Short focal length eyepiece and optical system

Abstract

This application discloses an optical system including a short-focal-length eyepiece and a display adapted to the eyepiece. The short-focal-length eyepiece has a focal length of 13.7 mm, a field of view of 40°, a magnification of 18x, an exit pupil diameter of 8 mm, an exit pupil distance of 20 mm, an operating temperature range of -40℃ to +60℃, and an operating wavelength range of 0.48 to 0.65 μm. The display is an OLED display with a resolution of 1024×768 and a pixel size of 7.8 μm. The short-focal-length eyepiece consists of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens arranged sequentially along the optical axis from the eye side to the image side. The first and second lenses are cemented together, and the fourth and fifth lenses are cemented together. This short-focal-length eyepiece can achieve clear imaging of a large target area, meets the requirements of low distortion, and adopts a non-thermal compensation method, exhibiting good imaging performance at different operating temperatures.

Description

Technical Field

[0001] This application belongs to the field of optical lens technology, specifically relating to a short focal length eyepiece and optical system. Background Technology

[0002] Visual wearable electronic devices are increasingly being used in military, industrial, medical, educational, and consumer fields. A typical visual wearable electronic device consists of a miniature image display and an eyepiece at its back end. The eyepiece is the core component for transmitting information to the human eye, magnifying the miniature image and displaying it on the pupil. For short-focal-length eyepieces, in addition to meeting the requirements of clear imaging across a large field of view and target surface, low distortion is also necessary; existing short-focal-length eyepieces struggle to meet these requirements simultaneously. Summary of the Invention

[0003] Therefore, it is necessary to provide a short-focal-length eyepiece and optical system that can meet the requirements of clear imaging of a large field of view and large target surface, and low distortion.

[0004] The technical solution proposed in this application is as follows: A short-focal-length eyepiece with a focal length of 13.7 mm and a field of view of 40° is provided. The short-focal-length eyepiece is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens arranged sequentially from the eye side to the image side along the optical axis. The first lens is a positive meniscus lens with its convex surface facing the image side, the second lens is a negative meniscus lens with its convex surface facing the image side, the third lens, the fourth lens, and the sixth lens are all positive meniscus lenses with their convex surfaces facing the eye side, and the fifth lens is a negative meniscus lens with its convex surface facing the eye side. The first lens and the second lens are cemented together, the fourth lens and the fifth lens are cemented together, and the air gap between the second lens and the third lens is 0.15 mm, the air gap between the third lens and the fourth lens is 0.15 mm, and the air gap between the fifth lens and the sixth lens is 2.65 mm.

[0005] Further, the first lens has a center thickness of 5 mm, an eye-side radius of curvature of -49.64 mm, and an image-side radius of curvature of -12.89 mm; the second lens has a center thickness of 1 mm and an image-side radius of curvature of -30.67 mm; the third lens has a center thickness of 3.2 mm, an eye-side radius of curvature of 24.99 mm, and an image-side radius of curvature of 96.91 mm; the fourth lens has a center thickness of 5.2 mm, an eye-side radius of curvature of 12.06 mm, and an image-side radius of curvature of 18.54 mm; the fifth lens has a center thickness of 2.4 mm and an image-side radius of curvature of 7.06 mm; and the sixth lens has a center thickness of 3 mm, an eye-side radius of curvature of 11.09 mm, and an image-side radius of curvature of 44.72 mm.

[0006] Furthermore, it is characterized by: The refractive index Nd1 of the first lens satisfies: 1.9 ≤ Nd1 ≤ 1.95; The refractive index Nd2 of the second lens satisfies: 1.9 ≤ Nd2 ≤ 2.0; The refractive index Nd3 of the third lens satisfies: 1.9 ≤ Nd3 ≤ 1.95; The refractive index Nd4 of the fourth lens satisfies: 1.9 ≤ Nd4 ≤ 1.95; The refractive index Nd5 of the fifth lens satisfies: 1.9 ≤ Nd5 ≤ 2.0; The refractive index Nd6 of the sixth lens satisfies: 1.9≤Nd6≤1.95.

[0007] Furthermore, it is characterized by: The Abbe number Vd1 of the first lens satisfies: 35 ≤ Vd1 ≤ 36; The Abbe number Vd2 of the second lens satisfies: 17 ≤ Vd2 ≤ 19; The Abbe number Vd3 of the third lens satisfies: 35≤Vd3≤36; The Abbe number Vd4 of the fourth lens satisfies: 35≤Vd4≤36; The Abbe number Vd5 of the fifth lens satisfies: 17≤Vd5≤19; The Abbe number Vd6 of the sixth lens satisfies: 35≤Vd6≤36.

[0008] Furthermore, the short-focal-length eyepiece has a magnification of 18x, an exit pupil diameter of 8mm, an exit pupil distance of 20mm, an operating temperature of -40℃ to +60℃, and an operating wavelength of 0.48 to 0.65μm.

[0009] Furthermore, both the eye-side and image-side surfaces of any lens are spherical.

[0010] An optical system includes the aforementioned short-focal-length eyepiece and a display adapted to the short-focal-length eyepiece.

[0011] Furthermore, the display has a resolution of 1024×768 and a pixel size of 7.8μm.

[0012] In summary, this application provides an optical system including a short-focal-length eyepiece and a display adapted to the eyepiece. The short-focal-length eyepiece has a focal length of 13.7 mm, a field of view of 40°, a magnification of 18x, an exit pupil diameter of 8 mm, an exit pupil distance of 20 mm, an operating temperature range of -40℃ to +60℃, and an operating wavelength range of 0.48 to 0.65 μm. The display is an OLED display with a resolution of 1024×768 and a pixel size of 7.8 μm. This short-focal-length eyepiece can achieve clear imaging of a large target surface, meets the requirements of low distortion, and adopts a non-thermal compensation method, exhibiting good imaging performance at different operating temperatures. Attached Figure Description

[0013] The accompanying drawings are provided to further understand this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof.

[0014] Figure 1 This is a schematic diagram of the optical path structure of a short-focal-length eyepiece provided in an embodiment of this application; Figure 2 MTF chart of a short-focal-length eyepiece at 20°C provided in an embodiment of this application; Figure 3 MTF chart of a short-focal-length eyepiece at 60°C provided in an embodiment of this application; Figure 4 MTF chart of a short-focal-length eyepiece at -40°C provided in an embodiment of this application; Figure 5 A dot diagram of a short-focal-length eyepiece provided in one embodiment of this application; Figure 6 Field curvature distortion diagram of a short-focal-length eyepiece provided in an embodiment of this application; Figure 7 This is a relative illumination diagram of a short-focal-length eyepiece provided in one embodiment of this application.

[0015] Label Explanation: 11. First lens; 12. Second lens; 13. Third lens; 14. Fourth lens; 15. Fifth lens; 16. Sixth lens. Detailed Implementation

[0016] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0017] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0018] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0019] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0020] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0021] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0022] This application provides an optical system including a short-focal-length eyepiece and a display adapted to the eyepiece. The short-focal-length eyepiece has a focal length of 13.7 mm, a field of view of 40°, a magnification of 18x, an exit pupil diameter of 8 mm, an exit pupil distance of 20 mm, an operating temperature range of -40℃ to +60℃, and an operating wavelength range of 0.48 to 0.65 μm. The display is an OLED display with a resolution of 1024×768 and a pixel size of 7.8 μm.

[0023] like Figure 1 As shown, in one embodiment, the short-focal-length eyepiece comprises a first lens 11, a second lens 12, a third lens 13, a fourth lens 14, a fifth lens 15, and a sixth lens 16 arranged sequentially from the eye side to the image side along the optical axis. The first lens 11 is a meniscus positive lens with its convex surface facing the image side, the second lens 12 is a meniscus negative lens with its convex surface facing the image side, the third lens 13, the fourth lens 14, and the sixth lens 16 are all meniscus positive lenses with their convex surfaces facing the eye side, and the fifth lens 15 is a meniscus negative lens with its convex surface facing the eye side. The first lens 11 and the second lens 12 are cemented together, and the fourth lens 14 and the fifth lens 15 are cemented together.

[0024] Please also refer to Table 1. In one embodiment, the air gap between the second lens 12 and the third lens 13 is 0.15 mm, the air gap between the third lens 13 and the fourth lens 14 is 0.15 mm, and the air gap between the fifth lens 15 and the sixth lens 16 is 2.65 mm.

[0025] Furthermore, the center thickness of the first lens 11 is 5 mm, the radius of curvature of the eye side is -49.64 mm, and the radius of curvature of the image side is -12.89 mm; the center thickness of the second lens 12 is 1 mm, and the radius of curvature of the image side is -30.67 mm; the center thickness of the third lens 13 is 3.2 mm, the radius of curvature of the eye side is 24.99 mm, and the radius of curvature of the image side is 96.91 mm; the center thickness of the fourth lens 14 is 5.2 mm, the radius of curvature of the eye side is 12.06 mm, and the radius of curvature of the image side is 18.54 mm; the center thickness of the fifth lens 15 is 2.4 mm, and the radius of curvature of the image side is 7.06 mm; and the center thickness of the sixth lens 16 is 3 mm, the radius of curvature of the eye side is 11.09 mm, and the radius of curvature of the image side is 44.72 mm.

[0026] In one embodiment, the refractive index Nd1 of the first lens 11 satisfies: 1.9 ≤ Nd1 ≤ 1.95; the refractive index Nd2 of the second lens 12 satisfies: 1.9 ≤ Nd2 ≤ 2.0; the refractive index Nd3 of the third lens 13 satisfies: 1.9 ≤ Nd3 ≤ 1.95; the refractive index Nd4 of the fourth lens 14 satisfies: 1.9 ≤ Nd4 ≤ 1.95; the refractive index Nd5 of the fifth lens 15 satisfies: 1.9 ≤ Nd5 ≤ 2.0; and the refractive index Nd6 of the sixth lens 16 satisfies: 1.9 ≤ Nd6 ≤ 1.95. The Abbe number Vd1 of the first lens 11 satisfies: 35 ≤ Vd1 ≤ 36; the Abbe number Vd2 of the second lens 12 satisfies: 17 ≤ Vd2 ≤ 19; the Abbe number Vd3 of the third lens 13 satisfies: 35 ≤ Vd3 ≤ 36; the Abbe number Vd4 of the fourth lens 14 satisfies: 35 ≤ Vd4 ≤ 36; the Abbe number Vd5 of the fifth lens 15 satisfies: 17 ≤ Vd5 ≤ 19; and the Abbe number Vd6 of the sixth lens 16 satisfies: 35 ≤ Vd6 ≤ 36.

[0027] Specifically Figure 1 In the illustrated embodiment, the refractive index Nd1 of the first lens 11 is 1.91; the refractive index Nd2 of the second lens 12 is 1.95; the refractive index Nd3 of the third lens 13 is 1.91; the refractive index Nd4 of the fourth lens 14 is 1.91; the refractive index Nd5 of the fifth lens 15 is 1.95; and the refractive index Nd6 of the sixth lens 16 is 1.91. The Abbe number Vd1 of the first lens 11 is 35.3; the Abbe number Vd2 of the second lens 12 is 17.9; the Abbe number Vd3 of the third lens 13 is 35.3; the Abbe number Vd4 of the fourth lens 14 is 35.3; the Abbe number Vd5 of the fifth lens 15 is 17.9; and the Abbe number Vd6 of the sixth lens 16 is 35.3. Thus, by cementing high-dispersion and low-dispersion materials together, dispersion distribution is achieved. At the same time, the different combinations and combined forces distribute the optical power, ensuring good optical performance of the short-focal-length eyepiece.

[0028] In one embodiment, both the eye-side and image-side surfaces of any lens are spherical, which facilitates processing and reduces manufacturing costs.

[0029] Table 1 Data for each lens It needs to be explained that, in Figure 1 In the illustrated embodiment, the left side is the eye side and the right side is the image side. Taking the first lens 11 and the second lens 12 as examples, the left side of the first lens 11 is the eye side, with surface number S1. The right side of the first lens 11 is cemented to the left side of the second lens 12. The left side of the second lens 12 is the eye side, with surface number S2, and the right side is the image side, with surface number S3. Other lenses are similar and will not be described in detail here.

[0030] Please see Figures 2 to 7 , Figure 2 This is the MTF plot of a short-focal-length eyepiece at 20°C. Figure 3 This is the MTF plot of a short-focal-length eyepiece at 60°C. Figure 4 This is the MTF plot of a short-focal-length eyepiece at -40°C. Figure 5 This is a dot plot of a short-focal-length eyepiece. Figure 6 This is a field curvature distortion diagram for a short-focal-length eyepiece. Figure 7 This is the relative illumination diagram for a short-focal-length eyepiece. Combined with... Figures 2 to 4 It can be seen that at the cutoff frequency of 30 lp / mm, the 0° field of view is close to the diffraction limit, indicating that the central region has sharp imaging and high contrast. The MTF value of the edge field of view (20°) at 30 lp / mm frequency remains above 0.3, meeting the conventional requirements of the eyepiece system for edge resolution. Meanwhile, within the temperature range of -40℃ to +60℃, the MTF curves of each field of view are consistent, with no significant decrease in the MTF value of the central field of view, indicating stable image quality. Combined with... Figure 5 It can be seen that the RMS spot radius is less than 25μm within the 0°–12° field of view, and the RMS radius at the edge field of view (20°) is controlled within 42.8μm. The spot distribution is concentrated and the shape is symmetrical. Therefore, this short-focal-length eyepiece provides clear imaging across the entire field of view, with balanced image quality at the center and edges. It also exhibits good detail resolution, especially in the edge areas of large target surfaces, making it well-suited for OLED displays with a resolution of 1024×768 and a pixel size of 7.8μm. Combined with… Figure 6 It is known that optical distortion can be controlled within -8% across the entire field of view, effectively suppressing barrel distortion and significantly reducing geometric distortion in imaging. There is no obvious stretching or compression distortion at the edges of the image during observation, making it particularly suitable for observation scenarios requiring precise spatial perception (such as head-mounted displays, electronic viewfinders, night vision devices, etc.), and it is less likely to cause visual fatigue during prolonged use. Combined with... Figure 7It can be seen that the relative illumination is close to 100% within the 0° to 12° field of view, and the edge field of view (20°) still maintains more than 50%, which is consistent with the typical design of eyepiece edge vignetting. In actual observation, there is no obvious dark corner and it does not affect the visual experience.

[0031] In summary, this application provides an optical system including a short-focal-length eyepiece and a display adapted to the eyepiece. The short-focal-length eyepiece has a focal length of 13.7 mm, a field of view of 40°, a magnification of 18x, an exit pupil diameter of 8 mm, an exit pupil distance of 20 mm, an operating temperature range of -40℃ to +60℃, and an operating wavelength range of 0.48 to 0.65 μm. The display is an OLED display with a resolution of 1024×768 and a pixel size of 7.8 μm. This short-focal-length eyepiece can achieve clear imaging of a large target surface, meets the requirements of low distortion, and adopts a non-thermal compensation method, exhibiting good imaging performance at different operating temperatures.

[0032] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A short focal length eyepiece, characterized by With a focal length of 13.7mm and a field of view of 40°, the short-focal-length eyepiece consists of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens arranged sequentially from the eye side to the image side along the optical axis. The first lens is a positive meniscus lens with its convex surface facing the image side, the second lens is a negative meniscus lens with its convex surface facing the image side, the third lens, the fourth lens, and the sixth lens are all positive meniscus lenses with their convex surfaces facing the eye side, and the fifth lens is a negative meniscus lens with its convex surface facing the eye side. The first lens and the second lens are cemented together, the fourth lens and the fifth lens are cemented together, and the air gap between the second lens and the third lens is 0.15 mm, the air gap between the third lens and the fourth lens is 0.15 mm, and the air gap between the fifth lens and the sixth lens is 2.65 mm.

2. The short focal length ocular of claim 1, wherein The first lens has a center thickness of 5 mm, an eye-side radius of curvature of -49.64 mm, and an image-side radius of curvature of -12.89 mm; the second lens has a center thickness of 1 mm and an image-side radius of curvature of -30.67 mm; the third lens has a center thickness of 3.2 mm, an eye-side radius of curvature of 24.99 mm, and an image-side radius of curvature of 96.91 mm; the fourth lens has a center thickness of 5.2 mm, an eye-side radius of curvature of 12.06 mm, and an image-side radius of curvature of 18.54 mm; the fifth lens has a center thickness of 2.4 mm and an image-side radius of curvature of 7.06 mm; and the sixth lens has a center thickness of 3 mm, an eye-side radius of curvature of 11.09 mm, and an image-side radius of curvature of 44.72 mm.

3. The short-focal-length eyepiece according to claim 1, characterized in that: The refractive index Nd1 of the first lens satisfies: 1.9 ≤ Nd1 ≤ 1.95; The refractive index Nd2 of the second lens satisfies: 1.9 ≤ Nd2 ≤ 2.0; The refractive index Nd3 of the third lens satisfies: 1.9 ≤ Nd3 ≤ 1.95; The refractive index Nd4 of the fourth lens satisfies: 1.9 ≤ Nd4 ≤ 1.95; The refractive index Nd5 of the fifth lens satisfies: 1.9 ≤ Nd5 ≤ 2.0; The refractive index Nd6 of the sixth lens satisfies: 1.9≤Nd6≤1.

95.

4. The short-focal-length eyepiece according to claim 1, characterized in that: The Abbe number Vd1 of the first lens satisfies: 35 ≤ Vd1 ≤ 36; The Abbe number Vd2 of the second lens satisfies: 17 ≤ Vd2 ≤ 19; The Abbe number Vd3 of the third lens satisfies: 35≤Vd3≤36; The Abbe number Vd4 of the fourth lens satisfies: 35≤Vd4≤36; The Abbe number Vd5 of the fifth lens satisfies: 17≤Vd5≤19; The Abbe number Vd6 of the sixth lens satisfies: 35≤Vd6≤36.

5. The short focal length ocular of claim 1, wherein The short-focal-length eyepiece has a magnification of 18x, an exit pupil diameter of 8mm, an exit pupil distance of 20mm, an operating temperature range of -40℃ to +60℃, and an operating wavelength range of 0.48 to 0.65μm.

6. The short-focal-length eyepiece according to claim 1, characterized in that, Both the eye-side and image-side surfaces of any lens are spherical.

7. An optical system, characterized in that, Includes the short-focal-length eyepiece as described in any one of claims 1-6 and a display adapted to the short-focal-length eyepiece.

8. The optical system according to claim 7, characterized in that, The display has a resolution of 1024×768 and a pixel size of 7.8μm.

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