Wide-angle video lens having focal length of 25 mm, large aperture and short flange back focal length

Abstract

A wide-angle video lens having a focal length of 25 mm, a large aperture and a short flange back focal length. The lens is sequentially provided with a first lens group (G1), a variable diaphragm (S) and a second lens group (G2) along the light incidence direction of an optical path; the first lens group (G1) is used as a fixed group, the focal power thereof is positive, and the first lens group (G1) consists of 10 lenses (L1-L10); the second lens group (G2) is used as a focusing group, the focal power thereof is positive, and the second lens group (G2) consists of five lenses (L11-L15); and the first lens group (G1) and the second lens group (G2) satisfy 1.7<f1 / f2<2.3, wherein f1 is the focal length value of the first lens group (G1), and f2 is the focal length value of the second lens group (G2). In this way, the short-focus lens having a focal length of 25 mm can reduce distortion, chromatic aberration and the total optical length while satisfying the requirements for high resolution and a large aperture, and can also be adapted to a camera module having a short flange back focal length.

Description

A wide-angle, large-aperture, short-flange video lens with a focal length of 25mm Technical Field

[0001] The invention belongs to the technical field of photographic lenses, and in particular relates to a wide-angle, large-aperture, short-flange video lens with a focal length of 25 mm. Background Art

[0002] With the rapid development of society and the economy, people's demand for film, television, and self-media is increasing, and the demand for video shooting scenes is increasing, which in turn leads to higher and higher requirements for video lens parameters. Among them, the key parameters for short-throw video lenses are high definition, large aperture, good chromatic aberration, and minimal distortion.

[0003] However, the applicant found that the short-focus video lenses currently on the market generally have shortcomings such as low resolution, large distortion, small aperture, excessive optical length and long flange back focus, which cannot meet the high requirements of the field of view required for movie shooting.

[0004] Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a wide-angle, large aperture, short flange video lens with a focal length of 25 mm.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] The present invention provides a wide-angle, large-aperture, short-flange video lens with a focal length of 25 mm, wherein the lens is provided with a first lens group, a variable aperture, and a second lens group in sequence along the incident direction of light along the optical path; wherein,

[0008] The first lens group is a fixed group with positive optical power, and the first lens group consists of 10 lenses;

[0009] The second lens group is a focusing group with positive optical power, and the second lens group is composed of 5 lenses;

[0010] Furthermore, the first lens group and the second lens group satisfy the following equation: 1.7 <f1 / f2<2.3

[0011] Wherein, f1 is the focal length of the first lens group, and f2 is the focal length of the second lens group.

[0012] Furthermore, the refractive index of at least four lenses in the first lens group is greater than 1.9.

[0013] Furthermore, the refractive index of at least one lens in the first lens group is greater than 1.8 and less than 1.9.

[0014] Furthermore, at least two lenses in the second lens group have an Abbe number greater than 80 and less than 100.

[0015] Furthermore, the second lens group has at least two lenses with a refractive index less than 1.5.

[0016] Furthermore, the optical system composed of the first lens group and the second lens group includes one doublet lens and two triplet lenses.

[0017] Furthermore, the optical system comprises two glass aspheric lenses, which are the second lens and the fifteenth lens from the incident direction of the light in the lens optical path.

[0018] Furthermore, the structure of the optical system composed of the first lens group and the second lens group is specifically as shown in the following table:

[0019] Among them, Surf represents the corresponding surface number in the optical system, Type represents the type of the surface, Radius represents the radius of curvature, Thickness represents the thickness, Index represents the refractive index, and ABB represents the Abbe number.

[0020] Furthermore, the structures of the two glass aspheric lenses are shown in the following table:

[0021] In the table, K is the quadratic curve constant, E4, E6, E8 and E10 are aspheric surface processing coefficients, and R1 and R2 are curvature radii.

[0022] Furthermore, the total length of the optical system composed of the first lens group and the second lens group is greater than 128 mm and less than 132 mm.

[0023] Beneficial effects of the present invention:

[0024] 1. The present invention adopts an optimized combination of 13 standard spherical lenses and 2 aspherical lenses to obtain a short-focus 25mm movie lens that can optimize small distortion and good chromatic aberration while meeting the requirements of optimizing high resolution and large aperture.

[0025] 2. The present invention optimizes the total optical length by adopting a compact optical structure, so that the total length of the optical system composed of the first lens group G1 and the second lens group G2 is greater than 128 mm and less than 132 mm, thereby reducing the total optical length; at the same time, it can also meet the requirements of matching camera modules with shorter flange back focus. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG1 is a schematic structural diagram of a wide-angle, large-aperture, short-flange video lens with a focal length of 25 mm according to the present invention;

[0027] FIG2 is a relative illumination curve diagram of a wide-angle, large-aperture, short-flange video lens with a focal length of 25 mm according to an embodiment of the present invention;

[0028] FIG3 is a diagram of lateral chromatic aberration of a wide-angle, large-aperture, short-flange video lens with a focal length of 25 mm according to an embodiment of the present invention;

[0029] FIG4 is a diagram showing the field curvature distortion of a wide-angle, large-aperture, short-flange video lens with a focal length of 25 mm according to an embodiment of the present invention;

[0030] FIG5 is an MTF curve diagram of a wide-angle, large-aperture, short-flange video lens with a focal length of 25 mm according to an embodiment of the present invention;

[0031] FIG6 is an MTF defocus curve diagram of a wide-angle, large-aperture, short-flange video lens with a focal length of 25 mm according to an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0033] As shown in FIG1 , the wide-angle, large-aperture, short-flange video lens with a focal length of 25 mm according to the present invention is provided with a first lens group G1, a variable aperture S, and a second lens group G2 in sequence along the incident direction of the light path.

[0034] The first lens group G1, as a fixed group, has positive optical power. The first lens group G1 consists of 10 lenses. Specifically, the first lens group G1 consists of lenses L1 to L10 arranged in sequence from the object side end to the camera connection end. The second lens group G2, as a focusing group, has positive optical power. The second lens group G2 consists of 5 lenses. Specifically, the second lens group G2 consists of lenses L11 to L15 arranged in sequence from the object side end to the camera connection end. The optical system composed of the first lens group G1 and the second lens group G2 contains two glass aspheric lenses, which are the second lens and the fifteenth lens from the incident direction of the light path of the lens (that is, lens L2 and lens L15 are glass aspheric lenses), and the remaining 13 lenses are all standard spherical lenses; the structure of the two glass aspheric lenses (lens L2 and lens L15) is specifically shown in Table 1 below:

[0035] Table 1

[0036] In Table 1, K is the conic constant, E4, E6, E8, and E10 are all aspherical machining coefficients, and R1 and R2 are the radii of curvature;

[0037] Moreover, the first lens group G1 and the second lens group G2 satisfy the following formula: 1.7 < f1 / f2 < 2.3

[0038] In the formula, f1 is the focal length value of the first lens group G1, and f2 is the focal length value of the second lens group G2.

[0039] When the wide-angle large-aperture short flange video lens with a focal length of 25 mm according to the present invention is working, the first lens group G1 remains stationary when the object moves from infinity to a short distance, and the second lens group G2 moves towards the object when the object moves from infinity to a short distance to achieve focus.

[0040] By adopting an optimized combination of 13G2GM (13 standard spherical lenses and 2 aspherical lenses), the present invention can obtain a short-focus 25 mm movie lens, and this lens can optimize small distortion and good chromatic aberration while meeting the requirements of optimized high resolution and large aperture. Specifically, by making the focal length fz of the first lens group G1 and the focal length f2 of the second lens group G2 satisfy 1.7 < f1 / f2 < 2.3, during the focusing process by moving the second lens group G2, high resolution and large aperture can be achieved while reducing the distortion and chromatic aberration generated during focusing.

[0041] In a possible implementation scheme, at least four lenses of the first lens group G1 have a refractive index greater than 1.9, and at least one lens of the first lens group G1 has a refractive index greater than <1.8 and less than 1.9; specifically as shown in Figure 1, the refractive indices of the first, third, seventh, and eighth lenses (i.e., lens L1, lens L3, lens L7, and lens L8) of the first lens group G1 are greater than 1.9. Through these four lenses, the high MTF resolution and small distortion under a large aperture can be improved. At the same time, the refractive index of the second lens (i.e., lens L2) is greater than 1.8 and less than 1.9, and through this lens, the small distortion under a large aperture can be further improved.

[0042] At least two lenses of the second lens group G2 have an Abbe number greater than 80 and less than 100, and at least two lenses of the second lens group have a refractive index less than 1.5; specifically as shown in Figure 1, the Abbe numbers of the eleventh and thirteenth lenses (i.e., lens L11 and lens L13) of the second lens group G2 are greater than 80 and less than 100, and the refractive index <1.5. Through these two lenses, on the one hand, the good chromatic aberration under a large aperture can be improved, and on the other hand, the high MTF resolution under a large aperture can be further improved.

[0043] The optical system consisting of the first lens group G1 and the second lens group G2 includes one doublet and two triplets. Specifically, as shown in Figure 1 , the fourth and fifth lenses (i.e., lens L4 and lens L5) form the doublet, while the eighth to tenth lenses (i.e., lenses L8 to L10) and the eleventh to thirteenth lenses (i.e., lenses L11 to L13) each form two triplets. These triplets optimize the lens's fine chromatic aberration and reduce sensitivity to assembly tolerances.

[0044] In addition, the total length of the optical system of the existing 25mm short-focus video lenses on the market is generally 150 mm. The present invention adopts the above-mentioned first lens group G1, variable aperture S and second lens group G2, so that the total length of the optical system composed of the first lens group G1 and the second lens group G2 is greater than 128 mm and less than 132 mm, and the total optical length is reduced, resulting in a lens with a more compact optical structure. The overall size of the lens is smaller, and it is lighter to use and carry. It can also meet the requirements of matching camera modules with shorter flange back focus. As shown in Figure 1, the flange back focus 100 of the camera module is about 30 mm, while the flange back focus of the existing 25mm short-focus video lenses on the market is mostly 40-50 mm.

[0045] The wide-angle, large-aperture, short-flange video lens with a focal length of 25 mm of the present invention will be further described below through examples.

[0046] Example

[0047] The video lens of this embodiment of the present invention includes a first lens group G1, a variable aperture S, and a second lens group G2, as shown in Figure 1 . The structures of the first lens group G1 and the second lens group G2 are as described above and will not be repeated here. The structure of the optical system formed by the first lens group G1 and the second lens group G2 in this embodiment is detailed in Table 2 below.

[0048] Table 2

[0049] Among them, Surf represents the corresponding surface number in the optical system, Type represents the type of the surface, Radius represents the radius of curvature, Thickness represents the thickness, Index represents the refractive index, and ABB represents the Abbe number.

[0050] The overall specifications of the optical system composed of the first lens group G1 and the second lens group G2 in this embodiment of the present invention are shown in Table 3 below.

[0051] Table 3

[0052] In the table, F represents focal length, in mm; Fno represents relative aperture, in mm; W represents wide angle, in mm; D(0) represents object distance, in mm (where INF represents infinity); D(19) represents the distance between the aperture and the eleventh lens (i.e., lens L11 in FIG1 ), in mm; and D(27) represents back focus, in mm.

[0053] When an object moves from infinity to a close distance, this embodiment achieves focus by fixing the first lens group G1 and moving the second lens group G2 toward the object, and has high resolution (see Figures 5 and 6), large aperture (see Figure 2, which shows the wavelength of 0.546000) of the video lens of the embodiment of the present invention. μm The advantages include relative illumination curve of light source test), small distortion (see Figure 4, which is a field curvature distortion diagram of the video lens of the embodiment of the present invention at a maximum field of view of 21.5000 mm) and small chromatic aberration (see Figure 3, which is a lateral chromatic aberration diagram of the video lens of the embodiment of the present invention at a maximum field of view of 21.5000 mm).

[0054] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A wide-angle, large-aperture, short-flange video lens with a focal length of 25 mm, characterized in that: The lens is provided with a first lens group, a variable aperture and a second lens group in sequence along the incident direction of light along the optical path; wherein, The first lens group is a fixed group with positive optical power, and the first lens group is composed of 10 lenses; The second lens group is a focusing group with positive optical power, and the second lens group is composed of 5 lenses; And the first lens group and the second lens group satisfy the following formula: 1.7 <f1 / f2<2.3 Wherein, f1 is the focal length of the first lens group, and f2 is the focal length of the second lens group.

2. The wide-angle, large-aperture, short-flange video lens with a focal length of 25 mm according to claim 1, characterized in that: The refractive index of at least four lenses in the first lens group is greater than 1.

9.

3. The wide-angle, large-aperture, short-flange video lens with a focal length of 25 mm according to claim 2, characterized in that: The refractive index of at least one lens in the first lens group is greater than 1.8 and less than 1.

9.

4. The wide-angle, large-aperture, short-flange video lens with a focal length of 25 mm according to claim 3, characterized in that: At least two lenses in the second lens group have an Abbe number greater than 80 and less than 100.

5. The wide-angle, large-aperture, short-flange video lens with a focal length of 25 mm according to claim 4, characterized in that: At least two lenses in the second lens group have a refractive index less than 1.

5.

6. The wide-angle, large-aperture, short-flange video lens with a focal length of 25 mm according to claim 1, characterized in that: The optical system formed by the first lens group and the second lens group includes a doublet lens and two triplet lenses.

7. The wide-angle, large-aperture, short-flange video lens with a focal length of 25 mm according to claim 6, characterized in that: The optical system comprises two glass aspherical lenses, which are the second lens and the fifteenth lens from the incident direction of the light in the lens optical path.

8. The wide-angle, large-aperture, short-flange video lens with a focal length of 25 mm according to claim 7, characterized in that: The structure of the optical system composed of the first lens group and the second lens group is specifically shown in the following table: Among them, Surf represents the corresponding surface number in the optical system, Type represents the type of the surface, Radius represents the radius of curvature, Thickness represents the thickness, Index represents the refractive index, and ABB represents the Abbe number.

9. The wide-angle, large-aperture, short-flange video lens with a focal length of 25 mm according to claim 8, characterized in that: The structures of the two glass aspherical lenses are as follows: In the table, K is the quadratic curve constant, E4, E6, E8 and E10 are aspheric surface processing coefficients, and R1 and R2 are the curvature radii.

10. The wide-angle, large-aperture, short-flange video lens with a focal length of 25 mm according to any one of claims 1 to 9, characterized in that: The total length of the optical system formed by the first lens group and the second lens group is greater than 128 mm and less than 132 mm.

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