An objective lens for ultra-wide angle fundus color imaging

Abstract

This invention employs a simplified optical structure. The eyepiece objective uses a combination of a meniscus lens and a set of cemented lenses to achieve a wide field of view for fundus imaging. The fewer lenses not only reduce the weight of the lens but also decrease stray light caused by reflections from the lens surfaces. Furthermore, the eyepiece objective uses a spherical cemented surface, which facilitates the cementing and processing of the lenses. The aspherical surface designed in this invention does not exhibit curvature, making it easy to process and inspect; the optical path does not have significant bends, allowing for larger tolerances and easier assembly. This invention offers a long working distance, ensuring patient comfort during imaging; it has high resolution, with a fundus resolution of approximately 10µm; and an image distance / focal length ratio >0.6, reducing stray light caused by reflections from the lens surfaces. While maintaining high resolution and eye comfort, this invention further increases the range of fundus imaging, providing a 110° image-square field of view, corresponding to an ultra-wide-angle 165° field of view for fundus imaging.

Description

Technical Field

[0001] This invention relates to the field of fundus imaging technology, and in particular to an eyepiece for ultra-wide-angle fundus color imaging. Background Technology

[0002] Retinal diseases are the third leading cause of blindness worldwide (WHO 2024). The 2024 Global Eye Health Report indicates that approximately 230 million people globally suffer from retinal diseases, seriously threatening human visual health. These diseases can cause varying degrees of vision impairment and even blindness. Clinically, vascular diseases, infantile eye diseases, retinal tears, and detachments are most common. These diseases often initially appear in the peripheral retina, gradually affecting the mid-periphery and posterior pole.

[0003] Traditional fundus imaging techniques have significant limitations, only able to capture images of the fundus region from 20° to 60°. While they can effectively display the two important fundus regions—the retina and the macula—primarily concentrated in the posterior pole (accounting for 30%-40% of the total retinal area), early lesions occur in the mid-peripheral and peripheral regions. These lesion areas cannot be captured by traditional fundus cameras, resulting in a missed diagnosis rate as high as 34% (2024 Ophthalmology Clinical Data Annual Report), thus missing the opportunity for early detection and treatment.

[0004] In recent years, significant breakthroughs have been made in increasing the field of view of fundus imaging based on ultra-wide-angle imaging technology. Fundus imaging devices with a 90° field of view have emerged, and the imaging area basically covers the posterior pole and middle periphery, but it is still impossible to observe the distal periphery of the retina. However, the early detection of lesions in this area is extremely important. In diabetic retinopathy, the detection rate of neovascularization in the distal periphery vortex vein region is 2.6 times that in the middle periphery; in high myopia peripheral degeneration, the rate of retinal thinning in the distal periphery is as high as 73%; and retinal tears near the vortex vein exit point account for 68% of all tears.

[0005] Therefore, pursuing a larger field of view for fundus imaging remains an important direction for the development of fundus imaging. Ultra-wide-angle fundus imaging can be achieved through scanning imaging. Ultra-wide-angle fundus imaging devices can obtain a large field of view fundus image in a single, non-mydriatic imaging session, which optimizes the ophthalmic diagnostic process and improves diagnostic efficiency. The eyepiece is a key component of ultra-wide-angle fundus imaging, possessing a large imaging field of view. The pupil is located in front of the eyepiece, and the working distance between the pupil and the eyepiece must be as large as possible. These factors place high demands on the design of the eyepiece. Summary of the Invention

[0006] In order to achieve the above-mentioned objectives and other advantages of the present invention, the objective of the present invention is to provide an eyepiece for ultra-wide-angle fundus color imaging, comprising an eyepiece single lens and an eyepiece cemented lens, wherein the eyepiece single lens and the eyepiece cemented lens are arranged sequentially from the pupil side to the image plane side.

[0007] The eyepiece objective lens is a meniscus lens, the concave surface of which is spherical and faces the pupil, and the convex surface of which is aspherical.

[0008] The eyepiece objective lens is cemented from the pupil side to the image plane side by a first aspherical lens, a biconcave lens, and a second aspherical lens cemented together.

[0009] The first aspherical lens is a biconvex lens, wherein the non-cemented surface and the cemented surface of the first aspherical lens are aspherical and spherical, respectively; the cemented surfaces on both sides of the biconcave lens are spherical; the second aspherical lens is a biconvex lens, wherein the cemented surface and the non-cemented surface of the second aspherical lens are spherical and aspherical, respectively.

[0010] Furthermore, the relationship between the image distance and focal length of the target object is: 0.6 < image distance / focal length < 1.

[0011] Furthermore, the concave surface curvature radius of the meniscus lens is -40 to -42 mm, and the net aperture of the concave surface of the meniscus lens is 20 to 22 mm.

[0012] Furthermore, the convex surface of the meniscus lens is a standard second-order aspherical surface, the radius of curvature of the convex surface of the meniscus lens is -20 to -22 mm, the net aperture of the convex surface of the meniscus lens is 23 to 25 mm, and the conic coefficient of the convex surface of the meniscus lens is -0.34 to -0.36.

[0013] Furthermore, the center thickness of the single lens of the eyepiece objective is 13-15 mm.

[0014] Furthermore, the net aperture of the cemented lens of the eyepiece objective is 38–40 mm.

[0015] Furthermore, the unbonded surface of the first aspherical lens is a standard secondary aspherical surface, the radius of curvature of the unbonded surface of the first aspherical lens is 67-69 mm, the conic coefficient of the unbonded surface of the first aspherical lens is -28 to -30, the radius of curvature of the bonded surface of the first aspherical lens is -64 to -66 mm, and the center thickness of the first aspherical lens is 16-18 mm.

[0016] Furthermore, the curvature radius of the bonding surface of the biconcave lens near the pupil is -64 to -66 mm, the curvature radius of the bonding surface of the biconcave lens away from the pupil is 100 to 102 mm, and the center thickness of the biconcave lens is 4 to 5 mm.

[0017] Furthermore, the radius of curvature of the cemented surface of the second aspherical lens is 100–102 mm, the uncemented surface of the second aspherical lens is a high-order even-order aspherical, the radius of curvature of the uncemented surface of the second aspherical lens is infinite, the conic coefficient of the uncemented surface of the second aspherical lens is 0, the fourth-order term of the uncemented surface of the second aspherical lens is -5.296E-06, the sixth-order term of the uncemented surface of the second aspherical lens is 3.885E-09, the eighth-order term of the uncemented surface of the second aspherical lens is -2E-12, the tenth-order term of the uncemented surface of the second aspherical lens is 4.338E-16, and the center thickness of the second aspherical lens is 15–16 mm.

[0018] Furthermore, the center distance between the convex surface of the single lens of the eyepiece and the non-cemented surface of the first aspherical lens is 0.3 to 0.5.

[0019] Furthermore, the refractive index Nd of the single lens of the eyepiece objective satisfies 1.6 < Nd < 1.8, and the Abbe number Vd satisfies 52 < Vd < 54; the refractive index Nd of the first aspherical lens satisfies 1.7 < Nd < 1.9, and the Abbe number Vd satisfies 45 < Vd < 47; the refractive index Nd of the biconcave lens satisfies 1.9 < Nd < 2.1, and the Abbe number Vd satisfies 17 < Vd < 19; and the refractive index Nd of the second aspherical lens satisfies 1.8 < Nd < 2, and the Abbe number Vd satisfies 40 < Vd < 42.

[0020] Furthermore, both the single lens and the cemented lens of the eyepiece objective are made of glass.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] An eyepiece for ultra-wide-angle fundus color imaging

[0023] This invention employs a simplified optical structure. The eyepiece objective uses a combination of a meniscus lens and a set of cemented lenses to achieve a wide field of view for fundus imaging. The fewer lens elements not only reduce the lens weight but also decrease stray light caused by reflections from the lens surfaces. Furthermore, the eyepiece objective uses a spherical cemented surface, which facilitates the cementing and fabrication of the lenses. The aspherical surface designed in this invention does not exhibit curvature, making it easy to manufacture and inspect. The optical path in this invention does not involve significant bends, allowing for larger tolerances and easier assembly.

[0024] This invention features a longer working distance (distance from the eyepiece to the pupil), ensuring patient comfort during imaging. It also boasts high resolution, with a fundus resolution of approximately 10µm. Furthermore, the image distance / focal length ratio is >0.6, reducing stray light emitted from the lens surface.

[0025] While ensuring high resolution and human eye comfort, this invention further increases the range of fundus imaging, providing a 110° image-square field of view, corresponding to a 165° ultra-wide-angle imaging field of view of the fundus.

[0026] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Specific embodiments of the present invention are given in detail below with reference to the accompanying drawings. Attached Figure Description

[0027] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0028] Figure 1 A schematic diagram of an eyepiece for ultra-wide-angle fundus color imaging;

[0029] Figure 2 A point-to-point graph;

[0030] Figure 3 MTF chart;

[0031] Figure 4 This is a distorted image.

[0032] In the diagram: 1. Single lens for eyepiece objective; 2. Cemented lens for eyepiece objective; 21. First aspherical lens; 22. Biconcave lens; 23. Second aspherical lens. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] In the accompanying drawings, shapes and dimensions may be enlarged for clarity, and the same reference numerals will be used in all figures to indicate the same or similar parts.

[0035] In the following description, terms such as center, thickness, height, length, front, back, rear, left, right, top, bottom, upper, and lower are defined relative to the structure shown in the accompanying drawings. In particular, "height" corresponds to the dimension from top to bottom, "width" corresponds to the dimension from left to right, and "depth" corresponds to the dimension from front to back. These are relative concepts and may vary depending on their location and usage. Therefore, these or other orientations should not be interpreted as restrictive terms.

[0036] Terms involving attachment, connection, etc. (e.g., “connection” and “attachment”) refer to the relationship in which these structures are directly or indirectly fixed or attached to each other through an intermediate structure, as well as movable or rigid attachments or relationships, unless otherwise explicitly stated.

[0037] Example 1

[0038] An eyepiece objective for ultra-wide-angle fundus color imaging, capable of 110° wide-field fundus imaging, achieves ultra-wide-angle fundus imaging through a rational optical structure design. For example... Figure 1 As shown, the eyepiece objective includes an eyepiece single lens 1 and an eyepiece cemented lens 2, which are arranged sequentially from the pupil side to the image plane side; that is, the eyepiece single lens 1 is located on the side closer to the pupil, and the eyepiece cemented lens 2 is located on the side farther away from the pupil.

[0039] The eyepiece objective lens is a meniscus lens, the concave surface of which is spherical and faces the pupil, and the convex surface of which is aspherical.

[0040] The eyepiece objective lens 2 is cemented from the pupil side to the image plane side by a first aspherical lens 21, a biconcave lens 22, and a second aspherical lens 23 cemented together; that is, the eyepiece objective lens 2 is cemented together by two aspherical lenses (i.e., the first aspherical lens 21 and the second aspherical lens 23) and a biconcave lens 22; among them, the one closer to the pupil is the first aspherical lens 21, the one in the middle is the middle biconcave lens 22, and the one farther away from the pupil is the second aspherical lens 23.

[0041] The first aspherical lens is a biconvex lens, wherein the non-cemented surface and the cemented surface of the first aspherical lens are aspherical and spherical, respectively; the cemented surfaces on both sides of the biconcave lens are spherical; the second aspherical lens is a biconvex lens, wherein the cemented surface and the non-cemented surface of the second aspherical lens are spherical and aspherical, respectively.

[0042] In some embodiments, the eyepiece objective has a focal length of 28–32 mm, a field of view of 114°, a working distance (distance between the eyepiece objective and the pupil) of 21 mm, an image distance of 13–15 mm, and is telecentrically aligned with the image side, with a telecentricity of <0.3% for each field of view. The long working distance ensures eye comfort during use of the eyepiece objective. The relationship between image distance and focal length is: 0.6 < image distance / focal length < 1, which reduces stray light caused by reflections from the eyepiece objective surface.

[0043] In some embodiments, the concave surface radius of curvature of the meniscus lens is -40 to -42 mm, and the net aperture of the concave surface of the meniscus lens is 20 to 22 mm. Further, the convex surface of the meniscus lens is a standard second-order aspherical surface, the convex surface radius of curvature of the meniscus lens is -20 to -22 mm, the net aperture of the convex surface of the meniscus lens is 23 to 25 mm, and the conicity of the convex surface of the meniscus lens is -0.34 to -0.36. Further, the center thickness of the single lens element of the eyepiece objective is 13 to 15 mm.

[0044] In some embodiments, the net aperture of the cemented lens of the eyepiece objective is 38–40 mm. Further, the uncemented surface of the first aspherical lens is a standard double aspherical surface, the radius of curvature of the uncemented surface of the first aspherical lens is 67–69 mm, the conic coefficient of the uncemented surface of the first aspherical lens is -28 to -30, the radius of curvature of the cemented surface of the first aspherical lens is -64 to -66 mm, and the center thickness of the first aspherical lens is 16–18 mm.

[0045] Furthermore, the curvature radius of the bonding surface of the biconcave lens near the pupil is -64 to -66 mm, the curvature radius of the bonding surface of the biconcave lens away from the pupil is 100 to 102 mm, and the center thickness of the biconcave lens is 4 to 5 mm.

[0046] Furthermore, the radius of curvature of the cemented surface of the second aspherical lens is 100–102 mm, the uncemented surface of the second aspherical lens is a high-order even-order aspherical, the radius of curvature of the uncemented surface of the second aspherical lens is infinite, the conic coefficient of the uncemented surface of the second aspherical lens is 0, the fourth-order term of the uncemented surface of the second aspherical lens is -5.296E-06, the sixth-order term of the uncemented surface of the second aspherical lens is 3.885E-09, the eighth-order term of the uncemented surface of the second aspherical lens is -2E-12, the tenth-order term of the uncemented surface of the second aspherical lens is 4.338E-16, and the center thickness of the second aspherical lens is 15–16 mm.

[0047] Furthermore, the center distance between the convex surface of the single lens of the eyepiece and the non-cemented surface of the first aspherical lens is 0.3 to 0.5.

[0048] Furthermore, the refractive index Nd of the single lens of the eyepiece objective satisfies 1.6 < Nd < 1.8, and the Abbe number Vd satisfies 52 < Vd < 54; the refractive index Nd of the first aspherical lens satisfies 1.7 < Nd < 1.9, and the Abbe number Vd satisfies 45 < Vd < 47; the refractive index Nd of the biconcave lens satisfies 1.9 < Nd < 2.1, and the Abbe number Vd satisfies 17 < Vd < 19; and the refractive index Nd of the second aspherical lens satisfies 1.8 < Nd < 2, and the Abbe number Vd satisfies 40 < Vd < 42.

[0049] In some preferred embodiments, the single-piece eyepiece objective lens and the cemented eyepiece objective lens are made of glass. It should be noted that the single-piece eyepiece objective lens and the cemented eyepiece objective lens can also be made of other materials such as plastic, depending on actual needs.

[0050] In one embodiment, the relevant parameters of each lens in the ultra-wide-angle eyepiece, including radius of curvature, thickness, net aperture, center-to-center distance, refractive index of the material, and Abbe number, are as follows:

[0051] The concave surface radius of curvature of the single lens 1 of the eyepiece objective is -41mm;

[0052] The radius of curvature of the convex surface of the single lens 1 of the eyepiece objective is -21.5 mm;

[0053] The radius of curvature of the non-cemented surface of the first aspherical lens 21 of the cemented lens 2 of the eyepiece objective is 68 mm.

[0054] The radius of curvature of the cemented surface of the first aspherical lens 21 of the eyepiece objective lens 2 is -65mm;

[0055] The radius of curvature of the cemented surface of the biconcave lens 22 near the pupil of the eyepiece objective lens 2 is -65mm;

[0056] The radius of curvature of the cemented surface of the biconcave lens 22 on the side furthest from the pupil is 100 mm.

[0057] The second aspherical lens 23 of the cemented lens 2 of the eyepiece objective lens has a cemented surface curvature radius of 100 mm.

[0058] The second aspherical lens 23 of the cemented eyepiece objective lens 2 has an infinite radius of curvature of its non-cemented surface.

[0059] The center thickness of the single lens 1 of the eyepiece objective is 15mm;

[0060] The center thickness of the first aspherical lens 21 of the cemented lens 2 of the eyepiece objective is 17 mm.

[0061] The center thickness of the biconcave lens 22 of the eyepiece objective lens 2 is 4.5 mm;

[0062] The center thickness of the second aspherical lens 23 of the cemented eyepiece objective lens 2 is 17mm;

[0063] The net aperture of the concave surface of the single lens 1 of the eyepiece objective is 21.618 mm;

[0064] The net aperture of the convex surface of the single lens 1 of the eyepiece objective is 24.05 mm;

[0065] The net aperture of the non-cemented surface of the first aspherical lens 21 of the cemented lens 2 of the eyepiece objective is 34.35 mm;

[0066] The net diameter of the cemented surface of the first aspherical lens 21 of the eyepiece objective lens 2 is 34.7 mm;

[0067] The net diameter of the cemented surface of the biconcave lens 22 near the pupil of the eyepiece objective lens 2 is 34.7 mm.

[0068] The net diameter of the cemented surface of the biconcave lens 22 on the side furthest from the pupil of the eyepiece objective lens 2 is 38.5 mm;

[0069] The net diameter of the cemented surface of the second aspherical lens 23 of the eyepiece objective lens 2 is 38.5 mm;

[0070] The net aperture of the non-cemented surface of the second aspherical lens 23 of the cemented lens 2 of the eyepiece objective is 39.15 mm;

[0071] The center distance between the convex surface of the single lens 1 of the eyepiece objective and the center of the non-cemented surface of the first aspherical lens 21 of the cemented lens 2 of the eyepiece objective is 0.4 mm;

[0072] The eyepiece objective lens 1 has a refractive index of 1.76 and an Abbe number of 52.3.

[0073] The first aspherical lens 21 of the cemented lens 2 of the eyepiece objective has a refractive index of 1.82 and an Abbe number of 46.6.

[0074] The biconcave lens 22 of the eyepiece objective lens 2 has a refractive index of 1.96 and an Abbe number of 17.5.

[0075] The second aspherical lens 23 of the cemented lens 2 of the eyepiece objective has a refractive index of 1.88 and an Abbe number of 40.8.

[0076] The image-side field of view of the eyepiece is designed to be 110°, but the actual value is 114°, which corresponds to an image angle of 165° on the fundus.

[0077] Figure 2 , Figure 3The dot plot and MTF plot of this invention show good image quality, close to the diffraction limit, indicating that the eyepiece objective has good imaging quality.

[0078] Figure 4 The distortion diagram of this invention shows that the maximum distortion of this invention is 15.9%, which is relatively small in a large field-of-view imaging lens.

[0079] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention. Applications, modifications, and variations of the invention will be readily apparent to those skilled in the art.

[0080] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

[0081] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0082] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0083] The above description is merely an embodiment of this specification and is not intended to limit the scope of one or more embodiments of this specification. Various modifications and variations can be made to one or more embodiments of this specification by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of one or more embodiments of this specification should be included within the scope of the claims of one or more embodiments of this specification.

Claims

1. An eyepiece objective for ultra-wide-angle fundus color imaging, comprising a single-piece eyepiece objective lens and a cemented eyepiece objective lens, characterized in that... The single lens of the eyepiece objective and the cemented lens of the eyepiece objective are arranged sequentially from the pupil side to the image plane side; The eyepiece objective lens is a meniscus lens, the concave surface of which is spherical and faces the pupil, and the convex surface of which is aspherical. The eyepiece objective lens is cemented from the pupil side to the image plane side by a first aspherical lens, a biconcave lens, and a second aspherical lens cemented together. The first aspherical lens is a biconvex lens, wherein the non-cemented surface and the cemented surface of the first aspherical lens are aspherical and spherical, respectively; the cemented surfaces on both sides of the biconcave lens are spherical; the second aspherical lens is a biconvex lens, wherein the cemented surface and the non-cemented surface of the second aspherical lens are spherical and aspherical, respectively. The relationship between the image distance and focal length of the target object is: 0.6 < image distance / focal length < 1; The concave surface curvature radius of the meniscus lens is -40 to -42 mm, and the net aperture of the concave surface of the meniscus lens is 20 to 22 mm. The convex surface of the meniscus lens is a standard second-order aspherical surface, the radius of curvature of the convex surface of the meniscus lens is -20 to -22 mm, the net aperture of the convex surface of the meniscus lens is 23 to 25 mm, and the conicity of the convex surface of the meniscus lens is -0.34 to -0.

36. The center thickness of the single lens of the eyepiece objective is 13~15mm; The unbonded surface of the first aspherical lens is a standard double aspherical surface, the radius of curvature of the unbonded surface of the first aspherical lens is 67~69mm, the conicity of the unbonded surface of the first aspherical lens is -28~-30, the radius of curvature of the bonded surface of the first aspherical lens is -64~-66mm, and the center thickness of the first aspherical lens is 16~18mm. The radius of curvature of the bonding surface of the biconcave lens near the pupil is -64 to -66 mm, the radius of curvature of the bonding surface of the biconcave lens away from the pupil is 100 to 102 mm, and the center thickness of the biconcave lens is 4 to 5 mm. The second aspherical lens has a bonding surface curvature radius of 100~102mm, an unbonded surface of the second aspherical lens is a high-order even-order aspherical, an infinitely large unbonded surface curvature radius, a conic coefficient of 0, a fourth-order term of -5.296E-06, a sixth-order term of 3.885E-09, an eighth-order term of -2E-12, a tenth-order term of 4.338E-16, and a center thickness of 15~16mm. The center distance between the convex surface of the single lens of the eyepiece and the non-cemented surface of the first aspherical lens is 0.3~0.5mm; The refractive index Nd of the single lens of the eyepiece objective satisfies 1.6 < Nd < 1.8, and the Abbe number Vd satisfies 52 < Vd < 54. The refractive index Nd of the first aspherical lens satisfies 1.7 < Nd < 1.9, and the Abbe number Vd satisfies 45 < Vd < 47. The refractive index Nd of the biconcave lens satisfies 1.9 < Nd < 2.1, and the Abbe number Vd satisfies 17 < Vd < 19. The refractive index Nd of the second aspherical lens satisfies 1.8 < Nd < 2, and the Abbe number Vd satisfies 40 < Vd < 42.

2. The eyepiece objective for ultra-wide-angle fundus color imaging as described in claim 1, characterized in that: The net aperture of the cemented lens of the eyepiece objective is 38~40mm.

3. The eyepiece objective for ultra-wide-angle fundus color imaging as described in claim 1, characterized in that: The single lens and the cemented lens of the eyepiece objective are made of glass.

Images