CN210488106U

CN210488106U - Fisheye lens

Info

Publication number: CN210488106U
Application number: CN201921120028.3U
Authority: CN
Inventors: 上官秋和; 李雪慧; 刘青天
Original assignee: Xiamen Leading Optics Co Ltd
Current assignee: Xiamen Leading Optics Co Ltd
Priority date: 2019-07-17
Filing date: 2019-07-17
Publication date: 2020-05-08
Anticipated expiration: 2029-07-17

Abstract

The utility model relates to a camera lens technical field relates to a fisheye camera lens especially. The utility model discloses a fish-eye lens, which comprises a first lens to an eighth lens from an object side to an image side along an optical axis in sequence; the first lens is a convex-concave lens with negative refractive index; the second lens is a convex-concave lens with negative refractive index; the third lens has a convex-concave or plano-concave lens with negative refractive index; the fourth lens is a convex lens with positive refractive index; the fifth lens is a plano-convex lens with positive refractive index; the sixth lens is a concave-convex lens with negative refractive index; the seventh lens is a convex lens with positive refractive index; the eighth lens is a concave-convex lens with negative refractive index; the fifth lens and the sixth lens are cemented to each other, and the seventh lens and the eighth lens are cemented to each other. The utility model has the advantages of resolution ratio is high, and the resolving power degree of consistency is good, fully corrects epaxial colour difference, off-axis colour difference, spherical aberration, makes the concatenation can not cause the color deviation, and effectively improves the ghost image.

Description

Fisheye lens

Technical Field

The utility model belongs to the technical field of the camera lens, specifically relate to a fisheye camera lens.

Background

The fisheye lens is an ultra-wide angle lens having a focal length of 16mm or less. The front lens of the lens is large in diameter and is in a parabolic shape, protrudes towards the front of the lens, is quite similar to the fish eye, and is commonly called as a fish eye lens. At present, the fisheye lens is widely applied to the fields of security monitoring, vehicle-mounted monitoring and the like, so that the requirements on the fisheye lens are higher and higher, but the conventional fisheye lens for panoramic stitching has low pixel and poor edge resolution; because the angle is large, various chromatic aberrations are difficult to correct, purple fringed blue edges are easy to appear, and splicing is affected; and edge ghost images are easy to generate, and the increasingly improved requirements cannot be met.

Disclosure of Invention

An object of the utility model is to provide a fisheye lens is used for solving the technical problem that above-mentioned exists.

In order to achieve the above object, the utility model adopts the following technical scheme: a fisheye lens comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens from an object side to an image side in sequence along an optical axis; the first lens element to the eighth lens element each include an object-side surface facing the object side and allowing the imaging light to pass therethrough and an image-side surface facing the image side and allowing the imaging light to pass therethrough;

the first lens element with negative refractive index has a convex object-side surface and a concave image-side surface;

the second lens element with negative refractive index has a convex object-side surface and a concave image-side surface;

the third lens element with negative refractive index has a convex or planar object-side surface and a concave image-side surface;

the fourth lens element with positive refractive index has a convex object-side surface and a convex image-side surface;

the fifth lens element with positive refractive index has a planar object-side surface and a convex image-side surface;

the sixth lens element with negative refractive index has a concave object-side surface and a convex image-side surface; the image side surface of the fifth lens is mutually glued with the object side surface of the sixth lens;

the seventh lens element with positive refractive power has a convex object-side surface and a convex image-side surface;

the eighth lens element with negative refractive index has a concave object-side surface and a convex image-side surface; the image side surface of the seventh lens is mutually glued with the object side surface of the eighth lens;

the fisheye lens has only eight lenses with refractive indexes.

Further, the optical diaphragm is arranged between the fourth lens and the fifth lens.

Further, the fisheye lens further satisfies: nd1>1.9, where nd1 is the refractive index of the first lens at the d-line.

Further, the fisheye lens further satisfies: -R12 | > 7mm, | R21 | > 30mm, G12 > 3.5mm, and | D12-D21 | > 2mm, wherein R12 is a radius of curvature of an image-side surface of the first lens, R21 is a radius of curvature of an object-side surface of the second lens, G12 is an air gap on an optical axis from the first lens to the second lens, D12 is a clear aperture of the image-side surface of the first lens, and D21 is a clear aperture of the object-side surface of the second lens.

Further, the fisheye lens further satisfies: nd4>1.9, where nd4 is the refractive index of the fourth lens at d-line.

Further, the fisheye lens further satisfies: vd5 > 50, vd6 < 30, and | vd5-vd6 | 30, where vd5 and vd6 represent the d-line abbe numbers of the fifth lens and the sixth lens, respectively.

Further, the fisheye lens further satisfies: vd7 > 60, vd8 < 20, and | vd7-vd8 | 40, where vd7 and vd8 represent the abbe number of the seventh lens and the eighth lens, respectively, in the d-line.

Further, the image side surface of the first lens is plated with an antireflection film of 600 +/-20 nm.

Further, the fisheye lens further satisfies: ALT <12mm, ALG <18mm, ALT/ALG <2, wherein ALG is the sum of air gaps between the first lens and an imaging surface on the optical axis, and ALT is the sum of eight lens thicknesses between the first lens and the eighth lens on the optical axis.

The utility model has the advantages of:

the utility model adopts eight lenses, and by correspondingly designing each lens, the resolution ratio is high, and the center-to-edge uniformity is high; the chromatic aberration on the axis, the chromatic aberration outside the axis and the spherical aberration are fully corrected, so that the color deviation cannot be caused by splicing; and effectively improve ghost image, can avoid appearing the advantage of marginal ghost image.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a first embodiment of the present invention;

FIG. 2 is a graph of MTF of visible light 0.4350-0.6560 μm according to a first embodiment of the present invention;

fig. 3 is a schematic view of a differential curve diagram on an axis according to a first embodiment of the present invention;

fig. 4 is a schematic diagram of a graph of off-axis chromatic aberration according to a first embodiment of the present invention;

fig. 5 is a schematic view of a spherical aberration according to a first embodiment of the present invention;

fig. 6 is a schematic diagram of a ghost simulation according to a first embodiment of the present invention;

fig. 7 is a schematic structural diagram of a second embodiment of the present invention;

FIG. 8 is a graph of MTF of visible light 0.4350-0.6560 μm according to example II of the present invention;

fig. 9 is a schematic view of an axial color difference curve according to a second embodiment of the present invention;

fig. 10 is a schematic diagram of an off-axis chromatic aberration curve according to the second embodiment of the present invention;

fig. 11 is a schematic view of a spherical aberration according to the second embodiment of the present invention;

fig. 12 is a schematic diagram of a ghost simulation according to a second embodiment of the present invention;

fig. 13 is a schematic structural view of a third embodiment of the present invention;

FIG. 14 is a graph of MTF of visible light 0.4350-0.6560 μm according to a third embodiment of the present invention;

fig. 15 is a schematic view of a differential curve on an axis according to a third embodiment of the present invention;

fig. 16 is a schematic diagram of an off-axis chromatic aberration curve according to a third embodiment of the present invention;

fig. 17 is a schematic view of a spherical aberration diagram according to a third embodiment of the present invention;

fig. 18 is a schematic diagram of ghost simulation according to a third embodiment of the present invention;

fig. 19 is a table of values of relevant important parameters according to three embodiments of the present invention.

Detailed Description

To further illustrate the embodiments, the present invention provides the accompanying drawings. The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the embodiments. With these references, one of ordinary skill in the art will appreciate other possible embodiments and advantages of the present invention. Elements in the figures are not drawn to scale and like reference numerals are generally used to indicate like elements.

The present invention will now be further described with reference to the accompanying drawings and detailed description.

The term "a lens element having positive refractive index (or negative refractive index)" means that the paraxial refractive index of the lens element calculated by Gaussian optics theory 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 fish-eye lens, which comprises a first lens to an eighth lens from an object side to an image side along an optical axis in sequence; the first lens element to the eighth lens element each include an object-side surface facing the object side and passing the image light, and an image-side surface facing the image side and passing the image light.

The first lens element with negative refractive index has a convex object-side surface and a concave image-side surface; the second lens element with negative refractive index has a convex object-side surface and a concave image-side surface; the third lens element with negative refractive index has a convex or planar object-side surface and a concave image-side surface; the fourth lens element with positive refractive index has a convex object-side surface and a convex image-side surface; the fifth lens element with positive refractive index has a planar object-side surface and a convex image-side surface; the sixth lens element with negative refractive index has a concave object-side surface and a convex image-side surface; the image side surface of the fifth lens is mutually glued with the object side surface of the sixth lens; the seventh lens element with positive refractive power has a convex object-side surface and a convex image-side surface; the eighth lens element with negative refractive index has a concave object-side surface and a convex image-side surface; the image side surface of the seventh lens is mutually glued with the object side surface of the eighth lens; the fisheye lens has only eight lenses with refractive indexes.

The utility model adopts eight lenses, and by correspondingly designing each lens, the resolution ratio is high, and the center-to-edge uniformity is high; the chromatic aberration on the axis, the chromatic aberration outside the axis and the spherical aberration are fully corrected, so that the color deviation cannot be caused by splicing; and effectively improve ghost image.

Preferably, the diaphragm is arranged between the fourth lens and the fifth lens, the overall performance is further improved, the overall light rays are relatively smooth, and the tolerance and the manufacturability are strong.

Preferably, the fisheye lens further satisfies: nd1>1.9, where nd1 is the refractive index of the first lens at d-line, facilitates compression of the first lens outer diameter while achieving a large angle.

Preferably, the fisheye lens further satisfies: | R12 | > 7mm, | R21 | > 30mm, G12 > 3.5mm, | D12-D21 | > 2mm, wherein R12 is the curvature radius of the image side surface of the first lens, R21 is the curvature radius of the object side surface of the second lens, G12 is the air gap on the optical axis from the first lens to the second lens, D12 is the clear aperture of the image side surface of the first lens, and D21 is the clear aperture of the object side surface of the second lens, so that ring ghost generated by reflection of the image side surface of the first lens and the object side surface of the second lens can be further avoided.

Preferably, the fisheye lens further satisfies: nd4>1.9, wherein nd4 is the refractive index of the fourth lens at the d line, and further improves the image quality.

Preferably, the fisheye lens further satisfies: vd5 > 50, vd6 < 30 and | vd5-vd6 | 30, wherein vd5 and vd6 respectively represent the d-line abbe numbers of the fifth lens and the sixth lens, further effectively controlling chromatic aberration and optimizing image quality.

Preferably, the fisheye lens further satisfies: vd7 > 60, vd8 < 20, and | vd7-vd8 | 40, wherein vd7 and vd8 respectively represent the d-line abbe numbers of the seventh lens and the eighth lens, further effectively controlling chromatic aberration and optimizing image quality.

Preferably, the image side surface of the first lens is plated with a 600 ± 20nm antireflection film (i.e. the film has the lowest reflectivity to 600 ± 20nm wavelength), the number of film layers is small, and the thickness is thin, so that the transmittance from the central region to the edge region is uniform, and ghost images are avoided, whereas the conventional film plating has a large number of film layers and a thick thickness, and since the ratio of the clear aperture to the curvature radius of the image side surface of the first lens of the fisheye lens is large, generally larger than 1.8, the fisheye lens is easy to cause unevenness, causes large edge reflection, and causes serious large-angle ghost images.

Preferably, the fisheye lens further satisfies: ALT <12mm, ALG <18mm, ALT/ALG <2, wherein ALG is the sum of air gaps between the first lens and an imaging surface on the optical axis, and ALT is the sum of eight lens thicknesses between the first lens and the eighth lens on the optical axis, so as to further shorten the system length of the fish-eye lens, and the fish-eye lens is easy to process and manufacture and optimizes the system configuration.

The following describes the fisheye lens of the present invention in detail with specific embodiments.

As shown in fig. 1, a fisheye lens includes, in order along an optical axis I, a first lens 1 to a fourth lens 4, a stop 9, a fifth lens 5 to an eighth lens 8, a protective sheet 100, and an image plane 110 from an object side a1 to an image side a 2; the first lens element 1 to the eighth lens element 8 each include an object-side surface facing the object side a1 and passing the image light, and an image-side surface facing the image side a2 and passing the image light.

The first lens element 1 has a negative refractive index, the object-side surface 11 of the first lens element 1 is a convex surface, and the image-side surface 12 of the first lens element 1 is a concave surface; the image side surface 12 of the first lens 1 is plated with an antireflection film of 600 +/-20 nm.

The second lens element 2 has a negative refractive index, and an object-side surface 21 of the second lens element 2 is convex and an image-side surface 22 of the second lens element 2 is concave.

The third lens element 3 has a negative refractive index, and an object-side surface 31 of the third lens element 3 is a flat surface and an image-side surface 32 of the third lens element 3 is a concave surface.

The fourth lens element 4 has a positive refractive index, and an object-side surface 41 of the fourth lens element 4 is convex and an image-side surface 42 of the fourth lens element 4 is convex.

The fifth lens element 5 has a positive refractive index, the object-side surface 51 of the fifth lens element 5 is a plane, and the image-side surface 52 of the fifth lens element 5 is a convex surface.

The sixth lens element 6 with negative refractive index has a concave object-side surface 61 of the sixth lens element 6 and a convex image-side surface 62 of the sixth lens element 6; the image-side surface 52 of the fifth lens element 5 and the object-side surface 61 of the sixth lens element 6 are cemented to each other.

The seventh lens element 7 has a positive refractive index, and an object-side surface 71 of the seventh lens element 7 is convex and an image-side surface 72 of the seventh lens element 7 is convex.

The eighth lens element 8 with negative refractive index has a concave object-side surface 81 of the eighth lens element 8 and a convex image-side surface 82 of the eighth lens element 8; the image-side surface 72 of the seven lens element 7 and the object-side surface 81 of the eighth lens element 8 are cemented to each other.

In this embodiment, the first lens element 1 to the eighth lens element 8 are made of glass, but not limited thereto, and in other embodiments, other materials such as plastic may be used.

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

Table 1-1 detailed optical data for example one

Please refer to fig. 19 for the values of the conditional expressions according to this embodiment.

Referring to FIG. 2, the MTF curve of the present embodiment can be seen to have a high transfer function and a high resolution, which can reach 250lp/mm > 0.3; referring to fig. 3, 4 and 5, the on-axis chromatic aberration, the off-axis chromatic aberration and the spherical aberration are respectively shown to be small and fully corrected; ghost simulation figure as shown in fig. 6, it can be seen that no circled ghost appears at the edge.

In this embodiment, the focal length f of the fisheye lens is 1.6mm, the aperture value FNO is 2.0, the field angle FOV is 180 °, and the maximum diameter of the dispersed spot is 2.8 μm.

Example two

As shown in fig. 7, the surface-type convexo-concave and refractive index of each lens element of this embodiment are substantially the same as those of the first embodiment, only the object-side surface 31 of the third lens element 3 of this embodiment is a convex surface, and the optical parameters such as the curvature radius of each lens element surface and the lens thickness are different.

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

TABLE 2-1 detailed optical data for example two

Referring to FIG. 8, the MTF curve of the present embodiment can be seen to have high transfer function and high resolution, which can substantially reach 250lp/mm > 0.3; referring to fig. 9, 10 and 11, the on-axis chromatic aberration, the off-axis chromatic aberration and the spherical aberration are respectively shown to be sufficiently corrected; ghost simulation figure as shown in fig. 12, it can be seen that no circled ghost appears at the edge.

In this embodiment, the focal length f of the fisheye lens is 1.6mm, the aperture value FNO is 2.0, the field angle FOV is 180 °, and the maximum diameter of the dispersed spot is 2.5 μm.

EXAMPLE III

As shown in fig. 13, the lens elements of this embodiment have the same surface irregularities and refractive index as those of the second embodiment, and only the optical parameters such as the curvature radius of the surface of each lens element and the lens thickness are different.

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

TABLE 3-1 detailed optical data for EXAMPLE III

Referring to FIG. 14, the MTF curve of the present embodiment can be seen to have high transfer function and high resolution, which can reach 250lp/mm > 0.25; referring to fig. 15, 16 and 17 for the on-axis chromatic aberration, off-axis chromatic aberration and spherical aberration diagrams, respectively, it can be seen that the on-axis chromatic aberration, off-axis chromatic aberration and spherical aberration are small and sufficiently corrected; ghost simulation figure as shown in fig. 18, it can be seen that no circled ghost appears at the edge.

In this embodiment, the focal length f of the fisheye lens is 1.6mm, the aperture value FNO is 2.0, the field angle FOV is 180 °, and the maximum diameter of the dispersed spot is 2.2 μm.

While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A fisheye lens characterized in that: the optical lens assembly sequentially comprises a first lens, a second lens, a third lens, a fourth lens and a fifth lens from the object side to the image side along an optical axis; the first lens element to the eighth lens element each include an object-side surface facing the object side and allowing the imaging light to pass therethrough and an image-side surface facing the image side and allowing the imaging light to pass therethrough;

the first lens element with negative refractive index has a convex object-side surface and a concave image-side surface, and the image-side surface of the first lens element is coated with 600 + -20 nm antireflection film;

the fisheye lens has only eight lenses with refractive indexes.

2. The fisheye lens of claim 1, wherein: and the diaphragm is arranged between the fourth lens and the fifth lens.

3. The fisheye lens of claim 1, further satisfying: nd1>1.9, where nd1 is the refractive index of the first lens at the d-line.

4. The fisheye lens of claim 1, further satisfying: -R12 | > 7mm, | R21 | > 30mm, G12 > 3.5mm, and | D12-D21 | > 2mm, wherein R12 is a radius of curvature of an image-side surface of the first lens, R21 is a radius of curvature of an object-side surface of the second lens, G12 is an air gap on an optical axis from the first lens to the second lens, D12 is a clear aperture of the image-side surface of the first lens, and D21 is a clear aperture of the object-side surface of the second lens.

5. The fisheye lens of claim 1, further satisfying: nd4>1.9, where nd4 is the refractive index of the fourth lens at d-line.

6. The fisheye lens of claim 1, further satisfying: vd5 > 50, vd6 < 30, and | vd5-vd6 | 30, where vd5 and vd6 represent the d-line abbe numbers of the fifth lens and the sixth lens, respectively.

7. The fisheye lens of claim 1, further satisfying: vd7 > 60, vd8 < 20, and | vd7-vd8 | 40, where vd7 and vd8 represent the abbe number of the seventh lens and the eighth lens, respectively, in the d-line.

8. The fisheye lens of claim 1, further satisfying: ALT <12mm, ALG <18mm, ALT/ALG <2, wherein ALG is the sum of air gaps between the first lens and an imaging surface on the optical axis, and ALT is the sum of eight lens thicknesses between the first lens and the eighth lens on the optical axis.