CN108873280A - Off-axis catadioptric medium-long wave infrared system based on spherical reflector - Google Patents

Abstract

The invention provides an off-axis catadioptric mid-long wave infrared system based on a spherical reflector, which is characterized in that: along the direction of light propagation, a spherical reflector and a plurality of imaging compensation lens groups with diaphragms are sequentially included; The imaging compensation lens group with a diaphragm constitutes a separate imaging channel; the whole system is an off-axis system, in order to ensure that the imaging compensation lens group does not block the incident light, the spherical mirror has a fixed eccentricity relative to the incident light axis, in order to Cooperating with the reflected light, the compensation lens group is tilted so that the incident chief ray is perpendicular to the compensation lens group; multiple imaging compensation lens groups are fan-shaped distributed at the light exit of the concentric spherical mirror, and are not on the same plane as the incident light; An imaging compensation lens group includes a plurality of short-focus compensation mirrors, a plurality of medium-focus compensation mirrors and a plurality of telephoto compensation mirrors, and the plurality of imaging compensation lens groups adopt compensation lens groups with different focal lengths to correct images for different fields of view. difference to ensure constant meta-resolution.

Description

An off-axis catadioptric mid- to long-wave infrared system based on a spherical mirror

technical field

The invention relates to the field of optical imaging, in particular to an off-axis catadioptric mid-long wave infrared system based on a spherical reflector. It is mainly used for space-borne large-scale medium-resolution meteorological observation, and can also be used in urban security monitoring, national land census, disaster prevention and mitigation and other fields.

Background technique

Satellite ocean remote sensing plays an important role in the observation and research of the global marine environment and marine resources. It is characterized by rapid, continuous, large-scale and simultaneous observation of multiple parameters. A number of meteorological satellites have been launched around the world to detect oceans. The main remote sensor includes a visible light multispectral scanning radiometer, which is characterized by high sensitivity and signal-to-noise ratio, wide scanning field of view, and small imaging distortion. The current satellite payloads all use a fixed-focus camera plus a scanning mechanism or a fixed-focus multi-camera array to achieve large field of view imaging, resulting in an excessively large resolution gap between the sub-satellite point and the edge field of view, which affects the results of meteorological detection. It is of great significance for meteorological detection to realize the geometic resolution of the full field of view and reduce the resolution gap between the sub-satellite point and the edge field of view.

The wide-field ocean remote sensor SeaWiFS carried on the Orbview-2 satellite adopts the sweep method to scan ±58.3°, achieving a super large width of 2800km, and the sub-satellite point resolution is 1.13km. The medium-resolution imaging spectrometer MODIS carried on the EOS Terra satellite adopts the sweep method to scan ±55°, achieving a scanning width of 2330km, and the sub-satellite point resolutions are 250m, 500m and 1000m in different spectral bands. The visible light infrared imaging radiometer VIIRS carried by the polar-orbiting operating environment satellite system NPOESS adopts the sweep method to scan ±55.8°, achieving a super large width of 3000km, and the sub-satellite point resolution is 390m. The MERIS carried on the Envisat-1 satellite uses a camera array composed of 5 fixed focal length cameras to realize push-broom imaging in a 68.5° field of view, and achieves 1150km wide imaging, with a sub-satellite point resolution of 250m. The OLCI carried on the Sentinel-3 satellite uses a camera array composed of five fixed-focus cameras to realize push-broom imaging in a 68.4° field of view, and achieves 1150km swath imaging with a sub-satellite point resolution of 300m. FY-1, my country's first generation of polar-orbiting meteorological satellite series, is equipped with a multi-channel visible light and infrared scanning radiometer (MVISR). is 4km, and the imaging width is about 2800km. The second-generation polar-orbiting meteorological satellite series FY-3 is equipped with a medium-resolution spectral imager (MERSI). km, and the imaging width is about 2800km. The ten-band water color scanner carried by the Haiyang-1 (HY-1) satellite adopts the swing sweep method to scan ±35.2°, and the sub-satellite point resolution is 1100m. It can be seen that the current meteorological satellite payload adopts the technical solutions of push broom and swing broom, which are based on a fixed focal length image distance combined with a scanning mechanism to achieve large field of view and low distortion imaging. Due to the use of a fixed focal length camera, the large field of view causes a large gap between the ground imaging angle and imaging distance between the sub-satellite point and the peripheral field of view, resulting in an excessively large resolution gap between the sub-satellite point and the peripheral field of view. Taking the MODIS medium-resolution imaging spectrometer carried on the EOS Terra satellite as an example, when the sub-satellite point resolution is 500m, the resolution of the edge field of view is about 2700m.

D.J.Brady of Duke University in the United States proposed a multi-scale optical system design scheme based on concentric spherical lenses to solve large field of view, low distortion, and high-resolution imaging. This solution divides the full field of view into multiple sub-fields of view, and each sub-field of view has an independent compensation mirror to compensate for local aberrations, ensuring good imaging quality and low distortion in a single sub-field of view, and multiple subsystems splicing to achieve a full field of view High image quality and low distortion. Many domestic units have also applied for related patents: in 2012, Beijing Institute of Space Mechatronics applied for the patent No. 103064171A "A New Type of High-Resolution Large Field of View Optical Imaging System", and in 2013, Soochow University applied for the patent No. 203838419U Patent "Optical Imaging System for Large-Scale and High-Resolution Remote Sensing Cameras", patent number 204188263U applied by Soochow University in 2014 Patent "A Large Field of View Staring Spectral Imaging System", applied by Xidian University in 2014 The patent No. 104079808A of the patent "ultra-high resolution wide-field imaging system" and the patent No. ZL 201610265166.5 applied by the Xi'an Institute of Optics and Fine Mechanics in 2016 "Based on a spherical mirror with a large dynamic range near hemispherical field of view constant resolution Multispectral Optical Systems". Although the above patents are different in content, they all have in common the concentric multi-scale design based on concentric spherical lenses. Affected by the low transmittance of infrared materials, the transmissive concentric multi-scale system scheme is difficult to apply in the infrared band.

Contents of the invention

Infrared band imaging is required in more and more application environments. To meet the needs of infrared bands with large field of view, low distortion, and high imaging quality optical systems, the present invention proposes an off-axis catadioptric mid- to long-wave infrared system based on spherical mirrors. . The optical system has the characteristics of high imaging quality, large imaging field of view, constant resolution of the whole field of view, and can work in the infrared band.

The technical solution of the present invention is to provide an off-axis catadioptric mid- to long-wave infrared system based on a spherical reflector, which is special in that it includes a spherical reflector and multiple imaging sensors with apertures along the direction of light propagation. compensation lens group;

The whole system is an off-axis system, and the incident optical axis, the spherical mirror and multiple imaging compensation lens groups with diaphragms are not coaxial;

A plurality of imaging compensation lens groups with diaphragms are fan-shaped distributed at the light exit of the spherical mirror, and are on different planes from the incident light incident on the same spherical mirror, and each imaging compensation lens group with diaphragms is composed of A separate imaging channel; the light reflected from the spherical mirror is vertically incident to the imaging compensation lens group with a diaphragm;

The above-mentioned imaging compensation lens group with a diaphragm includes a plurality of short-focus compensation mirrors, a plurality of medium-focus compensation mirrors and a plurality of telephoto compensation mirrors, and the above-mentioned multiple imaging compensation lens groups use compensation mirrors with different focal lengths for different fields of view The group corrects for aberrations to ensure constant meta-resolution.

The relationship between the same spherical mirror and each imaging compensation lens group is off-axis, and the direction of the narrow field of view is the coaxial field of view. There is a certain eccentricity of the spherical mirror relative to the zero field of view, so that the actual use part of the spherical mirror is only It is the off-axis part that deviates from the center of symmetry; since the direction of the narrow field of view of each channel is consistent, the center point of the reflector part used by each channel is the same, and all the systems can be spliced together by extending the spherical reflector , to achieve near hemispherical field of view imaging.

Preferably, a plurality of imaging compensation lens groups with diaphragms are fan-shaped and uniformly distributed at the light exit of the spherical reflector.

Preferably, the short-focus compensation mirror includes a first negative lens, a first positive lens, a cold diaphragm window, a second positive lens, a second negative lens, and a third negative lens arranged in sequence along the optical path; the optical characteristics of the above-mentioned first negative lens is: -2f' ₂ <f' ₂₁ <-f' ₂ , -3f' ₂ <R ₂₁ <-2f' ₂ , -5f' ₂ <R ₂₂ <-4f'₂; the optical characteristics of the above-mentioned first positive lens is: 2f' ₂ <f' ₂₂ <3f' ₂ ,-f' ₂ <R ₂₃ <0,-f' ₂ <R ₂₄ <0; the optical characteristics of the second positive lens are: 2f' ₂ <f' ₂₃ <3f' ₂ ,0<R ₂₅ <f' ₂ ,f' ₂ <R ₂₆ <2f'₂; the optical characteristics of the above-mentioned second negative lens are: -7f' ₂ <f' ₂₄ <-6f' ₂ , 2f' ₂ <R ₂₇ <3f' ₂ ,f' ₂ <R ₂₈ <2f'₂; the optical characteristics of the above-mentioned third negative lens are: -f' ₂ <f' ₂₅ <-0.5f' ₂ ,-3f' ₂ <R ₂₉ <-2f' ₂ ,-R ₂₁₀ <-6f'₂; where, f' ₂ is the focal length of the short focus compensation mirror, f' ₂ >0, f' ₂₁ , f' ₂₂ , f' ₂₃ , f' ₂₄ and f' ₂₅ are the focal lengths of the five lenses that make up the short-focus compensation mirror; R ₂₁ , R ₂₂ , R ₂₃ , R ₂₄ , R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ , R ₂₁₀ In turn, they are the 10 radii of curvature corresponding to the 5 lenses that make up the short-focus compensation mirror.

Preferably, the mid-focus compensation mirror includes a first negative lens, a first positive lens, a cold diaphragm window, a second positive lens, a second negative lens, and a third negative lens arranged in sequence along the optical path; wherein the optical characteristics of the first negative lens is: -2f' ₃ <f' ₃₁ <-f' ₃ , -2f' ₃ <R ₃₁ <-f' ₃ , -3f' ₃ <R ₃₂ <-2f'₃; the optical characteristics of the first positive lens are : f' ₃ <f' ₃₂ <2f' ₃ , -f' ₃ <R ₃₃ <0, -f' ₃ <R ₃₄ <0; the optical characteristics of the second positive lens are: f' ₃ <f' ₃₃ <2f' ₃ , 0<R ₃₅ <f' ₃ , f' ₃ <R ₃₆ <2f'₃; the optical characteristics of the second negative lens are: -7f' ₃ <f' ₃₄ <-6f' ₃ , 8f' ₃ <R ₃₇ <9f' ₃ , 4f' ₃ <R ₃₈ <5f'₃; the optical characteristics of the third negative lens are: -2f' ₃ <f' ₃₅ <-f' ₃ , -3f' ₃ <R ₃₉ <-2f' ₃ , R ₃₁₀ <-10f'₃; Among them, f' ₃ is the focal length of the mid-focus compensation lens, f' ₃ >0;f' ₃₁ , f' ₃₂ , f' ₃₃ , f' ₃₄ , f' ₃₅ are the focal lengths of the 5 lenses that make up the mid-focus compensation mirror; R ₃₁ , R ₃₂ , R ₃₃ , R ₃₄ , R ₃₅ , R ₃₆ , R ₃₇ , R ₃₈ , R ₃₉ , and R ₃₁₀ are the focal lengths that make up the mid-focus compensation lens. The 10 radii of curvature corresponding to the 5 lenses of the mirror.

Preferably, the telephoto compensation mirror includes a first negative lens, a first positive lens, a cold diaphragm window, a second positive lens, a second negative lens, and a third negative lens arranged in sequence along the optical path; wherein the optical characteristics of the first negative lens is: -2f' ₄ <f' ₄₁ <-f' ₄ , -2f' ₄ <R ₄₁ <-f' ₄ , -4f' ₄ <R ₄₂ <-3f'₄; the optical properties of the first positive lens are : 2f' ₄ <f' ₄₂ <3f' ₄ , -f' ₄ <R ₄₃ <0, -f' ₄ <R ₄₄ <0; the optical characteristics of the second positive lens are: f' ₄ <f' ₄₃ <2f' ₄ , 0<R ₄₅ <f' ₄ , f' ₄ <R ₄₆ <2f'₄; the optical characteristics of the second negative lens are: -5f' ₄ <f' ₄₄ <-4f' ₄ , 2f' ₄ <R ₄₇ <3f' ₄ , 1f' ₄ <R ₄₈ <2f'₄; the optical characteristics of the third negative lens are: -2f' ₄ <f' ₄₅ <-f' ₄ , -3f' ₄ <R ₄₉ <-2f' ₄ , R ₄₁₀ <-7f'₄; where, f' ₄ is the focal length of the telephoto compensation lens, f' ₄ >0;f' ₄₁ , f' ₄₂ , f' ₄₃ , f' ₄₄ , f' ₄₅ is the focal length of the 5 lenses that make up the telephoto compensation mirror; R ₄₁ , R ₄₂ , R ₄₃ , R ₄₄ , R ₄₅ , R ₄₆ , R ₄₇ , R ₄₈ , R ₄₉ , and R ₄₁₀ are the focal lengths of the telephoto compensation lenses. 10 radii of curvature corresponding to 5 lenses.

The system selects the push-broom imaging mode, and the field of view of each channel is selected as a narrow strip field of view. Preferably, the wide fields of view of different imaging channels overlap each other by 5% to cover the entire imaging field of view, and all narrow fields of view It is a narrow-band field of view at a certain angle away from the central field of view. The imaging compensating lens groups with diaphragms in the whole system are only arranged in the direction perpendicular to the push-broom direction.

Preferably, the short-focus compensation mirror, the medium-focus compensation mirror and the long-focus compensation mirror have the same relative aperture, so as to ensure the consistency of the imaging quality of each field of view.

Preferably, the distance between the spherical mirror and the imaging compensation lens group with a diaphragm is more than twice the focal length of the optical system, so as to ensure that there are enough imaging compensation lens groups arranged and that the compensation lens groups will not interfere with each other .

Preferably, the cold diaphragm window includes a diaphragm and a glass plate arranged at the diaphragm, and the cold diaphragm is realized by cooling part of the compensating lens.

The beneficial effects of the present invention are:

1. The present invention adopts a spherical reflector plus each compensating lens group to realize imaging quality close to the diffraction limit in the entire field of view, and sets the aperture inside the compensating lens group to make full use of the rotationally symmetric optical characteristics of the spherical reflector in the full field of view ; The effective field of view of the optical system can theoretically be close to 360°, combined with the push-broom imaging mode, a large imaging width can be obtained; within the full field of view close to 360°, the distortion of all fields of view is less than 5%;

2. The distance between the spherical mirror and the compensation lens group of the present invention is very wide, which can effectively separate the imaging beams of each channel, which is beneficial to the suppression of stray light; at the same time, it avoids the interference of local strong light sources on the entire field of view, and can realize large dynamic range of imaging detection;

3. The imaging spectrum of the present invention covers 8-12 μm, covering the commonly used long-wave infrared band;

4. In order to achieve constant resolution in different fields of view, three kinds of compensation lens groups are used to correct aberrations for different fields of view. On the basis of the same ball lens, short focus, medium focus and long focus are realized to ensure constant Geo-element high resolution; at the same time, the short, medium and telephoto systems have the same relative aperture F#, which further ensures the consistency of imaging quality in each field of view;

5. Combined with the push-broom imaging mode, the imaging compensation lens group of the whole system is only arranged in the direction perpendicular to the push-broom direction, which can greatly reduce the number of cameras compared to the area array imaging; at the same time, the entire spherical mirror can be cut ( What is left after cutting is the ring mirror) and only the required part is reserved, which can greatly reduce the volume and quality of the camera;

6. The total optical length of the short-focus, medium-focus and telephoto systems is designed to be long enough to ensure that there are enough cameras arranged on the image plane without interfering with each other; the distance between the spherical mirror and the compensation lens group It is long enough, which is good for stray light suppression in the later stage; at the same time, the lenses that make up the compensation lens group are arranged very closely, which is very beneficial for system installation and adjustment;

7. Considering that the long-wave infrared system often adopts cooling mode, the solution is generally solved by cold aperture in the usual solution; however, the cold aperture solution limits the imaging field of view of the system. In the present invention, the entire field of view is segmented, and each The field of view of the channel is limited, and a glass plate is set at the system diaphragm, and the cold diaphragm is realized by cooling part of the compensation lens.

Description of drawings

Fig. 1 is the incident light mosaic schematic diagram of optical system of the present invention;

Fig. 2 is the splicing diagram of the imaging compensation lens group of the optical system of the present invention;

Fig. 3a, Fig. 3b and Fig. 3c are schematic structural diagrams of the optical system of the present invention corresponding to short focus, medium focus and telephoto respectively;

Fig. 4a, Fig. 4b are the MTF curve corresponding to the short focus of the optical system of the present invention;

Fig. 4c and Fig. 4d are MTF curves corresponding to the optical system of the present invention in the middle focus;

Fig. 4e and Fig. 4f are MTF curves corresponding to the telephoto of the optical system of the present invention;

Fig. 5a, Fig. 5b and Fig. 5c are respectively the diffusion spot diagrams of the optical system of the present invention at short focus, medium focus and long focus;

Figure 6a, Figure 6b and Figure 6c are the field curvature and distortion curves of the optical system of the present invention at short focus, medium focus and telephoto respectively;

Figure 7a is a schematic diagram of the three-dimensional structure of the optical system of the present invention;

Figure 7b is a side view of Figure 7a.

The reference signs in the figure are: 1-spherical reflector; 2-short-focus compensation mirror, 3-medium-focus compensation mirror, 4-telephoto compensation mirror; 21-the first negative lens of the short-focus compensation mirror group, 22-short focus compensation mirror The first positive lens of the focus compensation lens group, 23-the window glass of the short focus compensation lens group, 24-the second positive lens of the short focus compensation lens group, 25-the second negative lens of the short focus compensation lens group, 26-short focus compensation lens group The third negative lens of the focus compensation lens group; 31-the first negative lens of the middle focus compensation lens group, 32-the first positive lens of the middle focus compensation lens group, 33-the window glass of the middle focus compensation lens group, 34-middle The second positive lens of the focus compensation lens group, 35-the second negative lens of the medium focus compensation lens group, 36-the third negative lens of the medium focus compensation lens group; 41-the first negative lens of the telephoto compensation lens group, 42 -the first positive lens of the telephoto compensation lens group, 43-the window glass of the telephoto compensation lens group, 44-the second positive lens of the telephoto compensation lens group, 45-the second negative lens of the telephoto compensation lens group, 46 - the third negative lens of the telephoto compensation lens group;

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

As shown in Fig. 1, Fig. 2, Fig. 7a and Fig. 7b, it is a schematic structural diagram of the optical system of the present invention, and a spherical mirror 1 is placed on the optical path. In order to separately suppress stray light for the imaging channel corresponding to each compensation mirror group, and make full use of the optical characteristics of the spherical mirror 1 full field of view rotational symmetry, each imaging compensation mirror is sequentially placed at the corresponding position in front of the spherical mirror 1 according to the optical design results group; the imaging beams of each imaging channel are effectively separated, which avoids the interference of local strong light sources on the entire field of view, and can realize imaging detection with a large dynamic range. Combined with the push-broom imaging mode, the imaging compensation lens group of the entire system is only arranged in the direction perpendicular to the push-broom direction, which can greatly reduce the number of cameras compared to area array imaging; at the same time, the entire ball lens can be cut to keep only what is needed The part can greatly reduce the size and quality of the camera.

The imaging compensation lens group system includes a short-focus compensation mirror 2, a medium-focus compensation mirror 3 and a telephoto compensation mirror 4; as shown in Figure 3a, Figure 3b and Figure 3c, the optical system of the present invention is separately provided in the short-focus and medium-focus And the structural diagram corresponding to the telephoto.

Among them, the short-focus compensation mirror is composed of 6 lenses, and along the optical path are: the first negative lens 21 of the short-focus compensation lens group, the first positive lens 22 of the short-focus compensation lens group, and the window glass 23 of the short-focus compensation lens group , the second positive lens 24 of the short-focus compensation lens group, the second negative lens 25 of the short-focus compensation lens group, and the third negative lens 26 of the short-focus compensation lens group; the optical characteristics of the above-mentioned first negative lens are: -2f' ₂ <f' ₂₁ <-f' ₂ ,-3f' ₂ <R ₂₁ <-2f' ₂ , -5f' ₂ <R ₂₂ <-4f'₂; the optical characteristics of the above first positive lens are: 2f' ₂ <f' ₂₂ <3f' ₂ ,-f' ₂ <R ₂₃ <0, -f' ₂ <R ₂₄ <0; the optical characteristics of the above-mentioned second positive lens are: 2f' ₂ <f' ₂₃ <3f' ₂ ,0<R ₂₅ <f' ₂ ,f' ₂ <R ₂₆ <2f'₂; the optical characteristics of the above-mentioned second negative lens are: -7f' ₂ <f' ₂₄ <-6f' ₂ ,2f' ₂ <R ₂₇ <3f' ₂ , f' ₂ <R ₂₈ <2f'₂; the optical characteristics of the above-mentioned third negative lens are: -f' ₂ <f' ₂₅ <-0.5f' ₂ , -3f' ₂ <R ₂₉ <-2f' ₂ , -R ₂₁₀ <-6f'₂; Among them, f' ₂ is the focal length of the short focus system, f' ₂ >0, f' ₂₁ , f' ₂₂ , f' ₂₃ , f' ₂₄ , f' _{25 is the focal length} of the _{five lenses} that _{make up} the _short -focus _compensation mirror; Corresponding to 10 radii of curvature.

The mid-focus compensation mirror is composed of 6 lenses, along the optical path are the first negative lens 31 of the mid-focus compensation lens group, the first positive lens 32 of the mid-focus compensation lens group, the window glass 33 of the mid-focus compensation lens group, and the mid-focus compensation lens group. The second positive lens 34 of the compensation lens group, the second negative lens 35 of the middle focus compensation lens group, and the third negative lens 36 of the middle focus compensation lens group; wherein the optical characteristics of the first negative lens are: -2f' ₃ <f ' ₃₁ <-f' ₃ , -2f' ₃ <R ₃₁ <-f' ₃ , -3f' ₃ <R ₃₂ <-2f'₃; the optical characteristics of the first positive lens are: f' ₃ <f' ₃₂ <2f' ₃ , -f' ₃ <R ₃₃ <0, -f' ₃ <R ₃₄ <0; the optical characteristics of the second positive lens are: f' ₃ <f' ₃₃ <2f' ₃ , 0<R ₃₅ <f' ₃ , f' ₃ <R ₃₆ <2f'₃; the optical characteristics of the second negative lens are: -7f' ₃ <f' ₃₄ <-6f' ₃ , 8f' ₃ <R ₃₇ <9f' ₃ , 4f' ₃ <R ₃₈ <5f'₃; the optical characteristics of the third negative lens are: -2f' ₃ <f' ₃₅ <-f' ₃ , -3f' ₃ <R ₃₉ <-2f' ₃ , R ₃₁₀ <-10f'₃; where, f' ₃ is the focal length of the mid-focus system, f' ₃ >0;f' ₃₁ , f' ₃₂ , f' ₃₃ , f' ₃₄ , and f' ₃₅ are the components of the mid-focus compensation mirror in turn The focal lengths of the five lenses; R ₃₁ , R ₃₂ , R ₃₃ , R ₃₄ , R ₃₅ , R ₃₆ , R ₃₇ , R ₃₈ , R ₃₉ , and R ₃₁₀ are the 10 radii of curvature corresponding to the five lenses in turn.

Above-mentioned telephoto compensating mirror is made up of 6 lenses, and along optical path is: the first negative lens 41 of telephoto compensating mirror group, the first positive lens 42 of telephoto compensating mirror group, the window glass 43 of telephoto compensating mirror group, The second positive lens 44 of the telephoto compensation lens group, the second negative lens 45 of the telephoto compensation lens group, and the third negative lens 46 of the telephoto compensation lens group; wherein the optical characteristics of the first negative lens are: -2f' ₄ <f' ₄₁ <-f' ₄ , -2f' ₄ <R ₄₁ <-f' ₄ , -4f' ₄ <R ₄₂ <-3f'₄; the optical characteristics of the first positive lens are: 2f' ₄ <f ' ₄₂ <3f' ₄ , -f' ₄ <R ₄₃ <0, -f' ₄ <R ₄₄ <0; the optical characteristics of the second positive lens are: f' ₄ <f' ₄₃ <2f' ₄ , 0< R ₄₅ <f' ₄ , f' ₄ <R ₄₆ <2f'₄; the optical characteristics of the second negative lens are: -5f' ₄ <f' ₄₄ <-4f' ₄ , 2f' ₄ <R ₄₇ <3f' ₄ , 1f' ₄ <R ₄₈ <2f'₄; the optical characteristics of the third negative lens are: -2f' ₄ <f' ₄₅ <-f' ₄ , -3f' ₄ <R ₄₉ <-2f' ₄ , R ₄₁₀ <-7f'₄; where, f' ₄ is the focal length of the telephoto compensation lens, f' ₄ >0;f' ₄₁ , f' ₄₂ , f' ₄₃ , f' ₄₄ , and f' ₄₅ are the constituent telephoto lenses in turn The focal length of the 5 lenses of the compensation mirror; R ₄₁ , R ₄₂ , R ₄₃ , R ₄₄ , R ₄₅ , R ₄₆ , R ₄₇ , R ₄₈ , R ₄₉ , and R ₄₁₀ are the 10 radii of curvature corresponding to the 5 lenses in turn. .

The system focal lengths of the optical system provided by this embodiment are 59.04mm, 65.51mm, and 90mm; the full field of view corresponding to different focal lengths is 22.12°, 20°, and 16°, corresponding to The pixel sizes of the detectors are 75μm, 50μm, and 25μm respectively, and a full field of view of 110° is achieved through splicing; the F# of the short-focus, medium-focus and telephoto systems are all 2, and there is no vignetting in the full field of view. As shown in Fig. 4a, Fig. 4b, Fig. 4c, Fig. 4d, Fig. 4e, Fig. 4f, Fig. 5a, Fig. 5b, Fig. 5c, Fig. 6a, Fig. 6b and Fig. 6c, in the range of 8μm-12μm, the full field of view The inner MTFs are all close to the diffraction limit, the relative distortion is less than 5%, and the energy centroid deviation of the diffuse spot relative to the central wavelength (10 μm) is within 5 μm. If the camera is applied to an 800km low-Earth orbit satellite, it can obtain imaging quality close to the diffraction limit with a constant geo-element resolution better than 1200m within a 110° field of view.

The optical system adopts the push-broom mode, so the imaging cameras only need to be distributed in the direction perpendicular to the push-broom, and the redundant spherical mirror parts can be cut off, which can greatly reduce the complexity of the optical system, and also Contributes to the miniaturization of the camera.

By scaling this embodiment, under the same F# and field of view conditions, it is possible to achieve an imaging quality close to the diffraction limit in a field of view close to 180° when the orbital flight altitude is less than 800km, and it can achieve Constant geometrix resolution across the field.

Claims (9)

1. An off-axis catadioptric mid- to long-wave infrared system based on a spherical reflector, characterized in that: along the direction of light propagation, a spherical reflector and a plurality of imaging compensation lens groups with an aperture are sequentially included; The incident optical axis, the same spherical mirror and multiple imaging compensation lens groups with diaphragms are not coaxial; A plurality of imaging compensation lens groups with diaphragms are fan-shaped distributed at the light exit of the same spherical mirror, and are on different planes from the incident light incident on the same spherical mirror, each imaging compensation lens group with diaphragms Constitute a separate imaging channel; the light reflected from the same spherical mirror is vertically incident to the imaging compensation lens group with a diaphragm; The imaging compensation lens group with a diaphragm includes multiple short focus compensation mirrors, multiple medium focus compensation mirrors and multiple telephoto compensation mirrors. 2. A kind of off-axis catadioptric medium and long-wave infrared system based on a spherical reflector according to claim 1, characterized in that: a plurality of imaging compensation lens groups with apertures are fan-shaped and uniformly distributed on the same spherical reflector of the light. 3. The off-axis catadioptric mid- to long-wave infrared system based on a spherical mirror according to claim 2, wherein the short-focus compensation mirror includes a first negative lens, a first positive lens, and a first positive lens arranged in sequence along the optical path. Cold diaphragm window, second positive lens, second negative lens, and third negative lens; the optical characteristics of the first negative lens are: -2f' ₂ <f' ₂₁ <-f' ₂ , -3f' ₂ <R ₂₁ <-2f' ₂ , -5f' ₂ <R ₂₂ <-4f'₂; the optical characteristics of the first positive lens are: 2f' ₂ <f' ₂₂ <3f' ₂ , -f' ₂ <R ₂₃ <0,-f' ₂ <R ₂₄ <0; the optical characteristics of the second positive lens are: 2f' ₂ <f' ₂₃ <3f' ₂ ,0<R ₂₅ <f' ₂ ,f' ₂ <R ₂₆ <2f'₂; the optical characteristics of the second negative lens are: -7f' ₂ <f' ₂₄ <-6f' ₂ , 2f' ₂ <R ₂₇ <3f' ₂ , f' ₂ <R ₂₈ <2f '₂; the optical characteristics of the third negative lens are: -f' ₂ <f' ₂₅ <-0.5f' ₂ , -3f' ₂ <R ₂₉ <-2f' ₂ , -R ₂₁₀ <-6f'₂; Wherein, f' ₂ is the focal length of the short-focus compensation mirror, f' ₂ >0, f' ₂₁ , f' ₂₂ , f' ₂₃ , f' ₂₄ , and f' ₂₅ are the five lenses that make up the short-focus compensation mirror in turn focal length; R ₂₁ , R ₂₂ , R ₂₃ , R ₂₄ , R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ , and R ₂₁₀ respectively represent the 10 curvatures corresponding to the 5 lenses that make up the short-focus compensation lens radius. 4. The off-axis catadioptric mid- to long-wave infrared system based on a spherical mirror according to claim 2, wherein the mid-focus compensation mirror includes a first negative lens, a first positive lens, and a first positive lens arranged in sequence along the optical path. Cold diaphragm window, second positive lens, second negative lens, and third negative lens; the optical characteristics of the first negative lens are: -2f' ₃ <f' ₃₁ <-f' ₃ , -2f' ₃ <R ₃₁ <-f' ₃ , -3f' ₃ <R ₃₂ <-2f'₃; the optical characteristics of the first positive lens are: f' ₃ <f' ₃₂ <2f' ₃ , -f' ₃ <R ₃₃ <0, -f' ₃ <R ₃₄ <0; the optical characteristics of the second positive lens are: f' ₃ <f' ₃₃ <2f' ₃ , 0<R ₃₅ <f' ₃ , f' ₃ <R ₃₆ <2f'₃; The optical characteristics of the second negative lens are: -7f' ₃ <f' ₃₄ <-6f' ₃ , 8f' ₃ <R ₃₇ <9f' ₃ , 4f' ₃ <R ₃₈ <5f'₃; the third negative lens The optical characteristics are: -2f' ₃ <f' ₃₅ <-f' ₃ , -3f' ₃ <R ₃₉ <-2f' ₃ , R ₃₁₀ <-10f'₃; among them, f' ₃ is a mid-focus compensation lens The focal length of f' ₃ >0;f' ₃₁ , f' ₃₂ , f' ₃₃ , f' ₃₄ , f' ₃₅ are the focal lengths of the five lenses that make up the mid-focus compensator; R ₃₁ , R ₃₂ , R ₃₃ , R ₃₄ , R ₃₅ , R ₃₆ , R ₃₇ , R ₃₈ , R ₃₉ , and R ₃₁₀ are sequentially the 10 radii of curvature corresponding to the 5 lenses that make up the mid-focus compensation mirror. 5. The off-axis catadioptric medium and long-wave infrared system based on a spherical mirror according to claim 2, wherein the telephoto compensation mirror includes a first negative lens, a first positive lens, and a first positive lens arranged in sequence along the optical path. Cold diaphragm window, second positive lens, second negative lens, and third negative lens; the optical characteristics of the first negative lens are: -2f' ₄ <f' ₄₁ <-f' ₄ , -2f' ₄ <R ₄₁ <-f' ₄ , -4f' ₄ <R ₄₂ <-3f'₄; the optical characteristics of the first positive lens are: 2f' ₄ <f' ₄₂ <3f' ₄ , -f' ₄ <R ₄₃ <0, -f' ₄ <R ₄₄ <0; the optical characteristics of the second positive lens are: f' ₄ <f' ₄₃ <2f' ₄ , 0<R ₄₅ <f' ₄ , f' ₄ <R ₄₆ <2f'₄; The optical characteristics of the second negative lens are: -5f' ₄ <f' ₄₄ <-4f' ₄ , 2f' ₄ <R ₄₇ <3f' ₄ , 1f' ₄ <R ₄₈ <2f'₄; the third negative lens The optical characteristics are: -2f' ₄ <f' ₄₅ <-f' ₄ , -3f' ₄ <R ₄₉ <-2f' ₄ , R ₄₁₀ <-7f'₄; among them, f' ₄ is a telephoto compensation lens The focal length of f' ₄ >0;f' ₄₁ , f' ₄₂ , f' ₄₃ , f' ₄₄ , f' ₄₅ are the focal lengths of the five lenses that make up the telephoto compensation mirror in turn; R ₄₁ , R ₄₂ , R ₄₃ , R ₄₄ , R ₄₅ , R ₄₆ , R ₄₇ , R ₄₈ , R ₄₉ , and R ₄₁₀ are successively the 10 radii of curvature corresponding to the 5 lenses forming the telephoto compensation mirror. 6. The off-axis catadioptric mid- to long-wave infrared system based on a spherical mirror according to claim 2, wherein the system selects the push-broom imaging mode, and the field of view of each imaging channel is selected as a narrow strip With a field of view, the wide fields of view of different imaging channels overlap each other by 5% to cover the entire imaging field of view, and all the narrow fields of view are narrow-band fields of view that deviate from the central field of view at a certain angle, and the imaging compensation lens group of the entire system is only in the vertical Arranged in the push-broom direction. 7. A kind of off-axis catadioptric medium and long-wave infrared system based on a spherical mirror according to any one of claims 1 to 5, characterized in that: the short-focus compensation mirror, the medium-focus compensation mirror and the telephoto compensation mirror have the same relative aperture. 8. A kind of off-axis catadioptric medium and long-wave infrared system based on a spherical reflector according to any one of claims 1 to 5, characterized in that: the distance between the spherical reflector and the imaging compensation lens group with a diaphragm The distance is more than twice the focal length of the optical system. 9. An off-axis catadioptric mid-long wave infrared system based on a spherical mirror according to any one of claims 3 to 5, wherein the cold aperture window includes an aperture and a glass plate arranged at the aperture.