CN114217414B

CN114217414B - Low-light-level objective optical system

Info

Publication number: CN114217414B
Application number: CN202111559837.6A
Authority: CN
Inventors: 张明超; 白晶; 梁国龙; 丁浩; 黄剑波; 张尧禹
Original assignee: Changchun Institute of Optics Fine Mechanics and Physics of CAS
Current assignee: Changchun Institute of Optics Fine Mechanics and Physics of CAS
Priority date: 2021-12-20
Filing date: 2021-12-20
Publication date: 2023-03-21
Anticipated expiration: 2041-12-20
Also published as: CN114217414A

Abstract

The utility model provides a shimmer objective optical system relates to optical system technical field, the problem of the light and effectual shimmer objective optical system that images of current demand quality has been solved, the device includes the first lens that sets up in order along the optical axis direction, the diaphragm, the second lens, the third lens, the fourth lens, fifth lens and sixth lens, the fifth lens constitutes double-cemented lens with the sixth lens, first lens, the second lens, fourth lens and fifth lens all have positive refractive index, third lens and sixth lens all have negative refractive index, double-cemented lens has negative power. According to the invention, the diaphragm is arranged between the first lens and the second lens, so that the imaging is clearer and the application range is wider; the invention is an objective lens imaging system with light weight, large caliber, high imaging quality and variable diaphragm.

Description

Low-light-level objective optical system

Technical Field

The invention relates to the technical field of optical systems, in particular to a low-light-level objective optical system.

Background

With the development of science and technology, night vision products come out endlessly, and civil night and day monitoring equipment, night auxiliary vehicle-mounted driving images, high-definition night vision cameras and the like are available; for military use, the system comprises a day and night universal sight glass, a vehicle-mounted or airborne pilot, border and river security monitoring and the like; with the development of technology, the demand of the day and night universal imaging system is continuously increased no matter individuals or countries, the day and night universal objective optical system is widely applied to various industries, and the development prospect is huge.

The design of the existing low-light-level objective optical system mainly comprises the design of a low-light-level night vision optical system disclosed in the journal Chen Yong and the like and a novel design of a head-mounted low-light-level night vision system disclosed in the journal Zhu Biao. However, the micro-optic objective optical system designed according to the above method still has difficulty in meeting the current requirements in terms of quality or aberration. The traditional objective lens mainly adopts a white light objective lens, the caliber is small, and the night imaging effect is poor; also for the shimmer camera lens of night design, the diaphragm is first lens bore generally, and because the bore is big under the highlight on daytime, it is bright partially to cause the visual field, and formation of image is unfavorable for observing. Therefore, it is desirable to design a low-light objective optical system with light weight and good imaging effect.

Disclosure of Invention

In order to solve the above problems, the present invention provides a micro-light objective optical system.

The technical scheme adopted by the invention for solving the technical problem is as follows:

a low-light objective optical system comprises a first lens, a diaphragm, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens which are sequentially arranged in the optical axis direction, wherein the fifth lens and the sixth lens form a double-cemented lens, the first lens, the second lens, the fourth lens and the fifth lens all have positive refractive indexes, the third lens and the sixth lens all have negative refractive indexes, and the double-cemented lens has negative focal power.

The invention has the beneficial effects that:

according to the low-light-level objective optical system, the diaphragm is arranged between the first lens and the second lens, and the F # of the optical system can be adjusted according to different environments, so that imaging is clearer, and the application range is wider.

The invention relates to a low-light-level objective optical system, which is an objective imaging system with light weight, large caliber, high imaging quality and variable diaphragm.

Drawings

Fig. 1 is a schematic diagram of a structure and an optical path of a micro-light objective optical system according to the present invention.

FIG. 2 is a MTF graph of a micro-optic objective optical system according to the present invention.

Fig. 3 is a star point diagram of each field of view of a micro-optic objective optical system of the present invention.

FIG. 4 is a field curvature diagram of a micro-light objective optical system according to the present invention.

FIG. 5 is a distortion diagram of a micro-light objective optical system according to the present invention.

In the figure: 1. the lens comprises a first lens, a second lens, a diaphragm, a third lens, a fourth lens, a fifth lens, a sixth lens and an image space, wherein the first lens is 2, the diaphragm is 3, the second lens is 4, the third lens is 5, the fourth lens is 6, the fifth lens is 7, and the sixth lens is 8.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples.

A micro-optic objective optical system, as shown in FIG. 1, includes a first lens 1, a diaphragm 2, a second lens 3, a third lens 4, a fourth lens 5 and a double cemented lens. The cemented doublet includes a fifth lens 6 and a sixth lens 7. The first lens 1, the diaphragm 2, the second lens 3, the third lens 4, the fourth lens 5, the fifth lens 6, the sixth lens 7 and the image space 8 are sequentially arranged along the optical axis direction from front to back along the light incidence direction. The first lens element 1, the second lens element 3, the fourth lens element 5 and the fifth lens element 6 all have positive refractive index, the third lens element 4 and the sixth lens element 7 all have negative refractive index, and the fifth lens element 6 and the sixth lens element 7 are cemented to form a double cemented lens with negative focal power.

The aperture of the first lens 1 is larger than the aperture of any one of the diaphragm 2, the second lens 3, the third lens 4, the fourth lens 5, the fifth lens 6 and the sixth lens 7. The first lens 1 is a convex-concave surface and has a positive refractive index, the surface facing the diaphragm 2 is a concave surface, the surface far away from the diaphragm 2 is a convex surface, the refractive index of d light of the first lens 1 is not less than 1.60, the Abbe constant of d light is not less than 62.1928, the first lens 1 bears the main focal power, light rays entering the micro-light objective optical system are greatly deflected like an optical axis, and meanwhile, the air interval between the first lens 1 and the diaphragm 2 and the second lens 3 is increased (the air interval between the first lens 1 and the diaphragm 2 is increased due to the fact that the first lens is set to be the convex-concave surface, the positive focal power is achieved, the air interval between the first lens 1 and the diaphragm 2 is increased), so that the calibers of the other lenses except the first lens 1 are greatly reduced, the volume of the optical system behind is effectively reduced, and the optical design characteristics of large caliber and small volume are formed.

The diaphragm 2 is arranged between the first lens 1 and the second lens 3, the diaphragm 2 is arranged at the position of 27.83mm of the first lens 1 along the optical axis, the light flux amount is controlled by the diaphragm 2, stray light is effectively inhibited, the design caliber of the diaphragm 2 is variable, and the F # of the system can be adjusted according to the use environment, so that the micro-light objective optical system can clearly image in wider environment, and can realize a closed type optical system with adjustable diaphragm based on the caliber of the diaphragm 2 designed according to requirements, and can be used under various severe environments; meanwhile, under the strong light in the daytime and in the time of high brightness of the visual field, the aperture can be adjusted to enable the visual field to be clear, and the observation is comfortable.

The second lens 3 is arranged at the position of 17.31mm behind the diaphragm 2 along the optical axis, the convex-concave surface design is adopted, the convex surface faces the diaphragm 2, the refractive index of d light of the material is not less than 1.7495, and the Abbe constant of the d light is not less than 35.0427; further converging light and further reducing the optical aperture of the system.

The third lens 4 is arranged at the position 3.12mm away from the optical axis behind the second lens 3, the double concave surface design is adopted, the refractive index is negative, the refractive index of d light of the material is not less than 1.95906, and the Abbe constant of d light is not less than 17.4724; the system is a large-aperture optical system, and in order to compensate for spherical aberration caused by the first lens 1 and the second lens 3, the third lens 4 is designed to compensate for the spherical aberration of the system by a negative lens.

The fourth lens 5 is arranged at the position of 30.49mm of the distance of the optical axis behind the third lens 4, the biconvex design is adopted, the positive refractive index is adopted, the refractive index of d light of the material is not less than 1.846658, and the Abbe constant of d light is not less than 23.8263; the light rays diverged by the third lens 4 are converged, and the system diameter is further reduced.

The fifth lens 6 and the sixth lens 7 form a double-cemented lens, the fifth lens 6 adopts a biconvex surface, and the sixth lens 7 adopts a biconcave surface design at the position of 5.74mm of the distance of the optical axis behind the fourth lens 5; the d-optical refractive index of the fifth lens 6 is not less than 1.6806, the d-optical Abbe constant is not less than 49.3471, the d-optical refractive index of the sixth lens 7 is not less than 1.9326, and the d-optical Abbe constant is not less than 27.9210; the cemented lens formed by the fifth lens 6 and the sixth lens 7 is used for eliminating chromatic aberration of the system and correcting aberration of the system.

The distance from the first lens 1 to the image space 8 along the optical axis direction is defined as ALT, the effective focal length of the system is EFL, and the ALT/EFL of the system is less than or equal to 1.7.

First lens 1, second lens 3, third lens 4, fourth lens 5, fifth lens 6 and sixth lens 7 all adopt the glass lens, because each lens all adopt the glass lens, avoid the plastic lens to receive the temperature influence easily to lead to the shortcoming that the imaging quality descends. The specific implementation parameters of the invention are shown in table 1, and the lens combination is adopted to form an effective focal length of 85mm, a viewing field of 11.2 degrees, an optical rear intercept of 6.1mm, an F #1.4 high-definition lens and an optical total length of 143mm. The MTF curve of the low-light-level objective optical system is shown in FIG. 2, and it can be known that the MTF is greater than 0.73 in the full field range and the spatial cutoff frequency is 32lp, so that the low-light-level objective optical system has the advantages of less energy loss, high contrast and good imaging effect. The star point diagram of each field of view of the low-light-level objective optical system is shown in fig. 3, and the known airy disk is less than 50um, and has small image dispersion, high resolution and clear image. The field curvature distortion of the low-light-level objective optical system is shown in figures 4 and 5, the field curvature is small, so that the deviation between the clear point position and the ideal image point of each field image is small, each field image is clear near an ideal image surface, and the phenomenon that the intermediate image and the edge point image cannot be adjusted clearly at the same time is avoided; the distortion under the maximum visual field is less than 0.05%, and the phenomenon of obvious bending can not occur under the deformation of the edge visual field. The glimmer objective optical system has the characteristics of small size and light weight, and is particularly suitable for a one-inch target surface glimmer imaging system.

The invention provides an objective lens imaging system with light weight, large caliber, high imaging quality and variable diaphragm 2, aiming at the requirements of all circles of the current society on day and night imaging. According to the invention, the diaphragm 2 is arranged between the first lens 1 and the second lens 3, and the F # of the lens can be adjusted according to different environments, so that the imaging is clearer and the application range is wider; meanwhile, the invention ensures the advantages of small volume and light weight while designing large caliber. The invention has the advantages of good imaging effect, high imaging quality and high resolution.

The invention reasonably distributes the focal power of each lens, simultaneously lengthens the distance between the first lens 1 and the second lens 3 and leaves enough space for the diaphragm 2, so that the system has wider application range compared with the traditional objective optical system; the focal power is reasonably distributed and the interval between the first lens 1 and the second lens 3 is lengthened, so that the apertures of the diaphragm 2 and the rest lenses except the first lens 1 are relatively smaller, and the characteristics of large aperture, light weight and small volume are realized.

TABLE 1

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. A low-light objective optical system is characterized by comprising a first lens, a diaphragm, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens which are sequentially arranged along an optical axis direction and a light incidence direction, wherein the fifth lens and the sixth lens form a double-cemented lens;

the first lens is a convex-concave lens, and the surface facing the diaphragm is a concave surface; the second lens is a convex-concave lens, and the surface facing the diaphragm is a convex surface; the third lens is a biconcave lens, the fourth lens is a biconvex lens, the fifth lens is a biconvex lens, and the sixth lens is a biconcave lens;

the objective optical system satisfies ALT/EFL < 1.7, ALT represents the distance between the first lens and the image side along the optical axis direction, and EFL represents the effective focal length of the objective optical system.

2. A micro objective optical system as claimed in claim 1, wherein the first lens, the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens are all made of glass.

3. A micro-optic objective optical system as claimed in claim 1, wherein the first lens has a larger aperture than any one of the stop, the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens.

4. A micro-optic objective optical system as claimed in claim 1, wherein the first lens has a refractive index of d-light equal to 1.60, abbe constant of d-light equal to 62.1928; the refractive index of d light of the second lens is equal to 1.7495, abbe constant of d light is equal to 35.0427; the refractive index of d light of the third lens is equal to 1.95906, abbe constant of d light is equal to 17.4724; the refractive index of d light of the fourth lens is equal to 1.846658, abbe constant of d light is equal to 23.8263; the refractive index of d light of the fifth lens is equal to 1.6806, abbe constant of d light is equal to 49.3471; the d-optical refractive index of the sixth lens is equal to 1.9326, and the d-optical Abbe constant is equal to 27.9210.

5. A micro-optic objective optical system as claimed in claim 1, wherein the first lens has a curvature radius of 76.85 on the surface facing the object side, a curvature radius of 794.44 on the surface facing the image side, and a focal length of 141.8mm; the distance between the diaphragm and the first lens is 27.83mm; the distance between the second lens and the diaphragm is 17.31mm, the curvature radius of the surface of the second lens facing the object space is 43.27, the curvature radius of the surface facing the image space is 289.16, and the focal length is 67.9mm; the distance between the third lens and the second lens is 3.12mm, the curvature radius of the surface facing the object side is-220.28, the curvature radius of the surface facing the image side is 37.69, and the focal length is-33.6 mm; the distance between the fourth lens and the third lens is 30.49mm, the curvature radius of the surface facing the object side is 87.55, the curvature radius of the surface facing the image side is-69.97, and the focal length is 45.9mm; the distance between the fifth lens and the fourth lens is 5.74mm, the curvature radius of the surface facing the object space is 32.57, and the focal length is 27.3mm; the curvature radius of the surface of the sixth lens facing the object side is-43.19, the curvature radius of the surface facing the image side is 25.72, and the focal length is-17.3 mm.