CN108181699B

CN108181699B - Reverse modulation cat eye optical system with large field of view approaching diffraction limit

Info

Publication number: CN108181699B
Application number: CN201711377422.0A
Authority: CN
Inventors: 梁丹华; 赵延仲; 张来线; 单聪淼; 郭惠超; 张廷华; 李迎春; 任建迎; 张天齐; 陈建彪
Original assignee: Peoples Liberation Army Strategic Support Force Aerospace Engineering University
Current assignee: Peoples Liberation Army Strategic Support Force Aerospace Engineering University
Priority date: 2017-12-19
Filing date: 2017-12-19
Publication date: 2020-10-30
Anticipated expiration: 2037-12-19
Also published as: CN108181699A

Abstract

The invention discloses a reverse modulation cat eye optical system, which adopts six simple and easy-to-process spherical mirrors, can obtain a reverse modulation cat eye optical system with a large view field close to a diffraction limit through parameter optimization design according to specific requirements, and ensures that a light beam with a large incident angle has a good modulation effect; meanwhile, the diffraction limit can be approached, and the good original path return characteristic of the system is ensured; the small F number is also ensured, the matching with a small-size modulator can be realized, the modulation contrast of the whole system is ensured, and the link stability is better; in addition, the system also has the advantages of small wavefront distortion and good energy concentration, so that the system can be widely applied to the field of inverse modulation laser communication and has the advantages of small volume, strong applicability, low cost and the like.

Description

Reverse modulation cat eye optical system with large field of view approaching diffraction limit

Technical Field

The invention belongs to the technical field of free space laser communication, and particularly relates to a large-field reverse modulation cat eye optical system close to a diffraction limit.

Background

The reverse modulation cat eye optical system is a receiving/transmitting antenna of a reverse modulator, determines the gain of the cat eye reverse modulator, has the performance directly related to the stability of a reverse modulator link, and has important significance for constructing a high-speed laser communication network. The key of the cat eye reverse modulator is a reverse modulation cat eye optical system with a reasonable design structure. The large field of view ensures that the optical system has good modulation effect on the light beam with large incident angle, and the proximity of the diffraction limit ensures the good original return characteristic of the system. At present, countries for studying the design of the cat-eye optical system abroad mainly comprise the United states and Sweden, and a refraction type diffraction limit cat-eye optical system is designed by the American navy research laboratory, wherein the field angle of the system is 30 degrees, the focal plane size is 1.4cm, and the effective F number is F/2. The Swedish defense research institute designs a reverse modulation cat eye optical system, and realizes the aperture of 12mm, the effective focal plane length of 13.3mm and the field angle of 18 degrees. However, both of these optical systems use aspherical mirror structures, which results in high cost, difficult processing and is not suitable for wide application. Domestic researches on the cat eye optical system mainly focus on the influence of optical system parameters on cat eye effect reflected light intensity, and no practical report is provided on the design and other contents of the cat eye optical system.

Disclosure of Invention

In view of the above, the present invention provides a large field near diffraction limit inverse modulation cat-eye optical system, which can make the system have the characteristics of near diffraction limit, large field and small F number under the condition that all the lenses use simple and easy-to-machine spherical mirrors.

A reverse modulation cat eye optical system 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 from an object plane to an image plane along an optical axis, wherein a diaphragm (7) is arranged between the third lens (3) and the fourth lens (4), all the lenses are spherical lenses, and the material is glass;

the first lens (1) is a plano-concave lens, the second lens (2) is a biconvex lens, the third lens (3) is a negative meniscus lens, the fourth lens (4) is a negative meniscus lens, the fifth lens (5) is a biconvex lens, and the sixth lens (6) is a positive meniscus lens; the focal lengths of the six lenses are respectively negative, positive, negative, positive and positive.

Preferably, the optical system has a field angle of at least 30 ° and an F-number of at most 1.3.

Preferably, the material of the six lenses is H-ZF7 LA.

Preferably, the six lenses are all plated with high-permeability films.

The invention has the following beneficial effects:

according to the reverse modulation cat eye optical system, six simple and easy-to-machine spherical mirrors are adopted, and the reverse modulation cat eye optical system with a large view field close to a diffraction limit can be obtained through parameter optimization design according to specific requirements, so that a good modulation effect on a light beam with a large incident angle is ensured; meanwhile, the diffraction limit can be approached, and the good original path return characteristic of the system is ensured; the small F number is also ensured, the matching with a small-size modulator can be realized, the modulation contrast of the whole system is ensured, and the link stability is better; in addition, the system also has the advantages of small wavefront distortion and good energy concentration, so that the system can be widely applied to the field of inverse modulation laser communication and has the advantages of small volume, strong applicability, low cost and the like.

Drawings

FIG. 1 is a schematic diagram of a large field of view near the diffraction limit of a retro-modulated cat-eye optical system of the present invention.

FIG. 2 is a schematic ray trace of a large field of view near the diffraction limit of an inverse modulated cat-eye optical system of the present invention.

FIG. 3 is a graph of the MTF of the cat eye optical system of the present invention.

The lens comprises a lens body, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a diaphragm, wherein the lens body comprises 1-the first lens, 2-the second lens, 3-the third lens, 4-the fourth lens, 5-the fifth lens, 6-the sixth lens and 7-the diaphragm.

Detailed Description

The invention is described in detail below by way of example with reference to the accompanying drawings.

The invention provides a cat eye optical system structure close to a diffraction limit, aiming at solving the problem that the existing reverse modulation optical system can not simultaneously meet the conditions of large field of view, reversibility, small F number and simple and easily-processed spherical mirrors adopted by all lenses.

As shown in fig. 1 and 2, the large-field inverse modulation cat-eye optical system close to the diffraction limit of the present invention mainly includes 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 the incident direction of light, wherein an aperture stop 7 is disposed between the third lens 3 and the fourth lens 4, and the off-axis aberration is adjusted and balanced by the front and rear lens groups. All the lenses are spherical lenses and are made of glass. The first lens 1 is a plano-concave lens; the second lens 2 is a biconvex lens; the third lens 3 is a negative meniscus lens; the fourth lens 4 is a negative meniscus lens; the fifth lens 5 is a biconvex lens; the sixth lens 6 is a positive meniscus lens; the focal lengths of the six lenses are respectively negative, positive, negative, positive and positive.

The parameters of the optical system can realize large field of view and approach diffraction limit through parameter optimization design according to specific requirements; finally, the cat eye optical system achieves a large field angle close to 30 degrees, the F number is 1.3, and all lenses are spherical mirrors.

The object side of the first lens 1 of the large-field-of-view inverse modulation cat-eye optical system of the invention, which is close to the diffraction limit, is a concave surface, and the image side is a flat surface.

The large-field-of-view inverse modulation cat eye optical system close to the diffraction limit has the aperture of 50mm, meets the requirement of design gain, has a full field angle of 30 degrees, and keeps good inverse reflection characteristics in the whole field angle. According to the optical imaging principle and the imaging requirement on the system, under the condition of 1550nm using wavelength, the system is made of H-ZF7LA, the focal length of the system is 26mm, the diameter of the entrance pupil of the system is 20mm, the F number is 1.3, the diameter of an imaging surface is 13.4mm, the total length is less than 80mm, the communication distance is 1km, and the half-image height of one kilometer after the system is reflected is close to 267 m. Since the light beam will re-enter the system through the reflective mirror, the transmittance of the single mirror of the system is required to be high during coating. The system has 6 sheets and 12 surfaces in total, and the system transmittance is higher than 94%.

The following are the structural parameters of an embodiment of the optical system.

TABLE 1

As shown in fig. 3, which is an MTF plot for this optical system, it can be seen that the transfer function curves for the different fields of view of the system are substantially close to the diffraction limit. The transfer function curve of the system can meet the resolution requirement of 2.5 mu m of the pixel size of the detector. The system can clearly image the slowly changing background and the thick object and has excellent performance on the aspect of detail resolving capability of the object.

The traditional reverse modulation cat eye optical system mostly adopts an aspherical mirror, has high manufacturing cost and difficult processing, adopts a standard spherical mirror which is easy to process, effectively reduces the system cost and is beneficial to wide application.

The inverse modulation cat eye optical system is close to the diffraction limit, meets the gain requirement, simultaneously achieves the full field angle of 30 degrees, and keeps good inverse reflection characteristics in the whole field angle.

In summary, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The cat eye reverse modulation optical system is characterized by comprising 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 from an object plane to an image plane along an optical axis, wherein a diaphragm (7) is arranged between the third lens (3) and the fourth lens (4), all the lenses are spherical lenses, and the materials are glass;

the first lens (1) is a planoconcave lens, the second lens (2) is a biconvex lens, the third lens (3) is a negative meniscus lens, the fourth lens (4) is a negative meniscus lens, the fifth lens (5) is a biconvex lens, and the sixth lens (6) is a positive meniscus lens; the focal lengths of the six lenses are respectively negative, positive, negative, positive and positive.

2. The retromodulating cat-eye optical system according to claim 1 wherein the optical system has a field angle of at least 30 ° and an F-number of at most 1.3.

3. A retro-modulating cat-eye optical system as claimed in claim 1 or 2, wherein the six lenses are of H-ZF7 LA.

4. A retro-modulating cat-eye optical system according to claim 1 or claim 2, wherein the six lenses are each coated with a high-transmission film.