CN109239893B

CN109239893B - Ultra-wide angle optical system with low chief ray incidence angle and working method thereof

Info

Publication number: CN109239893B
Application number: CN201811431780.XA
Authority: CN
Inventors: 林孝同; 周建宝; 张荣曜; 李俊攀
Original assignee: Fujian Forecam Optics Co Ltd
Current assignee: Fujian Forecam Optics Co Ltd
Priority date: 2018-11-28
Filing date: 2018-11-28
Publication date: 2023-08-11
Anticipated expiration: 2038-11-28
Also published as: CN109239893A

Abstract

The invention provides an ultra-wide angle optical system with a low chief ray incidence angle and a working method thereof, the ultra-wide angle optical system comprises a lens barrel and an optical system arranged in the lens barrel, wherein the optical system comprises a glued lens and a biconvex positive lens L7, wherein a meniscus negative lens L1, a meniscus negative lens L2, a biconvex positive lens L3, an aperture diaphragm S1, a meniscus positive lens L4, a biconvex positive lens L5 and a meniscus negative lens L6 are sequentially arranged in the direction of incidence of light on an imaging surface, a parallel flat plate P1 is arranged between the imaging surface and the biconvex positive lens L7, the optical lens system has a large field angle, can shoot a wide range of scenery, has relatively high illuminance, and particularly has a low chief ray incidence angle under the condition of a large field angle, and can be well matched with a CCD or CMOS chip with 500 ten thousand pixels for use.

Description

Ultra-wide angle optical system with low chief ray incidence angle and working method thereof

Technical Field

The invention relates to an ultra-wide angle optical system with a low incidence angle of principal ray and a working method thereof.

Background

The lens is an indispensable 'eye' of the video monitoring system, and along with the development of imaging chip technology, the requirements on the resolution of the lens are higher and higher, and the requirements on the matching degree of the lens and the imaging chip are also higher and higher. The wide-angle monitoring lens in the current market still has low relative illuminance and large incidence angle of main light rays and cannot be well matched with an imaging chip, so that when the monitoring lens is matched with a monitoring camera, the difference between the effect of an edge view field and a center view field is large, and the effect is more obvious especially under the condition that the resolution of the imaging chip is high. When the lens is matched with a camera, high resolution and day-night confocal are difficult to realize.

Disclosure of Invention

The invention improves the problems, namely the technical problems to be solved by the invention are the problems of low relative illuminance, large chief ray incidence angle and the like of the traditional video monitoring wide-angle lens, and the invention provides a video monitoring lens which has high relative illuminance, small chief ray incidence angle, high resolution and can be well matched with the CRA of an imaging chip.

The specific embodiments of the invention are: the utility model provides a low chief ray incident angle super wide angle optical system, includes the lens cone and sets up the optical system in the lens cone, optical system includes by light incidence to imaging surface direction set gradually meniscus negative lens L1, meniscus negative lens L2, biconvex positive lens L3, aperture diaphragm S1, meniscus positive lens L4, biconvex positive lens L5 and meniscus negative lens L6 constitutes the cemented lens and biconvex positive lens L7, be provided with parallel flat board P1 between imaging surface and the biconvex positive lens L7.

Further, the air interval between the negative meniscus lens L1 and the negative meniscus lens L2 is 2.7mm; the air interval between the meniscus negative lens L2 and the biconvex positive lens L3 is 1.9mm; the air interval between the biconvex positive lens L3 and the meniscus positive lens L4 is 1.2mm; the air interval between the meniscus positive lens L4 and the biconvex positive lens L5 in the glued lens is 0.1mm; the air spacing of the meniscus negative lens L6 and the biconvex positive lens L7 in the glue piece is 0.1mm.

Further, the focal length of the industrial lens is f; the combined focal length of the meniscus negative lens L1 and the meniscus negative lens L2 is fa; the focal length of the biconvex positive lens L7 is f7; the focal length of the combination of the cemented lens composed of the biconvex positive lens L5 and the meniscus negative lens L6 and the 7 th biconvex positive lens L7 is fb; the following relationship is satisfied: -2< fa/f < -0.5;3< f7/f <6;2< fb/f <4.5.

Further, the abbe numbers of the glass materials of the biconvex positive lens L5 and the biconvex positive lens L7 are v5 and v7 respectively, and the following relationship is satisfied: 55< v5<95, 55< v7<95.

The invention also comprises a working method of the low-chief ray incidence angle ultra-wide angle optical system, which utilizes the low-chief ray incidence angle ultra-wide angle optical system, wherein the lens with negative focal power of the meniscus negative lens L1 and the meniscus negative lens L2 compresses the incidence angle of light rays, so that the rear lens bears a smaller field angle to balance aberration, the focal power of the biconvex positive lens L3 and the focal power of the meniscus positive lens L4 are positive, and the lens mainly bears main axial aberration such as spherical aberration correction; the biconvex positive lens L5 and the meniscus negative lens L6 are combined to form a glued lens with positive focal power, and the biconvex positive lens L7 is taken as a positive lens, so that on-axis chromatic aberration and vertical-axis chromatic aberration are mainly corrected, and the 3 lenses are allocated to compress the incidence angle of principal rays, so that the monitoring optical lens still has a small incidence angle of principal rays under the condition of large viewing angle; the relative illumination of the lens is improved by controlling vignetting and adjusting the light height.

Compared with the prior art, the invention has the following beneficial effects: the smaller vignetting is set, and the angle of the chief ray is compressed, so that the relative illumination is high, the chief ray incidence angle is small, the CRA of the imaging chip is better matched, the illumination of the photographed image plane is more uniform, the distortion degree of the edge color is very low, and the imaging effect of the edge view field is close to that of the center view field; the chromatic aberration of the lens is balanced by reasonably distributing focal power and controlling chromatic aberration, so that the chromatic aberration of purple light is better controlled, and the phenomenon of the lens at purple edge is very slight; through reasonable selection and collocation of materials, the spherical aberration high-level quantity is corrected better, the MTF of a central view field and an edge view field is further improved, and the image quality in the whole view field range is improved; the refractive index of part of the materials is improved, the curvature radius of the lens with large focal power is increased, the sensitivity of the optical lens is reduced, the yield of mass production of the optical lens is higher, and the lens can be matched with a CCD or CMOS chip with 500 ten thousand pixels for use.

Drawings

FIG. 1 is a schematic view of an optical structure of the present invention.

Fig. 2 shows MTF values of an optical lens according to the present invention.

FIG. 3 shows the relative illumination of the optical lens of the present invention.

Fig. 4 shows the chief ray incidence angle of the present optical lens.

Detailed Description

The invention will be described in further detail with reference to the drawings and the detailed description.

As shown in fig. 1 to 4, an ultra-wide angle optical system with a low chief ray incidence angle comprises a lens barrel and an optical system arranged in the lens barrel, wherein the optical system comprises a glued lens and a biconvex positive lens L7 which are formed by a meniscus negative lens L1, a meniscus negative lens L2, a biconvex positive lens L3, an aperture stop S1, a meniscus positive lens L4, a biconvex positive lens L5 and a meniscus negative lens L6 which are sequentially arranged in the direction of incidence of light on an imaging surface, and a parallel flat plate P1 is arranged between the imaging surface and the biconvex positive lens L7.

In this embodiment, the air space between the negative meniscus lens L1 and the negative meniscus lens L2 is 2.7mm; the air interval between the meniscus negative lens L2 and the biconvex positive lens L3 is 1.9mm; the air interval between the biconvex positive lens L3 and the meniscus positive lens L4 is 1.2mm; the air interval between the meniscus positive lens L4 and the biconvex positive lens L5 in the glued lens is 0.1mm; the air spacing of the meniscus negative lens L6 and the biconvex positive lens L7 in the glue piece is 0.1mm.

In this embodiment, the focal length of the industrial lens is f; the combined focal length of the meniscus negative lens L1 and the meniscus negative lens L2 is fa; the focal length of the biconvex positive lens L7 is f7; the focal length of the combination of the cemented lens composed of the biconvex positive lens L5 and the meniscus negative lens L6 and the 7 th biconvex positive lens L7 is fb; the following relationship is satisfied: -2< fa/f < -0.5;3< f7/f <6;2< fb/f <4.5.

In this embodiment, the abbe numbers of the glass materials of the biconvex positive lens L5 and the biconvex positive lens L7 are v5 and v7, respectively, and satisfy the following relationship: 55< v5<95, 55< v7<95.

In this embodiment, the parameters of each lens are the following surfaces, where L1, L2, and L3 are names of corresponding lenses, S1, S2, and S3 … corresponding to each lens are two surfaces of each lens, for example, S1 and S2 are two surfaces of a meniscus negative lens L1 in the direction of the imaging plane, where light is incident on the two surfaces in sequence, the thickness corresponding to each surface is the thickness or the distance between the centers of S1 and S2, for example, the thickness 1 corresponding to S1 is 1mm, and in addition, because of the cemented lens composed of a biconvex positive lens L5 and a meniscus negative lens L6, S11 is the curved surface value of the biconvex positive lens L5 and the meniscus negative lens L6 in cooperative contact, S14 corresponds to the distance between the biconvex positive lens L7 and the image plane, S6 is the distance between the biconvex positive lens L3 and the aperture, and the refractive index of glass is the refractive index of the corresponding lens.

The functional system in this embodiment satisfies the following performance parameters

The specific performance parameters of the optical system are as follows:

(1) Focal length: effl=2.4 mm

(2) F number=2.1

(3) Angle of view: 2w is greater than or equal to 166 DEG

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

(5) The relative illuminance is more than 59%

(6) The incident angle of the chief ray is less than 5 DEG

(7) Working spectral range: 435 nm-850 nm

(8) The total optical length TTL is less than or equal to 23.9mm, and the optical post-intercept is more than or equal to 5mm

(9) The lens is suitable for a 500 ten thousand-pixel high-resolution CCD or CMOS camera

The lens with negative focal power of the meniscus negative lens L1 and the meniscus negative lens L2 of the optical system compresses the incident angle of light, so that the rear lens bears a smaller angle of view to balance aberration, the focal power of the biconvex positive lens L3 and the meniscus positive lens L4 is positive, and the lens mainly bears main axial aberration such as spherical aberration correction; the biconvex positive lens L5 and the meniscus negative lens L6 are combined to form a glued lens with positive focal power, and the biconvex positive lens L7 is taken as a positive lens, so that on-axis chromatic aberration and vertical-axis chromatic aberration are mainly corrected, and the 3 lenses are allocated to compress the incidence angle of principal rays, so that the monitoring optical lens still has a small incidence angle of principal rays under the condition of large viewing angle; the relative illumination of the lens is improved by controlling vignetting and adjusting the light height.

Any of the above-described embodiments of the present invention disclosed herein, unless otherwise stated, if they disclose a numerical range, then the disclosed numerical range is the preferred numerical range, as will be appreciated by those of skill in the art: the preferred numerical ranges are merely those of the many possible numerical values where technical effects are more pronounced or representative. Since the numerical values are more and cannot be exhausted, only a part of the numerical values are disclosed to illustrate the technical scheme of the invention, and the numerical values listed above should not limit the protection scope of the invention.

Any part provided by the invention can be assembled by a plurality of independent components, or can be manufactured by an integral forming process.

Finally, it should be noted that the above-mentioned embodiments are only for illustrating the technical scheme of the present invention and are not limiting; while the invention has been described in detail with reference to the preferred embodiments, those skilled in the art will appreciate that: modifications may be made to the specific embodiments of the present invention or equivalents may be substituted for part of the technical features thereof; without departing from the spirit of the invention, it is intended to cover the scope of the invention as claimed.

Claims

1. The ultra-wide angle optical system with the low incidence angle of the chief ray is characterized by comprising a meniscus negative lens L1, a meniscus negative lens L2, a biconvex positive lens L3, an aperture diaphragm S1, a meniscus positive lens L4, a biconvex positive lens L5, a meniscus negative lens L6 and a biconvex positive lens L7 in sequence from the direction of incidence of the ray on an imaging surface, wherein the biconvex positive lens L5 and the meniscus negative lens L6 form a cemented lens, and a parallel flat plate P1 is arranged between the imaging surface and the biconvex positive lens L7;

the air interval between the negative meniscus lens L1 and the negative meniscus lens L2 is 2.7mm; the air interval between the meniscus negative lens L2 and the biconvex positive lens L3 is 1.9mm; the air interval between the biconvex positive lens L3 and the meniscus positive lens L4 is 1.2mm; the air interval between the meniscus positive lens L4 and the biconvex positive lens L5 in the glued lens is 0.1mm; the air interval between the meniscus negative lens L6 and the biconvex positive lens L7 in the gluing piece is 0.1mm;

the focal length of the optical system head is f; the combined focal length of the meniscus negative lens L1 and the meniscus negative lens L2 is fa; the focal length of the biconvex positive lens L7 is f7; the focal length of the combination of the cemented lens composed of the biconvex positive lens L5 and the meniscus negative lens L6 and the 7 th biconvex positive lens L7 is fb; the following relationship is satisfied: -2< fa/f < -0.5;3< f7/f <6;2< fb/f <4.5;

the abbe numbers of the glass materials of the biconvex positive lens L5 and the biconvex positive lens L7 are v5 and v7 respectively, and the following relation is satisfied: 55< v5<95, 55< v7<95.