A long eye relief glass-plastic hybrid eyepiece and its optical system

Abstract

This utility model discloses a glass-plastic hybrid eyepiece with a long exit pupil distance and its optical system. The optical system includes an aperture stop, a first lens, a second lens, a third lens, and a fourth lens arranged sequentially from the image side to the object side. The second lens and the third lens form a cemented doublet lens. The first lens and the cemented doublet lens are glass lenses, and the fourth lens is a plastic lens. The eyepiece has a simple and lightweight structure and is easy to assemble and use.

Description

Technical Field

[0001] This invention relates to the field of eyepiece optics, specifically to a glass-plastic hybrid eyepiece with an extended exit pupil distance and its optical system. Background Technology

[0002] The eyepiece is a crucial component of optical visual instruments. Its function is to magnify the image formed by the objective lens to facilitate target recognition by the human eye. Therefore, studying the characteristics of the eyepiece and the human eye is of great significance. Considering the reception of light at different angles in different environments, the exit pupil diameter of an eyepiece system is typically set at around 5mm. Traditional eyepiece optical systems generally have an exit pupil distance of 20-25mm. However, with the advancement of technological innovation and the increasing demand for military instruments, the use of goggles and AR glasses has led to increasingly stringent requirements for eyepiece systems, making it difficult for traditional eyepiece optical systems to meet these demands. For example, one existing technology discloses a long exit pupil eyepiece for a head-mounted visual device, employing an aspherical glass design to achieve an exit pupil distance greater than 30mm. However, the exit pupil distance is still insufficient, resulting in overall image quality that is not clear enough. Another existing technology discloses a long exit pupil eyepiece optical system that, while meeting the 40mm exit pupil distance requirement, uses traditional spherical glass materials and employs seven glass elements, resulting in high material costs and weight, and failing to achieve lightweight design.

[0003] Portable handheld observation devices are often designed for portability by miniaturizing their size. Therefore, handheld observation products, especially those with small displays, face harsher operating environments compared to larger, less portable devices. They are exposed to severe shaking, extreme temperatures, and other extreme conditions. Furthermore, users may wear goggles or glasses, necessitating the installation of an eye shield between the eyepiece and the glasses. These requirements necessitate a longer exit pupil distance for the eyepiece. Therefore, developing an eyepiece with a longer exit pupil distance, a compact and lightweight overall structure, high clarity, and made from a glass-plastic hybrid material is of paramount importance. Summary of the Invention

[0004] The purpose of this invention is to provide a glass-plastic hybrid eyepiece with an extended interpupillary distance and its optical system, so as to achieve a lightweight eyepiece.

[0005] To solve the above-mentioned technical problems, the present invention provides an optical system for a glass-plastic hybrid eyepiece with an extended interpupillary distance, comprising an aperture, a first lens, a second lens, a third lens, and a fourth lens arranged sequentially from the image side to the object side, wherein the second lens and the third lens form a cemented doublet; the first lens and the cemented doublet are glass lenses, and the fourth lens is a plastic lens.

[0006] According to the above scheme, the focal length of the first lens is (30mm, 40mm), the focal length of the cemented doublet lens is (180mm, 185mm), and the focal length of the fourth lens group is (25mm, 30mm); among which, the focal length of the second lens is (25mm, 30mm), and the focal length of the third lens is (-30mm, -25mm).

[0007] According to the above scheme, the air gap between the aperture stop and the first lens is 50~55mm, and the air gap between the fourth lens and the image plane is 5~7mm.

[0008] According to the above scheme, the first lens is made of lanthanum flint glass, the second lens is made of lanthanum crown glass, the third lens is made of heavy flint glass, and the fourth lens is made of optical plastic PMMA.

[0009] According to the above scheme, the first lens, the second lens, and the fourth lens are all biconvex lenses, and the third lens is a biconcave lens.

[0010] According to the above scheme, the radius of curvature of the side of the first lens away from the second lens is [25mm, 35mm], and the radius of curvature of the side of the first lens close to the second lens is [-350mm, -340mm].

[0011] The radius of curvature of the side of the second lens away from the third lens is [20mm, 30mm], and the radius of curvature of the side of the second lens close to the third lens is [-80mm, -70mm].

[0012] The radius of curvature of the side of the third lens furthest from the second lens is [35mm, 45mm];

[0013] The radius of curvature of the side of the fourth lens closest to the third lens is [10mm, 20mm], and the radius of curvature of the side of the fourth lens furthest from the third lens is [-90mm, -80mm].

[0014] This utility model also provides a glass-plastic hybrid eyepiece with a long exit pupil distance, including an optical system and structural components;

[0015] The optical system includes an aperture stop, a first lens, a second lens, a third lens, and a fourth lens arranged sequentially from the image side to the object side. The second lens and the third lens form a cemented doublet. The first lens and the cemented doublet are glass lenses, and the fourth lens is a plastic lens.

[0016] The structural components include the eyepiece frame, pressure ring, first spacer, and second spacer;

[0017] The optical system is fixed inside the eyepiece frame by a pressure ring, the first spacer is located between the first lens and the second lens, and the second spacer is located between the third lens and the fourth lens.

[0018] According to the above scheme, a first sealing ring is provided between the fourth lens and the eyepiece frame.

[0019] According to the above scheme, a second sealing ring is provided between the pressure ring and the first lens.

[0020] Beneficial effects

[0021] This invention introduces a plastic lens as a component of the optical system, taking advantage of the lightweight nature of plastic to effectively reduce the overall weight of the optical system. Furthermore, through a special optical system composition, the number of lenses in the optical system is reduced, effectively shrinking the size and weight of the eyepiece and achieving lightweighting of the eyepiece.

[0022] Furthermore, by setting special optical system characteristic parameters, the optical system can have a longer exit pupil distance, which can adapt to the eyepiece usage requirements under specific conditions. Attached Figure Description

[0023] Figure 1 This is a structural diagram of the optical system of the glass-plastic hybrid eyepiece according to Embodiment 1 of this utility model;

[0024] Figure 2 This is a cross-sectional view of the glass-plastic hybrid eyepiece according to Embodiment 2 of this utility model;

[0025] Figure 3 This is the MTF curve of the optical system of the glass-plastic hybrid eyepiece of Embodiment 1 of this utility model under normal temperature conditions;

[0026] Figure 4 This is a dot diagram of the optical system of the glass-plastic hybrid eyepiece according to Embodiment 1 of this utility model;

[0027] Figure 5 This is a field curvature and distortion diagram of the optical system of the glass-plastic hybrid eyepiece according to Embodiment 1 of this utility model;

[0028] Figure 6 This is a relative illumination diagram of the optical system of the glass-plastic hybrid eyepiece according to Embodiment 1 of this utility model;

[0029] Figure 7 This is a three-dimensional view of the glass-plastic hybrid eyepiece according to Embodiment 2 of this utility model.

[0030] In the diagram: 1-First lens; 201-Second lens; 202-Third lens; 3-Fourth lens; 4-Eyepiece frame; 5-Pressure ring; 6-First spacer; 7-Second spacer; 8-First sealing ring; 9-Second sealing ring. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0032] Example 1:

[0033] See Figure 1 This embodiment provides an optical system for a glass-plastic hybrid eyepiece with a long interpupillary distance, including an aperture, a first lens 1, a second lens 201, a third lens 202, and a fourth lens 3 arranged sequentially from the image side to the object side. The second lens 201 and the third lens 202 form a cemented doublet lens. The first lens 1 and the cemented doublet lens are glass lenses, and the fourth lens 3 is a plastic lens.

[0034] Furthermore, the focal length of the first lens 1 is (30mm, 40mm), the focal length of the cemented doublet lens is (180mm, 185mm), and the focal length of the fourth lens group 3 is (25mm, 30mm); among which the focal length of the second lens 201 is (25mm, 30mm), and the focal length of the third lens 202 is (-30mm, -25mm).

[0035] Furthermore, the air gap between the aperture stop and the first lens 1 is 50~55mm (preferably 50.05mm), and the air gap between the fourth lens 3 and the image plane is 5~7mm (preferably 60.67mm); the exit pupil diameter of the optical system is 6mm.

[0036] Furthermore, the first lens 1 is made of lanthanum flint glass, the second lens 201 is made of lanthanum crown glass, the third lens 202 is made of heavy flint glass, and the fourth lens 3 is made of optical plastic PMMA (which significantly deflects light to reduce aberrations caused by sudden changes in light intensity). In this embodiment, the low-refractive-index, high-dispersion glass of the second lens 201 and the high-refractive-index, low-dispersion glass of the third lens 202 are bonded together, which eliminates chromatic aberration while also converging light, greatly simplifying the glass processing difficulty and structural tolerance complexity, and effectively correcting spherical aberration and chromatic aberration. In addition, the addition of plastic aspherical material makes the light refraction angle smoother, which is used to reduce aberrations caused by sudden changes in light intensity.

[0037] Furthermore, the first lens 1, the second lens 201, and the fourth lens 3 are all biconvex lenses (the fourth lens 3 is an aspherical lens), and the third lens 202 is a biconcave lens.

[0038] Furthermore, the radius of curvature of the side of the first lens 1 away from the second lens 201 is [25mm, 35mm], and the radius of curvature of the side of the first lens 1 close to the second lens 201 is [-350mm, -340mm].

[0039] The radius of curvature of the side of the second lens 201 away from the third lens 202 is [20mm, 30mm], and the radius of curvature of the side of the second lens 201 close to the third lens 202 is [-80mm, -70mm].

[0040] The radius of curvature of the side of the third lens 202 away from the second lens 201 is [35mm, 45mm];

[0041] The radius of curvature of the side of the fourth lens 3 close to the third lens 202 is [10mm, 20mm], and the radius of curvature of the side of the fourth lens 3 far from the third lens 202 is [-90mm, -80mm].

[0042] It should be understood that light rays travel along the visual direction through the lenses in the optical system to reach the focal plane. The radius of curvature of the convex surface through which the light rays pass is defined as a positive number, and the radius of curvature of the concave surface through which the light rays pass is defined as a negative number.

[0043] The dimensions and thickness / spacer parameters of each lens in the optical system in this embodiment are shown in the table below:

[0044] Table 1 Optical System Parameters of Glass-Plastic Hybrid Eyepiece

[0045]

[0046] Among them, the aspheric coefficient is calculated according to the even-order aspheric formula. ;

[0047] In the formula, r is the aperture perpendicular to the optical axis, Z is the distance vector from the vertex of the aspherical surface at a height of r along the optical axis, c is the vertex radius of curvature of the surface, k is the conic coefficient, and a is the higher-order aspherical coefficient. See the table below, where i is the order of the aspherical surface;

[0048] Table 2 Aspheric coefficient 1

[0049]

[0050] Table 2 Aspheric coefficients 2

[0051]

[0052] The characteristics of the optical system described in this embodiment are described in [reference]. Figures 3-6The optical system in this embodiment has a magnification of 14x, a total length of 80mm, and a total glass mass of 37.5g. At room temperature, the optical system has a center field-of-view resolution greater than 0.695@20lp / mm and an edge field-of-view resolution greater than 0.32@20lp / mm, providing clear image quality across the entire field of view, ensuring image integrity and stability, and guaranteeing a consistent and reliable viewing experience for the observer over extended periods. The root mean square radius of all fields of view is within 22μm, and the GEO radius does not exceed 54μm, resulting in concentrated imaging light energy; the relative illumination across the entire field of view is greater than 0.45. (See [link to relevant documentation]). Figure 5 This ensures sufficient light transmission at the edge of the field of view.

[0053] The optical system in this embodiment has a simple structure and innovatively adopts a combination of CDGM commonly used materials and optical plastics to achieve a lightweight optical system. By innovatively designing three lens groups with different focal lengths and specifically selecting the shape and material of each lens group, the glass-plastic hybrid eyepiece has the advantages of long exit pupil distance, light weight, and high clarity (exit pupil distance greater than 30cm is considered large).

[0054] Example 2:

[0055] See Figure 1 , Figure 2 , Figure 7 This embodiment discloses a glass-plastic hybrid eyepiece with a long exit pupil distance, including an optical system and structural components;

[0056] The optical system includes an aperture stop, a first lens 1, a second lens 201, a third lens 202, and a fourth lens 3, which are arranged sequentially from the image side to the object side. The second lens 201 and the third lens 202 form a cemented doublet lens. The first lens 1 and the cemented doublet lens are glass lenses, and the fourth lens 3 is a plastic lens.

[0057] The structural components include eyepiece frame 4, pressure ring 5, first spacer 6, and second spacer 7;

[0058] The optical system is fixed inside the eyepiece frame 4 by a retaining ring 5, a second spacer 7 is disposed between the first lens 1 and the second lens 201, and a first spacer 6 is disposed between the third lens 202 and the fourth lens 3.

[0059] In this embodiment, the glass in the eyepiece is supported by a spacer, which fits tightly with the eyepiece frame 4, ensuring a stable eyepiece structure and strong impact resistance. Sealing gaskets are located at both ends of the eyepiece frame 4, and the internal components are pressed together by pressure rings 5, guaranteeing good airtightness of the eyepiece. The eyepiece of this embodiment is characterized by resistance to high and low temperatures, vibration, impact, and water, as well as a long service life. Compared with existing traditional eyepieces, it has a larger exit pupil diameter, higher image quality, a longer exit pupil distance, and is lighter.

[0060] Furthermore, a first sealing ring 8 is provided between the fourth lens 3 and the eyepiece frame 4.

[0061] Furthermore, a second sealing ring 9 is provided between the pressure ring 5 and the first lens 1.

[0062] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0063] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An optical system of a hybrid glass- plastic eyepiece with an extended eye relief, characterized in that, It includes an aperture stop, a first lens, a second lens, a third lens, and a fourth lens arranged sequentially from the image side to the object side; the second lens and the third lens form a cemented doublet lens; the first lens and the cemented doublet lens are glass lenses, and the fourth lens is a plastic lens; The focal lengths of the first lens are (30mm, 40mm), the focal lengths of the cemented doublet lens are (180mm, 185mm), and the focal lengths of the fourth lens group are (25mm, 30mm); the focal lengths of the second lens are (25mm, 30mm), and the focal lengths of the third lens are (-30mm, -25mm).

2. The optical system of long eye relief glass-plastic hybrid eyepiece according to claim 1, characterized in that, The air gap between the aperture stop and the first lens is 50~55mm, and the air gap between the fourth lens and the image plane is 5~7mm.

3. The optical system of long eye relief glass-plastic hybrid eyepiece according to claim 1, wherein, The first lens is made of lanthanum flint glass, the second lens is made of lanthanum crown glass, the third lens is made of heavy flint glass, and the fourth lens is made of PMMA optical plastic.

4. The optical system of long eye relief eriscope according to claim 1, wherein, The first, second, and fourth lenses are all biconvex lenses, while the third lens is a biconcave lens.

5. The optical system of long eye relief eriscope according to claim 1, wherein, The radius of curvature of the side of the first lens away from the second lens is [25mm, 35mm], and the radius of curvature of the side of the first lens close to the second lens is [-350mm, -340mm]. The radius of curvature of the side of the second lens away from the third lens is [20mm, 30mm], and the radius of curvature of the side of the second lens close to the third lens is [-80mm, -70mm]. The radius of curvature of the side of the third lens furthest from the second lens is [35mm, 45mm]; The radius of curvature of the side of the fourth lens closest to the third lens is [10mm, 20mm], and the radius of curvature of the side of the fourth lens furthest from the third lens is [-90mm, -80mm].

6. A hybrid glass plastic eyepiece with an extended eye relief, characterized in that, Including optical systems and structural components; The optical system includes an aperture stop, a first lens, a second lens, a third lens, and a fourth lens arranged sequentially from the image side to the object side. The second lens and the third lens form a cemented doublet. The first lens and the cemented doublet are glass lenses, and the fourth lens is a plastic lens. The structural components include the eyepiece frame, pressure ring, first spacer, and second spacer; The optical system is fixed inside the eyepiece frame by a pressure ring, the first spacer is located between the first lens and the second lens, and the second spacer is located between the third lens and the fourth lens.

7. The long eye relief erector objective of claim 6 wherein, A first sealing ring is provided between the fourth lens and the eyepiece frame.

8. The long eye relief erector objective of claim 6 wherein, A second sealing ring is provided between the pressure ring and the first lens.

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