Lens of long exit pupil distance eyepiece

Abstract

The utility model provides a lens of a long exit pupil distance eyepiece, relates to the technical field of long exit pupil distance lenses, and comprises a diaphragm, a first lens, a second lens, a third lens, a fourth lens and a fifth lens which are sequentially arranged along an optical axis from an object side to an image side, clear imaging and high magnification are ensured; the negative focal length of the second lens effectively corrects aberration and improves the imaging quality; the fourth lens corrects chromatic aberration and aberration; the fifth lens enhances the overall imaging performance and ensures the definition of long-distance observation. According to the utility model, by optimizing the focal length ratio of each lens, the lens which has a long exit pupil distance and simultaneously gives consideration to high magnification and wide visibility adjustment is designed, so that not only is the requirement for equipment in a specific environment met, but also the comfort and observation effect of a user wearing protective equipment are improved.

Description

Technical Field

[0001] The utility model relates to the technical field of lenses with long exit pupil distance, in particular to a lens for an eyepiece with long exit pupil distance. Background Art

[0002] With the development of society, modern equipment is evolving at an increasingly rapid pace. Equipment such as rifle scopes is evolving towards intelligent, wide-field-of-view, and long-range capabilities. This is especially true in challenging environments like battlefields, where soldiers, in addition to wearing gas masks and goggles, must also protect their eyes from the high impact of heavy gunfire. Consequently, the demand for eyepieces with longer pupil distances has increased significantly. Furthermore, to accommodate different eye types, eyepieces require adjustable diopter. However, traditional eyepieces have a relatively short pupil distance (25-30mm), low optical magnification, and a short back focus, resulting in a narrow adjustment range for varying diopter. Utility Model Content

[0003] In order to overcome the defects of the prior art, the technical problem to be solved by the present invention is to propose a lens for an eyepiece with a long pupil distance, adopting the following technical solutions:

[0004] A lens for an eyepiece with a long pupil distance comprises, in order from the object side to the image side along the optical axis, an aperture, a first lens, a second lens, a third lens, a fourth lens, and a fifth lens, wherein:

[0005] The first lens has positive refractive power, and the image side surface of the first lens is convex;

[0006] The second lens has a negative refractive power, the object side surface of the second lens is concave, and the image side surface of the second lens is convex;

[0007] The third lens has positive refractive power, and the object side surface of the third lens is convex;

[0008] The fourth lens has a negative refractive power, the object side surface of the fourth lens is convex, and the image side surface of the fourth lens is concave;

[0009] The fifth lens has positive refractive power, the object side surface of the fifth lens is convex, and the image side surface of the fifth lens is concave.

[0010] In this technical solution, through reasonable light angle distribution, a lens of a long exit pupil distance eyepiece is designed, which has the advantages of long exit pupil distance, high magnification and a large diopter adjustment range.

[0011] For further improvement, the above lens satisfies the following relationship:

[0012] 1≤f1 / f≤2

[0013] Wherein, f1 is the focal length of the first lens, and f is the total focal length of the lens system.

[0014] In this technical solution, by making f1 satisfy the above relationship, the back focal length of the lens system is extended, the optical performance is optimized, and high-quality imaging is ensured while meeting the long exit pupil distance.

[0015] For further improvement, the above lens satisfies the following relationship:

[0016] -2≤f2 / f≤-1

[0017] Wherein, f2 is the focal length of the second lens, and f is the total focal length of the lens system.

[0018] In this technical solution, by making f2 satisfy the above relationship, the aberration caused by the positive lens is compensated, while the magnification is increased, the high magnification requirement of the lens system is balanced, and the overall imaging quality is optimized.

[0019] For further improvement, the above lens satisfies the following relationship:

[0020] 2≤f3 / f≤3

[0021] Wherein, f3 is the focal length of the third lens, and f is the total focal length of the lens system.

[0022] In this technical solution, by making f3 satisfy the above relationship, the exit pupil distance of the lens system is further optimized and the imaging quality is improved at the same time; the third lens is also used to correct the aberrations generated after processing by the first lens and the second lens, making the image clearer and reducing distortion.

[0023] For further improvement, the above lens satisfies the following relationship:

[0024] -2≤f4 / f≤-1.4

[0025] Wherein, f4 is the focal length of the fourth lens, and f is the total focal length of the lens system.

[0026] In this technical solution, the aberration of the optical system can be effectively corrected and the imaging quality can be improved through the relatively large negative focal length of the fourth lens.

[0027] For further improvement, the above lens satisfies the following relationship:

[0028] 0.8≤f5 / f≤1

[0029] Wherein, f5 is the focal length of the fifth lens, and f is the total focal length of the lens system.

[0030] In this technical solution, as the rear end of the lens system, the imaging quality of the lens system is further ensured by making f5 satisfy the above relationship.

[0031] For further improvement, the above lens satisfies the following relationship:

[0032] 1.1<|f1 / f5|<2

[0033] Wherein, f1 is the focal length of the first lens, and f5 is the focal length of the fifth lens.

[0034] In this technical solution, by making f1 and f5 satisfy the above relationship, a higher magnification is achieved while providing a larger diopter adjustment range, allowing a wide diopter adjustment to meet different needs.

[0035] As a further improvement, the first lens and the second lens are cemented together to form a cemented lens group.

[0036] In this technical solution, the bonding of the first lens and the second lens improves the structural strength of the front end of the lens, and is also beneficial to the overall lightweight design of the lens. In addition, it can also reduce light loss and improve imaging quality.

[0037] For further improvement, the above lens satisfies the following relationship:

[0038] 0.4≤BFL / h≤0.8

[0039] Among them, BFL is the optical back focal length value, and h is the actual image height value of the system.

[0040] In this technical solution, by making BFL and h satisfy the above relationship, the field of view angle is increased, a larger diopter adjustment margin is provided, clear imaging is ensured under different diopter conditions, and the compatibility of the lens is improved.

[0041] As a further improvement, the fourth lens is replaced by a sixth lens and a seventh lens cemented together, and the seventh lens is arranged on the image-side surface of the sixth lens.

[0042] In this technical solution, by replacing the fourth lens with two lenses cemented together, the flexibility of chromatic aberration and aberration correction is improved, while the processing difficulty is reduced.

[0043] In summary, the first and third lenses increase focal length, ensuring clear imaging and high magnification; the negative focal length of the second lens effectively corrects aberrations, improving image quality; the fourth lens corrects chromatic aberration and aberrations; and the fifth lens further enhances overall imaging performance, ensuring clarity for long-distance observation. By optimizing the focal length ratio of each lens, this utility model designs a lens with a long exit pupil distance, high magnification, and wide viewing angle adjustment. This not only meets the requirements of equipment in specific environments, but also improves user comfort and observation quality when wearing protective equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0045] Figure 1 This is a structural diagram of the optical system of the lens in Example 1 of the present utility model;

[0046] Figure 2 This is the MTF curve diagram of Example 1 of the present utility model;

[0047] Figure 3 This is a structural diagram of the optical system of the lens in Example 2 of the present utility model;

[0048] Figure 4 This is the MTF curve diagram of Example 2 of the present utility model;

[0049] Figure 5 This is a structural diagram of the optical system of the lens in Example 3 of the present utility model;

[0050] Figure 6 This is the MTF curve diagram of Example 3 of the present utility model;

[0051] Reference numerals:

[0052] L1-first lens; L2-second lens; L3-third lens; L4-fourth lens; L5-fifth lens; L6-sixth lens; L7-seventh lens; ST-aperture; I MA-imaging surface. DETAILED DESCRIPTION

[0053] In order to facilitate understanding by those skilled in the art, the structure of the present invention is further described in detail with reference to the following embodiments and accompanying drawings:

[0054] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be noted that the following examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Similarly, the following examples are only partial embodiments of the present invention and are not intended to be exhaustive. All other embodiments derived by persons of ordinary skill in the art without inventive effort are intended to fall within the scope of protection of the present invention.

[0055] The utility model provides a lens of an eyepiece with a long pupil distance, which comprises an aperture, a first lens, a second lens, a third lens, a fourth lens, and a fifth lens in order from the object side to the image side along the optical axis, wherein:

[0056] The first lens has positive refractive power, and the image side surface of the first lens is convex;

[0057] The second lens has a negative refractive power, the object side surface of the second lens is concave, and the image side surface of the second lens is convex;

[0058] The third lens has positive refractive power, and the object side surface of the third lens is convex;

[0059] The fourth lens has a negative refractive power, the object side surface of the fourth lens is convex, and the image side surface of the fourth lens is concave;

[0060] The fifth lens element has positive refractive power, the object-side surface of the fifth lens element is convex, and the image-side surface of the fifth lens element is concave. This embodiment has the beneficial effect of designing a lens for a long-exit-pupillary eyepiece by rationally distributing light angles, thereby achieving the advantages of a long exit-pupillary distance, high magnification, and a wide range of diopter adjustment.

[0061] In one specific embodiment, the lens satisfies 1≤f1 / f≤2, where f1 is the focal length of the first lens element and f is the total focal length of the lens system. This embodiment advantageously extends the back focal length of the lens system by ensuring that f1 satisfies the relationship, optimizing optical performance and ensuring high-quality imaging while meeting a long exit pupil distance.

[0062] In one specific embodiment, the lens satisfies -2 ≤ f2 / f ≤ -1, where f2 is the focal length of the second lens element and f is the total focal length of the lens system. This embodiment advantageously compensates for aberrations introduced by the positive lens by ensuring f2 satisfies the relationship, while simultaneously increasing magnification, balancing the high magnification requirements of the lens system and optimizing overall imaging quality.

[0063] In one specific embodiment, the lens satisfies 2≤f3 / f≤3, where f3 is the focal length of the third lens element and f is the total focal length of the lens system. This embodiment has the beneficial effect of further optimizing the exit pupil distance of the lens system and improving image quality by ensuring that f3 satisfies the relationship. The third lens element also corrects aberrations generated by the first and second lenses, resulting in clearer images and reduced distortion.

[0064] In one specific embodiment, the lens satisfies -2 ≤ f4 / f ≤ -1.4, where f4 is the focal length of the fourth lens element, and f is the total focal length of the lens system. This embodiment advantageously corrects optical aberrations through the relatively large negative focal length of the fourth lens element, improving image quality.

[0065] In one specific embodiment, the lens satisfies 0.8 ≤ f5 / f ≤ 1, where f5 is the focal length of the fifth lens element and f is the total focal length of the lens system. This embodiment has the beneficial effect of further ensuring the imaging quality of the lens system by ensuring that f5 satisfies the relationship at the rear end of the lens system.

[0066] In one specific embodiment, the lens satisfies 1.1<|f1 / f5|<2, where f1 is the focal length of the first lens element and f5 is the focal length of the fifth lens element. This embodiment advantageously achieves a high magnification while providing a wider diopter adjustment range, allowing for a wide range of diopter adjustments to suit diverse needs, by ensuring that f1 and f5 satisfy this relationship.

[0067] In a specific embodiment, the first lens and the second lens are cemented together to form a cemented lens group. This embodiment has the beneficial effects of increasing the structural strength of the front end of the lens and facilitating the overall lightweight design of the lens. In addition, it can also reduce light loss and improve imaging quality.

[0068] In one specific embodiment, the lens satisfies 0.4 ≤ BFL / h ≤ 0.8, where BFL is the optical back focal length and h is the actual image height of the system. This embodiment advantageously improves the field of view by ensuring that BFL and h satisfy the relationship, providing a greater diopter adjustment margin, ensuring clear imaging under varying diopter conditions, and improving the compatibility of the lens.

[0069] In one specific embodiment, the fourth lens is replaced by a sixth lens and a seventh lens cemented together, with the seventh lens positioned on the image-side surface of the sixth lens. This embodiment advantageously improves the flexibility of chromatic aberration and aberration correction by replacing the fourth lens with two cemented lenses, while also reducing manufacturing complexity.

[0070] The present invention will be described in more detail below in conjunction with the accompanying drawings and the following tables. It should be noted that the following tables are only specific embodiments of the present invention and are not intended to be limiting examples.

[0071] For the convenience of description, surface number 1 in the table is the surface of the aperture; surface number 2 is the object side surface of the first lens; surface number 3 and surface number 4 are the object side surface and image side surface of the second lens respectively; surface number 5 and surface number 6 are the object side surface and image side surface of the third lens respectively; surface number 7 and surface number 8 are the object side surface and image side surface of the fourth lens respectively; surface number 9 and surface number 10 are the object side surface and image side surface of the fifth lens respectively; surface number 11 and surface number 12 are the object side surface and image side surface of the protective sheet; surface number 13 is the imaging surface.

[0072] Example 1

[0073] Example 1 provides a lens system with an exit pupil distance greater than 50mm, a magnification greater than 12X, and a diopter adjustment meeting ±5DPT. Figure 1 As shown in the optical system structure diagram, it can be seen from the figure: the object-side surface and image-side surface of the first lens are convex; the object-side surface of the second lens is concave, and the image-side surface is convex; the object-side surface of the third lens is convex, and the image-side surface is concave; the object-side surface of the fourth lens is convex, and the image-side surface is concave; the object-side surface of the fifth lens is convex, and the image-side surface is concave.

[0074] Specific parameters of this embodiment 1 are shown in the following Table 1. In this embodiment, the focal length of the lens f=20.8 mm, the optical back focal length BFL=5.62 mm, the total length of the lens TTL=38.96 mm, and the image height h=10.4 mm.

[0075] Table 1 - Lens parameters of Example 1

[0076]

[0077]

[0078] Table 2 - Focal length arrangement of each lens in Example 1

[0079] The total focal length of the lens f 20.8 Focal length of the first lens f1 23.6 Focal length of the second lens f2 -37.3 The focal length of the third lens f3 50.8 Focal length of the fourth lens f4 -31.9 Focal length of the fifth lens f5 19.6

[0080] According to Table 1 and Table 2, the conditional formula of Example 1 of the present utility model can be read as follows:

[0081] (1)f1 / f=1.135;

[0082] (2)f2 / f=-1.793;

[0083] (3)f3 / f=2.442;

[0084] (4)f4 / f=-1.534;

[0085] (5)f5 / f=0.942;

[0086] (6)f1 / f5=1.204;

[0087] (7)BFL / h=0.540.

[0088] Figure 2 This is the MTF curve of Example 1. The horizontal axis is the frequency, and the unit is line pairs. The vertical axis is the MTF value, and the unit is none. The long pupil distance lens allows the observer to observe in a wider viewing angle range while having excellent imaging quality. Figure 2It can be seen that in the wavelength band of 0.435μm to 0.656μm, the MTF of all fields of view at 30Lp / mm is mostly concentrated above 0.4, indicating that the lens can achieve a long exit pupil distance and has extremely high resolution capabilities and excellent imaging.

[0089] Example 2

[0090] Example 2 provides a lens system with an exit pupil distance greater than 50mm, a magnification greater than 12X, and a diopter adjustment meeting ±5DPT. Figure 3 As shown in the optical system structure diagram, it can be seen from the figure: the object-side surface and image-side surface of the first lens are convex; the object-side surface of the second lens is concave, and the image-side surface is convex; the object-side surface of the third lens is convex, and the image-side surface is concave; the object-side surface of the fourth lens is convex, and the image-side surface is concave; the object-side surface of the fifth lens is convex, and the image-side surface is concave.

[0091] Specific parameters of this embodiment are shown in Table 3. In this embodiment, the focal length of the lens f=20.7 mm, the optical back focal length BFL=6.1 mm, the total length of the lens TTL=43.14 mm, and the image height h=10.2 mm.

[0092] Table 3 - Lens parameters of Example 2

[0093] Surface number surface Radius of curvature Thickness / spacing Material Refractive index Abbe number 1 aperture Infinity 52 2 First lens 59.06 9.3 Glass 1.74 44.9 3 Second lens -23.99 3 Glass 1.85 32.3 4 -83.96 0.8 5 The third lens 21.98 8.02 Glass 1.75 47.7 6 33.6 0.8 7 Fourth lens 19.77 6.02 Glass 1.86 22.7 8 10.02 2.55 9 Fifth lens 14.2 6.55 Glass 1.9 31.4 10 55.44 4.66 11 protective sheet Infinity 0.84 Glass 1.51 64.2 12 Infinity 0.6 13 Imaging surface Infinity

[0094] Table 4 - Focal length arrangement of each lens in Example 2

[0095]

[0096]

[0097] According to Table 3 and Table 4, the conditional formula of Example 2 of the present utility model can be read as follows:

[0098] (1)f1 / f=1.106;

[0099] (2)f2 / f=-1.792;

[0100] (3)f3 / f=2.396;

[0101] (4)f4 / f=-1.560;

[0102] (5)f5 / f=0.995;

[0103] (6)f1 / f5=1.112;

[0104] (7)BFL / h=0.598.

[0105] Figure 4This is the MTF curve of Example 2. The horizontal axis is the frequency, and the unit is line pairs. The vertical axis is the MTF value, and the unit is none. The long pupil distance lens allows the observer to observe in a wider viewing angle without sacrificing image quality. Figure 4 It can be seen that in the wavelength band of 0.435μm to 0.656μm, the MTF of all fields of view at 30Lp / mm is mostly concentrated above 0.4, indicating that the lens can achieve a long exit pupil distance and has extremely high resolution capabilities and excellent imaging.

[0106] Example 3

[0107] Example 3 provides a lens system with an exit pupil distance greater than 50mm, a magnification greater than 12X, and a diopter adjustment meeting ±5DPT. Figure 5 The optical system structure shown in the figure differs from Examples 1 and 2 in that the fourth lens element in Example 3 is replaced by a sixth and seventh lens element cemented together, with the seventh lens element positioned on the image-side surface of the sixth lens element. Specifically, the object-side surface of the first lens element is flat, and the image-side surface is convex; the object-side surface of the second lens element is concave, and the image-side surface is convex; the object-side surface of the third lens element is convex, and the image-side surface is concave; the object-side surface of the sixth lens element is convex, and the image-side surface is concave; the object-side surface of the seventh lens element is convex, and the image-side surface is concave; and the object-side surface of the fifth lens element is convex, and the image-side surface is concave.

[0108] For ease of description, surface number 1 in the table of Example 3 is the surface of the aperture; surface number 2 is the object-side surface of the first lens; surface number 3 and surface number 4 are the object-side surface and image-side surface of the second lens, respectively; surface number 5 and surface number 6 are the object-side surface and image-side surface of the third lens, respectively; surface number 7 is the object-side surface of the sixth lens, surface number 8 is the image-side surface of the sixth lens and the object-side surface of the seventh lens, and surface number 9 is the image-side surface of the seventh lens; surface number 10 and surface number 11 are the object-side surface and image-side surface of the fifth lens, respectively; surface number 12 and surface number 13 are the object-side surface and image-side surface of the protective sheet, respectively; and surface number 14 is the imaging surface.

[0109] Specific parameters of this embodiment 3 are shown in the following Table 5. In this embodiment, the focal length of the lens f=20.7 mm, the optical back focal length BFL=6.26 mm, the total length of the lens TTL=41.81 mm, and the image height h=10.4 mm.

[0110] Table 5 - Lens parameters of Example 3

[0111] Surface number surface Radius of curvature Thickness / spacing Material Refractive index Abbe number 1 aperture Infinity 53 2 First lens Infinity 9.6 Glass 1.73 54.7 3 Second lens -16.08 2 Glass 1.85 23.8 4 -57.57 0.2 5 The third lens 26.08 6.36 Glass 2 25.4 6 66.68 0.2 7 Sixth lens 19.76 7.78 Glass 1.75 52.3 8 Seventh lens 200 1.51 Glass 1.78 25.7 9 9.95 3.4 10 Fifth lens 18.24 4.5 Glass 1.9 31.3 11 Infinity 0.1 12 protective sheet Infinity 0.84 Glass 1.52 64.2 13 Infinity 5.32 14 Imaging surface Infinity

[0112] Table 6 - Focal length arrangement of each lens in Example 3

[0113]

[0114]

[0115] According to Table 5 and Table 6, the conditional formula of Example 3 of the present utility model can be read as follows:

[0116] (1)f1 / f=1.057;

[0117] (2)f2 / f=-1.279;

[0118] (3)f3 / f=2.035;

[0119] (4)f4 / f=-1.971;

[0120] (5)f5 / f=0.965;

[0121] (6)f1 / f5=1.100;

[0122] (7)BFL / h=0.602.

[0123] Figure 6 The MTF curve of Example 3 is shown in Figure 2. The horizontal axis is the frequency, and the unit is line pairs. The vertical axis is the MTF value, and the unit is none. The long pupil distance lens allows the observer to observe in a wider viewing angle without sacrificing image quality. Figure 6 It can be seen that in the wavelength band of 0.435μm to 0.656μm, the MTF of all fields of view at 30Lp / mm is mostly concentrated above 0.42, indicating that the lens can achieve a long exit pupil distance and has extremely high resolution capabilities and excellent imaging.

[0124] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A lens for an eyepiece with a long pupil distance, characterized in that: Along the optical axis, from the object side to the image side, the order is the aperture, the first lens, the second lens, the third lens, the fourth lens, and the fifth lens, among which, The first lens has positive refractive power, and the image side surface of the first lens is convex; The second lens has a negative refractive power, the object side surface of the second lens is concave, and the image side surface of the second lens is convex; The third lens has positive refractive power, and the object side surface of the third lens is convex; The object-side surface of the fourth lens is convex, and the image-side surface of the fourth lens is concave; The fifth lens has positive refractive power, the object side surface of the fifth lens is convex, and the image side surface of the fifth lens is concave or flat.

2. The lens of the eyepiece with a long exit pupil distance as claimed in claim 1, characterized in that: The lens satisfies the following relationship: 1≤f1 / f≤2 Wherein, f1 is the focal length of the first lens, and f is the total focal length of the lens system.

3. The lens of the eyepiece with a long exit pupil distance according to claim 1, characterized in that: The lens satisfies the following relationship: -2≤f2 / f≤-1 Wherein, f2 is the focal length of the second lens, and f is the total focal length of the lens system.

4. The lens of the eyepiece with a long exit pupil distance according to claim 1, wherein: The lens satisfies the following relationship: 2≤f3 / f≤3 Wherein, f3 is the focal length of the third lens, and f is the total focal length of the lens system.

5. The lens of the eyepiece with a long exit pupil distance as claimed in claim 1, characterized in that: The lens satisfies the following relationship: -2≤f4 / f≤-1.4 Wherein, f4 is the focal length of the fourth lens, and f is the total focal length of the lens system.

6. The lens of the eyepiece with a long exit pupil distance as claimed in claim 1, characterized in that: The lens satisfies the following relationship: 0.8≤f5 / f≤1 Wherein, f5 is the focal length of the fifth lens, and f is the total focal length of the lens system.

7. The lens of the eyepiece with a long exit pupil distance as claimed in claim 1, characterized in that: The lens satisfies the following relationship: 1.1<|f1 / f5|<2 Wherein, f1 is the focal length of the first lens, and f5 is the focal length of the fifth lens.

8. The lens of the eyepiece with a long exit pupil distance as claimed in claim 1, characterized in that: The first lens and the second lens are cemented together to form a first cemented lens group.

9. The lens of the eyepiece with a long exit pupil distance as claimed in claim 1, characterized in that: The lens satisfies the following relationship: 0.4≤BFL / h≤0.8 Among them, BFL is the optical back focal length value, and h is the actual image height value of the system.

10. The lens of the eyepiece with a long exit pupil distance according to claim 1, characterized in that: The fourth lens is a second cemented lens group, and the second cemented lens includes a sixth lens and a seventh lens cemented to each other, and the seventh lens is arranged on the image side surface of the sixth lens.

Images