Mydriasis-free fundus camera and imaging method thereof

Abstract

The invention discloses a mydriasis-free fundus camera and an imaging method thereof, and the mydriasis-free fundus camera comprises an imaging system which is used for shooting an image of a fundus to be detected; the illumination system is used for providing illumination light for the fundus to be detected; the lighting system comprises a first lighting module and a second lighting module which are asymmetrically arranged; the first illumination module and the second illumination module are arranged in a front-back staggered manner along the optical axis direction of the objective lens to form a distributed illumination structure; the light emitting surface of the first illumination module and the fundus to be detected are in a conjugate relationship; and the light emitting surface of the second illumination module and the fundus to be detected are in a non-conjugate relationship. By optimizing the layout of the illumination module and introducing the polaroid system, more uniform illumination is realized, smaller pupil diameter is supported, the equipment size is reduced, cornea reflection is weakened, and eyepiece ghosting is effectively inhibited.

Description

Technical Field

[0001] This application relates to the field of imaging technology, and more specifically, to a non-mydriatic fundus camera and its imaging method. Background Technology

[0002] A non-mydriatic fundus camera is a medical device that can directly capture images of the fundus without the use of mydriatic drugs. Its core features lie in its use of a special infrared light source and low-light imaging technology, enabling it to quickly acquire images of fundus structures such as the retina, optic disc, macula, and blood vessels under natural pupil conditions. Its main function is to achieve efficient and non-invasive screening for fundus diseases.

[0003] In existing technologies, non-mydriatic fundus cameras primarily employ internal illumination. The light source is guided to the fundus through a coaxial or paraxial optical path within the camera lens. While internal illumination can reduce external reflections, its technical drawback lies in the fact that the illumination and imaging optical paths are very close, making it difficult to completely avoid internal reflections and ghosting on the cornea and lens optics. These stray lights reduce image contrast and affect the identification of subtle lesions. Furthermore, to obtain sufficient visual field under small pupil conditions, internal illumination often requires a brighter light source, which may increase patient discomfort and the risk of potential light damage. Summary of the Invention

[0004] To address the aforementioned technical deficiencies, this application discloses a non-mydriatic fundus camera and its imaging method. By optimizing the layout of the illumination module and introducing a polarizer system, it achieves more uniform illumination, supports smaller pupil diameters, reduces device size, weakens corneal reflection, and effectively suppresses eyepiece ghosting. This approach allows the fundus camera to adapt to eyes with smaller pupils without mydriasis, ensuring a higher success rate of photography while the person is moving and improving image quality.

[0005] Specifically, the technical solution of this application is as follows: In a first aspect, this application discloses a non-mydriatic fundus camera, comprising: an imaging system and an illumination system; The imaging system is used to capture images of the fundus of the eye to be tested; the illumination system is used to provide illumination light for the fundus of the eye to be tested. The illumination system includes an asymmetrically arranged first illumination module and a second illumination module; the first illumination module and the second illumination module are arranged in a staggered manner along the optical axis of the objective lens to form a distributed illumination structure; the light-emitting surface of the first illumination module is conjugate to the fundus under test; the light-emitting surface of the second illumination module is non-conjugate to the fundus under test.

[0006] In some embodiments, the imaging system includes an eyepiece, an objective lens, and an analyzer. The objective lens includes a first lens module, a focusing lens, a second lens module, and an image sensor arranged sequentially along the imaging optical path. The analyzer is located in the imaging optical path between the first lens module and the focusing lens. The polarization angle of the analyzer is rotatably adjustable.

[0007] In some embodiments, the first lighting module includes a first light source and a first polarizer at the front end of the first light source; the second lighting module includes a second light source and a second polarizer at the front end of the second light source.

[0008] In some implementations, the polarization angle of the first polarizer is fixed; the polarization angle of the second polarizer is rotatably adjustable.

[0009] In some embodiments, the first illumination module and the second illumination module are located on the front and rear sides of the objective aperture, respectively; the first illumination module is disposed on the first side of the objective aperture; and the second illumination module is disposed on the rear side of the first illumination module, on the second side of the objective aperture.

[0010] In other embodiments, the first illumination module and the second illumination module are located on the upper and lower sides of the objective lens optical axis, respectively; the first vertical distance from the first principal optical axis of the first illumination module to the objective lens optical axis is equal to the second vertical distance from the second principal optical axis of the second illumination module to the objective lens optical axis.

[0011] Furthermore, the conjugate plane of the second illumination module is located on the side of the fundus under test near the eyepiece.

[0012] In some other embodiments, the non-mydriatic fundus camera has a number of second illumination modules greater than or equal to 1.

[0013] Based on the same technical concept, this application also discloses an imaging method for a non-mydriatic fundus camera, wherein the imaging method is performed based on a non-mydriatic fundus camera as described in any of the above embodiments, including: The difference between the polarization angles of the first polarizer and the second polarizer is set to be less than a preset angle threshold; the polarization angle of the first polarizer is fixed; the polarization angle of the second polarizer is adjustable by rotation. Adjust the polarization angle between the analyzer and the second polarizer to reduce the brightness of the image ghosting; The fundus of the eye under test is captured by an image sensor to obtain a first imaging result.

[0014] In some embodiments, adjusting the polarization angle between the analyzer and the second polarizer to reduce the brightness of the image ghosting includes: Observe the imaging results of the fundus of the eye under test, and fine-tune the analyzer to reduce the brightness of the first ghost point; fine-tune the second polarizer to reduce the brightness of the second ghost point; The imaging results are continuously observed to determine whether the imaging ghosting still exists; if so, the steps of adjusting the analyzer and the second polarizer are repeated until the imaging ghosting is no longer visible in the imaging results.

[0015] Compared with the prior art, this application has at least one of the following beneficial effects: 1. The non-mydriatic fundus camera designed in this application optimizes the layout of the illumination module and uses a dual-light source or multi-light source asymmetrical layout structure: by combining the light sources at the aperture and near the aperture plane, while maintaining a compact structure, it achieves perfect support and uniform illumination for small pupils, reducing the negative impact on image quality caused by human movement during photography.

[0016] 2. Based on the optimized layout of the lighting module, this application also introduces an adjustable polarizer system. The three-polarizer design (two polarizers and one analyzer) can achieve more uniform illumination, support a smaller pupil diameter, reduce the size of the device, reduce corneal reflection, and effectively suppress eyepiece ghosting.

[0017] 3. This application also discloses a method for adjusting the polarizer. By further adjusting the polarization angles of the analyzer and the rotatable polarizer, the fundus camera can be adapted to eyes with smaller pupils under non-mydriatic conditions, and can dynamically and accurately eliminate complex ghosting caused by multiple light sources. The lighting layout and ghosting elimination system are designed in synergy to ensure the imaging robustness of the device in various practical application scenarios and improve image quality. Attached Figure Description

[0018] The preferred embodiments will now be described in a clear and easy-to-understand manner, in conjunction with the accompanying drawings, to further explain the above-mentioned characteristics, technical features, advantages, and implementation methods of this application.

[0019] Figure 1 This is a schematic diagram of the illumination optical path and imaging optical path in one embodiment of a non-mydriatic fundus camera according to this application; Figure 2 This is a schematic diagram of the layout structure of the illumination module in another embodiment of a non-mydriatic fundus camera according to this application; Figure 3 This is a schematic diagram of the imaging optical path in another embodiment of a non-mydriatic fundus camera according to this application; Figure 4 This is a flowchart illustrating the steps of an embodiment of an imaging method using a non-mydriatic fundus camera according to this application.

[0020] Icon labels: 10-Fundus to be tested; 20-Eyepiece; 30-Objective lens; 31-First illumination module; 32-Second illumination module; 33-Analyzer; 34-Focusing lens; 35-Image sensor; 36-First lens module; 37-Second lens module; 38-Objective aperture; 311-First light source; 312-First polarizer; 321-Second light source; 322-Second polarizer. Detailed Implementation

[0021] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application can also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0022] It should be understood that, when used in this specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or sets.

[0023] To keep the drawings concise, each figure only schematically shows the parts relevant to the invention, and these do not represent the actual structure of the product. Furthermore, to facilitate understanding, in some figures, only one of components with the same structure or function is schematically depicted, or only one is labeled. In this document, "one" not only means "only one," but can also mean "more than one."

[0024] It should also be further understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0025] In this document, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0026] Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0027] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the specific implementation methods of this application will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without creative effort.

[0028] In existing technologies, illumination methods for non-mydriatic fundus cameras fall into two main categories: external illumination and internal illumination. External illumination typically refers to a light source projected onto the eyeball from outside the camera lens. Its main drawback is that the illumination light is easily affected by pupil size and the inhomogeneity of the eye's refractive media, easily generating strong reflections on the cornea and lens surface. These reflections can obscure some fundus details and interfere with image quality. Furthermore, the external light path is separated from the imaging light path, requiring a high degree of patient eye alignment. Even slight misalignment can lead to uneven illumination or insufficient brightness in certain areas of the image. Therefore, external illumination methods have gradually been abandoned by the market.

[0029] Currently, most products on the market use internal illumination. The basic principle of internal illumination is the conjugate of the illumination lamp and the pupil, ultimately achieving complete fundus illumination. There are two common types of internal illumination: Existing Technology 1: Hollow Mirror Illumination. This method uses an aperture as the position of a hollow mirror, adding an independent illumination path below it, and introducing a polarizer or black dot plate in this path to eliminate reflections. This method has a complex optical path, resulting in a large device size, and requires additional design of the illumination path. The placement of the black dot plate is also very sensitive, thus the optical design and manufacturing are both difficult and costly. Existing Technology 2: Single Light Source or Ring Illumination at the Aperture. This method places a single light source or ring light source directly at the aperture, resulting in a simple structure and small size. When using only one LED light and photographing a small pupil, the single illumination angle is easily blocked by the pupil, resulting in insufficient or uneven illumination of the fundus and poor image quality. If a ring LED light is used, the positioning requirements of the fundus camera are extremely high. The shaking of the human eye when taking pictures will also affect the relative position of the eye and the fundus camera, which will lead to obvious corneal reflection and seriously affect the image quality of the fundus.

[0030] In summary, the specific problems that need to be solved include: 1. Overcoming the illumination obstruction and unevenness issues caused by single-source illumination under small pupils. 2. Overcoming the image quality degradation caused by slight perturbations in ring-source illumination. 3. Avoiding the use of complex hollow mirror optical paths to reduce design difficulty and cost. 4. Solving the eyepiece ghosting problem introduced by multi-source illumination.

[0031] To address the aforementioned technical shortcomings, this application aims to design a solution that combines compact size with excellent illumination performance. By optimizing the layout of the illumination module and introducing a polarizer system, more uniform illumination and support for smaller pupil diameters are achieved, while simultaneously reducing device size, mitigating corneal reflection, and effectively suppressing eyepiece ghosting. This approach allows the fundus camera to adapt to eyes with smaller pupils without mydriasis, ensuring a higher success rate of photography while the person is moving and improving image quality.

[0032] Reference manual attached Figure 1 As shown, one embodiment of a non-mydriatic fundus camera of this application specifically includes: an imaging system and an illumination system; The imaging system is used to capture images of the fundus 10 to be tested; the illumination system is used to provide illumination light for the fundus 10 to be tested. The illumination system includes an asymmetrically arranged first illumination module 31 and a second illumination module 32; the first illumination module 31 and the second illumination module 32 are arranged in a staggered manner along the optical axis of the objective lens to form a distributed illumination structure; the light-emitting surface of the first illumination module 31 is conjugate to the fundus 10 under test; the light-emitting surface of the second illumination module 32 is non-conjugate to the fundus 10 under test.

[0033] refer to Figure 1 As shown, the imaging system and the illumination system are two independent but cooperative optical path systems. They interact and share resources through optical elements such as the eyepiece 20. Specifically, the fundus 10 to be tested is the retinal region of the eye. This application aims to overcome imaging ghosting by utilizing the distributed illumination structure of the light source through optical path design, without the need to use mydriatic drugs to dilate the pupil, thus enabling successful capture of fundus images even with a small pupil.

[0034] The objective optical axis is a theoretical reference straight line running through the entire objective lens 30, used to define the center of symmetry of the optical system. The objective optical axis passes through the center of curvature of each lens element of the objective lens and is perpendicular to the lens surface.

[0035] Compared to existing hollow reflector-type illumination, this embodiment is more compact, eliminates the complex beam splitting path, and has a more integrated structure. It simplifies the system structure, reducing optical design difficulty and manufacturing costs. Compared to single-source illumination at the aperture stop, it supports smaller pupils, and asymmetrical dual-angle illumination effectively prevents obstruction, expanding the applicable population. It also offers higher illumination uniformity, with multi-angle complementary illumination reducing shadows and hot spots.

[0036] Based on the above embodiments, this application discloses another embodiment of a non-mydriatic fundus camera. The imaging system includes an eyepiece 20, an objective lens 30, and an analyzer 33. The objective lens 30 includes a first lens module 36, a focusing lens 34, a second lens module 37, and an image sensor 35 arranged sequentially along the imaging optical path. The analyzer 33 is located in the imaging optical path between the first lens module 36 and the focusing lens 34. The polarization angle of the analyzer 33 is rotatably adjustable.

[0037] Reference manual attached Figure 2 As shown, Figure 2 This is a schematic diagram of the imaging optical path of a non-mydriatic fundus camera according to this embodiment. The first lens module 36 serves as the front objective lens of the system. Its main function is to receive the imaging light reflected from the fundus of the human eye and complete the initial collection and convergence. At the same time, it works with the illumination optical path to form good optical path separation at the pupil to suppress stray light such as corneal reflection.

[0038] The focusing lens 34 is an independent lens that can move back and forth along the optical axis. Its core function is to dynamically compensate for the myopia or hyperopia of different subjects through precise displacement, so as to ensure that the light from the fundus can be accurately focused on the subsequent image plane.

[0039] The second lens module 37 receives the light from the focusing lens 34, further transmits the light and forms an image, and corrects residual aberrations in the system.

[0040] The analyzer 33, located between the first lens module 36 and the focusing lens 34, has the core function of polarization state control. Since its polarization angle is adjustable, it can work in conjunction with the polarizer in the illumination optical path. By adjusting the polarization angle, it can selectively transmit fundus reflection signals with specific polarization directions, thereby efficiently filtering out strong specular reflection light generated by the corneal surface and significantly improving image quality.

[0041] The image sensor 35 is located at the end of the entire imaging optical path and is responsible for converting the optical image into a digital electrical signal to complete the final capture and recording of the fundus image. Optionally, the image sensor is a CMOS chip.

[0042] Specifically, this embodiment uses a dual-light source asymmetric layout structure as an example to illustrate this application. In some optional embodiments, the lighting system includes at least a first lighting module 31 and a second lighting module 32. (See attached specification.) Figure 3 As shown, the first lighting module 31 includes a first light source 311 and a first polarizer 312 at the front end of the first light source 311; the second lighting module 32 includes a second light source 321 and a second polarizer 322 at the front end of the second light source 321.

[0043] Optionally, the first light source 311 and the second light source 321 are LED lamps. In other embodiments, various other light sources can be selected according to specific imaging requirements. For example, infrared light sources, laser diodes, or xenon arc lamps, etc., are not specifically limited in this application.

[0044] In this embodiment, the analyzer 33 is designed to be rotatable. One of the two polarizers is fixed, while the other is designed to be rotatable. Preferably, the polarization angle of the first polarizer 312 is fixed; the polarization angle of the second polarizer 322 is rotatably adjustable. By adjusting the angles of the analyzer 33 and the polarizers, the optical path can be further fine-tuned, reducing ghosting.

[0045] Specifically, the second polarizer 322 imparts a specific and controllable linear polarization state to the illumination light emitted from the system. Since the polarization angle of the second polarizer 322 is adjustable, technicians can actively set the polarization direction of the beam incident on the human eye according to different shooting requirements or the polarization characteristics of the eye.

[0046] The second polarizer 322 and the analyzer 33 in the imaging optical path together constitute a polarization imaging assembly. By precisely coordinating the angle between their polarization directions, specular reflections from non-target tissues such as the anterior surface of the cornea can be greatly suppressed. Since these reflected lights largely retain the polarization state of the incident light, they are effectively blocked by the analyzer 33. At the same time, the polarization state of the target signal light diffusely scattered from the deep retina of the fundus changes randomly, and thus can be received by the image sensor 35 through the analyzer 33.

[0047] Based on the above embodiments, this application discloses another embodiment of a non-mydriatic fundus camera. In some optional embodiments, the first illumination module 31 and the second illumination module 32 are respectively located on the front and rear sides of the objective aperture 38; the first illumination module 31 is disposed on the first side of the objective aperture 38; the second illumination module 32 is disposed on the rear side of the first illumination module 31, located on the second side of the objective aperture 38.

[0048] The objective aperture is a component that determines the size of the light beam entering the objective lens. Located at the front of the objective lens, its opening size directly controls the numerical aperture of the imaging system, thus affecting the light throughput entering the optical system and the system's resolution.

[0049] Reference manual attached Figure 3 As shown. The first light source 311 is mounted at the aperture. The second light source 321 is mounted on an axis symmetrical to the first light source 311 with respect to the optical axis, but closer to the objective lens end and the image sensor 35 side in the optical axis direction.

[0050] In some alternative embodiments, the first illumination module 31 and the second illumination module 32 are located on the upper and lower sides of the objective lens optical axis, respectively; the first vertical distance from the first principal optical axis of the first illumination module 31 to the objective lens optical axis is equal to the second vertical distance from the second principal optical axis of the second illumination module 32 to the objective lens optical axis.

[0051] Specifically, this asymmetrical dual-light source layout allows light to enter from two different angles, effectively covering a smaller pupil area. When the light from one of the light sources is blocked by the edge of the pupil, the other light source can still provide effective illumination, thereby significantly improving the uniformity of illumination and adaptability to small pupils.

[0052] In some alternative embodiments, the light-emitting surface of the first illumination module 31 is conjugate with the fundus 10 to be tested; the light-emitting surface of the second illumination module 32 is non-conjugate with the fundus 10 to be tested.

[0053] In practical implementation, because the first illumination module 31 and the second module are asymmetrically distributed, one of the first illumination module 31 or the second illumination module 32 is set in a non-conjugate relationship with the fundus target detection. Specifically, the light-emitting surface of the first illumination module 31 at the lower aperture is conjugate with the fundus 10 to be tested. This means that the illumination light from the first illumination module 31 can be accurately and uniformly projected onto a specific area of ​​the fundus, forming a well-defined illumination spot with controllable intensity distribution. However, the light-emitting surface of the second illumination module 32 is non-conjugate with the fundus plane, meaning that the illumination source surface of the second illumination module 32 is not directly imaged onto the fundus. Its light typically forms a spot at or near the pupillary plane, and then illuminates the fundus in a more divergent or specially distributed manner.

[0054] In some alternative embodiments, the conjugate plane of the second illumination module 32 is located on the side of the fundus 10 under test near the eyepiece 20. Specifically, its theoretical conjugate position is within the space of the pupil near the cornea.

[0055] The dual-light source distribution design of this application enables the illumination light path and the imaging light path to be spatially separated at the pupil, thereby avoiding reflected light from the cornea and other anterior surfaces of the eyeball from entering the imaging path and achieving the technical effect of eliminating corneal reflection.

[0056] This application provides another embodiment of a non-mydriatic fundus camera, wherein, based on any of the embodiments of the above method, the number of the second illumination modules 32 is greater than or equal to 1.

[0057] Specifically, this application may also use a multi-source asymmetric layout structure. The lighting system includes at least a first lighting module 31, a second lighting module 32, and a third lighting module. Among them, the light-emitting surface of at least one lighting module is conjugate to the fundus 10 under test, while the light-emitting surfaces of the remaining lighting modules are non-conjugate to the fundus 10 under test.

[0058] Optionally, the third illumination module is similar to the second illumination module 32, and includes a third light source and a third polarizer at the front end of the third light source. Furthermore, in some alternative embodiments, other light sources, such as a fourth illumination module, can be placed at other angles, similarly positioned off-center from the aperture plane and closer to the objective lens and image sensor 35, with the light-emitting surface non-conjugate to the fundus 10 under test. The specific implementation details are consistent with those of the non-mydriatic fundus camera described in any of the above embodiments, and will not be repeated in this embodiment.

[0059] Based on the same concept, this application also discloses an imaging method for a non-mydriatic fundus camera. The imaging method is performed based on a non-mydriatic fundus camera as described in any of the above embodiments; for details, please refer to the appendix to the specification. Figure 4 As shown. One embodiment of the imaging method for a non-mydriatic fundus camera according to this application specifically includes: S1, the difference between the polarization angles of the first polarizer 312 and the second polarizer 322 is set to be less than a preset angle threshold; the polarization angle of the first polarizer 312 is fixed; the polarization angle of the second polarizer 322 is rotatably adjustable; S2, adjust the polarization angle between the analyzer 33 and the second polarizer 322 to reduce the brightness of the image ghosting; S3, the image sensor 35 is used to capture the fundus 10 under test to obtain the first imaging result.

[0060] Specifically, the main cause of ghosting in known fundus cameras is the reflection of light from various surfaces of the eyepiece. However, this application differs from existing fundus cameras in that two or more light sources are not on the same plane. The presence of two or more light sources reduces the brightness of each light source, thus reducing the intensity of the ghosting. This embodiment uses a dual-light source design as an example, placing a polarizer in front of each of the two light sources as a polarizer. A polarizer is placed at the rear of the objective lens as an analyzer 33.

[0061] In the initial or default calibration state of the system, the polarization angle between the polarizer in front of the light source and the analyzer 33 in the imaging optical path is set to be relatively small, for example, making their transmission axes nearly parallel. Such an initial setting allows a relatively large amount of light to pass through the entire polarization system, thereby facilitating the initial optical path alignment of the system, target finding, or obtaining a brighter preview image.

[0062] In some implementations, step S2 specifically includes the following sub-steps: S21, observe the imaging results of the fundus 10 under test, and fine-tune the analyzer 33 to reduce the brightness of the first ghost point.

[0063] S22, fine-tune the second polarizer 322 to reduce the brightness of the second ghost point.

[0064] In this embodiment, imaging ghosts (ghost points) refer to unwanted optical image points formed by multiple internal reflections between the surfaces of the lens. These points are superimposed on the target fundus image and interfere with observation.

[0065] Specifically, the first step of calibration, rotating the analyzer 33, changes the polarization receiving direction of the imaging optical path, making the polarization state of the ghost image formed by a specific reflected optical path orthogonal to the direction of the analyzer 33, thus significantly darkening or eliminating its intensity. After successfully suppressing one ghost image in the first step, the second step, adjusting the polarizer in front of the rotating light source, changes the polarization state of the incident light from the illumination source. Since the other ghost image has a different forming optical path and its polarization change characteristics are also independent, by finely adjusting the angle of the polarizer, polarization matching can be performed for the reflected light of this specific optical path, so that it is also suppressed to the maximum extent when passing through the analyzer 33, thereby achieving the effect of the darkest other ghost image point.

[0066] By independently adjusting the two controllable polarization elements, the second polarizer 322 and the analyzer 33, ghosting in the image is optimized and suppressed one by one, thereby eliminating multiple interfering image points from the field of view step by step, so as to improve the purity of the final image.

[0067] Based on the above embodiments, this application discloses another embodiment of an imaging method for a non-mydriatic fundus camera, which continuously observes the imaging results to determine whether the imaging ghost still exists; if so, steps S21-S22 of the above method are repeated until the imaging ghost is no longer visible in the imaging results.

[0068] Specifically, a single sequential adjustment of the polarizer and analyzer 33 may not achieve optimal results. If the ghosting is not completely suppressed after the initial adjustment, iterative fine-tuning is required. Iterative check and adjustment: Observe the imaging effect. If the ghosting still does not completely disappear, repeat the above steps for fine-tuning until the ghosting is basically eliminated.

[0069] Optionally, step S2 specifically includes: S21, adjusting the second polarizer 322 to darken one of the pairs of bright spots A in the center of the image.

[0070] S22, adjust analyzer 33 to darken another pair of bright spots B in the center of the image, and pre-lock the position of analyzer 33 at this time.

[0071] S23, adjust the second polarizer 322 to make the bright spot A the darkest, and lock the position at this time.

[0072] S24, adjust the analyzer 33 to make bright spot B the darkest, and lock the position at this time.

[0073] This process may require several iterations; the following iterative steps are omitted. Through this repeated, small-scale iteration of observation, feedback, and adjustment, the operator is essentially manually exploring and approximating the optimal combination of parameters for suppressing multiple stray lights in the entire polarization system. The ultimate goal is to minimize the brightness of all visible, interfering ghosting points caused by internal reflections within the field of view, achieving a visual state of "virtually disappearance."

[0074] The adjustable polarization system in this embodiment can accurately eliminate ghosting from multiple light sources and corneal reflections. It exhibits good robustness: even with inaccurate binocular positioning or eye movement, it can still obtain stable, high-quality images.

[0075] The non-mydriatic fundus camera and imaging method of this application have the same technical concept, and the technical details of the embodiments of the two are applicable to each other. In order to reduce repetition, they will not be repeated here.

[0076] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of program modules is merely an example. In practical applications, the above functions can be assigned to different program modules as needed, that is, the internal structure of the device can be divided into different program units or modules to complete all or part of the functions described above. The program modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one processing unit. The integrated unit can be implemented in hardware or as a software program unit. Furthermore, the specific names of the program modules are only for easy differentiation and are not intended to limit the scope of protection of this application.

[0077] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0078] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A non-mydriatic fundus camera, comprising: The imaging system and illumination system are characterized by: The imaging system is used to capture images of the fundus of the eye to be tested; the illumination system is used to provide illumination light for the fundus of the eye to be tested. The illumination system includes an asymmetrically arranged first illumination module and a second illumination module; the first illumination module and the second illumination module are arranged in a staggered manner along the optical axis of the objective lens to form a distributed illumination structure; the light-emitting surface of the first illumination module is conjugate to the fundus under test; the light-emitting surface of the second illumination module is non-conjugate to the fundus under test.

2. The non-mydriatic fundus camera as described in claim 1, characterized in that: The imaging system includes an eyepiece, an objective lens, and an analyzer. The objective lens includes a first lens module, a focusing lens, a second lens module, and an image sensor arranged sequentially along the imaging optical path. The analyzer is located in the imaging optical path between the first lens module and the focusing lens. The polarization angle of the analyzer is rotatably adjustable.

3. The non-mydriatic fundus camera as described in claim 1, characterized in that: The first lighting module includes a first light source and a first polarizer at the front end of the first light source; the second lighting module includes a second light source and a second polarizer at the front end of the second light source.

4. The non-mydriatic fundus camera as described in claim 3, characterized in that, The polarization angle of the first polarizer is fixed; the polarization angle of the second polarizer is adjustable by rotation.

5. A non-mydriatic fundus camera as described in claim 2, characterized in that, The first illumination module and the second illumination module are located on the front and rear sides of the objective lens aperture, respectively; the first illumination module is disposed on the first side of the objective lens aperture. The second illumination module is disposed to the side and rear of the first illumination module, located on the second side of the objective aperture.

6. A non-mydriatic fundus camera as described in claim 2, characterized in that, The first illumination module and the second illumination module are located on the upper and lower sides of the objective lens optical axis, respectively; the first vertical distance from the first principal optical axis of the first illumination module to the objective lens optical axis is equal to the second vertical distance from the second principal optical axis of the second illumination module to the objective lens optical axis.

7. A non-mydriatic fundus camera as described in claim 6, characterized in that, The conjugate plane of the second illumination module is located on the side of the fundus under test near the eyepiece.

8. A non-mydriatic fundus camera as described in any one of claims 1-7, characterized in that, The number of the second lighting modules is greater than or equal to 1.

9. An imaging method for a non-mydriatic fundus camera, characterized in that, The imaging method is performed based on a non-mydriatic fundus camera as described in any one of claims 1-8, comprising: The difference between the polarization angles of the first polarizer and the second polarizer is set to be less than a preset angle threshold; the polarization angle of the first polarizer is fixed; the polarization angle of the second polarizer is adjustable by rotation. Adjust the polarization angle between the analyzer and the second polarizer to reduce the brightness of the image ghosting; The fundus of the eye under test is captured by an image sensor to obtain a first imaging result.

10. The imaging method of a non-mydriatic fundus camera as described in claim 9, characterized in that, The adjustment of the polarization angle between the analyzer and the second polarizer to reduce the brightness of the image ghosting includes: Observe the imaging results of the fundus of the eye under test, and fine-tune the analyzer to reduce the brightness of the first ghost point; fine-tune the second polarizer to reduce the brightness of the second ghost point; The imaging results are continuously observed to determine whether the imaging ghosting still exists; if so, the steps of adjusting the analyzer and the second polarizer are repeated until the imaging ghosting is no longer visible in the imaging results.

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