Tube lens for realizing long entrance interpupillary distance through triplet lens

Abstract

The utility model relates to the technical field of optical equipment, and provides a tube lens realizing long entrance pupil distance through a triplet lens, which comprises a lens barrel, a triplet lens group and a pressing ring, the triplet lens group is arranged in the lens barrel, and the pressing ring is screwed into the lens barrel and tightly presses the triplet lens group; the triplet lens group is formed by sequentially gluing a first lens, a second lens and a third lens along the optical axis direction. According to the utility model, through the specific material combination (high dispersion L1 / L2 + low dispersion L3) and parameter matching (curvature radius R1-R4 and focal length range) of the triplet lens group, the axial chromatic aberration and spherical aberration can be effectively corrected, a longer entrance pupil distance can be ensured, and the arrangement of the lens group enables light to be refracted for multiple times before entering the camera, so that the imaging quality of the camera is improved. The entrance pupil distance can be increased to more than 400mm, and the lens group is made of a low-refractive-index material so as to reduce aberration and distortion.

Description

Technical Field

[0001] This utility model relates to the field of optical equipment technology, and in particular to a tube lens that achieves a long entrance pupil distance through a three-layer cemented lens. Background Technology

[0002] An optical tube is a precision optical instrument component that uses optical principles to focus, magnify, or reduce light, thereby enabling the observation and imaging of objects.

[0003] Traditional tube endoscope designs often suffer from short entrance pupil distances, which cause several inconveniences when using cameras for observation: 1. Increased optical system complexity: Short entrance pupil distances require complex lens designs to compensate for aberrations and distortions, increasing manufacturing costs and system size; 2. Affected image quality: Short entrance pupil distances can lead to limited field of view and increased edge distortion, affecting the overall image quality and usability; 3. Increased data processing complexity: Due to the optical problems (such as distortion and shadows) caused by short entrance pupil distances, the workload of subsequent data processing and image correction increases significantly.

[0004] Therefore, how to design a tube endoscope that can effectively extend the entrance pupil distance while ensuring image quality and simplifying the overall system design has become an urgent technical problem to be solved. Utility Model Content

[0005] The purpose of this invention is to solve the problem of short entrance pupil distance in the prior art.

[0006] To achieve the above objectives, this utility model adopts the following technical solution: a telescope that achieves a long entrance pupil distance using a cemented triplet lens, comprising a telescope barrel, a cemented triplet lens assembly, and a retaining ring. The cemented triplet lens assembly is inserted into the telescope barrel, and the retaining ring is screwed into the telescope barrel and presses the cemented triplet lens assembly tightly. The cemented triplet lens assembly is formed by cementing a first lens, a second lens, and a third lens sequentially along the optical axis, wherein:

[0007] The first lens is a convex lens, made of H-TF3L, with a refractive index Nd=1.6124, an Abbe number Vd=44.093, a front surface radius of curvature R1 of 300-400mm, a rear surface radius of curvature R2 of 30-50mm, and a focal length of 54-76mm.

[0008] The second lens is a concave lens made of H-F13 material with a refractive index of Nd=1.6259, an Abbe number of Vd=35.699, a front surface radius of curvature R2 of 30-50mm, a rear surface radius of curvature R3 of 40-62mm, and a focal length of 193-229mm.

[0009] The third lens is a convex lens made of H-ZPK7 material with a refractive index of Nd=1.5691, an Abbe number of Vd=71.304, a front surface radius of curvature R3 of 40-62mm, a rear surface radius of curvature R4 of 120-140mm, and a focal length of -68 to -83mm.

[0010] The entrance pupil distance of the triplex lens group is >400mm, the field of view is ≤26mm, and the entrance pupil diameter is ≤12.3mm.

[0011] In a preferred embodiment, optical adhesive is applied between the bonding surfaces of each lens in the triple-bonded lens group, with an adhesive layer thickness of 0.01-0.03 mm.

[0012] In a preferred embodiment, the entrance pupil distance of the triplex lens group 2 is >250mm.

[0013] In a preferred embodiment, the field of view of the triplex lens group 2 is ≤26mm and the entrance pupil diameter is ≤12.3mm.

[0014] Compared with the prior art, the advantages and positive effects of this utility model are as follows:

[0015] This invention utilizes a specific material combination (high dispersion L1 / L2 + low dispersion L3) and parameter matching (radius of curvature R1-R4, focal length range) of a triple-cemented lens group. This structure can effectively correct axial chromatic aberration and spherical aberration, ensuring a longer entrance pupil distance. The arrangement of the lens group causes light to undergo multiple refractions before entering the camera, which can increase the entrance pupil distance to over 400mm. Furthermore, the lens group uses low refractive index materials to reduce aberrations and distortion. Attached Figure Description

[0016] Figure 1 A cross-sectional schematic diagram of the overall structure for achieving a long entrance pupil distance using a three-layer cemented lens, provided by this utility model;

[0017] Figure 2 A cross-sectional schematic diagram of a cemented triplet lens that achieves a long entrance pupil distance using a cemented triplet lens, provided for this utility model;

[0018] Figure 3 This invention provides a diagram showing the lens group arrangement and its relationship with the optical axis of a tube lens that achieves a long entrance pupil distance using a three-layer cemented lens.

[0019] Legend:

[0020] 1. Lens tube; 2. Tri-laminated lens group; 3. Pressure ring; L1; First lens; L2; Second lens; L3; Third lens. Detailed Implementation

[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0022] Optical simulation verification shows that the entrance pupil distance of this solution can reach over 400mm. Specific implementation examples are shown below:

[0023] Please see Figure 1-3 This utility model provides a technical solution: a telescope that achieves a long entrance pupil distance using a cemented triplet lens, comprising a telescope barrel 1, a cemented triplet lens assembly 2, and a retaining ring 3. The cemented triplet lens assembly 2 is installed in the telescope barrel 1, and the retaining ring 3 is screwed into the telescope barrel 1 and presses the cemented triplet lens assembly 2 tightly. The cemented triplet lens assembly 2 is formed by cementing a first lens L1, a second lens L2, and a third lens L3 sequentially along the optical axis, wherein:

[0024] The first lens L1 is a convex lens made of H-TF3L with a refractive index of Nd=1.6124, an Abbe number of Vd=44.093, a front surface radius of curvature R1 of 300-400mm, a rear surface radius of curvature R2 of 30-50mm, and a focal length of 54-76mm.

[0025] The second lens L2 is a concave lens made of H-F13 with a refractive index of Nd=1.6259, an Abbe number of Vd=35.699, a front surface radius of curvature R2 of 30-50mm, a rear surface radius of curvature R3 of 40-62mm, and a focal length of 193-229mm.

[0026] The third lens L3 is a convex lens made of H-ZPK7 material with a refractive index of Nd=1.5691, an Abbe number of Vd=71.304, a front surface radius of curvature R3 of 40-62mm, a rear surface radius of curvature R4 of 120-140mm, and a focal length of -68 to -83mm.

[0027] The entrance pupil distance of the cemented lens group 2 is >400mm, the field of view is ≤26mm, and the entrance pupil diameter is ≤12.3mm. The cemented lens is coated with an anti-reflection coating and the incident angle is set from 0° to 10°. The lens group uses low refractive index material to reduce aberrations and distortions. The arrangement of the lens group causes light to undergo multiple refractions and reflections before entering the camera, which can ensure an entrance pupil distance of more than 400mm. By optimizing the arrangement and structural design of the lens group, the entire tube lens is kept compact while achieving a long entrance pupil distance.

[0028] The Abbe number difference between the first lens L1 (H-TF3L) and the second lens L2 (H-F13) is >20%, which is used to compensate for chromatic aberration;

[0029] The low dispersion characteristics (Vd=71.304) of the third lens L3 (H-ZPK7) further suppress spherical aberration.

[0030] like Figure 1-3 As shown, optical adhesive is applied between the bonding surfaces of each lens in the three-layer cemented lens group (2), with an adhesive layer thickness of 0.01-0.03 mm.

[0031] like Figure 1-3 As shown, the entrance pupil distance of the triplet lens group 2 is >250mm.

[0032] like Figure 1-3 As shown, the field of view of the triplet lens group 2 is ≤26mm, and the entrance pupil diameter is ≤12.3mm.

[0033] Working principle: Through a specific material combination (high dispersion L1 / L2 + low dispersion L3) and parameter matching (radius of curvature R1-R4, focal length range) of the triple-cemented lens group, this structure can effectively correct axial chromatic aberration and spherical aberration, ensuring a longer entrance pupil distance. The arrangement of the lens group causes light to undergo multiple refractions before entering the camera, which can increase the entrance pupil distance to over 400mm. In addition, the lens group uses low refractive index materials to reduce aberrations and distortion.

[0034] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present utility model without departing from the technical solution of the present utility model shall still fall within the protection scope of the technical solution of the present utility model.

Claims

1. A tube endoscope that achieves a long entrance pupil distance using a cemented triplet lens, characterized in that, The system includes a lens barrel (1), a cemented triplet lens assembly (2), and a retaining ring (3). The cemented triplet lens assembly (2) is installed in the lens barrel (1), and the retaining ring (3) is screwed into the lens barrel (1) and presses the cemented triplet lens assembly (2) tightly. The cemented triplet lens assembly (2) is formed by cementing a first lens (L1), a second lens (L2), and a third lens (L3) sequentially along the optical axis. The first lens (L1) is a convex lens, made of H-TF3L, with a refractive index Nd=1.6124, an Abbe number Vd=44.093, a front surface radius of curvature R1 of 300-400mm, a rear surface radius of curvature R2 of 30-50mm, and a focal length of 54-76mm. The second lens (L2) is a concave lens made of H-F13 with a refractive index of Nd=1.6259, an Abbe number of Vd=35.699, a front surface radius of curvature R2 of 30-50mm, a rear surface radius of curvature R3 of 40-62mm, and a focal length of 193-229mm. The third lens (L3) is a convex lens made of H-ZPK7 with a refractive index of Nd=1.5691, an Abbe number of Vd=71.304, a front surface radius of curvature R3 of 40-62mm, a rear surface radius of curvature R4 of 120-140mm, and a focal length of -68 to -83mm. The entrance pupil distance of the triplet lens group (2) is >400mm, the field of view size is ≤26mm, and the entrance pupil diameter is ≤12.3mm.

2. A tube endoscope according to claim 1 that achieves a long entrance pupil distance using a cemented triplet lens, characterized in that: The bonding surfaces of each lens in the triple-bonded lens group (2) are coated with optical adhesive, and the adhesive layer thickness is 0.01-0.03 mm.

3. A tube endoscope according to claim 1 that achieves a long entrance pupil distance using a cemented triplet lens, characterized in that: The entrance pupil distance of the triple-colloid lens group (2) is >250mm.

4. A tube endoscope according to claim 1 that achieves a long entrance pupil distance using a cemented triplet lens, characterized in that: The field of view of the triplex lens group (2) is ≤26mm, and the entrance pupil diameter is ≤12.3mm.

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