Wide-angle large-aperture long-flange video lens with focal length of 24mm

Abstract

The invention relates to a wide-angle large-aperture long-flange video lens with a focal length of 24mm, which comprises a first lens group and a second lens group which are sequentially arranged along the light incidence direction of a light path, and further comprises an iris diaphragm which is arranged in the second lens group; the first lens group serves as a fixed group, the focal power of the first lens group is positive, and the first lens group is composed of lenses L11-L18 which are sequentially arranged in the light incidence direction of a light path; the second lens group serves as a focusing group, the focal power of the second lens group is positive, and the second lens group is composed of lenses L21-L28 which are sequentially arranged in the light incidence direction of the light path; the first lens group and the second lens group satisfy 0.36 lt; f2 / f1lt; f1 represents the focal length value of the first lens group, and f2 represents the focal length value of the second lens group; therefore, the lens has the advantages of high resolution, large aperture, small distortion and small chromatic aberration.

Description

Technical Field

[0001] The invention belongs to the technical field of photographic lenses, and in particular relates to a wide-angle, large-aperture, long-flange video lens with a focal length of 24 mm. Background Art

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

[0003] However, the applicant found that the short-focus video lenses currently on the market generally have shortcomings such as low resolution, excessive distortion, small aperture, long optical length and short flange back focus, which cannot meet the high requirements of the field of view required for movie shooting, especially short-focus video lenses with a focal length of 24mm. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a wide-angle, large-aperture, long-flange video lens with a focal length of 24 mm.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions: The present invention provides a wide-angle, large-aperture, long-flange video lens with a focal length of 24 mm, the lens comprising a first lens group and a second lens group sequentially arranged along the incident direction of light along an optical path, and also comprising a variable iris, the variable iris being arranged in the second lens group; wherein, The first lens group is a fixed group with positive optical power, and is composed of lenses L11 to L18 arranged in sequence along the incident direction of the light path; The second lens group is a focusing group with positive optical power, and the second lens group is composed of lenses L21 to L28 arranged in sequence along the incident direction of the light path; And the first lens group and the second lens group satisfy the following formula: 0.36 <f2 / f1<0.44 Wherein, f1 represents the focal length value of the first lens group, and f2 represents the focal length value of the second lens group.

[0006] Furthermore, the variable aperture is arranged between the lens L22 and the lens L23.

[0007] Furthermore, the optical system contains two glass aspherical lenses, namely lens L13 of the first lens group and lens L28 of the second lens group.

[0008] Furthermore, the object side coefficients of the lens L13 are: K=-2.876523952, E4=0.000010495986460430, E6=-0.000000028363851874, E8=0.000000000071898491, E10=-0.0000000000000051943, R1=94.218758243; The image side coefficients of the lens L13 are: K=-1.008655314, E4=0.000005799440018926, E6=-0.0000000031003395997, E8=-0.0000000000123571109, E10=0.000000000000751939, E12=-0.0000000000000001723, R2=21.587115529; The object side coefficients of the lens L28 of the second lens group are: K=0.000000000, E4=-0.000014121315777320, E6=-0.000000030601349490, E8=0.0000000000097245102, E10=-0.000000000000442273, E12=0.000000000000000767, R1=-83.509908631; The image side coefficients of the lens L28 are: K=0.000000000, E4=-0.000008755901152306, E6=-0.000000026955244583, E8=0.000000000082106050, E10=-0.000000000000296455, E12=0.000000000000000438, R2=-51.501175972.

[0009] Furthermore, the optical system formed by the first lens group and the second lens group includes three groups of doublet-cemented lens sheets and one group of triplet-cemented lens sheets.

[0010] Furthermore, lens L14 and lens L15 of the first lens group constitute a first group of double-cemented lenses, lens L16 and lens L17 constitute a second group of double-cemented lenses, lens L21 and lens L22 of the second lens group constitute a third group of double-cemented lenses, and lenses L23 to L25 of the second lens group constitute a group of triple-cemented lenses.

[0011] Furthermore, at least three lenses in the first lens group have a refractive index greater than 1.65 and less than 1.75, and at least two lenses in the second lens group have a refractive index greater than 1.45 and less than 1.55.

[0012] Furthermore, at least two lenses in the first lens group have an Abbe number greater than 18 and less than 28, and at least two lenses in the second lens group have an Abbe number greater than 77 and less than 83.

[0013] 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, the focal length adjustment range of the optical system is 23.48 mm to 23.81 mm, and during the focal length adjustment range adjustment process of the optical system, the aperture adjustment range is 1.36 mm to 1.30 mm, the half field angle adjustment range is 42.603° to 42.641°, the object distance adjustment range is 141 mm to infinity, the distance adjustment range between the image side surface of lens L18 and the object side surface of lens L21 is 2.186779 mm to 5.5003 mm, and the back focus adjustment range is 40.324315 mm to 37.010793 mm.

[0014] 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: .

[0015] Beneficial effects of the present invention: 1. The present invention adopts an optimized combination of 14 standard spherical lenses and 2 aspherical lenses to obtain a short-focus 24mm movie lens that can optimize small distortion and good chromatic aberration while meeting the requirements of optimizing high resolution and large aperture.

[0016] 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 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 a camera module with a longer flange back focus. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of a wide-angle, large-aperture, long-flange video lens with a focal length of 24 mm according to the present invention; Figure 2 is a relative illumination curve diagram of a wide-angle, large-aperture, long-flange video lens with a focal length of 24 mm according to an embodiment of the present invention; Figure 3 is a lateral chromatic aberration diagram of a wide-angle, large-aperture, long-flange video lens with a focal length of 24 mm according to an embodiment of the present invention; Figure 4is a field curvature distortion diagram of a wide-angle, large-aperture, long-flange video lens with a focal length of 24 mm according to an embodiment of the present invention; Figure 5 is an MTF curve diagram of a wide-angle, large-aperture, long-flange video lens with a focal length of 24 mm according to an embodiment of the present invention; Figure 6 This is an MTF defocus curve diagram of a wide-angle, large-aperture, long-flange video lens with a focal length of 24 mm according to an embodiment of the present invention; Figure 7 is a lateral chromatic aberration diagram of the video lens test described in Comparative Example 1 of the present invention; Figure 8 is a field curvature distortion diagram of the video lens test described in Comparative Example 1 of the present invention; Fig. 9 is an MTF curve diagram of the video lens test described in Comparative Example 1 of the present invention; Fig.10 is a lateral chromatic aberration diagram of the video lens test described in Comparative Example 2 of the present invention; Fig.11 is a field curvature distortion diagram of the video lens test described in Comparative Example 2 of the present invention; Fig.12 It is an MTF curve diagram of the video lens test described in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0018] 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.

[0019] like Figure 1 As shown, the wide-angle, large-aperture, long-flange video lens with a focal length of 24 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. The first lens group G1, as a fixed group, has a positive focal power, and is composed of lenses L11 to L18 arranged in sequence along the light incident direction of the optical path; the second lens group G2, as a focusing group, has a positive focal power, and is composed of lenses L21 to L28 arranged in sequence along the light incident direction of the optical path; wherein the optical system composed of the first lens group G1 and the second lens group G2 contains two glass aspherical lenses, which are the third lens and the sixteenth lens from the light incident direction of the lens optical path (i.e., lens L13 of the first lens group and lens L28 of the second lens group), and the remaining 14 lenses are all standard spherical lenses; the structural parameters of the two glass aspherical lenses are specifically as shown in Table 1: Table 1

[0020] In the table, K is the quadratic curve constant, E4, E6, E8, E10 and E12 are aspheric surface processing coefficients, and R1 and R2 are curvature radii.

[0021] Moreover, the first lens group G1 and the second lens group G2 satisfy the following formula: 0.36 <f2 / f1<0.44 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 this formula is not satisfied, optical properties such as MTF, chromatic aberration and optical distortion will be attenuated.

[0022] For example Figure 1 As shown, the wide-angle, large-aperture, long-flange video lens with a focal length of 24 mm of the present invention further includes a variable iris S, and the variable iris S is arranged in the second lens group G2. Specifically, the variable iris S is arranged between the lens L22 and the lens L23.

[0023] When the wide-angle, large-aperture, long-flange video lens with a focal length of 24 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.

[0024] Through experimental tests, the total length of the optical system of the wide-angle, large aperture, long flange video lens with a focal length of 24 mm described in the present invention, which is composed of the above-mentioned first lens group G1 and the second lens group G2, is greater than 157 mm and less than 163 mm, which meets the requirements of matching the camera module 100 with a longer flange back focus. The focal length adjustment range of the optical system is 23.48 mm to 23.81 mm, and in the process of adjusting the focal length adjustment range, the aperture is adjusted in the range of 1.36 mm to 1.30 mm, the half field of view angle is adjusted in the range of 42.603° to 42.641°, the object distance is adjusted in the range of 141 mm to infinity, the distance between the image side surface of lens L18 and the object side surface of lens L21 is adjusted in the range of 2.186779 mm to 5.5003 mm, and the back focus is adjusted in the range of 40.324315 mm to 37.010793 mm.

[0025] By adopting the optimized combination of 14G2GM (14 standard spherical lenses and 2 aspherical lenses), the present invention can obtain a short-focus 24mm cine 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 f1 of the first lens group G1 and the focal length f2 of the second lens group G2 satisfy 0.36 < f2 / f1 < 0.44, 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.

[0026] In addition, the present invention also optimizes the overall optical length by adopting a compact optical structure, making the overall length of the optical system composed of the first lens group G1 and the second lens group G2 greater than 157 mm and less than 163 mm, reducing the overall optical length; at the same time, it can also meet the camera module 100 with a relatively long flange back focus.

[0027] In a possible implementation scheme, at least three lenses in the first lens group G1 have a refractive index greater than 1.65 and less than 1.75, at least two lenses in the second lens group G2 have a refractive index greater than 1.45 and less than 1.55, at least two lenses in the first lens group G1 have an Abbe number greater than 18 and less than 28, at least two lenses in the second lens group G2 have an Abbe number greater than 77 and less than 83, and the optical system composed of the first lens group G1 and the second lens group G2 includes three doublet lenses and one triplet lens.

[0028] The following further illustrates the wide-angle large-aperture long-flange video lens with a focal length of 24 mm according to the present invention through examples and comparative examples. Example

[0029] The video lens in the embodiment of the present invention includes the first lens group G1, the second lens group G2, and the variable aperture S as shown in Figure 1 The variable aperture 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 repeated here. Among them, 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 in this embodiment is: f2 / f1 = 0.397; the specific structure of the optical system composed of the first lens group G1 and the second lens group G2 is as shown in Table 2 below.

[0030] Table 2

[0031] 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 as shown in Table 3 below.

[0032] Table 3

[0033] 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 and high resolution (see Figure 5 and Figure 6 ), large aperture (see Figure 2 , 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), small distortion (see Figure 4 , which is a graph of the field curvature distortion and chromatic aberration 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) 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

[0034] 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 shown in Table 4 below.

[0035] Table 4

[0036] The structural parameters of the two glass aspherical lenses (lens L13 and lens L28) are shown in Table 5 below.

[0037] Table 5

[0038] The same method as in the embodiment was used for testing. From the test results of Comparative Example 1 ( Figure 7-9 ) compared with the embodiment, it is found that in the optical performance of the lens of comparative example 1, the lateral chromatic aberration becomes larger, the MTF resolution decreases and the optical distortion becomes larger. Comparative Example 2

[0039] This Comparative Example 2 is basically the same as the video lens described in the embodiment, including a first lens group G1, an iris diaphragm 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 = 0.44, 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.

[0040] Table 6

[0041] The structural parameters of two glass aspherical lenses (lens L13 and lens L28) are specifically as shown in Table 7 below.

[0042] Table 7

[0043] 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 ) and the embodiment, it was found that: like Comparative Example 1, for the lens of Comparative Example 2, in terms of optical performance, the lateral chromatic aberration becomes larger, the MTF resolution decreases, and the optical distortion becomes larger.

[0044] 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 0.36 < f2 / f1 < 0.44, it will lead to defects such as attenuation of optical performance such as MTF, chromatic aberration, and optical distortion.

[0045] 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 wide-angle, large-aperture, long-flange video lens with a focal length of 24 mm, characterized in that: The lens comprises a first lens group and a second lens group which are sequentially arranged along the incident direction of light along the optical path, and also comprises a variable diaphragm which is arranged in the second lens group; wherein, The first lens group is a fixed group with positive optical power, and is composed of lenses L11 to L18 arranged in sequence along the incident direction of the light path; The second lens group is a focusing group with positive optical power, and the second lens group is composed of lenses L21 to L28 arranged in sequence along the incident direction of the light path; And the first lens group and the second lens group satisfy the following formula: 0.36 <f2 / f1<0.44 Wherein, f1 represents the focal length of the first lens group, and f2 represents the focal length of the second lens group; The optical system composed of the first lens group and the second lens group contains two glass aspherical lenses, namely lens L13 of the first lens group and lens L28 of the second lens group; The object side coefficients of the lens L13 are: K=-2.876523952, E4=0.000010495986460430, E6=-0.000000028363851874, E8=0.000000000071898491, E10=-0.0000000000000051943, R1=94.218758243; The image side coefficients of the lens L13 are: K=-1.008655314, E4=0.000005799440018926, E6=-0.0000000031003395997, E8=-0.0000000000123571109, E10=0.000000000000751939, E12=-0.0000000000000001723, R2=21.587115529; The object side coefficients of the lens L28 of the second lens group are: K=0.000000000, E4=-0.000014121315777320, E6=-0.000000030601349490, E8=0.0000000000097245102, E10=-0.000000000000442273, E12=0.000000000000000767, R1=-83.509908631; The image side coefficients of the lens L28 are: K=0.000000000, E4=-0.000008755901152306, E6=-0.000000026955244583, E8=0.000000000082106050, E10=-0.000000000000296455, E12=0.000000000000000438, R2=-51.501175972.

2. The wide-angle, large-aperture, long-flange video lens with a focal length of 24 mm according to claim 1, characterized in that: The variable aperture is disposed between the lens L22 and the lens L23.

3. The wide-angle, large-aperture, long-flange video lens with a focal length of 24 mm according to claim 1, characterized in that: The optical system formed by the first lens group and the second lens group includes three groups of doublet-cemented lens sheets and one group of triplet-cemented lens sheets.

4. The wide-angle, large-aperture, long-flange video lens with a focal length of 24 mm according to claim 3, characterized in that: The lens L14 and the lens L15 of the first lens group constitute a first group of double-cemented lenses, the lens L16 and the lens L17 constitute a second group of double-cemented lenses, the lens L21 and the lens L22 of the second lens group constitute a third group of double-cemented lenses, and the lenses L23 to L25 of the second lens group constitute a group of triple-cemented lenses.

5. The wide-angle, large-aperture, long-flange video lens with a focal length of 24 mm according to claim 1, 2, 3 or 4, characterized in that: The refractive index of at least three lenses in the first lens group is greater than 1.65 and less than 1.75, and the refractive index of at least two lenses in the second lens group is greater than 1.45 and less than 1.

55.

6. The wide-angle, large-aperture, long-flange video lens with a focal length of 24 mm according to claim 5, characterized in that: At least two lenses in the first lens group have an Abbe number greater than 18 and less than 28, and at least two lenses in the second lens group have an Abbe number greater than 77 and less than 83.

7. The wide-angle, large-aperture, long-flange video lens with a focal length of 24 mm according to claim 1, 2, 3, 4, or 6, characterized in 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. The focal length adjustment range of the optical system is 23.48 mm to 23.81 mm. In the process of adjusting the focal length adjustment range, the adjustment range of the aperture is 1.36 mm to 1.30 mm, the adjustment range of the half field angle is 42.603° to 42.641°, the adjustment range of the object distance is 141 mm to infinity, the adjustment range of the distance between the image side surface of lens L18 and the object side surface of lens L21 is 2.186779 mm to 5.5003 mm, and the adjustment range of the back focus is 40.324315 mm to 37.010793 mm.

8. The wide-angle, large-aperture, long-flange video lens with a focal length of 24 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: 。

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