CN110346914B

CN110346914B - All-glass aspheric large-relative-aperture wide-angle optical lens system

Info

Publication number: CN110346914B
Application number: CN201910659951.2A
Authority: CN
Inventors: 江伟; 林孝同; 肖维军
Original assignee: Fujian Forecam Optics Co Ltd
Current assignee: Fujian Forecam Optics Co Ltd
Priority date: 2019-07-22
Filing date: 2019-07-22
Publication date: 2021-08-10
Anticipated expiration: 2039-07-22
Also published as: CN110346914A

Abstract

The invention relates to a wide-angle optical lens system with a full-glass aspheric surface and a large relative aperture, wherein a negative meniscus lens L1, a positive meniscus lens L2, an aperture diaphragm S1, a negative meniscus lens L3, a double convex positive lens L4 and a parallel flat plate P1 are sequentially arranged in the optical system of the lens from left to right in the incidence direction of light rays and positioned in front of an IMA image surface. The optical lens system has a large field angle, can shoot a large-range scenery, has high contrast, large relative aperture and high resolution, and can be matched with a CCD or CMOS chip with 600 ten thousand pixels for use.

Description

All-glass aspheric large-relative-aperture wide-angle optical lens system

Technical Field

The invention relates to an all-glass aspheric wide-angle optical lens system with a large relative aperture.

Background

With the small pixel of the high-resolution bar imaging chip and the limited light sensing capability of the chip, if the brightness of an image obtained by adopting a traditional lens with the relative aperture of 1:2.0 under the condition of low illumination is low, the requirements of monitoring and the like cannot be met, so that the lens with high resolution also needs to have a large relative aperture, and the image can obtain enough brightness under the environment with limited illumination. On the other hand, with the increase of the demand of security monitoring lenses, more and more lenses adopt plastic aspheric lenses, and because the plastic aspheric lenses have the main defects of thermal stability, mechanical property, spectral property and the like, the plastic materials have great absorption at high temperature or under the condition of exposing ultraviolet light, the photoelastic birefringence is higher than that of glass, the manufacturing and assembly are easy to have great stress, the working temperature is low, and the mechanical hardness is low, so that the application of the plastic aspheric lenses is greatly limited in many occasions.

Disclosure of Invention

Aiming at the defects, the invention provides the all-glass aspheric wide-angle optical lens system with a simple structure and a large relative aperture.

According to the technical scheme, the wide-angle optical lens system with the full-glass aspheric surface and the large relative aperture is characterized in that a negative meniscus lens L1, a positive meniscus lens L2, an aperture diaphragm S1, a negative meniscus lens L3, a double-convex positive lens L4 and a parallel flat plate P1 are sequentially arranged in the optical system of the lens in the direction of incidence of light rays from left to right and are positioned in front of an IMA image surface.

Further, the negative meniscus lens L1, the positive meniscus lens L2, the negative meniscus lens L3, and the double convex positive lens L4 are all glass aspheric lenses, and the glass material is low-melting glass.

Further, the air space between the negative meniscus lens L1 and the positive meniscus lens L2 was 2.3 mm; the air space between the positive meniscus lens L2 and the negative meniscus lens L3 was 4.2 mm; the air space between the meniscus negative lens L3 and the double convex positive lens L4 was 0.1 mm.

Further, setting the focal length of the lens to be f; the focal length of the meniscus negative lens L1 is f 1; the focal length of the meniscus positive lens L2 is f 2; the focal length of the meniscus negative lens L3 is f 3; the focal length of the biconvex positive lens L4 is f 4; the following relationship is satisfied: -2.5< f1/f < -1.5; -2.1< f3/f < -1.1; 0.8< f4/f < 1.2.

Further, abbe numbers of glass materials of the meniscus negative lens L3 and the double convex positive lens L4 are v3 and v4, respectively, and a refractive index of the glass material of the meniscus negative lens L3 is n3, which satisfy the following relationship: 15< v3< 30; 40< v4< 95; 1.80< n3< 2.17.

Compared with the prior art, the invention has the following beneficial effects: the all-glass aspheric wide-angle optical lens system with large relative aperture has a simple structure, has a large field angle, can shoot a large-range scene, has high contrast, large relative aperture and high resolution, and can be matched with a CCD or CMOS chip with 600 ten thousand pixels for use; the meniscus negative lens L3 adopts low-melting-point glass with high refractive index and low Abbe number, and the biconvex positive lens L4 adopts low-melting-point glass with high Abbe number, so that the secondary spectrum and spherical aberration are well corrected, and the chromatic aberration is well corrected by reasonably matching glass materials in the lens system; by reasonably distributing the focal power of the four lenses, the optical total length of the lens is compressed while the large relative aperture is maintained, so that the optical system has a compact structure and is beneficial to saving the use cost; by adopting the all-glass design, the transmittance of the glass does not change under the long-term high-temperature or ultraviolet irradiation condition, so that the use of the plastic lens is prevented from being influenced by the low transmittance under the long-term high-temperature or ultraviolet irradiation condition; by adopting the all-glass design, the glass has extremely low stress birefringence, thus avoiding image quality reduction caused by large stress of the plastic lens or stress focus leakage caused by stress release after long-time placement; by adopting the all-glass design, the softening temperature of the glass lens is far higher than that of the plastic lens, so that the glass lens can be used in high-temperature occasions where the plastic lens cannot be used; through adopting the design of full glass, the glass lens has higher mechanical strength than the plastic lens, can use occasions such as the scratch resistance that the plastic lens can not use.

Drawings

The invention is further described with reference to the following figures.

FIG. 1 is a schematic diagram of an optical configuration of an embodiment of the present invention;

FIG. 2 shows MTF values of an optical lens according to an embodiment of the present invention;

FIG. 3 shows relative illumination of an optical lens according to an embodiment of the present invention;

FIG. 4 shows the chief ray incident angle of the optical lens according to the embodiment of the present invention;

in the figure: l1 meniscus negative lens L1, L2 meniscus positive lens L2, S1 aperture stop S1, L3 meniscus negative lens L3, L4 biconvex positive lens L4, P1 parallel plate P1.

Detailed Description

The invention is further described with reference to the following figures and detailed description.

As shown in fig. 1 to 4, in an optical system of the lens, a negative meniscus lens L1, a positive meniscus lens L2, an aperture diaphragm S1, a negative meniscus lens L3, a double convex positive lens L4, and a parallel plate P1 are sequentially arranged in front of an IMA image plane along a left-to-right incident direction of light; the negative meniscus lens L1 mainly functions to compress the angle of view and the like, and the positive meniscus lens L2 mainly functions to correct curvature of field and high-order aberration.

In the present embodiment, the negative meniscus lens L1 mainly provides a large field angle for negative power, and compresses the field angle provided by the rear 3 lenses; the meniscus positive lens L2 is provided with a thicker thickness, so that the field curvature and the high-level aberration can be better corrected; the meniscus negative lens L3 and the biconvex positive lens L4 are reasonably matched with the refractive index and Abbe number of glass, so that the secondary spectrum and spherical aberration are well corrected, and the 4 aspheric lenses have small aspheric surface, thereby being beneficial to the die pressing manufacture of aspheric surfaces.

In this embodiment, the negative meniscus lens L1, the positive meniscus lens L2, the negative meniscus lens L3, and the positive biconvex lens L4 are all glass aspheric lenses, and the glass material is low-melting glass.

In the present embodiment, the air space between the meniscus negative lens L1 and the meniscus positive lens L2 is 2.3 mm; the air space between the positive meniscus lens L2 and the negative meniscus lens L3 was 4.2 mm; the air space between the meniscus negative lens L3 and the double convex positive lens L4 was 0.1 mm.

In this embodiment, the focal length of the lens is set to f; the focal length of the meniscus negative lens L1 is f 1; the focal length of the meniscus positive lens L2 is f 2; the focal length of the meniscus negative lens L3 is f 3; the focal length of the biconvex positive lens L4 is f 4; the following relationship is satisfied: -2.5< f1/f < -1.5; -2.1< f3/f < -1.1; 0.8< f4/f < 1.2.

In the present embodiment, abbe numbers of glass materials of the meniscus negative lens L3 and the double convex positive lens L4 are v3 and v4, respectively, and a refractive index of the glass material of the meniscus negative lens L3 is n3, which satisfy the following relationship: 15< v3< 30; 40< v4< 95; 1.80< n3< 2.17.

In the present embodiment, the optical system constituted by the lens group achieves the following optical indexes:

(1) focal length: EFFL =3.9 mm;

(2) f number = 1.6;

(3) the field angle: 2w =110 °;

(4) the diameter of the imaging circle is larger than phi 6.6 mm;

(5) the relative illumination is more than 60%;

(6) the incident angle of the chief ray is less than 6.3 degrees;

(7) working spectral range: 435 nm-656 nm;

(8) the total optical length TTL is less than or equal to 23mm, and the optical rear intercept is more than or equal to 6 mm;

(9) the lens is suitable for a 6M pixel high-resolution CCD or CMOS camera.

In the present embodiment, example data of the present optical lens system is shown in the following table:

in this embodiment, the aspherical surface has the following surface equation:

wherein z is a distance vector from a vertex of the aspheric surface when the aspheric surface is at a position with a height of R along the optical axis direction, c is a curvature of a paraxial of the aspheric surface, c =1/R, R is a curvature radius, c is a reciprocal of the curvature radius, k is a conic coefficient, a1 is an aspheric 2 nd order coefficient, a2 is an aspheric 4 th order coefficient, a3 is an aspheric 6 th order coefficient, a4 is an aspheric 8 th order coefficient, a5 is an aspheric 10 th order coefficient, a6 is an aspheric 12 th order coefficient, a7 is an aspheric 14 th order coefficient, a8 is an aspheric 16 th order coefficient, and the aspheric coefficients of the 4 aspheric lenses are as follows:

as can be seen from fig. 2, the optical lens has a higher resolution, and meets the MTF requirement of a6 megapixel high-resolution imaging chip; as can be seen from fig. 3, the optical lens has high relative illumination, and meets the requirement of imaging on brightness uniformity of the whole image surface range; as can be seen from fig. 4, the chief ray incident angle of the optical lens is less than 15 °, which can match the CRA of the imaging chip.

The above-mentioned preferred embodiments, further illustrating the objects, technical solutions and advantages of the present invention, should be understood that the above-mentioned are only preferred embodiments of the present invention and should not be construed as limiting the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The utility model provides a big relative aperture wide angle optical lens system of all-glass aspheric surface which characterized in that: a negative meniscus lens L1, a positive meniscus lens L2, an aperture diaphragm S1, a negative meniscus lens L3, a double convex positive lens L4 and a parallel flat plate P1 are sequentially arranged in an optical system of the lens along the incident direction of light rays from left to right, wherein the parallel flat plate P1 is positioned in front of an IMA image plane; the meniscus negative lens L1, the meniscus positive lens L2, the meniscus negative lens L3 and the double convex positive lens L4 are all glass aspheric lenses, and the glass material is low-melting-point glass; the air space between the meniscus negative lens L1 and the meniscus positive lens L2 was 2.3 mm; the air space between the positive meniscus lens L2 and the negative meniscus lens L3 was 4.2 mm; the air space between the meniscus negative lens L3 and the double convex positive lens L4 was 0.1 mm; setting the focal length of the lens as f; the focal length of the meniscus negative lens L1 is f 1; the focal length of the meniscus positive lens L2 is f 2; the focal length of the meniscus negative lens L3 is f 3; the focal length of the biconvex positive lens L4 is f 4; the following relationship is satisfied: -2.5< f1/f < -1.5; -2.1< f3/f < -1.1; 0.8< f4/f < 1.2; the abbe numbers of the glass materials of the meniscus negative lens L3 and the biconvex positive lens L4 are v3 and v4 respectively, the refractive index of the glass material of the meniscus negative lens L3 is n3, and the following relations are satisfied: 15< v3< 30; 40< v4< 95; 1.80< n3< 2.17; the relative aperture of the optical lens system is 1: 1.6.