Long-focus catadioptric photographic objective lens

Abstract

The utility model relates to a long-focus catadioptric photographic objective lens, which comprises a first lens, a catadioptric lens group and a rear lens group which are sequentially arranged along the propagation direction of a light path, wherein the first lens is a positive meniscus lens; the catadioptric lens group comprises a first reflector and a second reflector, the first reflector is a negative meniscus reflector, the front surface of the first reflector is a first light refraction area, and a first light reflection area is arranged between the edge area and the middle area of the rear surface of the first reflector; the second reflector is a positive meniscus reflector, the front surface of the second reflector is a second light reflection area, and the rear surface of the second reflector is a second light refraction area. The purpose of correcting aberration is achieved by simultaneously refracting and reflecting light back and forth through the first reflecting mirror and the second reflecting mirror, so that the number of used lenses is reduced, the size and the weight of the objective lens are further reduced, a hole does not need to be formed in the center of the first reflecting mirror, and production, processing, installation and adjustment are more simplified.

Description

Technical Field

[0001] The utility model belongs to the technical field of photographic objective lenses, and particularly relates to a long-focus catadioptric photographic objective lens. Background Art

[0002] Photographic objective lenses are commonly known as photographic lenses, which are lenses that form optical images (real images) in photography. However, the applicant has found that the long-focus refractive photographic objective lenses currently on the market have the problems of being large in size, heavy in weight, and inconvenient to carry. For photography enthusiasts, long-focus refractive photographic objective lenses cannot well meet the needs of long-distance shooting that requires frequent camera movement. Utility Model Content

[0003] In order to solve the above problems existing in the prior art, the utility model provides a telephoto catadioptric photography objective lens.

[0004] In order to solve the above technical problems, the utility model adopts the following technical solutions:

[0005] The utility model provides a telephoto catadioptric photography objective lens, comprising a first lens, a catadioptric lens group and a rear lens group arranged in sequence along the propagation direction of the light path; wherein:

[0006] The first lens is a positive meniscus lens;

[0007] The catadioptric lens group includes a first reflector and a second reflector, the first reflector is a negative meniscus reflector, the front surface of which is a first light refraction area, and the edge area and the middle area of ​​the rear surface of which is a first light reflection area; the second reflector is a positive meniscus reflector, the front surface of which is a second light reflection area, and the rear surface of which is a second light refraction area.

[0008] Furthermore, the effective focal lengths of the first reflector and the second reflector satisfy:

[0009] 0.25≤f2 / f≤0.48,

[0010] -0.48≤f3 / f≤-0.25;

[0011] f is the focal length of the optical system of the telephoto catadioptric photography objective lens, f2 is the effective focal length of the first reflector, and f3 is the effective focal length of the second reflector.

[0012] Furthermore, the effective focal length of the first lens satisfies:

[0013] 1.6≤f1 / f≤1.9;

[0014] f is the focal length of the optical system of the telephoto catadioptric photography objective lens, and f1 is the effective focal length of the first lens.

[0015] Furthermore, the rear lens group is composed of a second lens, a third lens, and a fourth lens which are sequentially arranged along the propagation direction of the light path, wherein the second lens is a negative meniscus lens, the third lens is a positive lens, and the fourth lens is a flat protective window.

[0016] Furthermore, the second lens and the third lens are glued together.

[0017] Furthermore, the effective focal length of the second lens and the third lens after being glued together satisfies:

[0018] -0.45≤f4 / f≤-0.25;

[0019] f is the focal length of the optical system of the telephoto catadioptric photography objective lens, and f4 is the effective focal length of the second lens and the third lens after being glued together.

[0020] Furthermore, the refractive index of the first lens is 1.65-1.85, and the dispersion coefficient is 40-60; the refractive index of the first reflector is 1.55-1.68, and the dispersion coefficient is 45-65; the refractive index of the second reflector is 1.65-1.85, and the dispersion coefficient is 40-60; the refractive index of the second lens is 1.45-1.60, and the dispersion coefficient is 55-70; the refractive index of the third lens is 1.75-1.85, and the dispersion coefficient is 40-55.

[0021] Further, the rear surface of the first reflector has a first total reflection film, and the front surface of the second reflector has a second total reflection film.

[0022] Furthermore, the first lens, the reflective lens group and the rear lens group are all independent modules, and the first lens and the rear lens group are detachably mounted on the light path incident end and the light path emitting end of the reflective lens group, respectively.

[0023] Furthermore, the focal length of the optical system of the telephoto catadioptric photography objective lens is 250 mm, the back focal length is 41 mm, the total length of the optical system is 100 mm, the total length of the optical parts is 60 mm, and the F number is 5.6.

[0024] Beneficial effects of the utility model:

[0025] The utility model can obtain a telephoto catadioptric photography objective lens with a focal length of 250 mm of the optical system through the above technical scheme, and achieves the purpose of correcting aberrations by utilizing the first reflector and the second reflector to refract and reflect light back and forth at the same time, thereby reducing the number of lenses used, thereby reducing the volume and weight of the objective lens, and there is no need to open a hole in the center of the first reflector, so that production, processing and assembly are further simplified. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1It is a structural schematic diagram of the telephoto catadioptric photography objective lens of the utility model;

[0027] Figure 2 is an MTF curve diagram of the telephoto catadioptric photography objective lens described in the embodiment of the utility model;

[0028] Figure 3 is an aberration diagram of the telephoto catadioptric photography objective lens described in the embodiment of the utility model;

[0029] Figure 4 is an axial aberration diagram of the telephoto catadioptric photography objective lens described in the embodiment of the utility model;

[0030] Figure 5 It is a vertical axis chromatic aberration diagram of the telephoto catadioptric photography objective lens described in the embodiment of the utility model;

[0031] Figure 6 is a relative illumination curve diagram of the telephoto catadioptric photography objective lens described in the embodiment of the utility model;

[0032] Figure 7 It is a field curvature distortion diagram of the telephoto catadioptric photography objective lens described in the embodiment of the utility model. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the utility model more clear, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model and are not used to limit the utility model.

[0034] like Figure 1 As shown, the telephoto catadioptric photography objective lens of the utility model comprises a first lens 100, a catadioptric lens group 200 and a rear lens group 300 which are sequentially arranged along the propagation direction of the light path. Among them, the first lens 100 is a positive meniscus lens.

[0035] The folding and reflecting lens group 200 includes a first reflector 201 and a second reflector 202, wherein the first reflector 201 is a negative meniscus reflector, whose front surface is a first light refraction area, and the area between the edge area and the middle area of ​​the rear surface is a first light reflection area, and the middle area is a light transmission area; the second reflector 202 is a positive meniscus reflector, whose front surface is a second light reflection area, and the rear surface is a second light refraction area; wherein the specific structure of the first light reflection area of ​​the first reflector 201 and the second light reflection area of ​​the second reflector 202 can be: the rear surface of the first reflector 201 has a first total reflection film (that is, the edge area and the middle area of ​​the rear surface of the first reflector 201 have a first total reflection film), and the front surface of the second reflector 202 has a second total reflection film, and preferably, the first total reflection film and the second total reflection film are both total reflection coatings.

[0036] The rear lens group 300 is composed of a second lens 301, a third lens 302, and a fourth lens 303 which are sequentially arranged along the propagation direction of the light path, wherein the second lens 301 is a negative meniscus lens, the third lens 302 is a positive lens, and the second lens 301 and the third lens 302 are glued together, and the fourth lens 303 is a flat protective window.

[0037] Furthermore, in order to ensure clear imaging, low chromatic aberration, and no stray light when using the telephoto catadioptric photography objective lens of the present invention, the effective focal lengths of the first lens 100, the first reflector 201, and the second reflector 202, as well as the effective focal lengths of the second lens 301 and the third lens 302 after being glued together, meet the following requirements:

[0038] 1.6≤f1 / f≤1.9,

[0039] 0.25≤f2 / f≤0.48,

[0040] -0.48≤f3 / f≤-0.25,

[0041] -0.45≤f4 / f≤-0.25;

[0042] f is the focal length of the optical system of the telephoto catadioptric photography objective lens, f1 is the effective focal length of the first lens 100, f2 is the effective focal length of the first reflector 201, f3 is the effective focal length of the second reflector 202, and f4 is the effective focal length of the second lens 301 and the third lens 302 after being glued together.

[0043] At the same time, the refractive index of the first lens 100 is 1.65-1.85, and the dispersion coefficient (Abbe number) is 40-60; the refractive index of the first reflector 201 is 1.55-1.68, and the dispersion coefficient (Abbe number) is 45-65; the refractive index of the second reflector 202 is 1.65-1.85, and the dispersion coefficient (Abbe number) is 40-60; the refractive index of the second lens 301 is 1.45-1.60, and the dispersion coefficient (Abbe number) is 55-70; the refractive index of the third lens 302 is 1.75-1.85, and the dispersion coefficient (Abbe number) is 40-55.

[0044] For example Figure 1The imaging process of the telephoto catadioptric photography objective lens of the utility model is as follows: first, after the light path passes through the first lens 100, it is transmitted (refracted) on the front surface of the first reflector 201, and after being reflected on the rear surface of the first reflector 201, it passes through the front surface of the first reflector 201, and after being transmitted (refracted) on the rear surface of the second reflector 202, it passes through the rear surface of the second reflector 202 after being reflected on the front surface of the second reflector 202, and then passes through the middle area of ​​the first reflector 201, the second lens 301, the third lens 302 and the fourth lens 303 in sequence to reach the imaging surface 400.

[0045] In this way, the utility model can obtain a telephoto catadioptric photography lens with a focal length of 250 mm by adopting the above-mentioned first lens 100, the catadioptric lens group 200 and the rear lens group 300. The rear focal length of the telephoto catadioptric photography lens is 41 mm, which can be adapted to cameras with more different specifications of bayonet mounts. The total length of the optical system and the total length of the optical parts are 100 mm and 60 mm respectively, which is conducive to the miniaturization and lightness of the photography lens. The F number is 5.6, which not only improves the shooting performance of the photography lens in a weak light environment, but also further reduces the size. The utility model is a novel object lens, and the first reflecting mirror 201 and the second reflecting mirror 202 are used to refract and reflect the light back and forth at the same time, so as to achieve the purpose of correcting the aberration, thereby reducing the number of lenses used, thereby reducing the volume and weight of the objective lens, and there is no need to open a hole in the center of the reflecting mirror like the existing objective lens, so that the production, processing and assembly of the objective lens of the utility model are simplified; and the above-mentioned rear lens group 300 can change the output image height of the catadioptric lens group 200 while correcting the aberration, so that the image height reaches a size that can be resolved by the camera, and the scope of application is wider.

[0046] In a preferred embodiment of the present invention, the first lens 100, the reflective lens group 200 and the rear lens group 300 are all independent modules, and the first lens 100 and the rear lens group 300 are detachably mounted on the incident end and the emitting end of the optical path of the reflective lens group 200, respectively. Specifically, the first lens 100, the reflective lens group 200 and the rear lens group 300 all have a connecting ring housing, and the connecting ring housings of the first lens 100 and the reflective lens group 200 are respectively mounted on the two ends of the connecting ring housing of the rear lens group 300 through a threaded structure. In this way, on the one hand, the production and processing difficulty of the telephoto folding reflective photography objective lens of the present invention is further reduced, on the other hand, the convenience of carrying is improved, and on the third hand, the first lens 100, the reflective lens group 200 and the rear lens group 300 of different specifications within the above range are selected according to the use requirements for combination, which is more flexible and convenient to use, and the scope of application is further expanded.

[0047] The telephoto catadioptric photography objective lens of the present invention will be further described below through embodiments.

[0048] Example

[0049] The video lens of the embodiment of the utility model includes: Figure 1 The first lens 100, the catadioptric lens group 200 and the rear lens group 300 are sequentially arranged along the propagation direction of the optical path. The specific structure is as described above and will not be described again. The effective focal lengths of the first lens 100, the first reflector 201 and the second reflector 202 of this embodiment, as well as the effective focal lengths of the second lens 301 and the third lens 302 after being glued together satisfy: f1 / f=1.8, f2 / f=0.42, f3 / f=-0.44, f4 / f=-0.42, wherein f is the focal length of the optical system of the telephoto catadioptric photography objective lens of this embodiment, f1 is the effective focal length of the first lens 100, f2 is the effective focal length of the first reflector 201, f3 is the effective focal length of the second reflector 202, and f4 is the effective focal length of the second lens 301 and the third lens 302 after being glued together.

[0050] The structure of the optical system composed of the first lens 100, the catadioptric lens group 200 and the rear lens group 300 is specifically shown in Table 1 below.

[0051] Table 1 (From top to bottom in the table are the light path propagation directions of the objective lens of this embodiment)

[0052]

[0053] The focal length of the optical system of the telephoto catadioptric photography objective lens of this embodiment is 250 mm, the back focal length is 41 mm, the total length of the optical system is 100 mm, the total length of the optical components is 60 mm (i.e., the distance between the object side surface of the first lens 100 and the image side surface of the fourth lens 303), and the F number is 5.6. The telephoto catadioptric photography objective lens of this embodiment is tested. From the test results, it can be seen that the objective lens has sharp imaging (see Figure 2 ), the image quality is consistent from the center to the edge of the field of view (see Figure 2 ), the axial and off-axial chromatic aberrations are extremely small (see Figure 4 and Figure 5 ), it is difficult to detect when shooting bright scenes, and even if there is a faint dark corner, it cannot be seen under sufficient light conditions ( Figure 6 ), distortion is less than 2% (see Figure 7 ), which is almost unnoticeable in actual shooting.

[0054] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the protection scope of the present invention.

Claims

1. A telephoto catadioptric photography objective lens, characterized in that: It comprises a first lens (100), a catadioptric lens group (200) and a rear lens group (300) which are sequentially arranged along the propagation direction of the light path; wherein: The first lens (100) is a positive meniscus lens; The catadioptric lens group (200) comprises a first reflector (201) and a second reflector (202); the first reflector (201) is a negative meniscus reflector, the front surface of which is a first light refraction area, and the area between the edge area and the middle area of ​​the rear surface is a first light reflection area; the second reflector (202) is a positive meniscus reflector, the front surface of which is a second light reflection area, and the rear surface of which is a second light refraction area.

2. The telephoto catadioptric photography objective lens according to claim 1, characterized in that: The effective focal lengths of the first reflector (201) and the second reflector (202) satisfy: 0.25≤f2 / f≤0.48, -0.48≤f3 / f≤-0.25; f is the focal length of the optical system of the telephoto catadioptric photography objective lens, f2 is the effective focal length of the first reflecting mirror (201), and f3 is the effective focal length of the second reflecting mirror (202).

3. The telephoto catadioptric photography objective lens according to claim 2, characterized in that: The effective focal length of the first lens (100) satisfies: 1.6≤f1 / f≤1.9; f is the focal length of the optical system of the telephoto catadioptric photography objective lens, and f1 is the effective focal length of the first lens (100).

4. The telephoto catadioptric photography objective lens according to any one of claims 1 to 3, characterized in that: The rear lens group (300) is composed of a second lens (301), a third lens (302), and a fourth lens (303) which are sequentially arranged along the propagation direction of the light path, wherein the second lens (301) is a negative meniscus lens, the third lens (302) is a positive lens, and the fourth lens (303) is a flat protective window.

5. The telephoto catadioptric photography objective lens according to claim 4, characterized in that: The second lens (301) and the third lens (302) are glued together.

6. The telephoto catadioptric photography objective lens according to claim 5, characterized in that: The effective focal length of the second lens (301) and the third lens (302) after being glued together satisfies: -0.45≤f4 / f≤-0.25; f is the focal length of the optical system of the telephoto catadioptric photography objective lens, and f4 is the effective focal length of the second lens (301) and the third lens (302) after being glued together.

7. The telephoto catadioptric photography objective lens according to claim 4, characterized in that: The refractive index of the first lens (100) is 1.65-1.85, and the dispersion coefficient is 40-60; the refractive index of the first reflector (201) is 1.55-1.68, and the dispersion coefficient is 45-65; the refractive index of the second reflector (202) is 1.65-1.85, and the dispersion coefficient is 40-60; the refractive index of the second lens (301) is 1.45-1.60, and the dispersion coefficient is 55-70; the refractive index of the third lens (302) is 1.75-1.85, and the dispersion coefficient is 40-55.

8. The telephoto catadioptric photography objective lens according to any one of claims 1 to 3 or any one of claims 5 to 7, characterized in that: The rear surface of the first reflector (201) has a first total reflection film, and the front surface of the second reflector (202) has a second total reflection film.

9. The telephoto catadioptric photography objective lens according to any one of claims 1 to 3 or any one of claims 5 to 7, characterized in that: The first lens (100), the reflective lens group (200) and the rear lens group (300) are all independent modules, and the first lens (100) and the rear lens group (300) are respectively detachably mounted on the light path incident end and the light path exit end of the reflective lens group (200).

10. The telephoto catadioptric photography objective lens according to any one of claims 1 to 3 or any one of claims 5 to 7, characterized in that: The focal length of the optical system of the telephoto catadioptric photography objective lens is 250 mm, the back focal length is 41 mm, the total length of the optical system is 100 mm, the total length of the optical parts is 60 mm, and the F number is 5.6.

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