Lens of long exit pupil distance eyepiece

Abstract

The utility model provides a lens of an eyepiece with long exit pupil distance, which relates to the technical field of lenses with long exit pupil distance, 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, the second lens and the third lens optimize the light convergence capability, reduce aberration and improve the imaging quality. The fourth lens ensures stable propagation of light, and the fifth lens compensates for optical distortion in the lens system. And by setting the proportion of the optical back focal length, the total length of the lens and the actual image height, the flexibility and the use comfort of the system can be enhanced. According to the utility model, through reasonable design and optimization of each lens of the eyepiece and the focal length relation thereof, the lens which has a long exit pupil distance and simultaneously gives consideration to high magnification and wide visibility adjustment is designed, the requirements for equipment in a specific environment are met, and the comfort and observation effect of a user wearing protective equipment are improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to long pupil distance lens technology field especially relates to a long pupil distance eyepiece lens. BACKGROUND

[0002] With the development of individual equipment, the head-mounted, sighting telescope and other equipment are expanding towards the direction of intelligentization, long distance and large field of view. The gun sight for medium or heavy machinery has large impact force when shooting, and the eyepiece optical system needs to have longer pupil distance. On the other hand, in order to adapt to different eyes, the diopter of the eyepiece needs to be adjustable. The pupil distance of the traditional eyepiece optical system is small, usually 25-30mm. The magnification of the traditional eyepiece optical system is small, and the field of view is small. The back focal length is short, and the diopter adjustment range is narrow. SUMMARY

[0003] In order to overcome the defects of the prior art, the technical problem to be solved by the utility model is to provide a long pupil distance eyepiece lens, which adopts the following technical scheme:

[0004] A long pupil distance eyepiece lens has a light barrier, 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.

[0005] The first lens has a negative refractive power, and the image side surface of the first lens is concave.

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

[0007] The third lens has a 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 a 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 scheme, the long pupil distance eyepiece lens is designed by reasonable light angle distribution, which has the advantages of long pupil distance, high magnification and large diopter adjustment range.

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

[0012] -2≤f1 / f≤-1

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

[0014] In the technical solution, by making f1 satisfy the above relationship, the initial divergence is controlled, the exit pupil distance of the eyepiece is increased, the optical performance is optimized, and good initial light distribution is provided for the entire optical system, preventing excessive divergence or excessive concentration of light, thereby reducing aberration and other optical distortions.

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

[0016] 0.8≤f2 / f≤2.0

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

[0018] In the technical solution, by making f2 satisfy the above relationship, the convergence ability of the lens system is optimized, the magnification is enhanced, while maintaining a large field of view and good imaging quality. This range reduces aberration and distortion, improves the stability of the optical system, and enhances the focal length adjustment capability, adapting to different observation needs.

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

[0020] 1.5≤f3 / f≤3.0

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

[0022] In the technical solution, by making f3 satisfy the above relationship, the light beam convergence is further enhanced, the magnification is improved, the aberration is corrected, the wide field of view and long exit pupil distance are maintained, while the distortion is reduced, the overall imaging quality and focal length adjustment capability are optimized.

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

[0024] -3.4≤f4 / f≤-1.2

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

[0026] In the technical solution, the large negative focal length of the fourth lens can effectively correct the aberration of the optical system and improve the imaging quality.

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

[0028] 0.8≤f5 / f≤2

[0029] Where 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, by making f5 satisfy the above relationship, the imaging quality of the lens system is further ensured.

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

[0032] 0.8 < |f1 / f5| < 2

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

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

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

[0036] In this technical solution, the cementing 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 lightweight design of the whole lens, in addition, it can also reduce light loss and improve imaging quality.

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

[0038] 0.01≤BFL / TTL / h≤0.1

[0039] Wherein, BFL is the optical back focal length value, TTL is the total length value of the lens, and h is the actual image height value of the system. In this technical solution, by making BFL, TTL and h satisfy the above relationship, the imaging quality and stability are improved, the use flexibility is enhanced, the system performance and user comfort are balanced, and the adjustment ability of the system is promoted.

[0040] In summary, the first lens with negative refractive power effectively controls the light divergence, enhances the exit pupil distance and magnification; the second and third lenses with positive refractive power further optimize the convergence ability, reduce aberration and improve imaging quality. The fourth lens with negative refractive power ensures stable propagation of light, and the design of the fifth lens compensates for optical distortion in the system. At the same time, by setting the ratio of optical back focal length to total length of the lens and actual image height, the flexibility and comfort of the system can be enhanced. The utility model designs a lens with long exit pupil distance, high magnification and wide diopter adjustment by reasonably designing and optimizing each lens of the ocular lens and the focal length relationship thereof, which not only meets the needs of equipment in specific environment, but also improves the comfort and observation effect of the user when wearing protective equipment. BRIEF DESCRIPTION OF DRAWINGS

[0041] In order to more clearly illustrate the technical scheme of the embodiments of the present application, the drawings used in the embodiments will be briefly introduced as follows. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be considered as limiting the scope. For those skilled in the art, other related drawings can be obtained without creative labor.

[0042] Figure 1 Optical system structure diagram of the lens in the embodiment 1 of the present application;

[0043] Figure 2 MTF curve diagram of the embodiment 1 of the present application;

[0044] Figure 3 Optical system structure diagram of the lens in the embodiment 2 of the present application;

[0045] Figure 4 MTF curve diagram of the embodiment 2 of the present application;

[0046] Figure 5 Optical system structure diagram of the lens in the embodiment 3 of the present application;

[0047] Figure 6 MTF curve diagram of the embodiment 3 of the present application;

[0048] Reference signs:

[0049] L1-first lens; L2-second lens; L3-third lens; L4-fourth lens; L5-fifth lens; L6-sixth lens; L7-seventh lens; ST-stop; IMA-imaging surface. DETAILED DESCRIPTION

[0050] In order to facilitate the understanding of those skilled in the art, the structure of the present application will be further described in detail in combination with the drawings:

[0051] The present application will be further described in detail in combination with the drawings and embodiments. It is particularly pointed out that the following embodiments are only used to illustrate the present application, but do not limit the scope of the present application. Similarly, the following embodiments are only some embodiments of the present application, not all embodiments. All other embodiments obtained by those skilled in the art without creative labor are within the scope of the present application.

[0052] The present application provides a long exit pupil eyepiece lens, which has a stop, a first lens, a second lens, a third lens, a fourth lens and a fifth lens in sequence from the object side to the image side along the optical axis.

[0053] The first lens has a negative refractive power, and an image-side surface of the first lens is a concave surface.

[0054] The second lens has a positive refractive power, and an object-side surface of the second lens is a convex surface, and an image-side surface of the second lens is a convex surface.

[0055] The third lens has a positive refractive power, and an object-side surface of the third lens is a convex surface.

[0056] The fourth lens has a negative refractive power, and an object-side surface of the fourth lens is a convex surface, and an image-side surface of the fourth lens is a concave surface.

[0057] The fifth lens has a positive refractive power, and an object-side surface of the fifth lens is a convex surface, and an image-side surface of the fifth lens is a concave surface. The embodiment has the beneficial effect that by reasonably distributing the light angle, the lens of the long eye relief eyepiece is designed, which has the advantages of long eye relief, high magnification, and large diopter adjustment range.

[0058] In a specific embodiment, the lens satisfies -2≤f1 / f≤-1, where f1 is the focal length of the first lens, and f is the total focal length of the lens system. The embodiment has the beneficial effect that by making f1 satisfy the above relationship, the initial divergence is controlled, the eye relief of the eyepiece is increased, the optical performance is optimized, and it also helps to provide good initial light distribution for the entire optical system, preventing excessive divergence or excessive concentration of light, thereby reducing aberration and other optical distortion.

[0059] In a specific embodiment, the lens satisfies 0.8≤f2 / f≤2.0, where f2 is the focal length of the second lens, and f is the total focal length of the lens system. The embodiment has the beneficial effect that by making f2 satisfy the above relationship, the convergence ability of the lens system is optimized, the magnification is enhanced, while maintaining a large field of view and good imaging quality. This range reduces aberration and distortion, improves the stability of the optical system, and enhances the focal length adjustment capability to adapt to different observation needs.

[0060] In a specific embodiment, the lens satisfies 1.5≤f3 / f≤3.0, where f3 is the focal length of the third lens, and f is the total focal length of the lens system. The embodiment has the beneficial effect that by making f3 satisfy the above relationship, the light beam convergence is further enhanced, the magnification is improved, the aberration is corrected, the wide field of view and long eye relief are maintained, while the distortion is reduced, the overall imaging quality and focal length adjustment capability are optimized.

[0061] In a specific embodiment, the lens satisfies -3.4≤f4 / f≤-1.2, where f4 is the focal length of the fourth lens, and f is the total focal length of the lens system. The embodiment has the beneficial effect that the aberration of the optical system can be effectively corrected, and the imaging quality can be improved by the larger proportion of negative focal length of the fourth lens.

[0062] In a specific embodiment, the lens satisfies 0.8≤f5 / f≤2, where f5 is the focal length of the fifth lens, and f is the total focal length of the lens system. The embodiment has the beneficial effect that the imaging quality of the lens system can be further ensured by satisfying the above relationship for f5 as the rear end of the lens system.

[0063] In a specific embodiment, the lens satisfies 0.8<|f1 / f5|<2, where f1 is the focal length of the first lens, and f5 is the focal length of the fifth lens. The embodiment has the beneficial effect that a larger accommodation range can be provided while achieving a high magnification by satisfying the above relationship for f1 and f5, allowing a wide diopter adjustment to adapt to different needs.

[0064] In a specific embodiment, the first lens and the second lens are cemented into a cemented lens group. The embodiment has the beneficial effect that the cementing of the first lens and the second lens improves the structural strength of the front end of the lens, is also conducive to the lightweight design of the whole lens, and in addition, can reduce light loss and improve imaging quality.

[0065] In a specific embodiment, the lens satisfies 0.01≤BFL / TTL / h≤0.1, where BFL is the optical back focal length, TTL is the total length of the lens, and h is the actual image height of the system. The embodiment has the beneficial effect that the imaging quality and stability are improved, the use flexibility is enhanced, the system performance and user comfort are balanced, and the adjustment ability of the system is promoted by satisfying the above relationship for BFL, TTL, and h.

[0066] The utility model will be described in more detail below in conjunction with the drawings of the specification and the following table. It should be noted that the following table is only a specific embodiment of the utility model, not a limiting example.

[0067] For the convenience of description, surface No. 1 in the table is the surface of the diaphragm; surface No. 2 is the object side surface of the first lens; surface No. 3 and surface No. 4 are the object side surface and the image side surface of the second lens respectively; surface No. 5 and surface No. 6 are the object side surface and the image side surface of the third lens respectively; surface No. 7 is the object side surface of the fourth lens; surface No. 8 and surface No. 9 are the object side surface and the image side surface of the fifth lens respectively; surface No. 10 and surface No. 11 are the object side surface and the image side surface of the protective sheet respectively; and surface No. 12 is the imaging surface.

[0068] Embodiment 1

[0069] Embodiment 1 provides a lens system with an exit pupil distance greater than 60mm, a magnification greater than 12.5X, and a diopter adjustment satisfying ±5DPT, please refer to the optical system structure diagram shown in Figure 1 As can be seen from the figure, the object side of the first lens is convex, the image side is concave; the object side of the second lens is convex, and is cemented with the image side of the first lens, and the image side is convex; the object side of the third lens is convex, and the image side is concave; the object side of the fourth lens is convex, and the image side is concave; the object side of the fifth lens is convex, and is in abutment with the image side of the fourth lens, and the image side is concave.

[0070] The specific parameters of this embodiment 1 are shown in Table 1 below. In this embodiment, the focal length of the lens f=20.8mm, the optical back focal length BFL=7.24mm, the total length of the lens TTL=41.89mm, and the image height h=10.4mm.

[0071] Table 1-Embodiment 1 lens parameter table

[0072] Surface No. Surface Radius of curvature Thickness / Interval Material Refractive index Abbe number 1 Stop Infinity 61 2 First lens 260 2 Glass 1.84 23.8 3 Second lens 26.099 10.8 Glass 1.77 49.6 4 -64.02 0.15 5 Third lens 26.2 8.3 Glass 1.75 52.3 6 117.754 5.2 7 Fourth lens 21.51 2 Glass 1.84 23.8 8 Fifth lens 12.07 6.2 Glass 1.91 35.2 9 19.1 3 10 Protective sheet Infinity 0.84 Glass 1.51 64.2 11 Infinity 3.4 12 Imaging surface Infinity

[0073] Table 2-Embodiment 1 lens corresponding focal length arrangement table

[0074] Total focal length value of the lens f 20.8 Focal length value of the first lens f1 -34 Focal length value of the second lens f2 25.2 Focal length value of the third lens f3 42.8 Focal length value of the fourth lens f4 -38.8 Focal length value of the fifth lens f5 25.2

[0075] According to Table 1 and Table 2, the conditional expressions of the embodiment 1 of the present application can be read as follows:

[0076] (1) f1 / f=-1.635;

[0077] (2) f2 / f=1.212;

[0078] (3) f3 / f=2.058;

[0079] (4) f4 / f=-1.865;

[0080] (5) f5 / f=1.212;

[0081] (6) |f1 / f5|=1.349;

[0082] (7) BF / TTL / h=0.017.

[0083] Figure 2 The MTF curve diagram of Embodiment 1 is shown in the figure. The horizontal coordinate is frequency, unit: line pair. The vertical coordinate is MTF value, unitless. The long exit pupil distance lens supports the observer to observe in a wider visual angle range, and has excellent imaging quality, from Figure 2It can be seen that: under the wavelength of 0.45-0.65μm, the MTF of all fields of view is mostly concentrated above 0.4 at 30Lp / mm, indicating that the lens can achieve a long back focal length and has a very high resolution capability, and the imaging is excellent.

[0084] Embodiment 2

[0085] Embodiment 2 provides a lens system with a back focal length greater than 60mm, a magnification greater than 12.5X, and a diopter adjustment satisfying ±5DPT, please refer to the optical system structure diagram shown in Figure 3 It can be seen from the figure that the object side of the first lens is convex, and the image side is concave; the object side and the image side of the second lens are convex; the object side of the third lens is convex, and the image side is concave; the object side of the fourth lens is convex, and the image side is concave; the object side of the fifth lens is convex, and the image side is concave.

[0086] The specific parameters of this embodiment are shown in Table 3. In this embodiment, the focal length of the lens f=20.6mm, the optical back focal length BFL=7.74mm, the total length of the lens TTL=43.64mm, and the image height h=10.2mm.

[0087] Table 3-Embodiment 2 lens parameter table

[0088] Surface No. Surface Radius of curvature Thickness / Interval Material Refractive index Abbe number 1 Stop Infinity 68 2 First lens 101.2 2.1 Glass 1.84 23.8 3 Second lens 20.908 14.5 Glass 1.77 49.6 4 -92.88 0.15 5 Third lens 29.784 8.96 Glass 1.77 49.6 6 256.057 0.14 7 Fourth lens 22.614 2.05 Glass 1.86 22.7 8 Fifth lens 15.22 8 Glass 1.91 35.2 9 27.68 3.4 10 Protective sheet Infinity 0.84 Glass 1.51 64.2 11 Infinity 3.5 12 Imaging surface Infinity

[0089] Table 4-Embodiment 2 lens corresponding focal length arrangement table

[0090] Total focal length value of the lens f 20.6 Focal length value of the first lens f1 -31.2 Focal length value of the second lens f2 23.2 Focal length value of the third lens f3 42.7 Focal length value of the fourth lens f4 -62.3 Focal length value of the fifth lens f5 28.2

[0091] According to Table 3 and Table 4, the conditional expressions of the embodiment 2 of the present application can be read as follows:

[0092] (1) f1 / f=-1.515;

[0093] (2) f2 / f=1.126;

[0094] (3) f3 / f=2.073;

[0095] (4) f4 / f=-3.024;

[0096] (5) f5 / f=1.369;

[0097] (6) |f1 / f5|=1.106;

[0098] (7) BFL / TTL / h=0.017.

[0099] Figure 4The MTF curve diagram of Example 2 is shown in the figure. In the figure, the abscissa is frequency, and the unit is line pair. The ordinate is MTF value, and the unit is none. The long pupil distance lens can support the observer to observe in a wider visual angle range without sacrificing the imaging quality, and the imaging is excellent. Figure 4 It can be seen that, in the wavelength range of 0.45 μm to 0.65 μm, the MTF of all fields of view is mostly concentrated above 0.4 at 30 Lp / mm, indicating that the lens can realize long pupil distance and has extremely high resolution capability, and the imaging is excellent.

[0100] Example 3

[0101] Example 3 provides a lens system with a long pupil distance greater than 60 mm, a magnification greater than 12.5X, and a diopter adjustment satisfying ±5DPT. Please refer to the optical system structure diagram shown in the figure, the object side of the first lens is convex, and the image side is concave; the object side and the image side of the second lens are convex; the object side of the third lens is convex, and the image side is concave; the object side of the fourth lens is convex, and the image side is concave; the object side of the fifth lens is convex, and the image side is concave. Figure 5

[0102] The specific parameters of this example 3 are shown in Table 5. The difference from Table 1 and Table 2 is that in Table 3, the surface sequence number 8 is the object side of the fourth lens, the surface sequence number 9 and the surface sequence number 10 are respectively the object side and the image side of the fifth lens; the surface sequence number 11 and the surface sequence number 12 are respectively the object side and the image side of the protective sheet, and the surface sequence number 13 is the imaging surface.

[0103] In this example, the focal length of the lens f = 20.5 mm, the optical back focal length BFL = 6.04 mm, the total length of the lens TTL = 44.01 mm, and the image height h = 10.2 mm.

[0104] Table 5-Example 3 lens parameter table

[0105] Surface No. Surface Radius of curvature Thickness / Interval Material Refractive index Abbe number 1 Stop Infinity 65 2 First lens 137.7948 1.6 Glass 1.95 17.9 3 Second lens 25.28486 13.4 Glass 1.73 54.6 4 -56.58642 0.06 5 Third lens 34.78079 8.4 Glass 1.91 35.2 6 392.2529 0.02 7 Fourth lens 20.36559 7.64 Glass 1.91 35.2 8 11.8816 1.59 9 Fifth lens 13.68543 5.26 Glass 2 25.4 10 30.52261 2.5 11 Protective sheet Infinity 0.84 Glass 1.51 64.2 12 Infinity 2.7 13 Imaging surface Infinity

[0106] Table 6-Example 3 lens corresponding focal length arrangement table

[0107] Total focal length value of the lens f 20.5 Focal length value of the first lens f1 -33.9 Focal length value of the second lens f2 25.7 Focal length value of the third lens f3 40.99 Focal length value of the fourth lens f4 -60.4 Focal length value of the fifth lens f5 23.3

[0108] According to Table 5 and Table 6, the conditional expression of the example 3 of the present application can be read as follows:

[0109] (1) f1 / f = -1.654;

[0110] (2) f2 / f = 1.254;

[0111] (3) f3 / f = 2.000;

[0112] (4) f4 / f = -2.946;​

[0113] (5) f5 / f = 1.137;

[0114] (6) |f1 / f5| = 1.455;

[0115] (7) BFL / TTL / h = 0.013.

[0116] Figure 6 is the MTF curve diagram of Example 3. In the diagram, the horizontal coordinate is frequency, and the unit is line pair. The vertical coordinate is MTF value, and the unit is none. The long eye relief lens supports the observer to observe in a wider visual angle range without sacrificing the imaging quality, and the imaging is excellent. Figure 6 It can be seen that, in the wavelength range of 0.45 μm to 0.65 μm, the MTF of all fields of view is mostly concentrated above 0.4 at 30 Lp / mm, indicating that the lens can realize long eye relief and has extremely high resolution capability, and the imaging is excellent.

[0117] The preferred embodiments of the present application are described above, but the present application is not limited to the above. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A lens for a long eye relief eyepiece, characterized by: In order from the object side to the image side along the optical axis, there are an aperture stop, a first lens, a second lens, a third lens, a fourth lens, and a fifth lens; The first lens has a negative refractive power, and an image-side surface of the first lens is a concave surface; The second lens has a positive refractive power, an object-side surface of the second lens is a convex surface, and an image-side surface of the second lens is a convex surface; The third lens has a positive refractive power, and an object-side surface of the third lens is a convex surface; The fourth lens has a negative refractive power, an object-side surface of the fourth lens is a convex surface, and an image-side surface of the fourth lens is a concave surface; The fifth lens has a positive refractive power, an object-side surface of the fifth lens is a convex surface, and an image-side surface of the fifth lens is a concave surface.

2. A lens for a long eye relief eyepiece according to claim 1, wherein: The lens satisfies the following relationship: -2≤f1 / f≤-1 wherein f1 is a focal length value of the first lens, and f is a total focal length value of the lens system.

3. A lens for a long eye relief eyepiece as claimed in claim 1, wherein: The lens satisfies the following relationship: 0.8≤f2 / f≤2.0 wherein f2 is a focal length value of the second lens, and f is a total focal length value of the lens system.

4. A lens for long eye relief eyepieces as described in claim 1, wherein: The lens satisfies the following relationship: 1.5≤f3 / f≤3.0 wherein f3 is a focal length value of the third lens, and f is a total focal length value of the lens system.

5. A lens for long eye relief eyepieces as described in claim 1, wherein: The lens satisfies the following relationship: -3.4≤f4 / f≤-1.2 wherein f4 is a focal length value of the fourth lens, and f is a total focal length value of the lens system.

6. A lens for long eye relief eyepieces as described in claim 1, wherein: The lens satisfies the following relationship: 0.8≤f5 / f≤2 wherein f5 is a focal length value of the fifth lens, and f is a total focal length value of the lens system.

7. A lens for long eye relief eyepieces as described in claim 1, wherein: The lens satisfies the following relationship: 0.8<|f1 / f5|<2 wherein f1 is a focal length value of the first lens, and f5 is a focal length value of the fifth lens.

8. A lens for long eye relief eyepieces as described in claim 1, wherein: The first lens and the second lens are cemented into a cemented lens group.

9. A lens for long eye relief eyepieces as described in claim 1, wherein: The lens satisfies the following relationship: 0.01≤BFL / TTL / h≤0.1 wherein BFL is an optical back focal length value, TTL is a total lens length value, and h is an actual image height value of the system.

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