CN108873280B - Off-axis catadioptric medium-long wave infrared system based on spherical reflector - Google Patents
Off-axis catadioptric medium-long wave infrared system based on spherical reflector Download PDFInfo
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Abstract
The invention provides an off-axis catadioptric medium-long wave infrared system based on a spherical reflector, which is characterized in that: the imaging compensation lens group comprises a spherical reflector and a plurality of imaging compensation lens groups with diaphragms in sequence along the light propagation direction; each imaging compensation lens group with a diaphragm forms a single imaging channel; the whole system is an off-axis system, in order to ensure that the imaging compensation lens group and incident light rays are not shielded mutually, the spherical reflector has a fixed eccentric amount relative to the incident optical axis, and in order to match with reflected light rays, the compensation lens group is inclined so that the incident principal light rays are perpendicular to the compensation lens group; the plurality of imaging compensation lens groups are distributed at the light outlet of the concentric sphere reflector in a fan shape and are not on the same plane with the incident light; the imaging compensation lens groups comprise a plurality of short-focus compensation lenses, a plurality of medium-focus compensation lenses and a plurality of long-focus compensation lenses, and the imaging compensation lens groups correct aberration by adopting the compensation lens groups with different focal lengths for different view fields so as to ensure high resolution of constant elements.
Description
Technical Field
The invention relates to the field of optical imaging, in particular to an off-axis catadioptric medium-long wave infrared system based on a spherical reflector. The method is mainly used for satellite-borne large-range medium-resolution meteorological observation, and can also be used in the fields of urban safety monitoring, homeland general investigation, disaster prevention, disaster reduction and the like.
Background
The satellite marine remote sensing has important roles in observing and researching global marine environment and marine resources, and is characterized by being capable of observing a plurality of parameters rapidly, continuously and in a large range at the same time. The main remote sensor comprises a visible light multispectral scanning radiometer and is characterized by high sensitivity and signal-to-noise ratio, wide scanning field of view and small imaging distortion. The current satellite load adopts a scheme of a fixed focal length camera and a scanning mechanism or a fixed focal length multi-camera array to realize large-view-field imaging, so that the resolution difference between the understar point and the edge view field is overlarge, and the weather detection result is influenced. The method realizes the equivalent ground element resolution of the full view field, reduces the resolution difference between the undersea point and the edge view field, and has important significance for meteorological detection.
The wide-field marine remote sensor SeaWiFS carried on the Orbview-2 satellite adopts a sweeping mode to scan + -58.3 degrees, so that the ultra-large width of 2800km is realized, and the resolution of the point under the satellite is 1.13km. The medium resolution imaging spectrometer MODIS carried on the EOS Terra satellite adopts a sweeping mode to scan +/-55 degrees, so as to realize the scanning breadth of 2330km, and the resolution of the points below the satellite is 250m,500m and 1000m respectively in different spectral bands. The visible light infrared imaging radiation instrument VIIRS carried by the polar orbit running environment satellite system NPOESS adopts a swinging scanning mode to scan +/-55.8 degrees, so that the ultra-large breadth of 3000km is realized, and the resolution of the point under the satellite is 390m. MERIS carried on the Envisat-1 satellite adopts a camera array formed by 5 fixed focal length cameras to realize push-broom imaging in a 68.5-degree view field, realizes 1150km breadth imaging, and has the resolution of 250m in the space. OLCI carried on Sentinel-3 satellite adopts a camera array formed by 5 fixed focal length cameras to realize push-broom imaging in 68.4-degree view field, 1150km breadth imaging is realized, and the resolution of points under the satellite is 300m. The first generation polar orbit meteorological satellite series FY-1 of China is provided with a multi-channel visible light and infrared scanning radiometer (MVISR), the scanning angle is +/-55.4 degrees, the resolution of the points under the satellite is 1.1km, the resolution of the edge view field is about 4km, and the imaging breadth is about 2800km. A medium resolution spectrum imager (MERSI) is mounted on the second generation polar orbit meteorological satellite series FY-3, the scanning angle is +/-55.4 degrees, the resolution of the satellite point under the satellite is 0.1km, the resolution of the edge view field is about 2.4km, and the imaging breadth is about 2800km. A ten-band water color scanner carried by a sea first number (HY-1) satellite adopts a sweeping mode to scan +/-35.2 degrees, and the resolution of an under-satellite point is 1100m. It can be seen that the technical schemes of push scanning and swing scanning are adopted for the load of the current meteorological satellite, and the large-view-field and low-distortion imaging is realized based on a fixed focal length image distance combined scanning mechanism. Because a fixed focal length camera is adopted, the large view field causes a large difference in the field angle and the imaging distance of the understar point and the edge view field, and the resolution difference between the understar point and the edge view field is excessively large. Taking a medium resolution imaging spectrometer MODIS carried on an EOS Terra satellite as an example, when the resolution of a point under the satellite is 500m, the resolution of an edge view field is about 2700m.
Multi-scale optical system designs based on concentric ball lenses were proposed by the university of duc, usa, d.j.brady et al to address large field of view, low distortion, high resolution imaging. According to the scheme, the full view field is divided into a plurality of sub view fields, each sub view field is provided with an independent compensation mirror for compensating local aberration, good imaging quality and small distortion in a single sub view field are guaranteed, and a plurality of sub systems are spliced to achieve high imaging quality and low distortion in the full view field. Related patents are also filed by a plurality of domestic units: patent No. 103064171a of the beijing spatial electromechanical study institute in 2012, "a novel high resolution large field of view optical imaging system", patent No. 203838419U of the university of su in 2013, "optical imaging system for large-scale high resolution remote sensing camera", patent No. 204188263U of the university of su in 2014, "a large field of view staring spectral imaging system", patent No. 104079808A of the university of su in 2014, "ultra high resolution wide field imaging system", and patent No. ZL 201610265166.5 of the institute of optical precision mechanical study in the 2016 of sa "based on spherical mirror large dynamic range near hemispherical field of view constant resolution multispectral optical system". The above patents, although differing in content, all share a concentric multiscale design based on concentric ball lenses. The transmissive concentric multi-scale system scheme is difficult to apply to the infrared band, subject to the low transmittance of infrared materials.
Disclosure of Invention
The invention provides an off-axis refraction-reflection type medium-long wave infrared system based on a spherical reflector aiming at the requirements of infrared band imaging in more and more application environments and the requirements of an optical system with large view field, low distortion and high imaging quality. The optical system has the characteristics of high imaging quality, large imaging view field, constant ground element resolution of the whole view field, capability of working in an infrared band and the like.
The technical scheme of the invention is to provide an off-axis catadioptric medium-long wave infrared system based on a spherical reflector, which is characterized in that: the imaging compensation lens group comprises a spherical reflector and a plurality of imaging compensation lens groups with diaphragms sequentially along the light propagation direction;
the whole system is an off-axis system, and an incident optical axis, the same spherical reflector and a plurality of imaging compensation lens groups with diaphragms are all not coaxial;
the imaging compensation lens groups with the diaphragms are distributed at the light outlet of the spherical reflecting mirror in a fan shape and are on different planes with the incident light incident to the same spherical reflecting mirror, and each imaging compensation lens group with the diaphragms forms an independent imaging channel; light reflected from the spherical reflecting mirror is vertically incident to an imaging compensation lens group with a diaphragm;
the imaging compensation lens group with the diaphragm comprises a plurality of short-focus compensation mirrors, a plurality of medium-focus compensation mirrors and a plurality of long-focus compensation mirrors, and the imaging compensation lens groups adopt the compensation lens groups with different focal lengths for different view fields to correct aberration so as to ensure constant element high resolution.
The spherical reflector and each imaging compensation lens group are in an off-axis relation, the narrow view field direction is an on-axis view field, and the spherical reflector has certain eccentricity relative to the zero view field, so that the actual use part of the spherical reflector is only an off-axis part deviating from the symmetry center; because the narrow view field direction of each channel is selected consistently, the center points of the reflecting mirror parts utilized by each channel are the same, and all the systems can be spliced together by extending the spherical reflecting mirror, so that near-hemispherical view field imaging is realized.
Preferably, a plurality of imaging compensation lens groups with diaphragms are uniformly distributed at the light emergent position of the spherical reflector in a fan shape.
Preferably, the short-focus compensation lens comprises 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 which are sequentially arranged along the light path; the optical characteristics of the first negative lens are as follows: -2f' 2 <f’ 21 <-f’ 2 ,-3f’ 2 <R 21 <-2f’ 2 ,-5f’ 2 <R 22 <-4f’ 2 The method comprises the steps of carrying out a first treatment on the surface of the 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 method comprises the steps of carrying out a first treatment on the surface of the 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 method comprises the steps of carrying out a first treatment on the surface of the The third negative lens has the following optical characteristics: -f' 2 <f’ 25 <-0.5f’ 2 ,-3f’ 2 <R 29 <-2f’ 2 ,-R 210 <-6f’ 2 The method comprises the steps of carrying out a first treatment on the surface of the Wherein f' 2 For compensating the focal length of the mirror for short focus, f' 2 >0， f’ 21 、f’ 22 、f’ 23 、f’ 24 、f’ 25 The focal lengths of 5 lenses forming the short-focus compensation lens are sequentially set; r is R 21 、R 22 、R 23 、R 24 、 R 25 、R 26 、R 27 、R 28 、R 29 、R 210 And the curvature radii of the 5 lenses which form the short-focus compensation lens are respectively 10 corresponding to each other in sequence.
Preferably, the method comprises the steps of, the middle focus compensation lens comprises a first negative lens, a second negative lens, a third lens, a fourth lens and a fourth lens which are sequentially arranged along the light path a first positive lens, a cold stop window, a second positive lens,A second negative lens and a third negative lens; 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 method comprises the steps of carrying out a first treatment on the surface of the The optical characteristics of the first positive lens are: f's' 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's' 3 <f’ 33 <2f’ 3 ， 0<R 35 <f’ 3 ，f’ 3 <R 36 <2f’ 3 The method comprises the steps of carrying out a first treatment on the surface of the 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 method comprises the steps of carrying out a first treatment on the surface of the 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 The method comprises the steps of carrying out a first treatment on the surface of the Wherein f' 3 For the focal length of the middle focus compensation mirror, f' 3 >0；f’ 31 、f’ 32 、f’ 33 、f’ 34 、f’ 35 The focal lengths of 5 lenses forming the middle focus compensation lens are sequentially set; r is R 31 、R 32 、R 33 、R 34 、R 35 、R 36 、R 37 、R 38 、R 39 、R 310 The curvature radii of the 5 lenses composing the middle focus compensation lens are 10 corresponding to each other.
Preferably, the tele compensation mirror comprises 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 which are sequentially arranged along the light path; 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 method comprises the steps of carrying out a first treatment on the surface of the 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's' 4 <f’ 43 <2f’ 4 ，0<R 45 <f’ 4 ，f’ 4 <R 46 <2f’ 4 The method comprises the steps of carrying out a first treatment on the surface of the 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 method comprises the steps of carrying out a first treatment on the surface of the 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 The method comprises the steps of carrying out a first treatment on the surface of the Wherein f' 4 For the focal length of the long-focus compensation mirror, f' 4 >0；f’ 41 、f’ 42 、f’ 43 、 f’ 44 、f’ 45 The focal lengths of 5 lenses forming the long-focus compensation lens are sequentially set; r is R 41 、R 42 、R 43 、R 44 、R 45 、R 46 、R 47 、 R 48 、R 49 、R 410 The curvature radii of the lens 5 lens composing the long focus compensation lens are 10 corresponding in turn.
The system selects a push-broom imaging mode, the view field of each channel is selected to be a narrow-band view field, preferably, the wide view fields of different imaging channels cover the whole imaging view field by overlapping each other by 5%, and all the narrow view fields are narrow-band view fields which deviate from the central view field by a certain angle. The imaging compensation lens group with the diaphragm of the whole system is only arranged in the direction perpendicular to the push-broom direction.
Preferably, the short-focus compensation mirror, the middle-focus compensation mirror and the long-focus compensation mirror have the same relative aperture, so that consistency of imaging quality of each field of view is ensured.
Preferably, the distance between the spherical reflecting mirror and the imaging compensation lens group with the diaphragm is more than one time of the focal length of the optical system, so as to ensure that enough imaging compensation lens groups are arranged and the imaging compensation lens groups do not interfere with each other.
Preferably, the cold diaphragm window comprises a diaphragm and a glass plate arranged at the diaphragm, and the cold diaphragm is realized by refrigerating part of the compensating lens.
The beneficial effects of the invention are as follows:
1. the invention adopts the spherical reflector and each compensating lens group to realize the imaging quality approaching to the diffraction limit on the whole view field, and the diaphragm is arranged in the compensating lens group, thereby fully utilizing the optical characteristics of the spherical reflector, such as full view field rotation symmetry; the effective field of view of the optical system can be close to 360 degrees in theory, and the imaging width can be extremely large by combining the push-broom imaging mode; in the full view field range of nearly 360 degrees, the distortion of all view fields is less than 5 percent;
2. the spherical reflector and the compensating lens group are spaced apart, so that imaging light beams of all channels can be effectively separated, and stray light suppression is facilitated; meanwhile, the interference of a local strong light source to the whole view field is avoided, and the imaging detection with a large dynamic range can be realized;
3. the imaging spectrum of the invention covers 8-12 mu m and common long-wave infrared wave bands;
4. in order to realize constant ground element resolution in different view fields, three compensation lens groups are adopted for correcting aberration for different view fields, and short focus, middle focus and long focus are realized on the basis of the same spherical lens to ensure constant ground element high resolution; meanwhile, the short, medium and long coke systems have the same relative aperture F#, so that the consistency of the imaging quality of each view field is further ensured;
5. in combination with the push-broom imaging mode, the imaging compensation lens groups of the whole system are only arranged in the direction perpendicular to the push-broom direction, so that the number of cameras can be greatly reduced relative to the area array imaging; meanwhile, the whole spherical reflector can be cut (the annular reflector is left after cutting), only the needed part is reserved, and the volume and the quality of the camera can be greatly reduced;
6. the total optical length is long enough when the short-focus, medium-focus and long-focus systems are designed, so that enough cameras can be arranged on an image plane without mutual interference among the cameras; the distance between the spherical reflecting mirror and the compensating lens group is long enough, which is beneficial to the post stray light suppression; meanwhile, the arrangement of the lenses forming the compensation lens group is very compact, which is very beneficial to the installation and adjustment of the system;
7. considering that a long-wave infrared system often adopts a refrigeration mode, the problem is generally solved by adopting a cold diaphragm mode in a common scheme; however, the adoption of cold diaphragm scheme limits the imaging view field of the system, the full view field is segmented, the view field of each channel is limited, and a glass plate is arranged at the system diaphragm, so that the cold diaphragm is realized by refrigerating part of compensation lenses.
Drawings
FIG. 1 is a schematic view of an optical system of the present invention;
FIG. 2 is a schematic view of an image compensation lens assembly of an optical system according to the present invention;
fig. 3a, fig. 3b and fig. 3c are schematic structural diagrams of the optical system according to the present invention in the short-focus, mid-focus and long-focus;
FIGS. 4a and 4b are graphs showing MTF curves corresponding to the optical system of the present invention at the short focal length;
FIGS. 4c and 4d are graphs showing MTF curves corresponding to the mid-focus of the optical system of the present invention;
FIGS. 4e and 4f are MTF curves corresponding to the long focal length of the optical system of the present invention;
FIGS. 5a, 5b and 5c are respectively views of diffuse spots of the optical system of the present invention in the short, medium and long foci;
FIGS. 6a, 6b and 6c are field curves and distortion curves of the optical system of the present invention at the short, medium and long foci, respectively;
FIG. 7a is a schematic diagram of a three-dimensional structure of an optical system according to the present invention;
fig. 7b is a side view of fig. 7 a.
The reference numerals in the drawings are: 1-a spherical mirror; 2-short-focus compensation mirror, 3-middle-focus compensation mirror and 4-long-focus compensation mirror; the lens comprises a first negative lens of a 21-short focal compensation lens group, a first positive lens of a 22-short focal compensation lens group, window glass of a 23-short focal compensation lens group, a second positive lens of a 24-short focal compensation lens group, a second negative lens of a 25-short focal compensation lens group and a third negative lens of a 26-short focal compensation lens group; 31-a first negative lens of a middle focus compensation lens group, 32-a first positive lens of a middle focus compensation lens group, 33-window glass of the middle focus compensation lens group, 34-a second positive lens of the middle focus compensation lens group, 35-a second negative lens of the middle focus compensation lens group and 36-a third negative lens of the middle focus compensation lens group; 41-a first negative lens of a long-focus compensation lens group, 42-a first positive lens of a long-focus compensation lens group, 43-window glass of the long-focus compensation lens group, 44-a second positive lens of the long-focus compensation lens group, 45-a second negative lens of the long-focus compensation lens group and 46-a third negative lens of the long-focus compensation lens group;
Detailed Description
The invention is further described below with reference to the accompanying drawings.
As shown in fig. 1, 2, 7a and 7b, which are schematic structural views of the optical system of the present invention, a spherical mirror 1 is disposed on an optical path. In order to independently inhibit stray light for the imaging channel corresponding to each compensation lens group and fully utilize the optical characteristics of the spherical reflector 1, which are rotationally symmetrical in the whole field of view, each imaging compensation lens group is sequentially placed at the corresponding position in front of the spherical reflector 1 according to the optical design result; the imaging light beams of each imaging channel are effectively separated, so that the interference of a local strong light source to the whole view field is avoided, and the imaging detection with a large dynamic range can be realized. In combination with the push-broom imaging mode, the imaging compensation lens groups of the whole system are only arranged in the direction perpendicular to the push-broom direction, so that the number of cameras can be greatly reduced relative to the area array imaging; meanwhile, only the needed part can be reserved for cutting the whole ball lens, and the volume and the quality of the camera can be greatly reduced.
The imaging compensation lens group system comprises a short-focus compensation lens 2, a middle-focus compensation lens 3 and a long-focus compensation lens 4; as shown in fig. 3a, 3b and 3c, schematic structural diagrams of the optical system of the present invention corresponding to the short-focus, medium-focus and long-focus are separately given.
The short-focus compensation lens consists of 6 lenses, and the short-focus compensation lens comprises the following components in sequence along a light path: a first negative lens 21 of the short-focus compensation lens group, a first positive lens 22 of the short-focus compensation lens group, a window glass 23 of the short-focus compensation lens group, a second positive lens 24 of the short-focus compensation lens group, a second negative lens 25 of the short-focus compensation lens group, a third negative lens of the short-focus compensation lens groupA mirror 26; the optical characteristics of the first negative lens are as follows: -2f' 2 <f’ 21 <-f’ 2 ,-3f’ 2 <R 21 <-2f’ 2 , -5f’ 2 <R 22 <-4f’ 2 The method comprises the steps of carrying out a first treatment on the surface of the 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 method comprises the steps of carrying out a first treatment on the surface of the 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 method comprises the steps of carrying out a first treatment on the surface of the The third negative lens has the following optical characteristics: -f' 2 <f’ 25 <-0.5f’ 2 ,-3f’ 2 <R 29 <-2f’ 2 ,-R 210 <-6f’ 2 The method comprises the steps of carrying out a first treatment on the surface of the Wherein f' 2 Is the focal length of a short focal system, f' 2 >0，f’ 21 、f’ 22 、f’ 23 、f’ 24 、f’ 25 The focal lengths of 5 lenses forming the short-focus compensation lens are sequentially set; r is R 21 、R 22 、R 23 、R 24 、R 25 、R 26 、R 27 、R 28 、R 29 、R 210 Sequentially, the curvature radii of the lens are 10 corresponding to 5 lenses.
The middle focus compensation lens consists of 6 lenses, and comprises a first negative lens 31 of a middle focus compensation lens group, a first positive lens 32 of the middle focus compensation lens group, window glass 33 of the middle focus compensation lens group, a second positive lens 34 of the middle focus compensation lens group, a second negative lens 35 of the middle focus compensation lens group and a third negative lens 36 of the middle focus compensation lens group in sequence along an optical path; 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 method comprises the steps of carrying out a first treatment on the surface of the The optical characteristics of the first positive lens are: f's' 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's' 3 <f’ 33 <2f’ 3 ，0<R 35 <f’ 3 ，f’ 3 <R 36 <2f’ 3 The method comprises the steps of carrying out a first treatment on the surface of the 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 method comprises the steps of carrying out a first treatment on the surface of the 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 The method comprises the steps of carrying out a first treatment on the surface of the Wherein f' 3 Is the focal length of the middle-focus system, f' 3 >0； f’ 31 、f’ 32 、f’ 33 、f’ 34 、f’ 35 The focal lengths of 5 lenses forming the middle focus compensation lens are sequentially set; r is R 31 、R 32 、R 33 、R 34 、 R 35 、R 36 、R 37 、R 38 、R 39 、R 310 Sequentially, the curvature radii of the lens are 10 corresponding to 5 lenses.
The long-focus compensation lens consists of 6 lenses, and the long-focus compensation lens comprises the following components in sequence along a light path: a first negative lens 41 of the long-focus compensation lens group, a first positive lens 42 of the long-focus compensation lens group, a window glass 43 of the long-focus compensation lens group, a second positive lens 44 of the long-focus compensation lens group, a second negative lens 45 of the long-focus compensation lens group and a third negative lens 46 of the long-focus 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 method comprises the steps of carrying out a first treatment on the surface of the 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's' 4 <f’ 43 <2f’ 4 ，0<R 45 <f’ 4 ，f’ 4 <R 46 <2f’ 4 The method comprises the steps of carrying out a first treatment on the surface of the 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 method comprises the steps of carrying out a first treatment on the surface of the 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 The method comprises the steps of carrying out a first treatment on the surface of the Wherein f' 4 For the focal length of the long-focus compensation mirror, f' 4 >0；f’ 41 、f’ 42 、f’ 43 、f’ 44 、f’ 45 The focal lengths of 5 lenses forming the long-focus compensation lens are sequentially set; r is R 41 、R 42 、R 43 、R 44 、R 45 、R 46 、R 47 、R 48 、R 49 、R 410 Sequentially, the curvature radii of the lens are 10 corresponding to 5 lenses.
The system focal length short focus, the middle focus and the long focus of the optical system provided by the embodiment are 59.04mm, 65.51mm and 90mm in sequence; the full view fields corresponding to different focal lengths are 22.12 degrees, 20 degrees and 16 degrees in sequence, the sizes of the corresponding detector pixels are 75 mu m,50 mu m and 25 mu m respectively, and the full view field of 110 degrees is realized through splicing; the system f# for short, medium and long focus is 2, and the full field of view is vignetting free. As shown in fig. 4a, 4b, 4c, 4d, 4e, 4f, 5a, 5b, 5c, 6a, 6b and 6c, the MTFs are all near the diffraction limit over the full field of view in the 8 μm-12 μm band, the relative distortion is less than 5%, and the dispersion spot energy centroid deviation from the center wavelength (10 μm) is within 5 μm. If the camera is applied to a near earth orbit satellite of 800km, the imaging quality near the diffraction limit with the constant element resolution being better than 1200m can be obtained in the field of view of 110 degrees.
The optical system adopts a push-broom mode, so that the imaging camera only needs to be distributed in the direction perpendicular to the push-broom, and redundant spherical reflecting mirror parts can be cut off, so that the complexity of the optical system can be greatly reduced, and the light miniaturization of the camera can be realized.
By scaling this embodiment equally, with equal F# and field of view, it is possible to achieve imaging quality near the diffraction limit in a field of view near 180 deg. with track fly heights less than 800km, and constant pixel resolution over a field of view of 110 deg..
Claims (5)
1. An off-axis catadioptric medium-long wave infrared system based on a spherical reflector is characterized in that: the system sequentially comprises a spherical reflecting mirror and a plurality of imaging compensation lens groups with diaphragms along the light propagation direction;
the incident optical axis, the same spherical reflector and a plurality of imaging compensation lens groups with diaphragms are all coaxial;
the imaging compensation lens groups with the diaphragms are distributed at the light outlet of the same spherical reflecting mirror in a fan shape and are on different planes with the incident light incident to the same spherical reflecting mirror, and each imaging compensation lens group with the diaphragms forms an independent imaging channel; light reflected by the co-spherical reflector is vertically incident to an imaging compensation lens group with a diaphragm;
the imaging compensation lens group with the diaphragm comprises a plurality of short-focus compensation mirrors, a plurality of medium-focus compensation mirrors and a plurality of long-focus compensation mirrors;
a plurality of imaging compensation lens groups with diaphragms are uniformly distributed at the light outlet positions of the same spherical reflector in a fan shape;
the short-focus compensation lens comprises 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 which are sequentially arranged along a light path; 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 method comprises the steps of carrying out a first treatment on the surface of the 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; by a means ofThe 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 method comprises the steps of carrying out a first treatment on the surface of the 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 method comprises the steps of carrying out a first treatment on the surface of the 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 The method comprises the steps of carrying out a first treatment on the surface of the Wherein f' 2 For compensating the focal length of the mirror for short focus, f' 2 >0，f’ 21 、f’ 22 、f’ 23 、f’ 24 、f’ 25 The focal lengths of 5 lenses forming the short-focus compensation lens are sequentially set; r is R 21 、R 22 、R 23 、R 24 、R 25 、R 26 、R 27 、R 28 、R 29 、R 210 Respectively forming 10 curvature radiuses corresponding to 5 lenses of the short-focus compensation lens in sequence;
or the middle focus compensation lens comprises 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 which are sequentially arranged along the light path; 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 method comprises the steps of carrying out a first treatment on the surface of the The optical characteristics of the first positive lens are: f's' 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's' 3 <f’ 33 <2f’ 3 ，0<R 35 <f’ 3 ，f’ 3 <R 36 <2f’ 3 The method comprises the steps of carrying out a first treatment on the surface of the 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 method comprises the steps of carrying out a first treatment on the surface of the 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 The method comprises the steps of carrying out a first treatment on the surface of the Wherein f' 3 For the focal length of the middle focus compensation mirror, f' 3 >0；f’ 31 、f’ 32 、f’ 33 、f’ 34 、f’ 35 The focal lengths of 5 lenses forming the middle focus compensation lens are sequentially set; r is R 31 、R 32 、R 33 、R 34 、R 35 、R 36 、R 37 、R 38 、R 39 、R 310 Sequentially 10 curvature radiuses corresponding to 5 lenses forming the middle focus compensation lens;
or the long-focus compensation lens comprises 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 which are sequentially arranged along the light path; 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 method comprises the steps of carrying out a first treatment on the surface of the 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's' 4 <f’ 43 <2f’ 4 ，0<R 45 <f’ 4 ，f’ 4 <R 46 <2f’ 4 The method comprises the steps of carrying out a first treatment on the surface of the 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 method comprises the steps of carrying out a first treatment on the surface of the 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 The method comprises the steps of carrying out a first treatment on the surface of the Wherein f' 4 For the focal length of the long-focus compensation mirror, f' 4 >0；f’ 41 、f’ 42 、f’ 43 、f’ 44 、f’ 45 The focal lengths of 5 lenses forming the long-focus compensation lens are sequentially set; r is R 41 、R 42 、R 43 、R 44 、R 45 、R 46 、R 47 、R 48 、R 49 、R 410 The curvature radii of the lens 5 lens composing the long focus compensation lens are 10 corresponding in turn.
2. The off-axis catadioptric medium-long wave infrared system based on the spherical reflector according to claim 1, wherein: the system selects a push-broom imaging mode, the view field of each imaging channel is selected to be a narrow-band view field, the narrow view fields of different imaging channels are mutually overlapped by 5% to cover the whole imaging view field, all the narrow view fields are narrow-band view fields deviating from the central view field by a certain angle, and the imaging compensation lens group of the whole system is only arranged in the direction vertical to the push-broom.
3. An off-axis catadioptric medium and long wave infrared system based on a spherical reflector as claimed in claim 1 or 2, wherein: the short-focus compensation mirror, the middle-focus compensation mirror and the long-focus compensation mirror have the same relative aperture.
4. An off-axis catadioptric medium and long wave infrared system based on a spherical reflector as claimed in claim 1 or 2, wherein: the distance between the spherical reflecting mirror and the imaging compensating lens group with diaphragm is more than one time of the focal length of the optical system.
5. The off-axis catadioptric medium-long wave infrared system based on the spherical reflector according to claim 1, wherein: the cold light stop window comprises a diaphragm and a glass plate arranged at the diaphragm.
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