Dual-band three-view-field switching zoom Offner spectral imaging system

Abstract

The invention relates to a dual-band three-field-of-view switching zoom Offner spectral imaging system, which comprises a front switching zoom group, a slit, a spectral beam splitting system, a reflex mirror, a rear relay system and a dual-color refrigeration type infrared detector which are sequentially arranged along a light path, wherein the front switching zoom group comprises a first front telescopic zoom objective lens group, a second front telescopic zoom objective lens group and a third front telescopic zoom objective lens group which are driven by a motor to cut in or out of a light path to realize three-view-field zoom, and the spectrum splitting system adopts a convex grating type Offner structure. Comprising a first light splitting reflector, a second light splitting reflector and a third light splitting reflector which are sequentially arranged from an object side to an image side, and the second light splitting reflector is a convex grating. According to the invention, infrared dual-waveband large-zoom-ratio three-view-field zoom spectral imaging is realized, and the system has the advantages of dual wavebands, high resolution, large zoom ratio, large zoom range, capability of quickly converting multiple view fields to obtain map information, high-quality imaging and the like.

Description

Technical Field

[0001] The invention relates to the technical field of spectral imaging, and in particular to a dual-band three-field-of-view switching zoom Offner spectral imaging system. Background Art

[0002] The spectrum imaging system combines the image and spectrum in one, and can simultaneously obtain the image information and spectral information of the target being measured, which is crucial for target detection and identification. For complex detection environments such as aviation detection, the infrared imaging spectrometer has strong anti-interference capabilities and unique advantages. Medium-wave infrared is good at detecting high-temperature targets, especially suitable for observations under humid and low-temperature conditions, and can analyze the radiation spectrum of high-temperature objects in detail; while long-wave infrared focuses on depicting the contour images of objects at normal temperature, and also demonstrates strong reconnaissance capabilities in environments with stray radiation or heat source radiation. The combined use of dual-band infrared can achieve more accurate detection of targets, so the advantages of dual-band infrared detection technology are obvious.

[0003] However, most of the infrared imaging spectrometers at home and abroad are single-band, single-field-of-view, and single-function. Dual-band infrared imaging spectrometers are also mostly fixed-focus structures, and mainly adopt a split-beam structure, sharing a telescope objective system with different detectors for reception. They are large in size, high in cost, complex in structure, and limited in use. They cannot achieve short-focus and large-field-of-view rapid target search, long-focus and small-field-of-view rapid identification, and accurate acquisition of the spatial and spectral information of the target object. Summary of the invention

[0004] In order to solve the problem that the existing infrared imaging spectrometer has too single application scenario and complex dual-band structure, and cannot realize the problem of fast target search with short focus and large field of view, fast identification with long focus and small field of view, and accurate acquisition of spatial information and spectral information of target objects, the present invention provides a dual-band three-field-of-view switching zoom Offner spectral imaging system, which is an integrated common optical path infrared dual-band large magnification switching zoom spectral imaging system combining transmission and catadioptric structures, and has a spectral range of 3.7μm~4.8μm and 7.7μm~9.5μm, and realizes three-field-of-view switching zoom with short focus and large field of view of 32mm (21.75°), medium focus and medium field of view of 200mm (3.52°), and long focus and small field of view of 800mm (0.88°).

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A dual-band three-field switching zoom Offner spectral imaging system, characterized in that it comprises a front switching zoom group, a slit, a spectral splitting system, a folding reflector, a rear relay system and a two-color refrigeration type infrared detector arranged in sequence along an optical path, wherein the slit is located at the imaging position of the front switching zoom group;

[0007] The front switching zoom group includes a first front telephoto zoom objective lens group, a second front telephoto zoom objective lens group and a third front telephoto zoom objective lens group which are driven by a motor to cut in or out of the optical path to achieve three-field zoom. When the first front telephoto zoom objective lens group cuts into the optical path, the spectral imaging system is a short-focus large-field optical path system, when the second front telephoto zoom objective lens group cuts into the optical path, the spectral imaging system is a medium-focus medium-field optical path system, and when the third front telephoto zoom objective lens group cuts into the optical path, the spectral imaging system is a long-focus small-field optical path system; the first front telephoto zoom objective lens group includes a third front telephoto zoom objective lens group which are coaxially arranged in sequence from the object side to the image side. A front telephoto zoom objective lens, a second front telephoto zoom objective lens, a third front telephoto zoom objective lens and a fourth front telephoto zoom objective lens; the second front telephoto zoom objective lens group includes a fifth front telephoto zoom objective lens, a sixth front telephoto zoom objective lens, a seventh front telephoto zoom objective lens and an eighth front telephoto zoom objective lens coaxially arranged in sequence from the object side to the image side; the third front telephoto zoom objective lens group adopts an RC reflector structure, including a first front telephoto zoom reflector and a second front telephoto zoom reflector coaxially arranged in sequence from the object side to the image side, and the first front telephoto zoom reflector and the second front telephoto zoom reflector are both hyperbolic reflectors;

[0008] The spectral spectrometer system adopts a convex grating type Offner structure, including a first spectrometer reflector, a second spectrometer reflector and a third spectrometer reflector arranged in sequence from the object side to the image side, and the second spectrometer reflector is a convex grating;

[0009] The light emitted by the spectral splitting system is folded by the folding reflector and then incident on the rear relay system, wherein the rear relay system comprises a first secondary imaging lens, a second secondary imaging lens, a third secondary imaging lens, a fourth secondary imaging lens, a fifth secondary imaging lens and a sixth secondary imaging lens which are coaxially arranged in sequence from the object side to the image side;

[0010] The light transmitted by the rear relay system is incident on the two-color refrigerated infrared detector for spectral imaging.

[0011] The dual-band three-field switching zoom Offner spectral imaging system of the present invention combines the advantages of the transmission type and the catadioptric optical system, adopts the convex grating type Offner structure with excellent optical performance as the spectral light splitting element, and realizes the infrared dual-band large zoom ratio three-field zoom spectral imaging by the method of switching different front telephoto zoom lens groups driven by a motor. Each subsystem in the present invention is relatively independent in the system design, with high optical transmittance, high resolution and good imaging quality. The present invention has a high degree of flexibility and can provide spectral imaging including short focus, medium focus and long focus for a variety of usage scenarios. It can not only quickly obtain target spectrum information within a large field of view with a short focal length, but also obtain fine spectral information of targets within a small field of view through a long focal length, and has a large zoom range. The present invention has the advantages of dual bands, high resolution, large zoom ratio, large zoom range, and the ability to quickly convert multiple fields of view to obtain spectrum information, high-quality imaging, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of the optical path of the spectral imaging system of the present invention when performing short-focus and large-field imaging;

[0013] Figure 2 A schematic diagram of the optical path when imaging the mid-focus field of view in the spectral imaging system of the present invention;

[0014] Figure 3 It is a schematic diagram of the optical path of the spectral imaging system of the present invention when performing telephoto and small field of view imaging;

[0015] Figure 4 It is the MTF curve diagram of the short-focus wave (4.25 μm) in the spectral imaging system of the present invention;

[0016] Figure 5 It is the MTF curve diagram of the long-wave (8.5 μm) short-focus of the spectral imaging system of the present invention;

[0017] Figure 6 The MTF curve of the mid-focus wave (4.25 μm) in the spectral imaging system of the present invention;

[0018] Figure 7 It is the MTF curve diagram of the long-wave (8.5 μm) mid-focus of the spectral imaging system of the present invention;

[0019] Figure 8 The MTF curve diagram of the long focus of wavelength (4.25 μm) in the spectral imaging system of the present invention;

[0020] Fig. 9 This is the MTF curve diagram of the long-wave (8.5 μm) telephoto of the spectral imaging system of the present invention.

[0021] Explanation of reference numerals: 1. first front telephoto zoom objective lens group; 11. first front telephoto zoom objective lens; 12. second front telephoto zoom objective lens; 13. third front telephoto zoom objective lens; 14. fourth front telephoto zoom objective lens; 2. second front telephoto zoom objective lens group; 21. fifth front telephoto zoom objective lens; 22. sixth front telephoto zoom objective lens; 23. seventh front telephoto zoom objective lens; 24. eighth front telephoto zoom objective lens; 3. third front telephoto zoom objective lens group; 31. first front telephoto Zoom reflector; 32, second front telephoto zoom reflector; 4, slit; 5, spectral spectrometer system; 51, first spectrometer reflector; 52, second spectrometer reflector; 53, third spectrometer reflector; 6, folding reflector; 7, rear relay system; 71, first secondary imaging lens; 72, second secondary imaging lens; 73, third secondary imaging lens; 74, fourth secondary imaging lens; 75, fifth secondary imaging lens; 76, sixth secondary imaging lens; 8, dual-color cooled infrared detector. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The present invention provides a dual-band three-field switching zoom Offner spectral imaging system, comprising a front switching zoom group, a slit 4, a spectral splitting system 5, a folding reflector 6, a rear relay system 7 and a two-color refrigeration type infrared detector 8 which are sequentially arranged along an optical path, wherein the front switching zoom group comprises a first front telephoto zoom objective lens group 1, a second front telephoto zoom objective lens group 2 and a third front telephoto zoom objective lens group 3, and the first front telephoto zoom objective lens group 1, the second front telephoto zoom objective lens group 2 and the third front telephoto zoom objective lens group 3 are driven by a motor to rotate and cut into or out of the optical path, thereby realizing three-field zoom.

[0024] like Figure 1 As shown, the first front telephoto zoom objective lens group 1 includes a first front telephoto zoom objective lens 11, a second front telephoto zoom objective lens 12, a third front telephoto zoom objective lens 13 and a fourth front telephoto zoom objective lens 14 which are coaxial and arranged in sequence from the object side to the image side. The first front telephoto zoom objective lens 11, the second front telephoto zoom objective lens 12, the third front telephoto zoom objective lens 13 and the fourth front telephoto zoom objective lens 14 respectively use zinc selenide lenses, germanium lenses, zinc sulfide lenses and zinc selenide lenses.

[0025] like Figure 2As shown, the second front telephoto zoom objective lens group 2 includes a fifth front telephoto zoom objective lens 21, a sixth front telephoto zoom objective lens 22, a seventh front telephoto zoom objective lens 23 and an eighth front telephoto zoom objective lens 24 which are coaxially arranged in sequence from the object side to the image side.

[0026] like Figure 3 As shown, the third front telephoto zoom objective lens group 3 adopts an RC mirror structure, including a first front telephoto zoom reflector 31 (MIRROR) and a second front telephoto zoom reflector 32 (MIRROR) which are coaxial and arranged in sequence from the object side to the image side, and the first front telephoto zoom reflector 31 and the second front telephoto zoom reflector 32 which serve as the primary mirror and the secondary mirror respectively are both hyperbolic mirrors.

[0027] The slit 4 is located at the imaging position of the front switching zoom group.

[0028] The spectral spectrometer system 5 adopts a convex grating type Offner structure, including a first spectroscopic reflector 51 (MIRROR), a second spectroscopic reflector 52 (MIRROR), and a third spectroscopic reflector 53 (MIRROR) arranged in sequence from the object side to the image side, and the second spectroscopic reflector 52 is a convex grating, and the line density value of the convex grating can be selected as 0.03 line / μm or other suitable values, which are not limited here. Further, referring to Tables 1 to 3, the curvature radius of the first spectroscopic reflector 51 ranges from 95mm to 110mm, the curvature radius of the second spectroscopic reflector 52 ranges from 40mm to 55mm, and the curvature radius of the third spectroscopic reflector 53 ranges from 95mm to 105mm.

[0029] The traditional infrared imaging spectrometer's spectroscopic element generally adopts a prism or a grating. Because the prism has high transmittance and no spectral overlap, the dispersion is related to the wavelength, is nonlinear, and has large spectral line bending and color distortion, so it is suitable for short wavelengths. The plane grating process technology is mature and easy to process, but it only works in a parallel light path and has large spectral line bending. Compared with the above two spectral spectroscopic elements, the convex grating type Offner structure adopted in the present invention is a concentric three-reflection system, in which the second spectroscopic reflector 52 is a convex grating, which has the characteristics of spherical aberration, coma, distortion, astigmatism, field curvature and chromatic aberration and other primary aberrations tending to zero, and has excellent optical performance, thereby further improving the performance of the spectral imaging system.

[0030] In order to make the structure of the system more compact and reasonable, a folding reflector 6 (MIRROR) for folding the light path is also provided in the spectral imaging system. The light emitted by the spectral splitting system 5 is folded by the folding reflector 6 and then incident on the rear relay system 7. In order to achieve cold stop matching, the spectral imaging system is also provided with a rear relay system 7, which adopts a secondary imaging method to achieve 100% cold stop efficiency. The rear relay system 7 includes a first secondary imaging lens 71, a second secondary imaging lens 72, a third secondary imaging lens 73, a fourth secondary imaging lens 74, a fifth secondary imaging lens 75, and a sixth secondary imaging lens 76, which are coaxial and arranged in sequence from the object side to the image side. The first secondary imaging lens 71, the second secondary imaging lens 72, the third secondary imaging lens 73, the fourth secondary imaging lens 74, the fifth secondary imaging lens 75, and the sixth secondary imaging lens 76 are respectively AMTIR-1 lens, germanium lens, AMTIR-1 lens, zinc sulfide lens, zinc selenide lens, and germanium lens.

[0031] The two-color refrigerated infrared detector 8 is used to receive the light transmitted by the secondary imaging lens group, i.e., the rear relay system 7, and perform spectral imaging. Optionally, the specification of the two-color refrigerated infrared detector 8 is 320×256, the pixel size is 30μm×30μm, the detector window is made of germanium material with a thickness of 1mm, the filter is made of germanium material with a thickness of 0.3mm, the applicable wavelength is: medium wave 3.7μm~4.8μm, long wave 7.7μm~9.5μm, the dispersion width is 7.2mm, the spectral resolution is 25nm, and the width of the slit 4 is 30μm.

[0032] The radial tube length of the spectral imaging system is 335 mm, and the F number of the optical system is 4.

[0033] The front switching zoom group is driven by a motor to rotate and switch to a different front telephoto zoom objective lens group to achieve three-field zoom. Specifically, when the first front telephoto zoom objective lens group 1 cuts into the optical path, the first front telephoto zoom lens group 1, the slit 4, the beam splitter reflector group 5, the folding reflector 6, the rear relay system 7 and the two-color refrigerated infrared detector 8 form a short-focus large-field optical path system, and the focal length of the short-focus large-field optical path system is 32mm, and the field of view angle is 21.75°; based on the short-focus large-field optical path system, when the motor drives the first front telephoto zoom lens group 1 to rotate and switch to the second front telephoto zoom lens group 2, the second front infrared objective lens group 2, the slit 4, the beam splitter reflector group 5, the folding reflector 6, the rear relay system 7 and the two-color refrigerated infrared detector 8 form a medium-focus medium-field optical path system, the focal length of the medium-focus medium-field optical path system is 200mm, and the field of view angle is 3.52°; based on the medium-focus medium-field optical path system, when the motor drives the second front telephoto zoom lens group 2 to continue to rotate and switch to the third front telephoto zoom reflector group 3, the third front telephoto zoom reflector group 3, the slit 4, the beam splitting reflector group 5, the folding reflector 6, the rear relay system 7 and the two-color refrigerated infrared detector 8 form a long-focus small-field optical path system, the focal length of the long-focus small-field optical path system is 800mm, and the field of view angle is 0.88°.

[0034] Optionally, the first front telephoto zoom objective lens 11 is a zinc selenide lens, the curvature radii of its front and rear surfaces are -35.8mm and -43.929mm respectively, and the thickness is 9mm; the second front telephoto zoom objective lens 12 is a germanium lens, the curvature radius of its front surface is -50.691mm, the rear surface is an even-order aspheric surface, the vertex curvature radius is -81.701mm, and the thickness is 8.399mm; the third front telephoto zoom objective lens 13 is a zinc sulfide lens, the curvature radii of its front and rear surfaces are 39.807mm and 20.286mm respectively, and the thickness is 9mm; the fourth front telephoto zoom objective lens 14 is a zinc selenide lens, the front and rear surfaces are even-order aspheric surfaces, the vertex curvature radii are 16.861mm and 69.163mm respectively, and the thickness is 5.438mm.

[0035] Optionally, the front and rear surfaces of the fifth front telephoto zoom objective lens 21 have a curvature radius of 89.424 mm and 59.326 mm, respectively, and a thickness of 11 mm; the front and rear surfaces of the sixth front telephoto zoom objective lens 22 have a curvature radius of 62.609 mm and 116.876 mm, respectively, and a thickness of 11 mm; the front and rear surfaces of the seventh front telephoto zoom objective lens 23 have a curvature radius of 220.240 mm and 135.219 mm, respectively, and a thickness of 11 mm; the front and rear surfaces of the eighth front telephoto zoom objective lens 24 are even-order aspherical surfaces, with vertex curvature radii of 53.112 mm and 66.350 mm, respectively, and a thickness of 7.235 mm.

[0036] Optionally, the curvature radius of the first front telephoto zoom reflector 31 is -432.684 mm, and the curvature radius of the second front telephoto zoom reflector 32 is 155.432 mm.

[0037] Optionally, the first secondary imaging lens 71 is an AMTIR-1 lens, the curvature radii of the front and rear surfaces of which are 38.668 mm and -30.657 mm, respectively, and the thickness is 4.003 mm; the second secondary imaging lens 72 is a germanium lens, the curvature radii of the front and rear surfaces of which are -20.478 mm and -44.900 mm, respectively, and the thickness is 4 mm; the third secondary imaging lens 73 is an AMTIR-1 lens, the front surface of which is an even-order aspheric surface, the vertex curvature radius is -13.672, the curvature radius of the rear surface is -14.532 mm, and the thickness is 5.984mm; the fourth secondary imaging lens 74 is a zinc sulfide lens, the curvature radii of its front and rear surfaces are 5161.251mm and 21.990mm respectively, and the thickness is 4.017mm; the fifth secondary imaging lens 75 is a zinc selenide lens, the curvature radii of its front and rear surfaces are 27.403mm and -26.939mm respectively, and the thickness is 5.626mm; the sixth secondary imaging lens 76 is a germanium lens, the front and rear surfaces are even-order aspheric surfaces, the vertex curvature radii are 13.746mm and 8.220mm respectively, and the thickness is 4.654mm.

[0038] Tables 1 to 3 are the lens parameters of the short-focus large-field-of-view optical system, the medium-focus medium-field-of-view optical system, and the long-focus small-field-of-view optical system, respectively. The units of the parameters are all mm.

[0039] Table 1 Lens parameters of short-focus and large-field-of-view optical system

[0040]

[0041]

[0042] Table 2 Lens parameters of the mid-focus mid-field optical system

[0043]

[0044]

[0045] Table 3 Lens parameters of telephoto small field of view optical system

[0046]

[0047]

[0048] See also Figures 4 to 9, respectively, are MTF curves of the spectral imaging system of the present invention during three-field zoom spectral imaging at medium wave (4.25μm) and long wave (8.5μm). It can be seen from the MTF curves that the spectral imaging system is close to the diffraction limit at the characteristic frequency of 17lp / mm, and the imaging quality is good.

[0049] The dual-band three-field switching zoom Offner spectral imaging system of the present invention combines the advantages of the transmission type and the catadioptric optical system, adopts the convex grating type Offner structure with excellent optical performance as the spectral light splitting element, and realizes the infrared dual-band 25 times large zoom ratio three-field zoom spectral imaging by the method of switching different front telephoto zoom lens groups driven by a motor. Each subsystem is relatively independent in the system design, with high optical transmittance, high resolution and good imaging quality. The present invention has a high degree of flexibility and can provide spectral imaging including short focus, medium focus and long focus for a variety of usage scenarios. It can not only quickly obtain target spectrum information within a large field of view with a short focal length, but also obtain fine spectrum information of targets within a small field of view through a long focal length, and has a large zoom range. The present invention has the advantages of dual bands, high resolution, large zoom ratio, large zoom range, and the ability to quickly convert multiple fields of view to obtain spectrum information, high-quality imaging, etc.

[0050] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0051] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A dual-band three-field switching zoom Offner spectral imaging system, characterized in that: It comprises a front switch zoom group, a slit (4), a spectral splitting system (5), a folding reflector (6), a rear relay system (7) and a two-color refrigeration type infrared detector (8) which are sequentially arranged along the optical path, wherein the slit (4) is located at the imaging position of the front switch zoom group; The front switchable zoom group comprises a first front telephoto zoom objective lens group (1), a second front telephoto zoom objective lens group (2) and a third front telephoto zoom objective lens group (3) which are driven by a motor to cut into or out of the optical path to realize three-field zoom; when the first front telephoto zoom objective lens group (1) cuts into the optical path, the spectral imaging system is a short-focus large-field optical path system; when the second front telephoto zoom objective lens group (2) cuts into the optical path, the spectral imaging system is a medium-focus medium-field optical path system; when the third front telephoto zoom objective lens group (3) cuts into the optical path, the spectral imaging system is a long-focus small-field optical path system; the first front telephoto zoom objective lens group (1) comprises a first front telephoto zoom objective lens (11), a second front telephoto zoom objective lens group (2) and a third front telephoto zoom objective lens group (3) which are coaxially arranged in sequence from the object side to the image side. A front telephoto zoom objective lens (12), a third front telephoto zoom objective lens (13) and a fourth front telephoto zoom objective lens (14); the second front telephoto zoom objective lens group (2) comprises a fifth front telephoto zoom objective lens (21), a sixth front telephoto zoom objective lens (22), a seventh front telephoto zoom objective lens (23) and an eighth front telephoto zoom objective lens (24) which are coaxially arranged in sequence from the object side to the image side; the third front telephoto zoom objective lens group (3) adopts an RC reflector structure, comprising a first front telephoto zoom reflector (31) and a second front telephoto zoom reflector (32) which are coaxially arranged in sequence from the object side to the image side, and the first front telephoto zoom reflector (31) and the second front telephoto zoom reflector (32) are both hyperbolic reflectors; The spectral spectroscopic system (5) adopts a convex grating type Offner structure, comprising a first spectroscopic reflector (51), a second spectroscopic reflector (52) and a third spectroscopic reflector (53) arranged in sequence from the object side to the image side, and the second spectroscopic reflector (52) is a convex grating; The light emitted by the spectral splitting system (5) is folded by the folding reflector (6) and then incident on the rear relay system (7), wherein the rear relay system (7) comprises a first secondary imaging lens (71), a second secondary imaging lens (72), a third secondary imaging lens (73), a fourth secondary imaging lens (74), a fifth secondary imaging lens (75) and a sixth secondary imaging lens (76) which are coaxially arranged in sequence from the object side to the image side; The light transmitted by the rear relay system (7) is incident on the two-color refrigerated infrared detector (8) for spectral imaging.

2. The dual-band three-field switching zoom Offner spectral imaging system according to claim 1, characterized in that: The curvature radius of the first beam splitter reflector (51) is in the range of 95 mm to 110 mm, the curvature radius of the second beam splitter reflector (52) is in the range of 40 mm to 55 mm, and the curvature radius of the third beam splitter reflector (53) is in the range of 95 mm to 105 mm.

3. The dual-band three-field switching zoom Offner spectral imaging system according to claim 2, characterized in that: The line density of the second beam splitting reflector (52) is 0.03 line / μm.

4. A dual-band three-field switching zoom Offner spectral imaging system according to claim 1 or 2, characterized in that: The first front telephoto zoom objective lens (11) is a zinc selenide lens, the curvature radii of the front and rear surfaces are -35.8 mm and -43.929 mm respectively, and the thickness is 9 mm; the second front telephoto zoom objective lens (12) is a germanium lens, the curvature radius of the front surface is -50.691 mm, the rear surface is an even-order aspheric surface, the vertex curvature radius is -81.701 mm, and the thickness is 8.399 mm; the third front telephoto zoom objective lens (13) is a zinc sulfide lens, the curvature radii of the front and rear surfaces are 39.807 mm and 20.286 mm respectively, and the thickness is 9 mm; the fourth front telephoto zoom objective lens (14) is a zinc selenide lens, the front and rear surfaces are even-order aspheric surfaces, the vertex curvature radii are 16.861 mm and 69.163 mm respectively, and the thickness is 5.438 mm.

5. A dual-band three-field switching zoom Offner spectral imaging system according to claim 1 or 2, characterized in that: The curvature radii of the front and rear surfaces of the fifth front telephoto zoom objective lens (21) are 89.424 mm and 59.326 mm respectively, and the thickness is 11 mm; the curvature radii of the front and rear surfaces of the sixth front telephoto zoom objective lens (22) are 62.609 mm and 116.876 mm respectively, and the thickness is 11 mm; the curvature radii of the front and rear surfaces of the seventh front telephoto zoom objective lens (23) are 220.240 mm and 135.219 mm respectively, and the thickness is 11 mm; the front and rear surfaces of the eighth front telephoto zoom objective lens (24) are even-order aspheric surfaces, the vertex curvature radii are 53.112 mm and 66.350 mm respectively, and the thickness is 7.235 mm.

6. A dual-band three-field switching zoom Offner spectral imaging system according to claim 1 or 2, characterized in that: The first front telephoto zoom reflector (31) has a curvature radius of -432.684 mm, and the second front telephoto zoom reflector (32) has a curvature radius of 155.432 mm.

7. A dual-band three-field switching zoom Offner spectral imaging system according to claim 1 or 2, characterized in that: The first secondary imaging lens (71) is an AMTIR-1 lens, the curvature radii of the front and rear surfaces of which are 38.668 mm and -30.657 mm respectively, and the thickness is 4.003 mm; the second secondary imaging lens (72) is a germanium lens, the curvature radii of the front and rear surfaces of which are -20.478 mm and -44.900 mm respectively, and the thickness is 4 mm; the third secondary imaging lens (73) is an AMTIR-1 lens, the front surface of which is an even-order aspheric surface, the vertex curvature radius is -13.672, the curvature radius of the rear surface is -14.532 mm, and the thickness is 5. 984mm; the fourth secondary imaging lens (74) is a zinc sulfide lens, the curvature radii of its front and rear surfaces are 5161.251mm and 21.990mm respectively, and the thickness is 4.017mm; the fifth secondary imaging lens (75) is a zinc selenide lens, the curvature radii of its front and rear surfaces are 27.403mm and -26.939mm respectively, and the thickness is 5.626mm; the sixth secondary imaging lens (76) is a germanium lens, the front and rear surfaces are even-order aspheric surfaces, the vertex curvature radii are 13.746mm and 8.220mm respectively, and the thickness is 4.654mm.

8. A dual-band three-field switching zoom Offner spectral imaging system according to claim 1 or 2, characterized in that: The focal length of the short-focus large-field-of-view optical system is 32 mm, and the field-of-view angle is 21.75°; the focal length of the medium-focus medium-field-of-view optical system is 200 mm, and the field-of-view angle is 3.52°; the focal length of the long-focus small-field-of-view optical system is 800 mm, and the field-of-view angle is 0.88°.

9. A dual-band three-field switching zoom Offner spectral imaging system according to claim 1 or 2, characterized in that: The specification of the two-color refrigerated infrared detector (8) is 320×256, the pixel size is 30 μm×30 μm, the window is made of germanium material with a thickness of 1 mm, and the filter is made of germanium material with a thickness of 0.3 mm.

10. A dual-band three-field switching zoom Offner spectral imaging system according to claim 1 or 2, characterized in that: The radial tube length of the spectral imaging system is 335 mm.

Images