An axial length measuring device based on polarization splitting OCT

Abstract

The application discloses an axial measurement device based on polarization splitting OCT. After sample arm light beams emitted from an OCT main module are split by a polarization splitting of a polarization dual-optical-path detection module, anterior segment light beams and posterior segment light beams are emitted from the polarization dual-optical-path detection module, the anterior segment light beams and the posterior segment light beams are reflected by a splitting element and then enter the anterior segment position and the posterior segment position of an eye to be measured through an objective lens, and the anterior segment imaging light beams and the posterior segment imaging light beams are returned to the OCT main module along the original light paths. In the application, the sample arm light beams are split into the anterior segment light beams and the posterior segment light beams by a polarization splitting prism, the optical paths of the anterior segment light beams and the posterior segment light beams are matched with the optical path of a reference arm by an optical path adjustment device, the cornea and the retina are simultaneously focused and imaged by the setting of the anterior segment and the posterior segment dual sample arms, and the axial length of the eye to be measured is measured according to the OCT imaging result and the displacement of the optical path adjustment device.

Description

Technical Field

[0001] This invention relates to an axial length measuring device in the field of medical device technology, specifically an axial length measuring device based on polarization-split OCT (Optical Coherence Tomography). Background Technology

[0002] Optical coherence tomography (OCT) technology, with its non-invasive and high-speed advantages, can provide high-resolution tomographic imaging of the internal microstructure of biological tissues. As an advanced medical imaging technology, it has received widespread attention in the market, especially in the field of clinical ophthalmology. However, limited by the imaging depth of the system and the differences in the optical structures required for imaging the anterior and posterior segments, traditional OCT systems can only focus and image a specific single region of the eye (the anterior cornea or the posterior retina). OCT systems used for axial length measurement, on the other hand, need to achieve imaging of both the anterior and posterior segments of the eye, i.e., whole-eye imaging. Whole-eye OCT systems allow us to view the eye as a whole, rather than as a separate, independent part.

[0003] Currently, there are several whole-eye OCT systems for measuring axial length, but they still have the following drawbacks: In the axial length measurement system and method disclosed in patent document 202011264580.7, time-separated imaging of the anterior and posterior segments is achieved by switching the optical path settings of the sample arm and the optical path of the reference arm. In the axial length measurement system and method disclosed in patent document 201820232006.5, time-separated imaging of the anterior and posterior segments is achieved by switching the optical paths of the anterior and posterior segments using different rotation angles of the galvanometer, but at the same time... Within the time frame, only one optical path assembly in the anterior and posterior segments allows the sample arm beam to pass through; in the axial length measurement systems and methods disclosed in patent documents such as 202010202763.X and 202121905127.X, a variable focus lens is added to the sample arm to dynamically focus on different positions of the subject's eye, achieving time-separated imaging of the anterior and posterior segments. However, at any given moment, only a single region of the eye (anterior segment cornea or posterior segment retina) can be focused and imaged; in patent document US20130301006 In the axial length measurement systems and methods disclosed in A1 et al., interference signals from the anterior and posterior segments are alternately transmitted to the spectrometer by setting an optical switch to achieve time-division alternating imaging of the anterior and posterior segments. However, the refractive objective lens in front of the eyepiece in this optical path is limited by the position of the anterior segment optical path, and cannot be adjusted according to the movement of the human eye with different refractive powers during actual measurement, affecting the actual measurement. These time-division imaging whole-eye OCT systems are easily affected by eye movement interference during axial length measurement, resulting in a large error in axial length measurement. In the axial length measurement systems and methods disclosed in patent documents such as 202011037937.8, simultaneous imaging of the anterior and posterior segments can be achieved, but only the anterior segment is focused, and the posterior segment only has a blurry imaging result, which cannot determine the accurate imaging position of the pigment epithelium in the retina, affecting the accuracy of axial length measurement. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies, this invention proposes an axial length measurement device based on polarization-splitting OCT. This device achieves simultaneous focusing and imaging of the anterior and posterior segments through polarization-splitting and the setup of dual sample arms.

[0005] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0006] This invention includes an OCT main module, a polarization dual-path detection module, a beam splitter, an eyepiece objective, an iris imaging module, and a fixation module;

[0007] The sample arm beam emitted from the OCT main module is polarized and split by the polarization dual-path detection module, resulting in an anterior segment beam and a posterior segment beam. The anterior segment beam is reflected by the beam splitter and transmitted through the eyepiece objective before entering the anterior segment of the subject's eye. The posterior segment beam is reflected by the beam splitter and transmitted through the eyepiece objective before entering the posterior segment of the subject's eye. The anterior and posterior segment beams simultaneously enter the corresponding positions of the subject's eye and are then reflected by the anterior and posterior segments to form an anterior segment imaging beam and a posterior segment imaging beam, respectively. The anterior and posterior segment imaging beams return to the OCT main module along the original optical path. The fixation beam emitted from the fixation module is polarized and split by the polarization dual-path detection module, the beam splitter, and the eyepiece objective before entering the subject's eye. The infrared illumination beam emitted from the iris imaging module is reflected by the subject's eye and returns to the iris imaging module for iris imaging.

[0008] The main OCT module includes a broadband light source, an optical fiber coupler, a polarization controller, a reference arm collimator, a reference arm focusing lens, a reference arm reflector, a sample arm polarization controller, a sample arm collimator, an OCT scanning device, and a detector module.

[0009] The first branch on one side of the fiber optic coupler is connected to a broadband light source, and the second branch on the same side is connected to a detector module. The first branch on the other side of the fiber optic coupler is connected to a reference arm mirror after passing through a polarization controller, a reference arm collimator, and a reference arm focusing lens in sequence. The second branch on the other side of the fiber optic coupler is connected to an OCT scanning device after passing through a sample arm polarization controller and a sample arm collimator. The OCT scanning device is connected to the first polarization beam splitter.

[0010] The polarization dual-path detection module includes a first polarization beam splitter, an anterior segment optical path assembly, a posterior segment optical path assembly, and a second polarization beam splitter.

[0011] The sample arm beam emitted from the OCT main module is incident on the first polarizing beam splitter to split the beam. The reflected beam from the first polarizing beam splitter is incident on the posterior segment optical path assembly. The reflected beam from the posterior segment optical path assembly is incident on the second polarizing beam splitter to obtain the posterior segment beam. The fixation module is connected to the posterior segment optical path assembly. The transmitted beam from the first polarizing beam splitter is incident on the anterior segment optical path assembly. The transmitted beam from the anterior segment optical path assembly is incident on the second polarizing beam splitter to obtain the anterior segment beam.

[0012] The anterior segment optical path assembly includes an anterior segment first relay lens, an anterior segment first reflector, an anterior segment second relay lens, and an anterior segment second reflector. The transmitted beam from the first polarizing beam splitter passes sequentially along the optical axis through the convergence of the anterior segment first relay lens, the reflection of the anterior segment first reflector, the transmission of the anterior segment second relay lens, and the reflection of the anterior segment second reflector before being incident on the second polarizing beam splitter for transmission, thus obtaining the anterior segment beam.

[0013] The posterior segment optical path assembly includes a posterior segment reflector, a posterior segment optical path adjustment device, a posterior segment refractive objective lens, and a first dichroic mirror. The reflected beam from the first polarizing beam splitter is reflected along the optical axis by the posterior segment reflector, transmitted through the posterior segment optical path adjustment device and the posterior segment refractive objective lens, and then reflected by the first dichroic mirror before being reflected by the second polarizing beam splitter to obtain a posterior segment beam. The fixation beam emitted from the fixation module is transmitted through the first dichroic mirror and then reflected by the second polarizing beam splitter.

[0014] The polarization dual-path detection module includes a first polarization beam splitter, an anterior segment optical path assembly, a posterior segment optical path assembly, and a second polarization beam splitter.

[0015] The sample arm beam emitted from the OCT main module is incident on the first polarizing beam splitter to split the beam. The reflected beam from the first polarizing beam splitter is incident on the anterior segment optical path assembly. The reflected beam from the anterior segment optical path assembly is incident on the second polarizing beam splitter to obtain the anterior segment beam. The transmitted beam from the first polarizing beam splitter is incident on the posterior segment optical path assembly. The transmitted beam from the posterior segment optical path assembly is incident on the second polarizing beam splitter to obtain the posterior segment beam. The fixation module is connected to the posterior segment optical path assembly.

[0016] The anterior segment optical path assembly includes an anterior segment first relay lens, an anterior segment first reflector, an anterior segment second relay lens, an anterior segment second reflector, an anterior segment third reflector, and an anterior segment fourth reflector. The reflected beam from the first polarizing beam splitter is reflected along the optical axis by the first anterior segment reflector, the third anterior segment reflector, the fourth anterior segment reflector, the convergence of the first anterior segment relay lens, the reflection of the second anterior segment reflector, and the transmission of the second anterior segment relay lens before being incident on the second polarizing beam splitter for reflection, thus obtaining the anterior segment beam.

[0017] The posterior segment optical path assembly includes a posterior segment optical path adjustment device, a posterior segment refractive objective lens, and a first dichroic mirror; the transmitted beam from the first polarizing beam splitter passes sequentially along the optical axis through the posterior segment optical path adjustment device and the posterior segment refractive objective lens before being transmitted to the second polarizing beam splitter to obtain a posterior segment beam; the fixation beam emitted from the fixation module passes through the posterior segment optical path adjustment device and the posterior segment refractive objective lens before being transmitted to the second polarizing beam splitter.

[0018] The posterior segment optical path adjustment device includes two reflective surfaces and an adjustment device displacement stage. Both reflective surfaces are mounted on the adjustment device displacement stage. The adjustment device displacement stage moves along the optical axis. The incident beam of the posterior segment optical path adjustment device is reflected by the two reflective surfaces in sequence and then becomes the output beam of the posterior segment optical path adjustment device.

[0019] The two reflecting surfaces are composed of one right-angle prism or two reflecting mirrors, and the adjustment device displacement stage is either a manual displacement stage or an electric displacement stage.

[0020] The iris imaging module includes an iris illumination source, an iris imaging diverging lens, an iris imaging focusing lens, and an iris camera. The iris illumination source is located on the side of the eyepiece objective lens. The light emitted by the iris illumination source is reflected by the cornea of ​​the subject's eye to form an iris imaging beam. The iris imaging beam passes sequentially along the optical axis through the eyepiece objective lens, the beam splitter, the iris imaging diverging lens, and the iris imaging focusing lens before entering the iris camera.

[0021] The fixation module includes a fixation lens and a fixation light source. The fixation beam emitted by the fixation module is transmitted through the first dichroic mirror and then becomes the fixation beam of the fixation module.

[0022] The OCT main module adopts one of the following methods:

[0023] A time-domain OCT imaging method using mechanical scanning and changing the optical path of the reference arm;

[0024] Alternatively, a spectrometer-based OCT imaging method can be used to record spectral interference signals;

[0025] Alternatively, a swept-frequency OCT imaging method can be used to record spectral interference signals by line scanning with a swept-frequency light source.

[0026] The beneficial effects and innovative points of this invention are as follows:

[0027] 1. Two polarizing beam splitters are set up. The first polarizing beam splitter splits the sample arm beam after reflection by the scanning galvanometer into P-polarized light and S-polarized light according to the polarization characteristics. These light enter the anterior segment optical path assembly and the posterior segment optical path assembly, respectively, and are referred to as the anterior segment beam and the posterior segment beam. The second polarizing beam splitter couples the anterior segment beam and the posterior segment beam together. By setting up the dual sample arms of the anterior segment optical path assembly and the posterior segment optical path assembly, the simultaneous focusing of the anterior segment and the posterior segment is achieved in the optical path.

[0028] 2. The posterior segment optical path assembly is equipped with an optical path adjustment device to enable the anterior segment optical path and the posterior segment optical path to share a single reference arm. In actual measurement, the optical paths of the anterior segment optical path, the posterior segment optical path and the reference arm are matched, which improves the accuracy of eye axis measurement. At the same time, the single reference arm setting saves system costs.

[0029] 3. The setting of the polarization beam splitter allows the imaging beam of the anterior segment and the imaging beam of the posterior segment to interfere with the corresponding components in the reference arm beam. Because the polarization states are orthogonal and the optical paths are different, the interference signals of the anterior and posterior segments do not interfere with each other, thus realizing simultaneous imaging of the anterior and posterior segments.

[0030] 4. By using polarization beam splitting, the imaging beams of the anterior segment and posterior segment of the eye return along the original optical path. After passing through the polarization beam splitting prism, there is no light energy loss. Compared with the use of traditional beam splitting prisms, the signal-to-noise ratio of OCT images is higher.

[0031] 5. In the main OCT module, the OCT full-range technology can also be used to introduce a certain phase modulation by the rotation axis of the bias scanning galvanometer to construct the corresponding imaginary part signal, which is then combined with the real part to form a complex analytical signal, eliminating the conjugate image caused by positive and negative frequencies, further extending the anterior segment range, and realizing full-range imaging of the human anterior segment. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the modules of the device of the present invention;

[0033] Figure 2 This is a schematic diagram of a module of one embodiment of the device of the present invention;

[0034] Figure 3 This is a schematic diagram of the structure of an example device of the present invention;

[0035] Figure 4 This is a schematic diagram of a module according to another embodiment of the device of the present invention;

[0036] Figure 5 This is a schematic diagram of the structure of another example device of the present invention;

[0037] Figure 6 An imaging result diagram of an exemplary embodiment of the present invention;

[0038] In the diagram: 101-Broadband light source; 102-Fiber optic coupler; 103-First polarization controller; 104-Reference arm collimator; 105-Reference arm focusing lens; 106-Reference arm mirror; 107-Second polarization controller; 108-Sample arm collimator; 109-Scanning galvanometer; 110-Spectrometer collimator; 111-Spectrometer reflective grating; 112-Spectrometer focusing lens; 113-Spectrometer camera; 2-First polarization beam splitter; 301-First relay lens of the anterior segment; 302-First mirror of the anterior segment; 303-Second relay lens of the anterior segment. 304 - Second reflecting mirror of the anterior segment; 305 - Third reflecting mirror of the anterior segment; 306 - Fourth reflecting mirror of the anterior segment; 4 - Second polarizing beam splitter prism; 501 - Reflecting mirror of the posterior segment; 502 - Optical path adjustment device of the posterior segment; 503 - Refractive objective lens of the posterior segment; 504 - First dichroic mirror; 6 - Eye under test; 701 - Iris illumination source; 702 - Eyepiece objective lens; 704 - Iris imaging diverging lens; 705 - Iris imaging focusing lens; 706 - Iris camera; 801 - Fixing lens; 802 - Fixing source; 9 - Polarizing dual-path detection module; 10 - Beam splitter element. Detailed Implementation

[0039] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this document. It should be noted that these descriptions and examples are merely illustrative and should not be construed as limiting the scope of the present invention. The scope of protection of the present invention is defined by the appended claims, and any modifications based on the claims of the present invention are within the scope of protection of the present invention.

[0040] To facilitate understanding of the embodiments of the present invention, each operation is described as a plurality of discrete operations; however, the order of description does not represent the order in which the operations are performed.

[0041] The embodiments of the present invention are as follows:

[0042] like Figure 1 As shown, the present invention includes an OCT main module 1, a polarization dual-path detection module 9, an eyepiece objective lens 702, a beam splitter 10, an iris imaging module 7, and a fixation module 8;

[0043] The sample arm beam emitted from the OCT main module 1 is polarized and split by the polarization dual-path detection module 9, resulting in an anterior segment beam and a posterior segment beam. The anterior segment beam is reflected by the beam splitter 10 and transmitted through the eyepiece objective 702 before entering the anterior segment (cornea) of the subject eye 6. The posterior segment beam is reflected by the beam splitter 10 and transmitted through the eyepiece objective 702 before entering the posterior segment (retina) of the subject eye 6. The anterior and posterior segment beams simultaneously enter the corresponding positions of the subject eye 6. The anterior segment beam reaches the anterior segment of the subject's eye 6 simultaneously with the posterior segment beam. After reflection from the anterior and posterior segments, they form an anterior segment imaging beam and a posterior segment imaging beam, which then return to the OCT main module 1. The OCT main module 1 simultaneously interferes with the corresponding components of the anterior and posterior segment imaging beams with the reference arm beam. This interference is received by the detector module to obtain the OCT imaging results of the anterior and posterior segments of the subject. The fixation beam emitted from the fixation module 8 passes sequentially through the refractive adjustment of the posterior segment optical path component 5 in the polarization dual-path detection module 9, the reflection of the beam splitter 10, and the eyepiece objective 702 before entering the subject's eye 6. It converges onto the retina to ensure fixed gaze during acquisition. The infrared illumination beam emitted from the iris imaging module 7 is reflected by the subject's eye 6 and returns to the iris imaging module 7 for iris imaging.

[0044] The OCT main module 1 includes a broadband light source 101, an optical fiber coupler 102, a polarization controller 103, a reference arm collimator 104, a reference arm focusing lens 105, a reference arm reflector 106, a sample arm polarization controller 107, a sample arm collimator 108, an OCT scanning device 109, and a detector module.

[0045] The first branch end on one side of the fiber optic coupler 102 is connected to the broadband light source 101, and the second branch end on one side of the fiber optic coupler 102 is connected to the detector module. Taking spectral domain OCT as an example, the detector module is a spectrometer, which includes a spectrometer collimator 110, a spectrometer reflective grating 111, a spectrometer focusing lens 112, and a spectrometer camera 113.

[0046] The second branch on one side of the fiber optic coupler 102 is connected to the spectrometer camera 113 after passing through the spectrometer collimator 110, the spectrometer reflective grating 111, and the spectrometer focusing lens 112 in sequence. The first branch on the other side of the fiber optic coupler 102 is connected to the reference arm mirror 106 after passing through the polarization controller 103, the reference arm collimator 104, and the reference arm focusing lens 105 in sequence. The reference arm mirror 106 is located at the focal point of the reference arm focusing lens 105. The second branch on the other side of the fiber optic coupler 102 is connected to the OCT scanning device 109 after passing through the sample arm polarization controller 107 and the sample arm collimator 108. The OCT scanning device 109 is connected to the first polarizing beam splitter 2.

[0047] The broadband light source 101 emits a sample arm beam and a reference arm beam after passing through the fiber coupler 102. The sample arm beam emitted from the fiber coupler 102 is adjusted into circularly polarized light by the second polarization controller 107, so that after the sample arm beam is emitted by the sample arm collimator 108, it is reflected by the scanning galvanometer 109 and then enters the first polarization beam splitter 2 for beam splitting. The ratio of the intensity of the reflected beam to the transmitted beam of the first polarization beam splitter 2 is 50:50. The reference arm beam emitted from the fiber coupler 102 passes sequentially along the optical axis through the first polarization controller 103, the reference arm collimator 104 and the reference arm reflector 106. After being reflected by the reference arm reflector 106, it returns to the fiber coupler 102 along the same path. The reference arm beam contains both P and S components.

[0048] Optical path matching is required for the anterior segment optical path, posterior segment optical path, and reference arm optical path, meaning that the optical paths of the anterior segment optical path, posterior segment optical path, and reference arm optical path are equal at the zero optical path position. In the actual image acquisition process, both the cornea and retina have a certain optical thickness. The optical path of the anterior and posterior segments optical paths only needs to satisfy the requirement that the difference between the optical path of the anterior and posterior segments optical paths and the optical path of the reference arm optical path is less than the system's imaging range. Furthermore, the closer the acquired image is to zero optical path, the better the image signal-to-noise ratio.

[0049] The anterior segment beam is converged on the cornea of ​​the human eye through the eyepiece objective 702 to form an anterior segment imaging beam carrying anterior segment information. It returns along the original optical path to the fiber coupler 102 and generates an anterior segment low coherence interference signal with the polarization state component corresponding to the anterior segment in the reference arm beam. The anterior segment low coherence interference signal finally enters the detector module along the optical axis and is collected by the detector module.

[0050] The posterior segment beam enters the human eye 6 as a parallel beam and is converged by the lens of the human eye onto the retina. The posterior segment imaging beam carrying the information of the human eye's retina returns along the original optical path to the fiber coupler 102 and the reference arm beam. The corresponding polarization state component of the posterior segment generates a low-coherence interference signal of the posterior segment. The low-coherence interference signal of the posterior segment finally enters the detector module along the optical axis and is acquired by the detector module.

[0051] like Figure 2 and 3 As shown, the polarization dual-path detection module 9 includes a first polarization beam splitter 2, an anterior segment optical path assembly 3, a posterior segment optical path assembly 5, and a second polarization beam splitter 4.

[0052] The sample arm beam emitted from the OCT main module 1 is incident on the first polarizing beam splitter 2, resulting in beam splitting (reflection and transmission). The beam after splitting by the first polarizing beam splitter 2 is polarized (P-polarized) and reflected (S-polarized). The reflected beam from the first polarizing beam splitter 2 is incident on the posterior segment optical path assembly 5. The reflected beam from the posterior segment optical path assembly 5 is then incident on the second polarizing beam splitter 4, resulting in a posterior segment beam. The fixation module 8 is connected to the posterior segment optical path assembly 5. The transmitted beam from the first polarizing beam splitter 2 is incident on the anterior segment optical path assembly 3. The transmitted beam from the anterior segment optical path assembly 3 is then incident on the second polarizing beam splitter 4, resulting in a anterior segment beam.

[0053] The anterior segment optical path assembly 3 includes an anterior segment first relay lens 301, an anterior segment first reflector 302, an anterior segment second relay lens 303, and an anterior segment second reflector 304. The transmitted beam from the first polarizing beam splitter 2 passes sequentially along the optical axis through the convergence of the anterior segment first relay lens 301, the reflection of the anterior segment first reflector 302, the transmission of the anterior segment second relay lens 303, and the reflection of the anterior segment second reflector 304 before being incident on the second polarizing beam splitter 4 for transmission, thus obtaining the anterior segment beam.

[0054] The posterior segment optical path assembly 5 includes a posterior segment reflector 501, a posterior segment optical path adjustment device 502, a posterior segment refractive objective lens 503, and a first dichroic mirror 504. The reflected beam from the first polarizing beam splitter 2 passes sequentially along the optical axis through reflection by the posterior segment reflector 501, transmission by the posterior segment optical path adjustment device 502 and the posterior segment refractive objective lens 503, and reflection by the first dichroic mirror 504 before being reflected by the second polarizing beam splitter 4 to obtain the posterior segment beam. The fixation beam emitted from the fixation module 8 is transmitted through the first dichroic mirror 504 and then reflected by the second polarizing beam splitter 4. The first dichroic mirror 504 is a short-pass dichroic mirror.

[0055] The posterior segment optical path adjustment device 502 includes two reflective surfaces and an adjustment device displacement stage. Both reflective surfaces are mounted on the adjustment device displacement stage and can move along... Figure 3 or Figure 5As shown by the arrow, the adjustment device moves along the optical axis. The incident beam of the posterior segment optical path adjustment device 502 is reflected by two reflective surfaces in sequence and becomes the output beam of the posterior segment optical path adjustment device 502. The movement of the posterior segment optical path adjustment device 502 adjusts the optical path of the posterior segment optical path so that the optical path of the posterior segment optical path matches the optical path of the reference arm optical path. The posterior segment beam and the fixation beam are incident on the posterior segment (i.e., the retina).

[0056] The two reflecting surfaces include, but are not limited to, one right-angle prism or two reflecting mirrors, and the adjustment device displacement stage includes, but is not limited to, a manual displacement stage or an electric displacement stage.

[0057] The iris imaging module 7 includes an iris illumination source 701, an iris imaging diverging lens 704, an iris imaging focusing lens 705, and an iris camera 706. The iris illumination source 701 is located on the side of the eyepiece objective lens. The light emitted by the iris illumination source 22 is reflected by the cornea of ​​the eye under test 6 to form an iris imaging beam. The iris imaging beam passes through the transmission of the eyepiece objective lens 702, the transmission of the beam splitter 10, the transmission of the iris imaging diverging lens 704, and the transmission of the iris imaging focusing lens 705 along the optical axis before entering the iris camera 706. The iris camera 706 is used to acquire clear iris images and guide OCT whole-eye imaging.

[0058] The fixation module 8 includes a fixation lens 801 and a fixation light source 802. The fixation beam emitted by the fixation module is transmitted through the first dichroic mirror 504 and then becomes the fixation beam of the fixation module 8.

[0059] OCT main module 1 uses one of the following methods:

[0060] A time-domain OCT imaging method using mechanical scanning and changing the optical path of the reference arm;

[0061] Alternatively, a spectrometer-based OCT imaging method can be used to record spectral interference signals;

[0062] Alternatively, a swept-frequency OCT imaging method can be used to record spectral interference signals by line scanning with a swept-frequency light source.

[0063] like Figure 4 and 5As shown, the polarization dual-path detection module 9 includes a first polarization beam splitter 2, an anterior segment optical path assembly 3, a posterior segment optical path assembly 5, and a second polarization beam splitter 4. The sample arm beam emitted from the OCT main module 1 is incident on the first polarization beam splitter 2, resulting in beam splitting, i.e., reflection and transmission. The reflected beam from the first polarization beam splitter 2 is incident on the anterior segment optical path assembly 3, and the reflected beam from the anterior segment optical path assembly 3 is incident on the second polarization beam splitter 4, where it is reflected to obtain the anterior segment beam. The transmitted beam from the first polarization beam splitter 2 is incident on the posterior segment optical path assembly 5, and the transmitted beam from the posterior segment optical path assembly 5 is incident on the second polarization beam splitter 4, where it is transmitted to obtain the posterior segment beam. The fixation module 8 is connected to the posterior segment optical path assembly 5.

[0064] The anterior segment optical path assembly 3 includes an anterior segment first relay lens 301, an anterior segment first reflector 302, an anterior segment second relay lens 303, an anterior segment second reflector 304, an anterior segment third reflector 305, and an anterior segment fourth reflector 306. The reflected beam from the first polarizing beam splitter 2 passes along the optical axis through the reflection of the first anterior segment first reflector 302, the reflection of the third anterior segment third reflector 305, the reflection of the fourth anterior segment fourth reflector 306, the convergence of the first anterior segment relay lens 301, the reflection of the second anterior segment second reflector 304, and the transmission of the second anterior segment second relay lens 303 before being incident on the second polarizing beam splitter 4 for reflection, thus obtaining the anterior segment beam.

[0065] The posterior segment optical path assembly 5 includes a posterior segment optical path adjustment device 502, a posterior segment refractive lens 503, and a first dichroic mirror 504. The transmitted beam from the first polarizing beam splitter 2 passes sequentially along the optical axis through the posterior segment optical path adjustment device 502 and the posterior segment refractive lens 503 before being transmitted to the second polarizing beam splitter 4 to obtain a posterior segment beam. The fixation beam emitted from the fixation module 8 is transmitted through the second optical path adjustment mirror of the posterior segment optical path adjustment device 502 and the posterior segment refractive lens 503 before being transmitted to the second polarizing beam splitter 4. At this time, the second optical path adjustment mirror is a short-pass dichroic mirror.

[0066] During the axial length measurement, the broadband light source 101 emits an OCT beam. After passing through the fiber coupler 102, the OCT beam exits from the first branch end on the other side of the fiber coupler 102 as a reference arm beam, and from the second branch end on the other side of the fiber coupler 102 as a sample arm beam. The reference arm beam passes through the first polarization controller 103 and the reference arm collimator 104 in sequence, and then is converged on the reference arm reflector 106 by the reference arm focusing lens 105. After being reflected by the reference arm reflector 106, it returns to the fiber coupler 102 along the original reference arm optical path, forming the reference arm beam.

[0067] by Figure 3Taking the embodiment as an example, the sample arm beam is adjusted to a circular polarization state by the second polarization controller 107, and after passing through the sample arm collimator 108, it is reflected by the OCT scanning device 109 to the first polarization beam splitter 2. The first polarization beam splitter 2 splits the sample arm beam, and the light transmitted into the anterior segment optical path assembly is P-polarized light, denoted as the anterior segment beam, while the light reflected into the posterior segment optical path assembly is S-polarized light, denoted as the posterior segment beam. The anterior segment beam is transmitted through the first polarization beam splitter prism and the first relay lens 301 of the anterior segment, reflected by the first reflecting mirror 302 of the anterior segment, and then transmitted through the second relay lens 303 of the anterior segment, and reflected by the second reflecting mirror 304 of the anterior segment. It is then transmitted as a parallel beam through the second polarization beam splitter prism, reflected by the beam splitter element 10, transmitted through the eyepiece objective lens 702, and finally converged on the cornea of ​​the human eye under test. The anterior segment imaging beam carrying corneal information returns along the original optical path to the fiber coupler 102, where it undergoes weak coherent interference with the P component of the reference arm beam at the fiber coupler 102. The posterior segment beam, after being reflected by the second polarizing beam splitter 2 and the posterior segment mirror 501, enters the posterior segment optical path adjustment device 502. After posterior segment optical path adjustment, it passes through the posterior segment refractive lens 503 and is reflected by the first dichroic mirror 504 into the second polarizing beam splitter 4. The second polarizing beam splitter 4 and the beam splitter element 10 reflect it to the eyepiece objective 702. The posterior segment beam enters the human eye 6 as a parallel beam and converges onto the retina through the lens of the human eye. The posterior segment imaging beam carrying retinal information returns along the original optical path to the fiber coupler, where it undergoes weak coherent interference with the S component of the reference arm beam at the fiber coupler 102.

[0068] Because the polarization states are orthogonal and the optical paths are different, the interference signals from the anterior and posterior segments of the eye do not interfere with each other. The interference signal enters the spectrometer, passes through the spectrometer collimator 110, and then enters the spectrometer reflective grating 111. The spectrometer reflective grating 111 splits the interference signal according to wavelength. The split interference signal is then focused by the spectrometer focusing lens 112 and converged onto the spectrometer camera 113. Through computer analysis and processing of the spectral signal, OCT images of the anterior and posterior segments of the human eye are obtained. Based on the OCT imaging results of the anterior and posterior segments of the human eye under test, such as... Figure 6 As shown, the edge recognition method is used to process the OCT two-dimensional imaging results of the human eye 6 under test to obtain the pixel positions of the anterior corneal surface and the retinal pigment epithelial cell layer of the human eye 6 under test. Let d1 be the distance between the vertex of the anterior corneal surface of the human eye under test and the position of zero optical path difference, d2 be the distance between the retinal pigment epithelial layer and the position of zero optical path difference, and d3 be the displacement of the optical path adjustment module of the posterior segment of the eye. Then the axial length D of the human eye under test satisfies D=d2-d1+d3.

Claims

1. An eye axis measurement device based on polarization-spectral OCT, characterized in that, It includes an OCT main module (1), a polarization dual-path detection module (9), a beam splitter (10), an eyepiece (702), an iris imaging module (7), and a fixation module (8); The sample arm beam emitted from the OCT main module (1) is polarized and split by the polarization dual-path detection module (9), resulting in anterior segment beam and posterior segment beam. The anterior segment beam is reflected by the beam splitter (10) and transmitted through the eyepiece objective (702) before entering the anterior segment of the human eye (6) under test. The posterior segment beam is reflected by the beam splitter (10) and transmitted through the eyepiece objective (702) before entering the posterior segment of the human eye (6) under test. The anterior segment beam and posterior segment beam are simultaneously incident on the corresponding segments of the human eye (6) under test. The beam is positioned and then reflected by the anterior and posterior segments of the eye to form an anterior segment imaging beam and a posterior segment imaging beam. The anterior segment imaging beam and the posterior segment imaging beam return to the OCT main module (1) along the original optical path. The fixation beam emitted from the fixation module (8) passes through the polarization dual-path detection module (9), the beam splitter (10) and the eyepiece objective (702) in sequence and then enters the eye (6) of the subject. The infrared illumination beam emitted by the iris imaging module (7) is reflected by the eye (6) of the subject and returns to the iris imaging module (7) for iris imaging. The polarization dual-path detection module (9) includes a first polarization beam splitter (2), an anterior segment optical path assembly (3), a posterior segment optical path assembly (5), and a second polarization beam splitter (4). The posterior segment optical path assembly (5) includes a posterior segment optical path adjustment device (502), a posterior segment refractive objective lens (503), and a first dichroic mirror (504). The OCT main module (1) is used to simultaneously interfere with the corresponding components in the anterior segment imaging beam, the posterior segment imaging beam and the reference arm beam. The posterior segment optical path adjustment device (502) includes two reflective surfaces and an adjustment device displacement stage. Both reflective surfaces are mounted on the adjustment device displacement stage. The adjustment device displacement stage moves along the optical axis. The incident beam of the posterior segment optical path adjustment device (502) is reflected by the two reflective surfaces in sequence and then becomes the outgoing beam of the posterior segment optical path adjustment device (502).

2. The axial length measurement device based on polarization-splitting OCT according to claim 1, characterized in that, The OCT main module (1) includes a broadband light source (101), an optical fiber coupler (102), a polarization controller (103), a reference arm collimator (104), a reference arm focusing lens (105), a reference arm reflector (106), a sample arm polarization controller (107), a sample arm collimator (108), an OCT scanning device (109), and a detector module; The first branch end on one side of the fiber optic coupler (102) is connected to the broadband light source (101), and the second branch end on one side of the fiber optic coupler (102) is connected to the detector module; the first branch end on the other side of the fiber optic coupler (102) is connected to the reference arm mirror (106) after passing through the polarization controller (103), the reference arm collimator (104) and the reference arm focusing lens (105) in sequence; the second branch end on the other side of the fiber optic coupler (102) is connected to the OCT scanning device (109) after passing through the sample arm polarization controller (107) and the sample arm collimator (108); and the OCT scanning device (109) is connected to the first polarization beam splitter (2).

3. The axial length measurement device based on polarization-splitting OCT according to claim 1, characterized in that, The sample arm beam emitted from the OCT main module (1) is incident on the first polarizing beam splitter (2) and the beam is split. The reflected beam from the first polarizing beam splitter (2) is incident on the posterior segment optical path assembly (5). The reflected beam from the posterior segment optical path assembly (5) is incident on the second polarizing beam splitter (4) and after reflection, the posterior segment beam is obtained. The fixation module (8) is connected to the posterior segment optical path assembly (5). The transmitted beam from the first polarizing beam splitter (2) is incident on the anterior segment optical path assembly (3). The transmitted beam from the anterior segment optical path assembly (3) is incident on the second polarizing beam splitter (4) and after transmission, the anterior segment beam is obtained.

4. The axial length measurement device based on polarization-splitting OCT according to claim 3, characterized in that, The anterior segment optical path assembly (3) includes an anterior segment first relay lens (301), an anterior segment first reflector (302), an anterior segment second relay lens (303) and an anterior segment second reflector (304); the transmitted beam of the first polarizing beam splitter (2) passes along the optical axis through the convergence of the anterior segment first relay lens (301), the reflection of the anterior segment first reflector (302), the transmission of the anterior segment second relay lens (303) and the reflection of the anterior segment second reflector (304) before being incident on the second polarizing beam splitter (4) to obtain the anterior segment beam; The posterior segment optical path assembly (5) also includes a posterior segment reflector (501); the reflected beam from the first polarizing beam splitter (2) passes along the optical axis through the reflection of the posterior segment reflector (501), the posterior segment optical path adjustment device (502), the transmission of the posterior segment refractive lens (503), and the reflection of the first dichroic mirror (504) before being reflected by the second polarizing beam splitter (4) to obtain the posterior segment beam; the fixation beam emitted from the fixation module (8) is transmitted through the first dichroic mirror (504) and then reflected by the second polarizing beam splitter (4).

5. The axial length measurement device based on polarization-splitting OCT according to claim 1, characterized in that, The sample arm beam emitted from the OCT main module (1) is incident on the first polarizing beam splitter (2) and the beam is split. The reflected beam from the first polarizing beam splitter (2) is incident on the anterior segment optical path assembly (3). The reflected beam from the anterior segment optical path assembly (3) is incident on the second polarizing beam splitter (4) and after reflection, the anterior segment beam is obtained. The transmitted beam from the first polarizing beam splitter (2) is incident on the posterior segment optical path assembly (5). The transmitted beam from the posterior segment optical path assembly (5) is incident on the second polarizing beam splitter (4) and after transmission, the posterior segment beam is obtained. The fixation module (8) is connected to the posterior segment optical path assembly (5).

6. The axial length measurement device based on polarization-splitting OCT according to claim 5, characterized in that, The anterior segment optical path assembly (3) includes an anterior segment first relay lens (301), an anterior segment first reflector (302), an anterior segment second relay lens (303), an anterior segment second reflector (304), an anterior segment third reflector (305) and an anterior segment fourth reflector (306); the reflected beam of the first polarizing beam splitter (2) passes along the optical axis through the reflection of the first anterior segment first reflector (302), the reflection of the third anterior segment third reflector (305), the reflection of the fourth anterior segment fourth reflector (306), the convergence of the first anterior segment relay lens (301), the reflection of the second anterior segment second reflector (304) and the transmission of the second anterior segment second relay lens (303) before being incident on the second polarizing beam splitter (4) for reflection, thus obtaining the anterior segment beam; The transmitted beam from the first polarizing beam splitter (2) passes through the posterior segment optical path adjustment device (502) and the posterior segment refractive lens (503) along the optical axis before being transmitted to the second polarizing beam splitter (4) to obtain the posterior segment beam; the fixation beam emitted from the fixation module (8) is transmitted through the posterior segment optical path adjustment device (502) and the posterior segment refractive lens (503) before being transmitted to the second polarizing beam splitter (4).

7. The axial length measurement device based on polarization-splitting OCT according to claim 1, characterized in that, The two reflecting surfaces are composed of one right-angle prism or two reflecting mirrors, and the adjustment device displacement stage is either a manual displacement stage or an electric displacement stage.

8. The axial length measurement device based on polarization-splitting OCT according to claim 1, characterized in that, The iris imaging module (7) includes an iris illumination source (701), an iris imaging diverging lens (704), an iris imaging focusing lens (705), and an iris camera (706). The iris illumination source (701) is located on the side of the eye-contact lens. The light emitted by the iris illumination source is reflected by the cornea of ​​the eye (6) to form an iris imaging beam. The iris imaging beam passes sequentially along the optical axis through the eye-contact lens (702), the beam splitter (10), the iris imaging diverging lens (704), and the iris imaging focusing lens (705) before entering the iris camera (706).

9. The axial length measurement device based on polarization-splitting OCT according to claim 1, characterized in that, The fixation module (8) includes a fixation lens (801) and a fixation light source (802). The fixation beam emitted by the fixation module is transmitted through the first dichroic mirror (504) and becomes the fixation beam of the fixation module (8).

10. The axial length measurement device based on polarization-splitting OCT according to claim 1, characterized in that, The OCT main module (1) adopts one of the following methods: A time-domain OCT imaging method using mechanical scanning and changing the optical path of the reference arm; Alternatively, a spectrometer-based OCT imaging method can be used to record spectral interference signals; Alternatively, a swept-frequency OCT imaging method can be used to record spectral interference signals by line scanning with a swept-frequency light source.

Images