]. Figure 2 The system includes: a broadband light source 101, a polarization controller 102, a circulator 103, a polarization beam splitter 104, a polarization-maintaining coupler 105, a collimator 106, a quarter-wave plate 107, a dispersion compensator 108, an aperture 109, a mirror 110, a second collimator 111, a second quarter-wave plate 112, an eye scanning module 400, a second polarization beam splitter 113, a first balanced detector 114, a second balanced detector 115, and a signal processing device 116. Specifically, the broadband light source 101 uses a 1060nm or 1310nm swept frequency light source.

[0067] for Figure 2 The sweep frequency light source PS-OCT imaging system shown in the diagram outputs linearly polarized light vertically from the broadband light source 101 after passing through the polarization controller 102. This linearly polarized light enters the circulator 103, and the light exiting the circulator 103 is split into a reference beam and a sample beam after passing through the polarization beam splitter 104 and the polarization-maintaining coupler 105a (50:50). The reference beam passes through the collimator 106, a quarter-wave plate 107 (with a fast axis angle of 22.5° to the vertical direction), a dispersion compensator 108, and an aperture 109, and is reflected back to the polarization-maintaining coupler 105c by the mirror 110. The sample beam passes through the collimator 111 and a quarter-wave plate 112 (with a fast axis angle of 45° to the vertical direction), converting the sample beam from linearly polarized to circularly polarized. The sample beam illuminates the eye through the eye scanning module 400, and the light scattered from the eye returns to the polarization-maintaining coupler 105d along the original path. The reference light entering the polarization-maintaining coupler 105c and the sample light entering the polarization-maintaining coupler 105d interfere, and the interfered light exits from the polarization-maintaining coupler 105. The light exiting from the polarization-maintaining coupler 105a enters the polarization beam splitter 104; the vertical light passes through the circulator 103 and enters the balanced detector 114, while the horizontal light enters the balanced detector 115. The light exiting from the polarization-maintaining coupler 105b enters the polarization beam splitter 113; the vertical light enters the balanced detector 114, while the horizontal light enters the balanced detector 115. The balanced detectors 114 and 115 receive the light and convert it into electrical signals, which are then transmitted to the signal processing device 116 for calculation.

[0068] The eye scanning module 400 provided in this embodiment is shown below. Figure 5-1 and Figure 5-2 It includes two imaging modes: fundus imaging and anterior segment imaging. The eye scanning module 400 switches between these modes via lens switching to achieve whole-eye imaging. See [link to fundus imaging mode description] for details. Figure 5-1 The system includes a scanning galvanometer 401, a first convex lens 402, a second convex lens 403, and the eye under test 404. In this embodiment, the sample beam is focused onto the fundus after passing through the eye scanning module, achieving fundus imaging. See the anterior segment imaging mode for details. Figure 5-2 The system includes a scanning galvanometer 401, a first convex lens 402, a third concave lens 405, a fourth convex lens 406, a second convex lens 403, and the eye under test 404. In this embodiment, the sample beam is focused onto the anterior segment of the eye after passing through the eye scanning module, achieving anterior segment imaging.

[0069] In this embodiment, the signal processing device 116 is a computing device such as a computer or engineering machine equipped with a high-speed acquisition card, which executes the PS-OCT-based whole-eye imaging method to calculate the polarization image of the eye.

[0070] Example 2

[0071] In yet another embodiment, a spectral-domain PS-OCT system is employed; see [link to relevant documentation]. Figure 3 The system includes: a broadband light source 201, a linear polarizer 202, a non-polarizing beam splitter 203, a first quarter-wave plate 204, a dispersion compensator 205, an aperture 206, a reflector 207, a second quarter-wave plate 208, an eye scanning module 400, a polarizing beam splitter 209, a first signal detector 210, a second signal detector 211, and a signal processing device 212. Specifically, the broadband light source 201 uses an 830nm or 1060nm broadband light source.

[0072] For the spectral domain PS-OCT imaging system, the light output from the broadband light source 201 is linearly polarized vertically after passing through the linear polarizer 202. This linearly polarized light then enters a 50:50 unpolarized beam splitter 203 and is evenly split into a reference beam and a sample beam. The reference beam passes through a first quarter-wave plate 204 with a fast axis angle of 22.5° to the vertical direction, a dispersion compensator 205, and an aperture 206, and is reflected back to the unpolarized beam splitter 203 by a mirror 207. The sample beam passes through a second quarter-wave plate 208 with a fast axis angle of 45° to the vertical direction, causing the sample beam to change from a linearly polarized state to a circularly polarized state. The sample beam illuminates the eye through the eye scanning module 400, and the light scattered from the eye returns to the unpolarized beam splitter 203 along its original path. The reference light and sample light entering the non-polarizing beam splitter 203 interfere with each other. The polarizing beam splitter 209 then splits the interfered light into two beams, one vertically polarized and the other horizontally polarized. These beams are received by signal detector 210 and signal detector 211, respectively. In this embodiment, the signal detectors consist of a spectrometer and a linear array camera. After receiving the light, signal detectors 210 and 211 convert it into electrical signals, which are then transmitted to the signal processing device 212 for calculation.

[0073] The eye scanning module 400 described in this embodiment is the same as the eye scanning module 400 in Embodiment 1.

[0074] In this embodiment, the signal processing device 212 is a computing device such as a computer or engineering machine equipped with a high-speed acquisition card, which executes the PS-OCT-based whole-eye imaging method to calculate the polarization image of the eye.

[0075] In a spectral OCT system, a spectrometer is used to disperse the signal, and a linear array camera receives the signal to achieve depth scanning of the eye.

[0076] Example 3

[0077] In yet another embodiment, a time-domain PS-OCT system is employed; see [link to relevant documentation]. Figure 4The system includes a broadband light source 301, a linear polarizer 302, a non-polarizing beam splitter 303, a first quarter-wave plate 304, a dispersion compensator 305, an aperture 306, a reflector 307, a second quarter-wave plate 308, an eye scanning module 400, a polarizing beam splitter 309, a first signal detector 310, a second signal detector 311, and a signal processing device 312. Specifically, the broadband light source 301 uses an 830nm or 1060nm broadband light source.

[0078] The light output from the broadband light source 301 is linearly polarized vertically after passing through the linear polarizer 302. This linearly polarized light then enters a 50:50 unpolarized beam splitter 303 and is split into a reference beam and a sample beam. The reference beam passes through a first quarter-wave plate 304 (with a fast axis angle of 22.5° to the vertical), a dispersion compensator 305, and an aperture 306, and is reflected back to the unpolarized beam splitter 303 by a mirror 307. The sample beam passes through a second quarter-wave plate 308 (with a fast axis angle of 45° to the vertical), converting the sample beam from linearly polarized to circularly polarized. The sample beam then illuminates the eye through the eye scanning module 400, and the light scattered from the eye returns to the unpolarized beam splitter 303 along its original path. The reference light and sample light entering the non-polarizing beam splitter 303 interfere with each other. The polarizing beam splitter 309 then splits the interfered light into two beams, one vertically polarized and the other horizontally polarized. These beams are received by a first signal detector 310 and a second signal detector 311, respectively. In this embodiment, the signal detectors are point detectors. After receiving the light, the first signal detector 310 and the second signal detector 311 convert it into electrical signals, which are then transmitted to the signal processing device 312 for calculation.

[0079] The eye scanning module 400 described in this embodiment is the same as the eye scanning module 400 in Embodiment 1.

[0080] In this embodiment, the signal processing device 312 is a computing device such as a computer or engineering machine equipped with a high-speed acquisition card, which executes the PS-OCT whole-eye imaging method to calculate the polarization image of the eye.

[0081] In a time-domain OCT system, the signal detector is a point detector, and the mirror moves longitudinally to achieve eye depth scanning.

Claims

1. A whole-eye imaging system based on polarization-sensitive optical coherence tomography (PS-OCT), characterized in that, The eye was scanned using a PS-OCT imaging system, which can be a time-domain OCT, spectral-domain OCT, or frequency-sweeping light source OCT. The PS-OCT imaging system is configured as a swept-frequency light source PS-OCT system, including a broadband light source, a polarization controller, a circulator, a polarization beam splitter I, a polarization-maintaining coupler, a collimator I, a quarter-wave plate I, a dispersion compensator, an aperture, a mirror, a collimator II, a quarter-wave plate II, an eye scanning module, a polarization beam splitter II, a balanced detector I, a balanced detector II, and a signal processing device. The light output from the broadband light source is linearly polarized vertically after passing through the polarization controller. This linearly polarized light enters the circulator, and the light exiting the circulator is split into a reference beam and a sample beam after passing through polarization beam splitter I and the a-end of a 50:50 polarization-maintaining coupler. The reference beam passes through collimator I, a quarter-wave plate I with a 22.5° angle between the fast axis and the vertical direction, the dispersion compensator, and the aperture, and is reflected back to the polarization-maintaining coupler by the mirror. The sample beam passes through collimator two and a quarter-wave plate two with a 45° angle between the fast axis and the vertical direction, converting the sample beam from linear polarization to circular polarization. The sample beam illuminates the eye through the eye scanning module, and the light scattered from the eye returns to the polarization-maintaining coupler d along the original path. The reference light entering the polarization-maintaining coupler c and the sample light entering the polarization-maintaining coupler d interfere, and the interfered light exits the polarization-maintaining coupler. The light exiting the polarization-maintaining coupler a enters polarization beam splitter one, and the vertical light passes through a circulator to enter balanced detector one, while the horizontal light enters balanced detector two. The light exiting the polarization-maintaining coupler b passes through polarization beam splitter two, and the vertical light enters balanced detector one, while the horizontal light enters balanced detector two. Balanced detector one and balanced detector two receive the light and convert it into electrical signals, which are then transmitted to the signal processing device. The eye scanning module is used to focus and scan the sample beam at different positions throughout the eye, including fundus imaging mode and anterior segment imaging mode. The eye scanning module switches between fundus and anterior segment imaging modes by switching lenses to achieve whole-eye imaging. When the eye scanning module executes fundus imaging mode, its structure along the optical path includes a scanning galvanometer, a first convex lens, and a second convex lens. The sample beam is focused onto the fundus after passing through the eye scanning module to achieve fundus imaging. When the eye scanning module executes anterior segment imaging mode, its structure along the optical path includes a scanning galvanometer, a first convex lens, a third concave lens, a fourth convex lens, and a second convex lens. The sample beam is focused onto the anterior segment after passing through the eye scanning module to achieve anterior segment imaging.

2. The whole-eye imaging system based on polarization-sensitive optical coherence tomography as described in claim 1, characterized in that, The PS-OCT imaging system is either fiber optic OCT or spatial light OCT.

3. The whole-eye imaging system based on polarization-sensitive optical coherence tomography as described in claim 1, characterized in that, The PS-OCT imaging system is configured as a spectral domain PS-OCT imaging system, including: a broadband light source, a linear polarizer, a non-polarizing beam splitter, a first quarter-wave plate, a dispersion compensator, an aperture, a mirror, a second quarter-wave plate, an eye scanning module, a polarizing beam splitter, a signal detector one, a signal detector two, and a signal processing device. The light output from the broadband light source is linearly polarized vertically after passing through a linear polarizer. This linearly polarized light then enters a 50:50 unpolarized beam splitter and is split into a reference beam and a sample beam. The reference beam passes through a first quarter-wave plate (22.5° angle between the fast axis and the vertical), a dispersion compensator, and an aperture, and is reflected back to the unpolarized beam splitter by a mirror. The sample beam passes through a second quarter-wave plate (45° angle between the fast axis and the vertical), converting it from linearly polarized to circularly polarized. The sample beam illuminates the eye through an eye scanning module, and the light scattered from the eye returns to the unpolarized beam splitter along its original path. The reference and sample beams entering the unpolarized beam splitter interfere with each other, and the polarized beam splitter splits the interfered light into two beams with vertical and horizontal polarization directions, which are received by signal detector one and signal detector two, respectively. Signal detector one and signal detector two convert the received light into electrical signals, which are then transmitted to a signal processing device.

4. A whole-eye imaging system based on polarization-sensitive optical coherence tomography as described in claim 3, characterized in that, The signal detector includes a spectrometer and a linear array camera.

5. A whole-eye imaging system based on polarization-sensitive optical coherence tomography as described in claim 1, characterized in that, The PS-OCT imaging system is configured as a time-domain PS-OCT imaging system, including: a broadband light source, a linear polarizer, a non-polarizing beam splitter, a first quarter-wave plate, a dispersion compensator, an aperture, a mirror, a second quarter-wave plate, an eye scanning module, a polarizing beam splitter, a first signal detector, a second signal detector, and a signal processing device. The light output from the broadband light source is linearly polarized vertically after passing through a linear polarizer. This linearly polarized light then enters a 50:50 unpolarized beam splitter and is split into a reference beam and a sample beam. The reference beam passes through a first quarter-wave plate (22.5° angle between the fast axis and the vertical), a dispersion compensator, and an aperture, and is reflected back to the unpolarized beam splitter by a mirror. The sample beam passes through a second quarter-wave plate (45° angle between the fast axis and the vertical), converting it from linearly polarized to circularly polarized. The sample beam illuminates the eye through an eye scanning module, and the light scattered from the eye returns to the unpolarized beam splitter along its original path. The reference and sample beams entering the unpolarized beam splitter interfere, and the polarized beam splitter splits the interfered light into two beams with vertical and horizontal polarization directions, which are received by a first signal detector and a second signal detector, respectively. The first and second signal detectors convert the received light into electrical signals, which are then transmitted to a signal processing device.

6. A whole-eye imaging system based on polarization-sensitive optical coherence tomography as described in claim 5, characterized in that, The signal detector is set as a point detector, and the reflector moves longitudinally to achieve depth scanning.

7. A whole-eye imaging system based on polarization-sensitive optical coherence tomography as described in claim 1, characterized in that, The system is used to implement a whole-eye imaging method based on polarization-sensitive optical coherence tomography (PS-OCT), including: scanning the eye with a PS-OCT imaging system to obtain two interference signals with horizontal and vertical polarization directions, using Stokes vectors to represent the polarization state of light, and performing real-time image reconstruction. The specific steps include: Step 1: Acquire data with the polarization direction horizontal. and vertical direction Two interference signals; Step 2: After preprocessing the two interference signals by removing background light and zero-padding, the results are obtained. and The wavenumber domain signal; performing an inverse Fourier transform on the wavenumber domain signal yields the complex amplitudes of the two interference signals in the horizontal and vertical directions, expressed as: Among them, parameters z Represents the depth coordinates along the axial direction. A and These represent the amplitude and phase of the interference signal, respectively; subscripts. H and V These represent the horizontal and vertical directions, respectively; based on the above formula, the interference signal measured from two orthogonal polarization channels can be used to obtain the relationship between depth and direction. z Relevant eye information; Step 3: Calculate the Stokes vector Describing the polarization state of light: Calculating the polarization image, based on the principle of polarization-sensitive optical coherence tomography, firstly, the corresponding Stokes vector is calculated. : Among them, the Stokes vector is the expression describing polarization. I, Q, U, V The parameters of the Stokes vector; phase difference V This describes the phase difference of the interference light measured in two orthogonal polarization channels; Step 4: Further calculate the reflection intensity based on the Stokes vector. I Cumulative phase delay δ Accumulated optical axis θ Polarization uniformity DOPU The four parameters are as follows: in, δ and θ The measurement ranges are [0, π / 2] and [-π / 2, π / 2], respectively, used to describe the cumulative polarization state change of the eye from the surface to the measurement depth. DOPU This indicates the overall degree of polarization within the selected window, used to describe the depolarization characteristics of the eye.

Images