Low-distortion video communication optical system and camera device

Abstract

The application provides a low-distortion video communication optical system, which comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens arranged in sequence along the direction from the object side to the image side, wherein the first lens is a glass lens with negative optical power; the second lens is a plastic aspheric lens with negative optical power; the third lens is a plastic aspheric lens with positive optical power; the fourth lens is a glass lens with positive optical power; the fifth lens is a plastic aspheric lens with negative optical power; and the sixth lens is a plastic aspheric lens with positive optical power. The low-distortion video communication optical system is composed of lenses with specific structural shapes and reasonable optical power distribution, effectively improves the MTF resolution and reduces the distortion of the lens, and has the following advantages: the MTF resolution is high and uniform, and can meet the requirement of 4K high-definition pixels; the 2G4P glass-plastic hybrid technology structure is adopted, four plastic lenses reduce the cost and the weight of the lens, and high and low temperature stability is also achieved; the field angle is large, the TV distortion is small and positive, and the shooting effect is better.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical imaging technology, in particular to a low-distortion video communication optical system and a camera device. BACKGROUND

[0002] With the increase and upgrading of off-site office and network classroom tutoring needs, the demand for camera devices for video communication conference systems is also rapidly rising. Traditional audio and video communication cannot meet the needs of users, and optical systems and camera devices with high definition, large angle, small distortion and automatic zoom are becoming the goal pursued in the industry. The video communication optical systems and camera devices on the existing market mostly have low and uneven MTF resolution, cannot match more than 8 million pixel chips, have complex structures, high costs, large lens volume and length, poor high and low temperature stability, small angle and negative distortion, and poor camera effect than positive distortion.

[0003] Therefore, a low-distortion video communication optical system and a camera device are provided. SUMMARY

[0004] The present application aims to solve the problems of low and uneven MTF resolution, poor high and low temperature stability, small field of view, and large distortion of the video communication optical systems and camera devices on the existing market, and provides a low-distortion video communication optical system and a camera device.

[0005] The specific technical solutions are as follows:

[0006] A low-distortion video communication optical system comprises, in order from the object side to the image side, a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens, wherein:

[0007] The first lens is a glass lens with negative optical power; the second lens is a plastic aspheric lens with negative optical power; the third lens is a plastic aspheric lens with positive optical power; the fourth lens is a glass lens with positive optical power; the fifth lens is a plastic aspheric lens with negative optical power; and the sixth lens is a plastic aspheric lens with positive optical power.

[0008] The low-distortion video communication optical system described above, wherein the refractive index of the second lens and the sixth lens is equal to 1.54, and the Abbe number is greater than 55 and less than 56.5; the refractive index of the third lens and the fifth lens is equal to 1.66, and the Abbe number is greater than 20 and less than 22; and the refractive index of the first lens and the fourth lens is greater than 1.6 and less than 1.9, and the Abbe number is greater than 45 and less than 65.

[0009] In the aforementioned low-distortion video communication optical system, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the focal length of the fourth lens is f4, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, and the overall focal length of the optical system is f. The optical power satisfies the following relationship:

[0010] -7.5 <f1 / f<-5.5;

[0011] -3.5 <f2 / f<-2;

[0012] 4 <f3 / f<6;

[0013] 2 <f4 / f<3.5;

[0014] -3.5 <f5 / f<-1.5;

[0015] 1 <f6 / f<3。

[0016] The aforementioned low-distortion video communication optical system, wherein,

[0017] The first lens has a convex surface facing the object side and a concave surface facing the image side;

[0018] The second lens has a convex surface facing the object side and a concave surface facing the image side;

[0019] The third lens has a convex surface facing the object side and a concave surface facing the image side.

[0020] The fourth lens has two convex surfaces; the fifth lens has two concave surfaces.

[0021] The sixth lens has two convex surfaces.

[0022] The aforementioned low-distortion video communication optical system further includes an aperture stop ST located between the third lens and the fourth lens.

[0023] In the aforementioned low-distortion video communication optical system, the total optical length (TTL) of the optical system satisfies the following condition: 19.5mm ≤ TTL ≤ 21mm.

[0024] In the aforementioned low-distortion video communication optical system, a protective glass is also provided between the sixth lens and the image plane.

[0025] The present invention also proposes a camera device, including the low-distortion video communication optical system described in any of the above claims.

[0026] The present invention has the following beneficial effects:

[0027] The low-distortion video communication optical system provided by this invention includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens arranged sequentially along the object-side to the image-side. The first and fourth lenses are glass lenses, while the second, third, fifth, and sixth lenses are all plastic aspherical lenses. This optical system, composed of lenses with specific structural shapes and a reasonable power distribution, effectively improves MTF resolution and reduces lens distortion. This low-distortion video communication optical system has the following advantages:

[0028] 1. The MTF resolution is high and uniform, which can meet the requirements of 4K high-definition pixels;

[0029] 2. It adopts a 2G4P glass-plastic hybrid technology structure, with four plastic lenses to reduce costs and lens weight, while also achieving high and low temperature stability;

[0030] 3. It has a large field of view, small TV distortion and positive distortion, resulting in better video quality. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of a low-distortion video communication optical system provided in an embodiment of the present invention;

[0032] Figure 2 The MTF (Mean Transformation Graph) of the low-distortion video communication optical system provided in this embodiment of the invention at 20°C is 125 lp / mm.

[0033] Figure 3 A defocus curve of 125 lp / mm for a low-distortion video communication optical system provided in an embodiment of the present invention at 20°C;

[0034] Figure 4 A defocus curve of 125 lp / mm at 85°C for a low-distortion video communication optical system provided in an embodiment of the present invention;

[0035] Figure 5 A defocus curve of 125 lp / mm for a low-distortion video communication optical system provided in an embodiment of the present invention at -40℃;

[0036] Figure 6 A relative illumination diagram of a low-distortion video communication optical system provided in an embodiment of the present invention;

[0037] Figure 7 Field curvature diagram of a low-distortion video communication optical system provided in an embodiment of the present invention;

[0038] Figure 8 The TV distortion diagram of a low-distortion video communication optical system provided in an embodiment of the present invention. Detailed Implementation

[0039] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0040] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual images. They should not be construed as limiting the scope of this patent. To better illustrate the embodiments of the present invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0041] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present patent. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0042] In the description of this invention, unless otherwise explicitly specified and limited, the term "connection" or similar designation indicating a connection between components should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0043] like Figures 1-8 As shown, the low-distortion video communication optical system provided in this embodiment of the invention includes: a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, and a sixth lens E6 arranged sequentially along the direction from the object side to the image side, wherein:

[0044] The first lens E1 is a glass lens with negative optical power; the second lens E2 is a plastic aspherical lens with negative optical power; the third lens E3 is a plastic aspherical lens with positive optical power; the fourth lens E4 is a glass lens with positive optical power; the fifth lens E5 is a plastic aspherical lens with negative optical power; and the sixth lens E6 is a plastic aspherical lens with positive optical power.

[0045] Specifically, in this embodiment, the refractive index of the second lens E2 and the sixth lens E6 are both equal to 1.54, and the Abbe coefficients are both greater than 55 and less than 56.5; the refractive index of the third lens E3 and the fifth lens E5 are both equal to 1.66, and the Abbe coefficients are both greater than 20 and less than 22; the refractive index of the first lens E1 and the fourth lens E4 are both greater than 1.6 and less than 1.9, and the Abbe coefficients are both greater than 45 and less than 65.

[0046] Specifically, in this embodiment, the focal length of the first lens E1 is f1, the focal length of the second lens E2 is f2, the focal length of the third lens E3 is f3, the focal length of the fourth lens E4 is f4, the focal length of the fifth lens E5 is f5, the focal length of the sixth lens E6 is f6, and the overall focal length of the optical system is f. The optical power satisfies the following relationship: -7.5 <f1 / f<-5.5;-3.5<f2 / f<-2;4<f3 / f<6;2<f4 / f<3.5;-3.5<f5 / f<-1.5;1<f6 / f<3。

[0047] Specifically, in this embodiment,

[0048] The object-side surface of the first lens E1 is convex, and the image-side surface is concave.

[0049] The second lens E2 has a convex surface facing the object side and a concave surface facing the image side;

[0050] The third lens E3 has a convex surface facing the object side and a concave surface facing the image side;

[0051] The fourth lens E4 has two convex surfaces; the fifth lens E5 has two concave surfaces.

[0052] The sixth lens, E6, has two convex surfaces.

[0053] Specifically, in this embodiment, the aforementioned low-distortion video communication optical system further includes an aperture stop device ST, which is located between the third lens E3 and the fourth lens E4.

[0054] Specifically, in this embodiment, the total optical length (TTL) of the optical system satisfies the following condition: 19.5mm ≤ TTL ≤ 21mm.

[0055] Specifically, in this embodiment, a protective glass is provided between the sixth lens E6 and the image plane.

[0056] The present invention also provides a camera device, including the low-distortion video communication optical system of any of the above.

[0057] Specifically, in this embodiment, the parameters S1-17 of the lens group composed of the first lens E1, the second lens E2, the third lens E3, the fourth lens E4, the fifth lens E5, and the sixth lens E6 are listed in the following order:

[0058] In Table 1:

[0059] surf Radius Thickness Index ABB EFL-E OBJ infinity infinity 1 12.4 0.9 1.77 49.6 -12.031 2 5.145 1.163372991 3 7.32 1.41 1.54 55.8 -5.298 4 1.910 3.076242431 5 5.953 4.25 1.66 20.4 8.969 6 500 0.114192269 7 infinity 0 8 infinity 0.4 STO infinity 0.340767302 10 22.1 1.8 1.73 54.7 4.337 11 -3.579 0.1 12 -6.000856129 0.6 1.66 20.4 -4.504 13 6.287501827 0.2 14 4.465 2.47 1.54 55.7 3.935 15 -3.237464879 0.5 16 infinity 0.7 1.52 64.2 17 infinity 2.348194916 IMA infinity 0

[0060] Table 1

[0061] Aspherical coefficients are shown in Table 2:

[0062]

[0063]

[0064]

[0065] Table 2

[0066] The aspherical coefficients satisfy the following equation:

[0067]

[0068] Where z is the aspherical sagitta, c is the paraxial curvature of the aspherical surface, y is the lens aperture, k is the conic coefficient, a4 is the 4th order aspherical coefficient, a6 is the 6th order aspherical coefficient, a8 is the 8th order aspherical coefficient, a10 is the 10th order aspherical coefficient, and a12 is the 12th order aspherical coefficient.

[0069] Specifically, the R-values ​​and thicknesses of each lens surface in this embodiment are shown in Table 1, and the aspherical parameters are shown in Table 2.

[0070] The optical system provided in Table 1 has an effective focal length of 1.85mm, an aperture of f / 2.5, a total length of 20.3mm, a full field of view of 125°, and a full image height of φ6.97mm. In Table 1, mirror numbers 1 and 2 represent the two mirrors of lens 1 along the direction of light incidence, mirror numbers 3 and 4 represent the two mirrors of lens 2 along the direction of light incidence, mirror numbers 5 and 6 represent the two mirrors of lens 3 along the direction of light incidence, mirror numbers 10 and 11 represent the two mirrors of lens 4 along the direction of light incidence, mirror numbers 12 and 13 represent the two mirrors of lens 5 along the direction of light incidence, mirror numbers 14 and 15 represent the two mirrors of lens 6 along the direction of light incidence, and mirror numbers 16 and 17 represent the two mirrors of the filter along the direction of light incidence.

[0071] In an embodiment of the present invention, Figure 2The graph shows the modulation transfer function (MTF) curve, representing the overall resolving power of an optical system. The horizontal axis represents spatial frequency (cycles per millimeter), and the vertical axis represents the MTF value. The MTF value is used to evaluate the image quality of a lens, ranging from 0 to 1. It's important to note that the optical transfer function is a relatively accurate, intuitive, and common way to evaluate the image quality of an optical system. A higher and smoother curve indicates better image quality and a stronger ability to reproduce the true image. Figure 2 It can be seen that in the visible light band, at a spatial frequency of 125 lp / mm, the MTF of the imaging area near the center is >0.6, and the imaging quality is very good. The optical system provided by this specific implementation method corrects various aberrations, such as spherical aberration, coma, astigmatism, field curvature, magnification chromatic aberration, and positional chromatic aberration, thereby improving the resolution. Figure 3 This is the defocusing curve at 20℃ with a resolution of 125 lp / mm. Figure 4 This is the defocusing curve at 125 lp / mm at a high temperature of 85℃. Figure 5 This is a defocusing curve at a low temperature of -40℃ with a focal length of 125 lp / mm. Figure 6 This is a relative illumination map. Figure 7 and Figure 8 These represent the field curvature diagram and the TV distortion diagram, respectively, by Figures 2-8 As can be seen, the optical system in this embodiment can effectively correct aberrations by reasonably allocating the focal lengths of positive and negative lenses, thereby improving MTF resolution, reducing TV distortion of the lens, and solving the focus drift problem caused by ambient temperature.

[0072] In summary, the low-distortion video communication optical system provided by this invention includes a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, and a sixth lens E6 arranged sequentially along the object-to-image direction. The first lens E1 and the fourth lens E4 are glass lenses, while the second lens E2, the third lens E3, the fifth lens E5, and the sixth lens E6 are all plastic aspherical lenses. This optical system, composed of lenses with specific structural shapes and a reasonable power distribution, effectively improves MTF resolution and reduces lens distortion. This low-distortion video communication optical system has the following advantages:

[0073] 1. The MTF resolution is high and uniform, which can meet the requirements of 4K high-definition pixels;

[0074] 2. It adopts a 2G4P glass-plastic hybrid technology structure, with four plastic lenses to reduce costs and lens weight, while also achieving high and low temperature stability;

[0075] 3. It has a large field of view, small TV distortion and positive distortion, resulting in better video quality.

[0076] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-distortion video communication optical system, characterized in that, include: The six lenses arranged sequentially from the object side to the image side are the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens, wherein: The first lens is a glass lens with negative optical power; the second lens is a plastic aspherical lens with negative optical power; the third lens is a plastic aspherical lens with positive optical power; the fourth lens is a glass lens with positive optical power; the fifth lens is a plastic aspherical lens with negative optical power; and the sixth lens is a plastic aspherical lens with positive optical power. The refractive index of the second lens and the sixth lens is 1.54, and the Abbe number is greater than 55 and less than 56.5; the refractive index of the third lens and the fifth lens is 1.66, and the Abbe number is greater than 20 and less than 22; the refractive index of the first lens and the fourth lens is greater than 1.6 and less than 1.9, and the Abbe number is greater than 45 and less than 65. The first lens has a focal length of f1, the second lens has a focal length of f2, the third lens has a focal length of f3, the fourth lens has a focal length of f4, the fifth lens has a focal length of f5, the sixth lens has a focal length of f6, and the overall focal length of the optical system is f. The optical power satisfies the following relationship: -7.5 <f1 / f<-5.5;-3.5<f2 / f<-2;4<f3 / f<6;2<f4 / f<3.5; -3.5 <f5 / f<-1.5; 1 <f6 / f<3; The second lens has a convex surface facing the object side and a concave surface facing the image side; The first lens has a convex surface facing the object side and a concave surface facing the image side; The third lens has a convex surface facing the object side and a concave surface facing the image side. The fourth lens has two convex surfaces; the fifth lens has two concave surfaces. The sixth lens has two convex surfaces.

2. The low-distortion video communication optical system according to claim 1, characterized in that, It also includes an aperture stop device ST, which is located between the third lens and the fourth lens.

3. The low-distortion video communication optical system according to claim 1, characterized in that, The total optical length (TTL) of the optical system satisfies the following condition: 19.5mm ≤ TTL ≤ 21mm.

4. The low-distortion video communication optical system according to claim 1, characterized in that, A protective glass is also provided between the sixth lens and the image plane.

5. A camera device, characterized in that, Includes the low-distortion video communication optical system according to any one of claims 1-4.

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