阅读说明：本技术 一种制冷型大相对孔径离轴四反光学系统 (Refrigeration type large-relative-aperture off-axis four-mirror optical system ) 是由 廖志远 白瑜 操超 陈炳旭 于 2019-09-25 设计创作，主要内容包括：本发明公开了一种制冷型大相对孔径离轴四反光学系统,该光学系统沿光线传递方向包括第一平面反射镜(1)、第二平面反射镜(2)、第一反射镜(3)、第二反射镜(4)、分光平板(5)、第三反射镜(6)、第四反射镜(7)、冷光阑(8)和探测器像面(9)。第二反射镜(4)和第三反射镜(6)具有负的光焦度,第一反射镜(3)和第四反射镜(7)具有正的光焦度。该系统采用制冷型红外探测器,满足100％冷光阑匹配效率；光学系统焦距长,可以实现对较远距离目标进行观测；冷光阑(8)和探测器像面(9)相对于第四反射镜(7)的出射光线同轴使用,系统可以采用同轴杜瓦瓶,成本低；系统通过分光平板(5),可以根据使用需求添加其它探测光路。(The invention discloses a refrigeration type large-relative-aperture off-axis four-mirror optical system which comprises a first plane reflector (1), a second plane reflector (2), a first reflector (3), a second reflector (4), a light splitting flat plate (5), a third reflector (6), a fourth reflector (7), a cold diaphragm (8) and a detector image surface (9) along the light ray transmission direction. The second reflector (4) and the third reflector (6) have negative focal power, and the first reflector (3) and the fourth reflector (7) have positive focal power. The system adopts a refrigeration type infrared detector, and meets the matching efficiency of a 100% cold diaphragm; the optical system has long focal length, and can realize observation of a target at a longer distance; the cold diaphragm (8) and the detector image surface (9) are coaxially used relative to the emergent ray of the fourth reflector (7), and the system can adopt a coaxial Dewar flask, so that the cost is low; the system can add other detection light paths according to the use requirement through the light splitting flat plate (5).)

1. A refrigeration type large-relative-aperture off-axis four-mirror optical system is characterized in that: the optical system comprises a first plane reflector (1), a second plane reflector (2), a first reflector (3), a second reflector (4), a light splitting flat plate (5), a third reflector (6), a fourth reflector (7), a cold diaphragm (8) and a detector image surface (9); the method comprises the following steps that light rays enter from infinity, sequentially pass through a first plane reflector (1), a second plane reflector (2), a first reflector (3), a second reflector (4), a light splitting flat plate (5), a third reflector (6), a fourth reflector (7) and a cold diaphragm (8), and finally reach a detector image surface (9); the optical system adopts a refrigeration type infrared detector, and the matching efficiency of the cold diaphragm is 100 percent.

2. The refrigeration-type large relative aperture off-axis four-mirror optical system of claim 1, wherein: the inclination value of the first plane reflector (1) is between 20 and 50 degrees; the inclination value of the second plane reflector (2) is between 45 and 85 degrees; the first reflector (3) has positive focal power, the curvature radius is 600-800 mm, the off-axis quantity value is 20-30 mm, and the inclination quantity value is 0-10 degrees; the second reflecting mirror (4) has negative focal power, the curvature radius of the second reflecting mirror is 400-500 mm, the off-axis quantity value of the second reflecting mirror is 42-68 mm, and the inclination quantity value of the second reflecting mirror is 0-3 degrees; the third reflector (6) has negative focal power, the radius of the third reflector is 260-310 mm, the off-axis quantity value of the third reflector is 15-42 mm, and the inclination quantity value of the third reflector is 8-16 degrees; the fourth reflector (7) has positive focal power, the radius of the fourth reflector is 210-280 mm, the off-axis value of the fourth reflector is-45-22 mm, and the inclination value of the fourth reflector is 12-21 degrees.

3. The refrigeration-type large relative aperture off-axis four-mirror optical system of claim 1, wherein: the value of the inclination amount of the first plane reflector (1) is 37.5 degrees; the inclination value of the second plane reflector (2) is 75 degrees; the first reflector (3) has positive focal power, the curvature radius is 743.36mm, the off-axis value is 23.2mm, and the inclination value is-3.08 degrees; the second reflector (4) has negative focal power, the curvature radius is 460.5mm, the off-axis value is 52mm, and the inclination value is 0.65 degrees; the third reflector (6) has negative focal power, the curvature radius is 305.94mm, the off-axis value is 25.92mm, and the inclination value is 12.89 degrees; the fourth mirror (7) has a positive power, a radius of curvature of 258.98mm, an off-axis value of-31.4 mm, and a tilt value of 17.85 degrees.

4. The refrigeration-type large relative aperture off-axis four-mirror optical system of claim 1, wherein: the first plane mirror (1) and the second plane mirror (2) are used for folding the light path in front of the system.

5. The refrigeration-type large relative aperture off-axis four-mirror optical system of claim 1, wherein: the first plane mirror (1) is used for carrying out two-dimensional space scanning on a detection field of view.

6. The refrigeration-type large relative aperture off-axis four-mirror optical system of claim 1, wherein: a field diaphragm can be placed on an intermediate image plane between the second reflector (4) and the third reflector (6) to inhibit stray light; a light splitting plate (5) is arranged between the second reflecting mirror (4) and the third reflecting mirror (6), and other detection light paths can be added according to the use requirement.

7. The refrigeration-type large relative aperture off-axis four-mirror optical system of claim 1, wherein: the cold diaphragm and the detector image surface are coaxially used relative to the emergent light of the fourth reflector (7), and the optical system adopts a coaxial Dewar flask, so that the debugging difficulty and the cost of the system are reduced.

Technical Field

The invention relates to the field of imaging optical system design working in an infrared band, in particular to the field of off-axis reflection type optical system design based on a refrigeration type infrared detector.

Background

Compared with a transmission type optical system, the reflection type imaging optical system has the advantages of no chromatic aberration, large caliber, light weight, good thermal stability and the like, and is widely applied to the field of space remote sensing. Compared with the coaxial reflection type optical system, the off-axis reflection type optical system has no central barrier and high energy utilization rate. The infrared imaging optical system is a passive imaging optical system and has the advantages of good concealment, strong anti-interference capability, good environmental adaptability and the like.

Compared with a non-refrigeration infrared detector, the refrigeration infrared detector has higher signal-to-noise ratio and sensitivity due to lower working temperature. In order to reduce background noise, a cold diaphragm is arranged in a dewar of the refrigeration type infrared detector, and an infrared optical system matched with the refrigeration type infrared detector is used.

In an off-axis reflection type imaging optical system with a large relative aperture, the matching of a system aperture diaphragm and a cold diaphragm is difficult, and the design difficulty is high. At present, related domestic patents are few, in related foreign patents U.S. patent 4,265,510, U.S. patent 4,834,517 and U.S. patent 5,550,672, in an off-axis reflection type imaging optical system based on a refrigeration type infrared detector, a cold diaphragm and a detector are mostly used off-axis, and the system needs to use an off-axis dewar bottle, so that the cost is high; in addition, the existing off-axis reflection type optical system design based on the refrigeration type infrared detector has small relative aperture, no light splitting device, no addition of other detection light paths and limited application.

Disclosure of Invention

The purpose of the invention is to overcome the following problems: the existing refrigeration off-axis reflection type optical system is high in cost due to the off-axis use of a cold diaphragm and a detector image surface; the relative aperture is small, which is not beneficial to observing a target at a longer distance. The invention provides a refrigeration type off-axis four-mirror optical system with large relative aperture, which adopts a coaxial Dewar flask and has low cost; the system has a large relative aperture, and can observe a target at a longer distance; the system can add other detection light paths according to the use requirement through the light splitting flat plate.

The technical scheme adopted by the invention is as follows: a refrigeration type large-relative-aperture off-axis four-mirror optical system comprises a first plane reflector 1, a second plane reflector 2, a first reflector 3, a second reflector 4, a light splitting flat plate 5, a third reflector 6, a fourth reflector 7, a cold diaphragm 8 and a detector image surface 9.

The light enters from infinity, sequentially passes through a first plane reflector 1, a second plane reflector 2, a first reflector 3, a second reflector 4, a light splitting flat plate 5, a third reflector 6, a fourth reflector 7 and a cold diaphragm 8, and finally reaches a detector image surface 9; the optical system adopts a refrigeration type infrared detector, and the matching efficiency of the cold diaphragm is 100 percent.

The value of the inclination amount of the first plane reflector 1 is between 20 and 50 degrees; the inclination value of the second plane reflector 2 is 45-85 degrees; the first reflector 3 has positive focal power, the curvature radius is 600-800 mm, the off-axis quantity value is 20-30 mm, and the inclination quantity value is 0-10 degrees; the second reflecting mirror 4 has negative focal power, the curvature radius of the second reflecting mirror is 400-500 mm, the numerical value of the off-axis quantity of the second reflecting mirror is 42-68 mm, and the numerical value of the inclination quantity of the second reflecting mirror is 0-3 degrees; the third reflector 6 has negative focal power, the radius of the third reflector is 260-310 mm, the numerical value of the off-axis quantity of the third reflector is 15-42 mm, and the numerical value of the inclination quantity of the third reflector is 8-16 degrees; the fourth reflector 7 has positive focal power, the radius of the fourth reflector is 210-280 mm, the off-axis value of the fourth reflector is-45-22 mm, and the inclination value of the fourth reflector is 12-21 degrees.

The value of the inclination amount of the first plane mirror 1 is 37.5 degrees; the inclination value of the second plane mirror 2 is 75 degrees; the first mirror 3 has a positive power, a radius of curvature of 743.36mm, an off-axis amount of 23.2mm, and a tilt amount of-3.08 degrees; the second reflector (4) has negative focal power, the curvature radius is 460.5mm, the off-axis value is 52mm, and the inclination value is 0.65 degrees; the third reflector 6 has a negative power, a radius of curvature of 305.94mm, an off-axis value of 25.92mm, and a tilt value of 12.89 degrees; the fourth mirror 7 has a positive power, a radius of curvature of 258.98mm, an off-axis value of-31.4 mm, and a tilt value of 17.85 degrees.

A first plane mirror 1 and a second plane mirror 2 are used in front of the system to fold the optical path.

The first plane mirror 1 is used for two-dimensional space scanning of the detection field of view.

A field diaphragm can be placed on an intermediate image plane between the second reflector 4 and the third reflector 6 to inhibit stray light; and a light splitting plate 5 is arranged between the second reflecting mirror 4 and the third reflecting mirror 6, and other detection light paths can be added according to the use requirement.

The cold diaphragm and the detector image surface are coaxially used relative to the emergent light of the fourth reflector 7, and the optical system adopts a coaxial Dewar flask, so that the debugging difficulty and the cost of the system are reduced.

The invention has the advantages that: the system has a large relative aperture, so that a target at a longer distance can be observed; the cold diaphragm 8 and the detector image surface 9 are coaxially used relative to the emergent light of the fourth reflector 7, and the system can adopt a coaxial Dewar flask, so that the assembly difficulty is low and the cost is low; a field diaphragm can be placed on an intermediate image plane between the second reflector 4 and the third reflector 6 to inhibit stray light; and a light splitting plate 5 is arranged between the second reflecting mirror 4 and the third reflecting mirror 6, and other detection light paths can be added according to the use requirement.

Drawings

Fig. 1 is an optical layout diagram of an optical system of the present invention.

Fig. 2 is a schematic diagram of an optical Modulation Transfer Function (MTF) of the optical system of the present invention.

In the figure: the system comprises a first plane reflector 1, a second plane reflector 2, a first reflector 3, a second reflector 4, a light splitting flat plate 5, a third reflector 6, a fourth reflector 7, a cold diaphragm 8 and a detector image surface 9.

Detailed Description

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

The invention is implemented according to the optical path shown in figure 1, the working wavelength band is 7.5-13.0 μm, the focal length of the image space is 405mm, the aperture of the entrance pupil is 160mm, the relative aperture is 1/2.53, and the angle of view is 2.4 degrees multiplied by 1.92 degrees. The value of the inclination amount of the first plane mirror 1 is 37.5 degrees; the inclination value of the second plane mirror 2 is 75 degrees; the first mirror 3 has a positive power, a radius of curvature of 743.36mm, an off-axis amount of 23.2mm, and a tilt amount of-3.08 degrees; the second reflecting mirror 4 has negative focal power, the curvature radius is 460.5mm, the off-axis value is 52mm, and the inclination value is 0.65 degrees; the third reflector 6 has a negative power, a radius of curvature of 305.94mm, an off-axis value of 25.92mm, and a tilt value of 12.89 degrees; the fourth mirror 7 has a positive power, a radius of curvature of 258.98mm, an off-axis value of-31.4 mm, and a tilt value of 17.85 degrees. The light splitting flat plate 5 and the middle image surface are arranged between the second reflector 4 and the third reflector 6, the system meets the cold diaphragm efficiency of 100%, and the distance from the cold diaphragm to the image surface is 45 mm.

The Modulation Transfer Function (MTF) is a comprehensive evaluation index of the optical lens, and it can be seen from fig. 2 that the MTF of each field of view of the system is close to the diffraction limit, which shows that the imaging quality of the optical system is good in the full field of view.