A telephoto, large aperture, long flange video lens with a focal length of 85mm

Abstract

The present invention relates to a long focal length large aperture long flange video lens with a focal length of 85 mm, which includes a first lens group, a variable aperture, and a second lens group arranged in sequence along the light incident direction of the optical path; the first lens group is a fixed group that cannot be moved, with a positive optical power, and is composed of lenses L11 to L16 arranged in sequence along the light incident direction of the optical path, including a set of four cemented lenses and a set of doublet lenses; the second lens group is a movable focusing group, with a positive optical power, and is composed of lenses L21 to L27 arranged in sequence along the light incident direction of the optical path, and lenses L21 to L28 are composed of a set of four cemented lenses and a set of doublet lenses; moreover, the focal length value f1 of the first lens group and the focal length value f2 of the second lens group satisfy 0.36 < f2 / f1 < 0.43. This lens achieves a large aperture, high resolution, small distortion, and low dispersion, and the overall optical length is reduced, meeting the requirements of a camera module with a longer flange back focal length.

Description

Technical Field

[0001] The invention belongs to the technical field of photographic lenses, and in particular relates to a long-focus, large-aperture, long-flange video lens with a focal length of 85 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 has led to higher requirements for the index parameters of video lenses. Among them, the important indicators of telephoto video lenses are large aperture, high resolution, small distortion and low dispersion.

[0003] However, the applicant has found that the telephoto video lenses currently on the market generally have shortcomings such as insufficient resolution, insufficient aperture, insufficient distortion, large dispersion, and insufficient flange back focus, which cannot meet the high requirements of the telephoto movie shooting market, especially telephoto video lenses with a focal length of 85mm. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a long-focus, large-aperture, long-flange video lens with a focal length of 85 mm.

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

[0006] The present invention provides a long-focus, large-aperture, long-flange video lens with a focal length of 85 mm, the lens comprising 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:

[0007] The first lens group is an immovable fixed group with positive optical power. The first lens group is composed of lenses L11 to L16 arranged in sequence along the incident direction of the light path, including a group of four cemented lenses and a group of two cemented lenses;

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

[0009] And the focal lengths of the first lens group and the second lens group satisfy the following equation:

[0010] 0.36 <f2 / f1<0.43

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

[0012] Furthermore, the lenses L11 to L14 of the first lens group constitute a first group of four-cemented lenses, and the lens L15 and lens L16 constitute a first group of two-cemented lenses; the lenses L21 to L24 of the second lens group constitute a second group of four-cemented lenses, and the lens L25 and lens L26 constitute a second group of two-cemented lenses.

[0013] Furthermore, the refractive index of the lens L15 in the first lens group is greater than 1.4 and less than 1.5, and the refractive index of the lens L21, the lens L23 and the lens L27 in the second lens group is greater than 1.6 and less than 1.7.

[0014] Furthermore, the Abbe number of lens L12 in the first lens group is greater than 65 and less than 70, and the Abbe numbers of lens L21, lens L22 and lens L25 in the second lens group are greater than 60 and less than 70.

[0015] Furthermore, the focal length adjustment range of the optical system composed of the first lens group and the second lens group is 79.66mm~85.56mm, and during the focal length adjustment range adjustment process of the optical system, the adjustment range of the relative aperture is 1.43mm~1.35mm, the adjustment range of the half field of view angle is 14.043°~14.253°, the adjustment range of the object distance is 740.35mm~infinity, the adjustment range of the distance between the variable aperture surface and the image side surface of the lens L16 is 7.722108mm~18.6067mm, and the adjustment range of the back focus is 47.980175mm~37.095582mm.

[0016] Furthermore, the total length of the optical system formed by the first lens group and the second lens group is greater than 156 mm and less than 163 mm.

[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] .

[0019] Beneficial effects of the present invention:

[0020] 1. The present invention adopts 14G (14 standard spherical lenses) to optimize the combination, thereby obtaining a telephoto video lens with a focal length of 85 mm, achieving large aperture, high resolution, small distortion and low dispersion.

[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 156 mm and less than 163 mm, the total optical length is reduced, the cost is reduced, and at the same time, it can also meet the requirements of matching camera modules with longer flange back focus. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of a long-focus, large-aperture, long-flange video lens with a focal length of 85 mm according to the present invention;

[0023] Figure 2 This is a longitudinal aberration diagram of a test of a long-focus, large-aperture, long-flange video lens with a focal length of 85 mm according to an embodiment of the present invention;

[0024] Figure 3 This is a lateral chromatic aberration diagram of a test of a long-focus, large-aperture, long-flange video lens with a focal length of 85 mm according to an embodiment of the present invention;

[0025] Figure 4 This is a field curvature distortion diagram of a test of a long-focus, large-aperture, long-flange video lens with a focal length of 85 mm according to an embodiment of the present invention;

[0026] Figure 5 This is an MTF defocus curve diagram of a test of a long-focus, large-aperture, long-flange video lens with a focal length of 85 mm according to an embodiment of the present invention;

[0027] Figure 6 This is an MTF curve diagram of a test of a long-focus, large-aperture, long-flange video lens with a focal length of 85 mm according to an embodiment of the present invention;

[0028] Figure 7 is a relative illumination curve diagram of a test of a long-focus, large-aperture, long-flange video lens with a focal length of 85 mm according to an embodiment of the present invention;

[0029] Figure 8 is a lateral chromatic aberration diagram of the video lens test described in Comparative Example 1 of the present invention;

[0030] Fig. 9 is a field curvature distortion diagram of the video lens test described in Comparative Example 1 of the present invention;

[0031] Fig.10 is a relative illumination curve diagram of the video lens test described in Comparative Example 1 of the present invention;

[0032] Fig.11 is a lateral chromatic aberration diagram of the video lens test described in Comparative Example 2 of the present invention;

[0033] Fig.12 : is an MTF defocus curve diagram of the video lens test described in Comparative Example 2 of the present invention;

[0034] Fig.13 is an MTF curve diagram of the video lens test described in Comparative Example 2 of the present invention;

[0035] Fig.14 It is a relative illumination curve diagram of the video lens test described in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0036] 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.

[0037] like Figure 1 As shown, the telephoto large aperture long flange video lens with a focal length of 85 mm described in 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. Among them,

[0038] 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 L16 arranged in sequence along the incident direction of light along the optical path, including a group of four-cemented lenses and a group of two-cemented lenses. Specifically, the lenses L11 to L14 constitute a first group of four-cemented lenses, and the lens L15 and lens L16 constitute a first group of two-cemented lenses; the refractive index of the lens L15 is greater than 1.4 and less than 1.5, and the Abbe number of the lens L12 is greater than 65 and less than 70.

[0039] The second lens group G2, as a movable focusing group, has positive optical power. The second lens group G2 is composed of lenses L21 to L28 arranged in sequence along the light incident direction of the optical path, including a group of four-cemented lenses and a group of two-cemented lenses. Specifically, the lenses L21 to L24 constitute a second group of four-cemented lenses, and the lens L25 and lens L26 constitute a second group of two-cemented lenses; the refractive index of the lens L21, the lens L23 and the lens L27 is greater than 1.6 and less than 1.7, and the Abbe number of the lens L21, the lens L22 and the lens L25 is greater than 60 and less than 70.

[0040] Moreover, the focal lengths of the first lens group G1 and the second lens group G2 of the telephoto large aperture long flange video lens with a focal length of 85 mm according to the present invention satisfy the following formula:

[0041] 0.36 <f2 / f1<0.43

[0042] Among them, 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; this formula expresses the corresponding relationship between the optical focal lengths of the first lens group G1 and the second lens group G2. If this formula is not satisfied, the back focus working distance of the optical system is too short, and it is impossible to match the camera module 100 with a long flange back focus.

[0043] Through experimental testing, the total length of the optical system of the long - focal - length large - aperture long - flange video lens with a focal length of 85 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 156 mm and less than 163 mm, meeting the requirements of a camera module 100 with a relatively long flange back - focal length. The focal - length adjustment range of the optical system is 79.66 mm to 85.56 mm. Moreover, during the adjustment process of the focal - length adjustment range, its relative aperture is adjusted in the range of 1.43 mm to 1.35 mm, the half - field angle is adjusted in the range of 14.043° to 14.253°, the object distance is adjusted in the range of 740.35 mm to infinity, the distance between the variable - aperture plane and the image - side surface of lens L16 is adjusted in the range of 7.722108 mm to 18.6067 mm, and the back - focal length is adjusted in the range of 47.980175 mm to 37.095582 mm.

[0044] When the long - focal - length large - aperture long - flange video lens with a focal length of 85 mm according to the present invention works, 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.

[0045] The present invention adopts an optimized combination of 14G (14 standard spherical lenses) to obtain a long - focal - length video lens with a focal length of 85 mm. When the focal - length values of the first lens group G1 and the second lens group G2 satisfy 0.36 < f2 / f1 < 0.43, by simultaneously using a set of four - cemented lenses and a set of double - cemented lenses in both the first lens group G1 and the second lens group G2 for compensation and adjustment, the optical path is optimized (because the long - flange back - focal length will affect the light - propagation path, increasing the refraction, reflection, and diffraction effects in the optical system). Moreover, the two sets of four - cemented lenses play a crucial role in correcting aberrations, especially in apochromatism, thereby improving the MTF resolution, optimizing chromatic aberration, reducing dispersion, ensuring that the optical system can still achieve the expected imaging effect, while reducing the total optical length of the optical system of the long - focal - length video lens, improving the assembly yield, and reducing costs. In short, the long - focal - length video lens according to the present invention realizes a large aperture, high resolution, small distortion, and low dispersion through the above - mentioned technical solutions, and can also meet the requirements of a camera module with a relatively long flange back - focal length.

[0046] The following further illustrates the long - focal - length large - aperture long - flange video lens with a focal length of 85 mm according to the present invention through examples and comparative examples. Example

[0047] The video lens in the embodiment of the present invention includes as Figure 1The first lens group G1, the variable aperture S and the second lens group G2 are shown in the figure. 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=0.39; the structure of the optical system composed of the first lens group G1 and the second lens group G2 is specifically shown in Table 1 below.

[0048] Table 1

[0049]

[0050] 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 2 below.

[0051] Table 2

[0052]

[0053] When the object moves from infinity to a close distance, the first lens group G1 is fixed in this embodiment, and the second lens group G2 moves toward the object to achieve focus, and the lens has a large aperture (see Figure 7 , which is a graph showing the video lens of the embodiment of the present invention for wavelength 0.546000 μm Relative illumination curve of light source test), high MTF resolution (see Figure 5 and Figure 6 ), small distortion (see Figure 4 , which is a field curvature distortion diagram of the video lens of the embodiment of the present invention tested with light sources of wavelengths of 0.435μm, 0.486μm, 0.546μm, 0.587μm and 0.656μm at a maximum field of view of 21.500 mm) and low dispersion (see Figure 2 and Figure 3 ,in Figure 2 This is a longitudinal aberration diagram of the video lens of the embodiment of the present invention tested with light sources having wavelengths of 0.435 μm, 0.486 μm, 0.546 μm, 0.587 μm and 0.656 μm when the pupil radius is 31.0034 mm. Figure 3 The lateral chromatic aberration diagram is a test of the video lens of the embodiment of the present invention under the maximum field of view of 21.5000 mm and the wavelength of 0.546000 μm. Comparative Example 1

[0054] 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=0.36, 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 as shown in Table 3 below.

[0055] Table 3

[0056]

[0057] The same method as in the embodiment was used for testing. From the test results of Comparative Example 1 ( Figure 8-10 ) compared with the embodiment found that:

[0058] 1. The total optical length of Example 1 increases by 28.78mm, resulting in increased costs, while the optical back focus decreases by 11.19mm, making it impossible to match the long flange camera module;

[0059] 2. The lateral chromatic aberration of comparative example 1 becomes larger, the optical distortion becomes larger, and the relative illumination decreases. Comparative Example 2

[0060] This comparative example 2 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 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=0.43, 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.

[0061] Table 4

[0062]

[0063] The same method as in the embodiment was used for testing. From the test results of Comparative Example 2 ( Figure 11-14 ) compared with the embodiment found that:

[0064] 1. The total optical length of Example 2 increases by 20.2mm, resulting in increased costs, while the optical back focus decreases by 11.13mm, making it impossible to match the long flange camera module;

[0065] 2. The lateral chromatic aberration of Comparative Example 2 becomes larger, the MTF resolution decreases, and the relative illumination decreases.

[0066] Therefore, it can be seen from the above embodiments and Comparative Examples 1 and 2 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 0.36 < f2 / f1 < 0.43, it will result in an excessively long overall optical length, an excessively short back focal length that cannot match a long flange camera, and defects such as attenuation of optical performance such as MTF, relative illumination, and chromatic aberration.

[0067] The above are the preferred embodiments 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 telephoto, large aperture, long flange video lens with a focal length of 85 mm, characterized in that: The lens is composed of a first lens group, a variable aperture and a second lens group which are sequentially arranged along the incident direction of light along the optical path; wherein, The first lens group is an immovable fixed group with positive optical power. The first lens group is composed of lenses L11 to L16 arranged in sequence along the incident direction of the light path, including a group of four cemented lenses and a group of two cemented lenses. Specifically, the lenses L11 to L14 of the first lens group constitute a first group of four cemented lenses, and the lens L15 and the lens L16 constitute a first group of two cemented lenses; The second lens group is a movable focusing group with positive focal power. The second lens group is composed of lenses L21 to L28 arranged in sequence along the incident direction of the light path, including a group of four cemented lenses and a group of two cemented lenses. Specifically, the lenses L21 to L24 of the second lens group constitute a second group of four cemented lenses, the lenses L25 and L26 constitute a second group of two cemented lenses, and single lenses L27 and L28; The structure of the optical system composed of the first lens group and the second lens group is specifically shown in the following table: 。 2. The long focal length, large aperture, long flange video lens with a focal length of 85 mm according to claim 1, characterized in that: The focal length adjustment range of the optical system composed of the first lens group and the second lens group is 79.66mm~85.56mm, and during the focal length adjustment process, the adjustment range of the relative aperture is 1.43mm~1.35mm, the adjustment range of the half field angle is 14.043°~14.253°, the adjustment range of the object distance is 740.35mm~infinity, the adjustment range of the distance between the variable aperture surface and the image side surface of the lens L16 is 7.722108mm~18.6067mm, and the adjustment range of the back focus is 47.980175mm~37.095582mm.

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