Medium-focus and large-aperture short flange video lens with focal length of 35 mm

Abstract

A medium-focus and large-aperture short flange video lens with a focal length of 35 mm, the video lens comprising: a first lens group (G1), a variable diaphragm (S) and a second lens group (G2) which are sequentially arranged along a light incident direction of an optical path, wherein the first lens group (G1) is a non-movable fixed group, the focal power thereof is positive, and the first lens group (G1) is composed of 10 pieces of lenses (L1-L10) which are sequentially arranged along the light incident direction of the optical path, the 10 pieces of lenses (L1-L10) at least comprising three groups of doublet lenses, and the first lens (L1) and the second lens (L2) being meniscus lenses; the second lens group (G2) is a movable focusing group, the focal power thereof is positive, and the second lens group (G2) is composed of five pieces of lenses (L11-L15) sequentially arranged along the light incident direction of the optical path, the five pieces of lenses (L11-L15) at least comprising one group of triplet lenses; and the focal length values of the first lens group (G1) and the second lens group (G2) satisfy 1.2<f1 / f2<1.7.

Description

A medium-focus, large-aperture, short-flange video lens with a focal length of 35mm Technical Field

[0001] The invention belongs to the technical field of photographic lenses, and in particular relates to a medium-focus, large-aperture, short-flange video lens with a focal length of 35mm. 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 a continuous improvement in the performance parameters of video lenses. Among them, the key performance indicators of medium-focus video lenses are high definition, large aperture, good chromatic aberration, and low distortion.

[0003] However, the applicant found that the mid-focus video lenses currently on the market generally have shortcomings such as insufficient resolution, large distortion, small aperture, excessive total optical length and long flange back focus, which cannot meet the high requirements of video shooting field of view, especially video lenses with a focal length of 35mm.

[0004] Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a medium-focus, large-aperture, short-flange video lens with a focal length of 35 mm.

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

[0007] The present invention provides a medium focal length, large aperture, short flange video lens with a focal length of 35 mm, which comprises a first lens group, a variable aperture, and a second lens group arranged in sequence along the incident direction of light along the optical path; wherein,

[0008] The first lens group is an immovable fixed group with positive optical power, and is composed of 10 lenses arranged in sequence along the incident direction of the light path, wherein the 10 lenses include at least three groups of doublet lenses, and the first lens and the second lens are meniscus lenses;

[0009] The second lens group is a movable focusing group with positive optical power. The second lens group is composed of five lenses arranged in sequence along the incident direction of the light path, and the five lenses include at least one triplet lens group;

[0010] Furthermore, the first lens group and the second lens group satisfy the following equation: 1.2 <f1 / f2<1.7

[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 one lens in the first lens group is greater than 1.9 and less than 2.0, and the refractive index of at least three lenses in the first lens group is greater than 1.6 and less than 1.7.

[0013] Furthermore, the Abbe number of at least one lens in the second lens group is greater than 90 and less than 100, and the refractive index of at least one lens is greater than 1.4 and less than 1.5.

[0014] Furthermore, the fifth lens in the second lens group, counted from the incident direction of light, is a glass aspherical lens.

[0015] Furthermore, the structure of the glass aspheric lens is as shown in the following table:

[0016] 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.

[0017] 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:

[0018] 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.

[0019] Beneficial effects of the present invention:

[0020] 1. The present invention adopts the above-mentioned 14G1GM optimized combination to obtain a video lens with a focal length of 35mm, which takes into account the requirements of high resolution and large aperture, achieves small distortion and good chromatic aberration.

[0021] 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

[0022] FIG1 is a schematic structural diagram of a medium focal length, large aperture, short flange video lens with a focal length of 35 mm according to the present invention;

[0023] FIG2 is a relative illumination curve diagram of a test of a medium focal length, large aperture, short flange video lens with a focal length of 35 mm according to an embodiment of the present invention;

[0024] FIG3 is a diagram of lateral chromatic aberration of a medium focal length, large aperture, short flange video lens with a focal length of 35 mm according to an embodiment of the present invention;

[0025] FIG4 is a field curvature distortion diagram of a medium focal length, large aperture, short flange video lens with a focal length of 35 mm according to an embodiment of the present invention;

[0026] FIG5 is an MTF curve diagram of a medium focal length, large aperture, short flange video lens with a focal length of 35 mm according to an embodiment of the present invention;

[0027] FIG6 is an MTF defocus curve diagram of a medium focal length, large aperture, short flange video lens with a focal length of 35 mm according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] 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.

[0029] As shown in FIG1 , the present invention provides a medium focal length, large aperture, short flange video lens with a focal length of 35 mm. The lens 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.

[0030] The first lens group G1 is an immovable fixed group with positive optical power. The first lens group G1 is composed of 10 lenses arranged in sequence along the incident direction of light along the optical path, and the first lens and the second lens are meniscus lenses. At the same time, the first lens group G1 includes at least three groups of doublet lenses. As shown in Figure 1, the first lens group G1 is composed of lenses L1 to L10 arranged in sequence from the object side end to the camera connection end, among which lens L1 and lens L2 are meniscus lenses, and lens L1 and lens L2, lens L3 and lens L4, and lens L5 and lens L6 respectively constitute doublet lenses, totaling three groups.

[0031] The second lens group G2 is a movable focusing group with positive optical power. The second lens group is composed of five lenses arranged in sequence along the incident direction of the light path. The second lens group includes at least one set of three cemented lenses. As shown in Figure 1, the second lens group G2 is composed of lenses L11 to L15 arranged in sequence from the object side end to the camera connection end, among which lenses L11 to L13 constitute a set of three cemented lenses.

[0032] Furthermore, the focal lengths of the first lens group G1 and the second lens group G2 satisfy the following formula: 1.2 <f1 / f2<1.7

[0033] Where f1 is the focal length of the first lens group, and f2 is the focal length of the second lens group. If the focal lengths of the first lens group G1 and the second lens group G2 do not satisfy this formula, the back working distance of the optical system will be too long, making it unsuitable for camera modules with short flange back focus.

[0034] When the medium focal length large aperture short flange video lens with a focal length of 35 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.

[0035] By adopting an optimized combination of 14G1GM (14 standard spherical lenses and 1 non-spherical lens), the present invention obtains a video lens with a focal length of 35 mm. And this lens can achieve small distortion and good chromatic aberration while taking into account the requirements of high resolution and large aperture by only introducing one glass aspherical lens. Specifically: by using meniscus lenses for the first and second lenses of the first lens group G1, it can increase the field angle while ensuring the improvement of resolution, realizing a large aperture and high resolution. At the same time, by controlling the focal length values of the first lens group G1 and the second lens group G2 within 1.2 < f1 / f2 < 1.7, and adopting a structure of three groups of doublet lenses in the first lens group G1 and one group of triplet lenses in the second lens group G2, on the one hand, it can effectively optimize chromatic aberration, reduce dispersion, and improve color reproducibility, achieving small distortion and low dispersion. On the other hand, by using triplet lenses, it can effectively reduce the sensitivity of assembly tolerance and improve the excellent rate of assembled products (this triplet lens is formed by gluing lens L11 to lens L13 together to form a group of lenses, enabling light to pass through the lens smoothly during propagation, effectively reducing the tolerance sensitivity of eccentricity and tilt, which is very helpful for improving the assembly yield).

[0036] In a possible implementation scheme, as shown in Figure 1, at least one lens of the first lens group G1 has a refractive index greater than 1.9 and less than 2.0, and at least three lenses have a refractive index greater than 1.6 and less than 1.7; at least one lens of the second lens group G2 has an Abbe number greater than 90 and less than 100, and at least one lens has a refractive index greater than 1.4 and less than 1.5; specifically as shown in Figure 1, the refractive index of the 4th lens (i.e., lens L4) of the first lens group G1 is greater than 1.9 and less than 2.0, and the refractive indices of the 2nd, 5th, and 7th lenses (i.e., lens L2, lens L5, and lens L7) are greater than 1.6 and less than 1.7; the refractive index of the 1st lens (i.e., lens L11) of the second lens group G2 is greater than 1.4 and less than 1.5, and the Abbe number of the 1st lens (i.e., lens L11) is greater than 90 and less than 100. In this way, it can not only improve the high MTF resolution and small distortion under a large aperture, but also effectively correct the imaging chromatic aberration under a large aperture, and further improve the high resolution and contrast performance under a large aperture.

[0037] In one possible implementation, as shown in FIG1 , the optical system of the present invention includes a glass aspheric lens element, which is the fifteenth lens element from the left. Specifically, the fifth lens element in the second lens group G2, as counted from the direction of light incidence, is a glass aspheric lens. The structure of the glass aspheric lens is shown in Table 1. This glass aspheric lens can improve MTF resolution, reduce lens weight, and minimize distortion and chromatic aberration.

[0038] Table 1

[0039] In Table 1, K is the quadratic constant, E4, E6, E8, and E10 are the aspheric processing coefficients, and R1 and R2 are the radii of curvature. This glass aspheric lens can achieve the goal of optimizing high resolution and large aperture while also optimizing small distortion and good chromatic aberration.

[0040] In addition, the total length of the optical system of the existing 35mm medium-focus video lenses on the market is generally 150-160 mm; as shown in Figure 1, 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, the total optical length is reduced, and a lens with a more compact optical structure is obtained. The overall size of the lens is smaller, and it is lighter to use and carry, and 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 29.5 mm, while the flange back focus of the existing 35mm medium-focus video lenses on the market is mostly 40-50 mm.

[0041] The following is a further description of the medium focal length, large aperture, short flange video lens with a focal length of 35 mm according to the present invention through embodiments.

[0042] Example

[0043] 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 are not 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.

[0044] Table 2

[0045] 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.

[0046] Table 3

[0047] When an object moves from infinity to a close distance, this embodiment achieves focus by fixing the first lens group G1 while the second lens group G2 moves toward the object. This achieves both high resolution and a large aperture (see FIG2 , which is a relative illumination curve plotted for a video lens according to an embodiment of the present invention tested with a light source having a wavelength of 0.546000 μm). This achieves low distortion (see FIG4 , which is a plot of field curvature distortion plotted for a video lens according to an embodiment of the present invention tested with a light source having a wavelength of 0.435 μm at a maximum field of view of 21.5000 mm) and good chromatic aberration (see FIG3 , which is a plot of lateral chromatic aberration plotted for a video lens according to an embodiment of the present invention tested with a light source having a wavelength of 0.546000 μm at a maximum field of view of 21.5000 mm).

[0048] 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 medium focal length, large aperture, short flange video lens with a focal length of 35 mm, characterized in that: The lens comprises a first lens group, a variable aperture and a second lens group which are sequentially arranged along the incident direction of light of the optical path; wherein, The first lens group is an immovable fixed group with positive optical power, and the first lens group is composed of 10 lenses arranged in sequence along the incident direction of the light path, the 10 lenses include at least three groups of doublet lenses, and the first lens and the second lens are meniscus lenses; The second lens group is a movable focusing group with positive optical power. The second lens group is composed of five lenses arranged in sequence along the incident direction of the light path, and the five lenses include at least one set of three cemented lenses; And the first lens group and the second lens group satisfy the following formula: 1.2 <f1 / f2<1.7 Wherein, f1 is the focal length of the first lens group, and f2 is the focal length of the second lens group.

2. The medium focal length, large aperture, short flange video lens with a focal length of 35 mm according to claim 1, characterized in that: The refractive index of at least one lens in the first lens group is greater than 1.9 and less than 2.0, and the refractive index of at least three lenses in the first lens group is greater than 1.6 and less than 1.

7.

3. The medium focal length, large aperture, short flange video lens with a focal length of 35 mm according to claim 2, characterized in that: The Abbe number of at least one lens in the second lens group is greater than 90 and less than 100, and the refractive index of at least one lens in the second lens group is greater than 1.4 and less than 1.

5.

4. The medium focal length, large aperture, short flange video lens with a focal length of 35 mm according to claim 3, characterized in that: The fifth lens of the second lens group from the incident direction of light is a glass aspherical lens.

5. The medium focal length, large aperture, short flange video lens with a focal length of 35 mm according to claim 4, characterized in that: The structure of the glass aspheric lens is 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.

6. The medium focal length, large aperture, short flange video lens with a focal length of 35 mm according to claim 5, 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:

7. The medium focal length, large aperture, short flange video lens with a focal length of 35 mm according to any one of claims 1 to 6, 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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