CN216387548U

CN216387548U - Positive distortion fisheye lens

Info

Publication number: CN216387548U
Application number: CN202123155270.4U
Authority: CN
Inventors: 范智宇; 张荣曜; 李智发; 杜鹏伟
Original assignee: Xiamen Leading Optics Co Ltd
Current assignee: Xiamen Leading Optics Co Ltd
Priority date: 2021-12-15
Filing date: 2021-12-15
Publication date: 2022-04-26
Anticipated expiration: 2031-12-15

Abstract

The utility model discloses a positive distortion fisheye lens which comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens which are sequentially arranged from an object side to an image side along an optical axis, wherein the first lens has negative diopter, the second lens has negative diopter, the third lens has positive diopter, the fourth lens has positive diopter, the fifth lens has negative diopter, and the sixth lens has positive diopter. The positive distortion fisheye lens has high resolution, small volume and convenient installation and use, and can still keep high-definition color imaging in a low-illumination environment due to the large-light-transmission design; meanwhile, the distortion is small and is a positive value, the pixel proportion of edge imaging is improved, and later-stage algorithm processing is facilitated.

Description

Positive distortion fisheye lens

Technical Field

The utility model relates to the technical field of optical lenses, in particular to a positive distortion fisheye lens.

Background

A fisheye lens is a lens having a focal length of 16mm or less and a viewing angle close to or equal to 180 °. It is an extreme wide-angle lens, and the "fish-eye lens" is its common name. In order to maximize the angle of view of the lens, the front lens of the lens is short in diameter and is parabolic and convex toward the front of the lens, much like the fish eye, so called "fish-eye lens".

The prior fisheye lens has a larger field angle, so that the light passing is generally smaller; the lenses are more in use, the TTL is longer, the structure is complex, the size is large, and the installation is not facilitated; in addition, the F-theta distortion of the existing fisheye lens is usually negative, the edge imaging is compressed, and the requirement of edge high-definition imaging cannot be met.

In view of the above, the inventors of the present application invented a positive distortion fisheye lens.

SUMMERY OF THE UTILITY MODEL

The utility model aims to provide a fisheye lens with large light transmission, small volume and positive F-theta distortion.

In order to achieve the purpose, the utility model adopts the following technical scheme: a positive distortion fisheye lens comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens which are sequentially arranged from an object side to an image side along an optical axis, wherein the first lens to the sixth lens respectively comprise an object side surface facing the object side and allowing imaging light rays to pass and an image side surface facing the image side and allowing the imaging light rays to pass;

the first lens has negative diopter, and the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface;

the second lens has negative diopter, and the object side surface of the second lens is a convex surface, and the image side surface of the second lens is a concave surface;

the third lens has positive diopter, the object side surface of the third lens is a concave surface, and the image side surface of the third lens is a convex surface;

the fourth lens has positive diopter, and the object side surface of the fourth lens is a convex surface, and the image side surface of the fourth lens is a convex surface;

the fifth lens has negative diopter, the object side surface of the fifth lens is a concave surface, and the image side surface of the fifth lens is a concave surface;

the sixth lens element has a positive refractive power, and an object-side surface of the sixth lens element is a convex surface and an image-side surface of the sixth lens element is a convex surface.

Further, the first lens and the second lens are meniscus lenses.

Furthermore, the second lens, the fourth lens and the fifth lens are all plastic aspheric lenses, and the object-side surface and the image-side surface of the second lens, the fourth lens and the fifth lens are all aspheric surfaces.

Further, the lens satisfies: 1.69< nd1<1.85, 1.6< nd2<1.7, 1.9< nd3<2.051.5< nd4<1.6, 1.6< nd5<1.7, 1.5< nd6<1.6,

and nd1, nd2, nd3, nd4, nd5 and nd6 are refractive indexes of the first lens, the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens respectively.

Further, the lens satisfies: 45< vd1<60, 20< vd2<30, 20< vd3<35, 45< vd4<60, 20< vd5<30, 65< vd6<85,

wherein vd1, vd2, vd3, vd4, vd5 and vd6 are the abbe numbers of the first lens, the second lens and the third lens respectively.

Further, the lens further comprises a diaphragm, and the diaphragm is arranged on the object side surface of the third lens.

Further, the effective apertures of the first lens to the sixth lens are all smaller than 13 mm.

Further, the light transmittance F/#ofthe lens is 1.7.

Further, the optical TTL of the lens is <19 mm.

After the technical scheme is adopted, the utility model has the following advantages:

the positive distortion fisheye lens has high resolution, small volume and convenient installation and use, and can still keep high-definition color imaging in a low-illumination environment due to the large-light-transmission design; meanwhile, the distortion is small and is a positive value, the pixel proportion of edge imaging is improved, and later-stage algorithm processing is facilitated.

Drawings

FIG. 1 is a light path diagram of embodiment 1 of the present invention;

fig. 2 is a graph of MTF under visible light of the lens in embodiment 1 of the present invention;

FIG. 3 is a graph of field curvature and F-theta distortion under visible light for a lens in example 1 of the present invention;

FIG. 4 is a light path diagram of embodiment 2 of the present invention;

fig. 5 is a graph of MTF under visible light of the lens in embodiment 2 of the present invention;

FIG. 6 is a graph of field curvature and F-theta distortion of a lens in visible light according to embodiment 2 of the present invention;

FIG. 7 is a light path diagram of embodiment 3 of the present invention;

fig. 8 is a graph of MTF under visible light for a lens in embodiment 3 of the present invention;

FIG. 9 is a graph of field curvature and F-theta distortion under visible light for a lens in embodiment 3 of the present invention;

FIG. 10 is a light path diagram of embodiment 4 of the present invention;

fig. 11 is a graph of MTF under visible light for a lens in embodiment 4 of the present invention;

FIG. 12 is a graph of field curvature and F-theta distortion under visible light for a lens in embodiment 4 of the present invention.

Description of reference numerals:

1. a first lens; 2. a second lens; 3. a third lens; 4. a fourth lens; 5. a fifth lens; 6. a sixth lens; 7. protective glass & filter.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the utility model and are not intended to limit the utility model.

In the present invention, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are all based on the orientation or positional relationship shown in the drawings, and are only for convenience of describing the present invention and simplifying the description, but do not indicate or imply that the apparatus or element of the present invention must have a specific orientation, and thus, should not be construed as limiting the present invention.

As used herein, the term "a lens element having a positive refractive index (or a negative refractive index)" means that the paraxial refractive index of the lens element calculated by Gaussian optics is positive (or negative). The term "object-side (or image-side) of a lens" is defined as the specific range of imaging light rays passing through the lens surface. The determination of the surface shape of the lens can be performed by the judgment method of a person skilled in the art, i.e., by the sign of the curvature radius (abbreviated as R value). The R value may be commonly used in optical design software, such as Zemax or CodeV. The R value is also commonly found in lens data sheets (lens data sheets) of optical design software. When the R value is positive, the object side is judged to be a convex surface; and when the R value is negative, judging that the object side surface is a concave surface. On the contrary, regarding the image side surface, when the R value is positive, the image side surface is judged to be a concave surface; when the R value is negative, the image side surface is judged to be convex.

The utility model discloses a positive distortion fisheye lens, which comprises a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5 and a sixth lens 6 which are sequentially arranged along an optical axis from an object side to an image side, wherein the first lens 1 to the sixth lens 6 respectively comprise an object side surface facing the object side and allowing imaging light rays to pass and an image side surface facing the image side and allowing the imaging light rays to pass;

the first lens 1 has negative diopter, and the object side surface of the first lens 1 is a convex surface, and the image side surface is a concave surface;

the second lens element 2 has negative diopter, and the object-side surface of the second lens element 2 is a convex surface and the image-side surface is a concave surface;

the third lens 3 has positive diopter, and the object side surface of the third lens 3 is a concave surface, and the image side surface is a convex surface;

the fourth lens 4 has positive diopter, and the object side surface of the fourth lens 4 is a convex surface, and the image side surface is a convex surface;

the fifth lens 5 has negative diopter, and the object side surface of the fifth lens 5 is a concave surface, and the image side surface is a concave surface;

the sixth lens element 6 has a positive refractive power, and an object-side surface of the sixth lens element 6 is a convex surface and an image-side surface thereof is a convex surface;

the number, focal power and concave-convex surface of the lens are reasonably designed, so that the cost of the lens can be effectively reduced, the length of the lens can be shortened, and the system performance can be maintained.

The lens further comprises a diaphragm, and the diaphragm is arranged on the object side surface of the third lens 3. By adjusting the position of the diaphragm, astigmatism can be corrected, and coma, distortion and vertical axis aberration can be corrected well.

The first lens 1 and the second lens 2 are meniscus lenses. Two negative focal power meniscus lenses bent to the diaphragm are continuously used, so that the angle of emergent rays corresponding to rays with an incident angle can be reduced, the FOV of the lens reaches 180 degrees, and simultaneously, the design of the bent diaphragm reduces the coma and the spherical aberration of the system.

The lens satisfies the following conditions: 1.69< nd1<1.85, 1.6< nd2<1.7, 1.9< nd3<2.051.5< nd4<1.6, 1.6< nd5<1.7 and 1.5< nd6<1.6, wherein nd1, nd2, nd3, nd4, nd5 and nd6 are refractive indexes of the first lens 1, the second lens 2, the third lens 633, the fourth lens 4, the fifth lens 5 and the sixth lens 6 respectively.

The lens satisfies the following conditions: 45< vd1<60, 20< vd2<30, 20< vd3<35, 45< vd4<60, 20< vd5<30, 65< vd6<85, wherein vd1, vd2, vd3, vd4, vd5, and vd6 are the abbe numbers of the first lens 1, the second lens 2, and the third lens 3, respectively.

The second lens 2, the fourth lens 4 and the fifth lens 5 are all plastic even-order aspheric lenses, and the object side surfaces and the image side surfaces of the second lens 2, the fourth lens 4 and the fifth lens 5 are all aspheric surfaces. Through increasing the use of even aspheric surface lens, improve the availability factor of lens to reduce the use quantity of lens, the effectual volume that reduces the camera lens reaches better imaging simultaneously.

The optical TTL of the lens is <19 mm. The effective apertures of the first lens 1 to the sixth lens 6 are all less than 13 mm. The lens is small in size and convenient to mount and use.

The light transmission F/#ofthe lens is 1.7, and the lens can still keep high-definition color imaging in a low-illumination environment due to the large light transmission design.

The imaging target surface is more than 6mm and can meet the requirement of 1/2' sensor imaging at most.

The MTF value of the lens is larger than 0.4 in the full field of view under the frequency of 150lp/mm, and the requirement of high-definition imaging is met.

The F-theta distortion of the lens is less than + 10%, the distortion is a positive value, the pixel proportion of edge imaging is effectively improved, and the later-stage algorithm processing is facilitated.

The mini infrared imaging lens of the present invention will be described in detail with specific embodiments.

Example 1

Referring to fig. 1, the present invention discloses a positive distortion fisheye lens, including a first lens element 1, a second lens element 2, a third lens element 3, a fourth lens element 4, a fifth lens element 5, and a sixth lens element 6, which are sequentially disposed along an optical axis from an object side to an image side, wherein each of the first lens element 1 to the sixth lens element 6 includes an object side surface facing the object side and allowing an imaging light to pass therethrough and an image side surface facing the image side and allowing the imaging light to pass therethrough;

in this embodiment, the lens further includes a diaphragm, and the diaphragm is disposed on the object-side surface of the third lens 3.

In this embodiment, the first lens element 1 and the second lens element 2 are meniscus lens elements. The detailed optical data of this embodiment are shown in Table 1-1.

Table 1-1 detailed optical data for example 1

In this embodiment, the second lens element 2, the fourth lens element 4, and the fifth lens element 5 are all plastic even-order aspheric lens elements, and the object-side surface and the image-side surface of the second lens element 2, the fourth lens element 4, and the fifth lens element 5 are all aspheric surfaces. The equation for the surface curve of an aspherical lens is expressed as follows:

wherein,

z: depth of the aspheric surface (the vertical distance between a point on the aspheric surface that is y from the optical axis and a tangent plane tangent to the vertex on the optical axis of the aspheric surface);

c: the curvature of the aspheric vertex (the vertex curvature);

k: cone coefficient (Conic Constant);

radial distance (radial distance);

r_n: normalized radius (normalysis radius (NRADIUS));

u：r/r_n；

a_m: mth order Q^conCoefficient (is the m)^thQ^con coefficient)；

Q_m ^con: mth order Q^conPolynomial (the m)^thQ^con polynomial)。

The aspherical surface data in this example is shown in tables 1 to 2.

Table 1-2 aspheric data of example 1

In this embodiment, please refer to fig. 2 for an MTF graph of the lens under visible light, and it can be seen from the graph that when the spatial frequency of the lens reaches 150lp/mm, MTF values of all fields are greater than and equal to 0.4, the resolution of the lens is high, and the requirement of high definition imaging is met. Referring to fig. 3, it can be seen that the field curvature of each wavelength is substantially overlapped, the chromatic aberration of the lens is better corrected, meanwhile, the optical distortion of the system is less than + 10%, the distortion is small and positive, the pixel ratio of the edge imaging is effectively improved, and the post algorithm processing is facilitated.

Example 2

As shown in fig. 4, this embodiment is different from embodiment 1 mainly in the optical parameters such as the curvature radius of each lens surface and the lens thickness.

The detailed optical data of this embodiment is shown in Table 2-1.

Table 2-1 detailed optical data for example 2

In this embodiment, the second lens element 2, the fourth lens element 4, and the fifth lens element 5 are all plastic even-order aspheric lens elements, and the object-side surface and the image-side surface of the second lens element 2, the fourth lens element 4, and the fifth lens element 5 are all aspheric surfaces. The aspherical surface data in this embodiment is shown in table 2-2.

Table 2-2 aspheric data of example 2

In this embodiment, please refer to fig. 5 for an MTF graph of the lens under visible light, and it can be seen from the graph that when the spatial frequency of the lens reaches 150lp/mm, the minimum MTF value is still about 0.4, the resolution of the lens is high, and the requirement of high definition imaging is met. Referring to fig. 6, it can be seen that the field curvature of each wavelength is substantially overlapped, the chromatic aberration of the lens is better corrected, meanwhile, the optical distortion of the system is less than + 10%, the distortion is small and positive, the pixel ratio of the edge imaging is effectively improved, and the post algorithm processing is facilitated.

Example 3

As shown in fig. 7, this embodiment is different from embodiment 1 mainly in the optical parameters such as the curvature radius of each lens surface and the lens thickness.

The detailed optical data of this embodiment is shown in Table 3-1.

Table 3-1 detailed optical data for example 3

In this embodiment, the second lens element 2, the fourth lens element 4, and the fifth lens element 5 are all plastic even-order aspheric lens elements, and the object-side surface and the image-side surface of the second lens element 2, the fourth lens element 4, and the fifth lens element 5 are all aspheric surfaces. The aspherical surface data in this example is shown in Table 3-2.

Table 3-2 aspheric data of example 3

In this embodiment, please refer to fig. 8 for an MTF graph of the lens under visible light, and it can be seen from the graph that when the spatial frequency of the lens reaches 150lp/mm, MTF values of all fields are greater than and equal to 0.4, and the resolution of the lens is high, thereby satisfying the requirement of high definition imaging. Referring to fig. 9, it can be seen that the field curvature of each wavelength is substantially overlapped, the chromatic aberration of the lens is better corrected, meanwhile, the optical distortion of the system is less than + 10%, the distortion is small and positive, the pixel ratio of the edge imaging is effectively improved, and the post algorithm processing is facilitated.

Example 4

As shown in fig. 10, this embodiment is different from embodiment 1 mainly in the optical parameters such as the curvature radius of each lens surface and the lens thickness.

The detailed optical data of this embodiment is shown in Table 4-1.

Table 4-1 detailed optical data for example 4

In this embodiment, the second lens element 2, the fourth lens element 4, and the fifth lens element 5 are all plastic even-order aspheric lens elements, and the object-side surface and the image-side surface of the second lens element 2, the fourth lens element 4, and the fifth lens element 5 are all aspheric surfaces. The aspherical surface data in this example is shown in Table 4-2.

Table 4-2 aspheric data of example 4

In this embodiment, please refer to fig. 11 for an MTF graph of the lens under visible light, and it can be seen from the graph that when the spatial frequency of the lens reaches 150lp/mm, MTF values of all fields are greater than and equal to 0.4, and the resolution of the lens is high, thereby satisfying the requirement of high definition imaging. Referring to fig. 12, it can be seen that the field curvature of each wavelength is substantially overlapped, the chromatic aberration of the lens is better corrected, meanwhile, the optical distortion of the system is less than + 10%, the distortion is small and positive, the pixel ratio of the edge imaging is effectively improved, and the post algorithm processing is facilitated.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A positive distortion fisheye lens, characterized in that: the imaging lens comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens which are sequentially arranged from an object side to an image side along an optical axis, wherein the first lens to the sixth lens respectively comprise an object side surface facing the object side and allowing imaging light rays to pass and an image side surface facing the image side and allowing the imaging light rays to pass;

2. A positive distortion fisheye lens as claimed in claim 1, characterized in that: the first lens and the second lens are meniscus lenses.

3. A positive distortion fisheye lens as claimed in claim 1 or 2, characterized in that: the second lens, the fourth lens and the fifth lens are all plastic aspheric lenses, and the object side surfaces and the image side surfaces of the second lens, the fourth lens and the fifth lens are all aspheric surfaces.

4. A positive distortion fisheye lens as claimed in claim 1, characterized in that: the lens satisfies the following conditions: 1.69< nd1<1.85, 1.6< nd2<1.7, 1.9< nd3<2.051.5< nd4<1.6, 1.6< nd5<1.7, 1.5< nd6<1.6,

5. A positive distortion fisheye lens as claimed in claim 1 or 4, characterized in that: the lens satisfies the following conditions: 45< vd1<60, 20< vd2<30, 20< vd3<35, 45< vd4<60, 20< vd5<30, 65< vd6<85,

6. A positive distortion fisheye lens as claimed in claim 1, characterized in that: the lens further comprises a diaphragm, and the diaphragm is arranged on the object side face of the third lens.

7. A positive distortion fisheye lens as claimed in claim 1, characterized in that: the effective apertures of the first lens to the sixth lens are all smaller than 13 mm.

8. A positive distortion fisheye lens as claimed in claim 1, characterized in that: the clear light F/#ofthe lens is 1.7.

9. A positive distortion fisheye lens as claimed in claim 1, characterized in that: the optical TTL of the lens is <19 mm.