A medium focal length, large aperture, long flange video lens with a focal length of 35mm

Abstract

The present invention relates to a medium - focal - length large - aperture long - flange video lens with a focal length of 35 mm, which includes a first lens group and a second lens group arranged successively along the light - incident direction of the optical path, and also includes a variable aperture disposed within the second lens group; the first lens group, as an immovable fixed group, has a positive optical power and is composed of lenses L11 - L17 arranged successively along the light - incident direction of the optical path; the second lens group, as a movable focusing group, has a positive optical power and is composed of lenses L21 - L28 arranged successively along the light - incident direction of the optical path; both the first lens group and the second lens group each contain at least one triplet lens and one doublet lens; moreover, the focal length value f1 of the first lens group and the focal length value f2 of the second lens group satisfy 0.41 < f2 / f1 < 0.58. In this way, the lens can achieve small distortion and good chromatic aberration while taking into account the requirements of high resolution and large aperture.

Description

Technical Field

[0001] The invention belongs to the technical field of photographic lenses, and in particular relates to a medium-focus, large-aperture, long-flange video lens with a focal length of 35 mm. Background Art

[0002] With the rapid development of social economy, people's demand for film and television and self-media is increasing, and the demand for video shooting scenes is increasing, which leads to the continuous improvement of video lens parameters. Among them, the important parameters of medium-focus video lenses are high resolution, large aperture, good chromatic aberration effect and small distortion.

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

[0004] In order to solve the above problems existing in the prior art, the present invention provides a medium focal length, large aperture and long flange video lens with a focal length of 35 mm.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The present invention provides a medium focal length large aperture long flange video lens with a focal length of 35 mm, the lens comprises a first lens group and a second lens group arranged in sequence along the incident direction of light along the optical path, and also comprises a variable iris, the variable iris being arranged in the second lens group; wherein,

[0007] The first lens group is an immovable fixed group with positive optical power, and the first lens group is composed of lenses L11 to L17 arranged in sequence along the incident direction of the light along the optical path;

[0008] The second lens group is a movable focusing group with positive focal power, and the second lens group is composed of lenses L21 to L28 arranged in sequence along the incident direction of the light path;

[0009] The first lens group and the second lens group each include at least one group of triplet lenses and one group of doublet lenses;

[0010] And the first lens group and the second lens group satisfy the following formula:

[0011] 0.41 <f2 / f1<0.58

[0012] Wherein, f1 represents the focal length value of the first lens group, and f2 represents the focal length value of the second lens group.

[0013] Furthermore, lenses L12 to L14 of the first lens group constitute a first group of three-cemented lenses, and lenses L15 and L16 constitute a first group of two-cemented lenses; lenses L24 to L26 of the second lens group constitute a second group of three-cemented lenses, and lenses L22 and L23 constitute a second group of two-cemented lenses.

[0014] Furthermore, the variable aperture is arranged between the lens L23 and the lens L24.

[0015] Furthermore, the lens L11 of the first lens group is a meniscus lens.

[0016] Furthermore, the lens L28 of the second lens group is a glass aspherical lens.

[0017] Further, the object side coefficients of the lens L28 of the second lens group are: K=0.000000000, E4=0.000026005180962950, ​​E6=0.000000007447377772, E8=-0.0000000000055001393, E10=0.000000000000050197, E12=-0.0000000000000000005, R1=-29.318736777;

[0018] The image side coefficients of the lens L28 are: K=0.000000000, E4=0.000027038936873470, E6=0.000000011186593327, E8=-0.0000000000052052943, E10=0.000000000000052460, E12=-0.000000000000000029, R2=-34.983740594;

[0019] Where K is the quadratic curve constant, E4, E6, E8, E10 and E12 are aspheric surface processing coefficients, and R1 and R2 are the curvature radii.

[0020] Furthermore, the refractive index of at least one lens in the first lens group is greater than 2.0, and the refractive index of at least three lenses in the second lens group is greater than 1.6 and less than 1.7.

[0021] Furthermore, at least two lenses in the first lens group have an Abbe number greater than 41 and less than 48, and at least one lens in the second lens group has an Abbe number greater than 93 and less than 97.

[0022] Furthermore, the focal length adjustment range of the optical system composed of the first lens group and the second lens group is 35.06mm~35.8mm, and during the focal length adjustment range adjustment process of the optical system, the adjustment range of the aperture is 1.42mm~1.35mm, the adjustment range of the half field angle is 30.932°~31.155°, the adjustment range of the object distance is 291mm~infinity, the adjustment range of the distance between the image side surface of the lens L17 and the object side surface of the lens L21 is 1.126857mm~5.3685mm, and the adjustment range of the back focus is 40.239348mm~35.997705mm.

[0023] Furthermore, the total length of the optical system formed by the first lens group and the second lens group is greater than 157 mm and less than 163 mm.

[0024] 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:

[0025] Beneficial effects of the present invention:

[0026] 1. The present invention adopts the above-mentioned 14G1GM optimized combination to obtain a video lens with a focal length of 35mm that takes into account the requirements of high resolution and large aperture and achieves small distortion and good chromatic aberration.

[0027] 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 and the second lens group is greater than 157 mm and less than 163 mm, and the total optical length is reduced; at the same time, it can also meet the requirements of matching camera modules with longer flange back focus. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of a medium focal length, large aperture, long flange video lens with a focal length of 35 mm according to the present invention;

[0029] Figure 2 is a relative illumination curve diagram of a medium focal length, large aperture, long flange video lens with a focal length of 35 mm according to an embodiment of the present invention;

[0030] Figure 3 is a lateral chromatic aberration diagram of a medium focal length, large aperture, long flange video lens with a focal length of 35 mm according to an embodiment of the present invention;

[0031] Figure 4 is a field curvature distortion diagram of a medium focal length, large aperture, long flange video lens with a focal length of 35 mm according to an embodiment of the present invention;

[0032] Figure 5is an MTF curve diagram of a medium focal length, large aperture, long flange video lens with a focal length of 35 mm according to an embodiment of the present invention;

[0033] Figure 6 This is an MTF defocus curve diagram of a medium focal length, large aperture, long flange video lens with a focal length of 35 mm according to an embodiment of the present invention;

[0034] Figure 7 is a lateral chromatic aberration diagram of the video lens test described in Comparative Example 1 of the present invention;

[0035] Figure 8 is a field curvature distortion diagram of the video lens test described in Comparative Example 1 of the present invention;

[0036] Fig. 9 is an MTF curve diagram of the video lens test described in Comparative Example 1 of the present invention;

[0037] Fig.10 is a lateral chromatic aberration diagram of the video lens test described in Comparative Example 2 of the present invention;

[0038] Fig.11 is a field curvature distortion diagram of the video lens test described in Comparative Example 2 of the present invention;

[0039] Fig.12 It is an MTF curve diagram of the video lens test described in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with 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 used to limit the present invention.

[0041] like Figure 1 As shown, the medium focal length, large aperture, long flange video lens with a focal length of 35 mm described in the present invention is provided with a first lens group G1 and a second lens group G2 in sequence along the incident direction of the light path.

[0042] The first lens group G1, as an immovable fixed group, has positive optical power. The first lens group G1 is composed of lenses L11 to L17 arranged in sequence along the incident direction of light along the optical path, and the first lens group G1 includes a group of three-cemented lenses and a group of two-cemented lenses. Specifically, as shown in the figure, lenses L12 to L14 of the first lens group G1 constitute a first group of three-cemented lenses, lens L15 and lens L16 constitute a first group of two-cemented lenses, and lens L11 in the first lens group G1 is a meniscus lens.

[0043] The second lens group G2, as a movable focusing group, has a positive focal power. The second lens group G2 is composed of lenses L21 to L28 arranged in sequence along the incident direction of the light path, and the variable aperture is arranged between lens L23 and lens L24; and the second lens group G2 also includes a group of three-cemented lenses and a group of two-cemented lenses, as shown in the figure, the lenses L24 to L26 of the second lens group constitute a second group of three-cemented lenses, and the lens L22 and the lens L23 constitute a second group of two-cemented lenses; and the lens L28 of the second lens group is a glass aspherical lens, and its structural parameters are specifically as shown in Table 1:

[0044] Table 1

[0045]

[0046] 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.

[0047] The first lens group G1 and the second lens group G2 satisfy the following equation:

[0048] 0.41 <f2 / f1<0.58

[0049] In the formula, f1 represents the focal length value of the first lens group G1, and f2 represents the focal length value of the second lens group G2; this formula expresses the corresponding relationship between the optical powers of the first lens group G1 and the second lens group G2. If the focal length values ​​of the first lens group G1 and the second lens group G2 do not satisfy this formula, it will lead to the attenuation of optical properties such as MTF, chromatic aberration and optical distortion of the lens, and at the same time cause the back focus working distance of the optical system to be too short, which cannot meet the matching requirements of the camera module with a long flange back focus.

[0050] When the medium-focus large aperture long flange video lens with a focal length of 35 mm described in the present invention is working, the first lens group G1 is fixed when the object moves from infinity to a close distance, and the second lens group G2 moves toward the object when the object moves from infinity to a close distance to achieve focusing.

[0051] After experimental testing, the total length of the optical system of the medium - focal - length large - aperture long - flange video lens with a focal length of 35 mm according to the present invention, which is composed of the above - mentioned first lens group G1 and second lens group G2, is greater than 157 mm and less than 163 mm, meeting the requirements of a camera module 100 with a relatively long back - focal length. The focal - length adjustment range of the optical system is 35.06 mm to 35.8 mm. Moreover, during the adjustment process of the focal - length adjustment range, its aperture is adjusted in the range of 1.42 mm to 1.35 mm, the semi - field - of - view angle is adjusted in the range of 30.932° to 31.155°, the object distance is adjusted in the range of 291 mm to infinity, the distance between the image side of lens L17 and the object side of lens L21 is adjusted in the range of 1.126857 mm to 5.3685 mm, and the back - focal length is adjusted in the range of 40.239348 mm to 35.997705 mm.

[0052] The present invention adopts an optimized combination of 14G1GM (14 standard spherical lenses and 1 aspherical lens) to obtain a video lens with a focal length of 35 mm. This lens can achieve small distortion and good chromatic aberration while taking into account the requirements of high resolution and large aperture. Specifically: by using a meniscus lens for lens L11 in the first lens group G1 and cooperating with the glass aspherical lens (lens L28) in the second lens group G2, the lens can increase the field - of - view angle while optimizing the resolution and reducing distortion. Then, by controlling the focal - length values of the first lens group G1 and the second lens group G2 within 0.41 < f2 / f1 < 0.58, and by using a set of triplet lenses and a set of doublet lenses in both the first lens group G1 and the second lens group G2, on the one hand, it can effectively optimize chromatic aberration, reduce dispersion, and improve color reproducibility.

[0053] In a possible implementation scheme, at least one lens in the first lens group G1 has a refractive index greater than 2.0, and at least two lenses have an Abbe number greater than 41 and less than 48; at least three lenses in the second lens group have a refractive index greater than 1.6 and less than 1.7, and at least one lens has an Abbe number greater than 93 and less than 97.

[0054] The following further illustrates the medium - focal - length large - aperture long - flange video lens with a focal length of 35 mm according to the present invention through examples and comparative examples. Example

[0055] The video lens described in the embodiment of the present invention includes as Figure 1The first lens group G1, the second lens group G2 and the variable iris S are shown, and the variable iris S is arranged in the second lens group G2. The structures of the first lens group G1 and the second lens group G2 are as described above, and will not be described again. In this embodiment, the ratio of the focal length value f1 of the first lens group G1 to the focal length value f2 of the second lens group G2 is: f2 / f1=0.506; the structure of the optical system composed of the first lens group G1 and the second lens group G2 is specifically shown in Table 2 below.

[0056] Table 2

[0057]

[0058] The overall specifications of the optical system composed of the first lens group G1 and the second lens group G2 in the embodiment of the present invention are shown in Table 3.

[0059] Table 3

[0060]

[0061] When an object moves from infinity to a close distance, in this embodiment, the first lens group G1 is fixed and the second lens group G2 moves toward the object to achieve focus, while taking into account high resolution (see Figure 5 and Figure 6 ) and large aperture (see Figure 2 , which is a relative illumination curve of the video lens of the embodiment of the present invention tested with a light source of wavelength 0.546000μm) to achieve small distortion under the requirements (see Figure 4 , which is a field curvature distortion diagram of the video lens of the embodiment of the present invention tested with a wavelength of 0.435μm at a maximum field of view of 21.5000mm) and good chromatic aberration (see Figure 3 , which is a lateral chromatic aberration diagram of the video lens of an embodiment of the present invention tested with a light source of wavelength 0.546000μm at a maximum field of view of 21.5000mm). Comparative Example 1

[0062] This comparative example 1 is basically the same as the video lens described in the embodiment, and includes a first lens group G1, a variable aperture S, and a second lens group G2. The difference is that in this comparative example 1, the ratio of the focal length value f1 of the first lens group G1 to the focal length value f2 of the second lens group G2 is: f2 / f1=0.41, f1 represents the focal length value of the first lens group G1, f2 represents the focal length value of the second lens group G2, and the structure of the optical system composed of the first lens group G1 and the second lens group G2 is specifically shown in Table 4 below.

[0063] Table 4

[0064]

[0065] Among them, the structural parameters of the glass aspherical lens L28 are specifically as shown in Table 5 below.

[0066] Table 5

[0067]

[0068] The same method as in the embodiment was used for testing. From the comparison between the test results of Comparative Example 1 ( Figure 7-9 ), it was found that in the optical performance of the lens of Comparative Example 1, the lateral chromatic aberration became larger, the MTF resolution decreased, and the optical distortion became larger. Comparative Example 2

[0069] This Comparative Example 2 is basically the same as the video lens described in the embodiment, including the first lens group G1, the variable aperture S, and the second lens group G2. The difference is that in this Comparative Example 2, the ratio of the focal length value f1 of the first lens group G1 to the focal length value f2 of the second lens group G2 is: f2 / f1 = 0.58, where f1 represents the focal length value of the first lens group G1 and f2 represents the focal length value of the second lens group G2, and the structure of the optical system composed of the first lens group G1 and the second lens group G2 is specifically as shown in Table 6 below.

[0070] Table 6

[0071]

[0072] Among them, the structural parameters of the glass aspherical lens L28 are specifically as shown in Table 7 below.

[0073] Table 7

[0074]

[0075] The same method as in the embodiment was used for testing. From the comparison between the test results of Comparative Example 2 ( Figure 10-12 ), it was found that the lens of Comparative Example 2, like that of Comparative Example 1, had an increase in lateral chromatic aberration, a decrease in MTF resolution, and a large optical distortion in terms of optical performance.

[0076] Therefore, from the above embodiments and Comparative Examples 1 and 2, it can be seen that if the focal length value f1 of the first lens group and the focal length value f2 of the second lens group of the lens according to the present invention do not satisfy 0.41 < f2 / f1 < 0.58, it will lead to defects such as attenuation of optical performance such as MTF, chromatic aberration, and optical distortion of the lens.

[0077] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A medium focal length, large aperture, long flange video lens with a focal length of 35 mm, characterized in that: The lens has two lens groups, including a first lens group and a second lens group arranged in sequence along the incident direction of the light path, and also includes a variable iris, which is arranged in the second lens group; wherein, The first lens group is an immovable fixed group with positive focal power. The first lens group is composed of lens L11, lens L12, lens L13, lens L14, lens L15, lens L16 and lens L17 arranged in sequence along the incident direction of the light path, wherein the lens L12, lens L3 and lens L14 constitute a first group of three-cemented lenses, and the lens L15 and lens L16 constitute a first group of two-cemented lenses; the lens L11 is a meniscus lens, the focal power of the lens L11, lens L12, lens L14 and lens L15 is negative, and the focal power of the lens L13, lens L16 and lens L17 is positive; The second lens group is a movable focusing group with positive focal power. The second lens group is composed of lens L21, lens L22, lens L23, lens L24, lens L25, lens L26, lens L27 and lens L28, which are arranged in sequence along the incident direction of the light path. The lens L24, lens L25 and lens L26 form a second group of triplet lenses, and the lens L22 and lens L23 form a second group of doublet lenses. The focal power of the lens L21, lens L22, lens L24, lens L26 and lens L27 is positive, and the focal power of the lenses L23, L25 and L28 is negative. And the first lens group and the second lens group satisfy the following formula: 0.41 <f2 / f1<0.58 Wherein, f1 represents the focal length of the first lens group, and f2 represents the focal length of the second lens group; The focal length adjustment range of the optical system composed of the first lens group and the second lens group is 35.06mm~35.8mm, and during the focal length adjustment range adjustment process of the optical system, the adjustment range of the aperture is 1.42mm~1.35mm, the adjustment range of the half field angle is 30.932°~31.155°, the adjustment range of the object distance is 291mm~infinity, the adjustment range of the distance between the image side surface of lens L17 and the object side surface of lens L21 is 1.126857mm~5.3685mm, and the adjustment range of the back focus is 40.239348mm~35.997705mm.

2. The medium focal length, large aperture, long flange video lens with a focal length of 35 mm according to claim 1, characterized in that: The variable aperture is disposed between the lens L23 and the lens L24.

3. The medium focal length, large aperture, long flange video lens with a focal length of 35 mm according to claim 1 or 2, characterized in that: The lens L28 of the second lens group is a glass aspherical lens.

4. The medium focal length, large aperture, long flange video lens with a focal length of 35 mm according to claim 3, characterized in that: The object side coefficients of the lens L28 of the second lens group are: K=0.000000000, E4=0.000026005180962950, ​​E6=0.000000007447377772, E8=-0.0000000000055001393, E10=0.000000000000050197, E12=-0.000000000000000005, R1=-29.318736777; The image side coefficients of the lens L28 are: K=0.000000000, E4=0.000027038936873470, E6=0.000000011186593327, E8=-0.0000000000052052943, E10=0.000000000000052460, E12=-0.000000000000000029, R2=-34.983740594; Where K is the quadratic curve constant, E4, E6, E8, E10 and E12 are aspheric surface processing coefficients, R1 and R2 are the curvature radii, and the unit is mm.

5. The medium focal length, large aperture, long flange video lens with a focal length of 35 mm according to claim 4, characterized in that: The refractive index of at least one lens in the first lens group is greater than 2.0, the refractive index of at least three lenses in the second lens group is greater than 1.6 and less than 1.7, the Abbe number of at least two lenses in the first lens group is greater than 41 and less than 48, and the Abbe number of at least one lens in the second lens group is greater than 93 and less than 97.

6. The medium focal length, large aperture, long flange video lens with a focal length of 35 mm according to claim 1, 2, 4 or 5, characterized in that: The total length of the optical system formed by the first lens group and the second lens group is greater than 157 mm and less than 163 mm.

7. The medium focal length, large aperture, long flange video lens with a focal length of 35 mm according to claim 1, 2, 4 or 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: 。

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