A slitless mid-wave infrared spectral system based on dyson improved concentric structure

Abstract

The present application relates to infrared spectrum system, specifically to a kind of slitless mid-wave infrared spectrum system based on Dyson improved concentric structure, for solving the insufficient places of limited slit line field of view, the processing and manufacturing difficulty coefficient of concave reflection grating is larger, and the distance between the edge of object plane and image plane is difficult to increase, which limits the engineering application of Dyson structure in infrared spectrum imaging system.The mid-wave infrared spectrum system based on Dyson improved concentric structure includes pre-objective lens group, Dyson spectral spectroscope group and relay lens group;Among them, Dyson spectral spectroscope group abandons the concave reflection grating with larger processing difficulty, adopts plane reflection grating to pull apart the distance between the edge of object plane and image plane, separates object plane and image plane, overcomes the limited distance between the edge of object plane and image plane of traditional Dyson spectrometer, avoids the interference of object and image, and reduces the difficulty of overall structure layout and engineering development.

Description

Technical Field

[0001] This invention relates to infrared spectroscopy systems, and more specifically to a slitless mid-wave infrared spectroscopy system based on a Dyson improved concentric structure. Background Technology

[0002] Mid-wave infrared spectroscopy imaging is a technique that uses multiple channels to detect and image the radiation spectrum of a target. This technology can be used not only to analyze the radiation spectrum of an object's composition, but also to analyze the radiation spectrum of high-temperature objects such as aircraft exhaust plumes, as well as to detect volcanic activity and monitor forest fires. It has broad application prospects in both civilian and industrial fields.

[0003] The key to infrared spectral imaging systems lies in improving the target radiation signal-to-noise ratio in the infrared band to ensure high light transmittance. Therefore, cooled infrared detectors are typically used to achieve high sensitivity and low noise performance.

[0004] The Dyson concentric structure is a concentric optical system composed of a plano-convex lens and a concave mirror. The light beam is imaged by the plano-convex lens onto the concave mirror, then reflected back to the plano-convex lens and finally imaged onto the image plane. This system has a magnification of -1x, and the incident and outgoing beams share the same imaging path, exhibiting the characteristic of "optical path multiplexing." The system's Seidel aberration approaches zero, and it boasts advantages such as simple structure, small size, light weight, and large numerical aperture. In the infrared band, due to the high light absorption of the lens material, this structure can well meet the high optical efficiency requirements of infrared spectral imaging systems.

[0005] However, when applying the Dyson concentric structure to infrared spectral imaging systems, the concave mirror is replaced with a concave reflective grating as the beam-splitting element. This improvement faces certain challenges in engineering applications, including the difficulty in fabricating and inspecting the concave reflective grating. Furthermore, the field of view of existing infrared spectral imaging systems is limited to a single slit-sized linear field of view, requiring a scanning mechanism to acquire the target's spectral data cube. The object plane and image plane are both located near the plane of the plano-convex lens, resulting in an overly compact structure, making interference between the object and image highly likely, and making it difficult to increase the distance between the edges of the object and image planes, thus limiting the engineering application of the Dyson structure in infrared spectral imaging systems. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of the Dyson structure in the engineering application of infrared spectral imaging systems, namely the limited field of view of the slit line, the high difficulty in manufacturing concave reflection gratings, and the difficulty in increasing the distance between the edges of the object plane and the image plane. The invention provides a slitless mid-wave infrared spectral system based on an improved concentric Dyson structure.

[0007] To address the shortcomings of the existing technology, the present invention provides the following technical solution:

[0008] A slitless mid-wave infrared spectroscopy system based on a Dyson improved concentric structure is characterized by comprising a front objective lens group, a Dyson spectral spectroscope group, and a relay lens group.

[0009] The front objective lens group is used to focus the wide-field infrared beam radiated by the target onto the primary image plane. The front objective lens group has the characteristic of telecentric pupil on the image side and includes a primary reflector, a secondary reflector, a first front objective lens, and a second front objective lens arranged sequentially along the optical path. The wide-field infrared beam radiated by the target passes sequentially through the primary reflector, the secondary reflector, the central through-hole on the primary reflector, the first front objective lens, and the second front objective lens before being focused onto the primary image plane.

[0010] The Dyson spectral beam splitter assembly is used to spectrally split the wide-field infrared beam focused at the primary image plane by the front objective lens assembly to obtain an infrared spectral beam, and then focus it onto the secondary image plane. The Dyson spectral beam splitter assembly has the characteristic of dual telecentric pupils on both the object and image sides, and includes a first lens, a second lens, a third lens, a plane reflection grating, and a folding mirror. The wide-field infrared beam focused by the front objective lens assembly passes through the first lens, the second lens, and the third lens in sequence, is then projected onto the plane reflection grating for spectral splitting and reflection, and then passes through the third lens, the second lens, the first lens, and the folding mirror in sequence to focus it onto the secondary image plane, and is spread out along the wavelength along the dispersion direction.

[0011] The relay lens group is used to image the infrared spectral beam focused at the secondary image plane by the Dyson spectral beam splitter group onto the image plane. The relay lens group has a telecentric pupil feature on the object side and includes a fourth lens, a fifth lens, and a sixth lens arranged sequentially along the optical path. The infrared spectral beam separated by the Dyson spectral beam splitter group is imaged onto the image plane by the fourth lens, the fifth lens, and the sixth lens in sequence. The exit pupil of the relay lens group is used to coincide with the cold screen of the infrared detector, and the image plane is used to coincide with the target surface of the infrared detector.

[0012] Furthermore, the first lens is a lens with a positive optical power and a curved planar reflection grating, and the side away from the second lens is a high-order aspherical surface containing even-order 10; the second lens is a lens with a positive optical power and a curved planar reflection grating; the third lens is a lens with a negative optical power and a curved planar reflection grating containing a high-order double-sided aspherical surface containing even-order 8; and the planar reflection grating is a planar reflection blazed grating.

[0013] Furthermore, the first lens, the second lens, and the third lens are made of Ge, Si, and Ge, respectively.

[0014] Furthermore, the reflecting surface of the primary reflector is a parabolic surface with negative optical power, the reflecting surface of the secondary reflector is a hyperboloid with negative optical power, the first front objective lens is a biconvex lens with positive optical power and the incident surface is an aspheric surface containing even-order 8; the second front objective lens is a biconcave lens with negative optical power and the incident surface is an aspheric surface containing even-order 8.

[0015] Furthermore, the first front objective lens and the second front objective lens are made of ZnSe and ZnS, respectively.

[0016] Furthermore, the centerline obstruction ratio of the primary reflector and the secondary reflector is 0.35.

[0017] Furthermore, the fourth lens is a lens that bends towards the image plane and has positive optical power, the fifth lens is a lens that bends towards the image plane, contains an 8th even-order double-sided aspherical surface, and has negative optical power, and the sixth lens is a lens with positive optical power.

[0018] According to a further claim, the fourth lens, the fifth lens, and the sixth lens are made of Si, Ge, and Si, respectively.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] (1) The present invention provides a mid-wave infrared spectroscopy system based on a Dyson improved concentric structure, comprising a front objective lens group, a Dyson spectral beam splitter group, and a relay lens group; wherein the Dyson spectral beam splitter group abandons the concave reflection grating which is difficult to process, and adopts a planar reflection grating to increase the distance between the edges of the object plane and the image plane, thereby separating the object plane and the image plane, overcoming the limited distance between the object plane and the image plane in traditional Dyson spectrometers, avoiding interference between the object and the image, and reducing the difficulty of overall structural layout and engineering development.

[0021] (2) This invention breaks the limited field of view of the traditional Dyson spectrometer by eliminating the entrance slit and having the ability to perform spectral imaging under a wide field of view. It can simultaneously obtain spectral imaging in both spatial and spectral dimensions, thus broadening the imaging field of view and eliminating the need for a swivel scanning mechanism to achieve spectral imaging in the spatial dimension.

[0022] (3) Each lens assembly in this invention adopts a modular design approach, and each lens assembly can be assembled separately before being integrated into the whole machine. The assembly process is simple and facilitates the integration of the whole system. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of an embodiment of a slitless mid-wave infrared spectroscopy system based on a Dyson improved concentric structure according to the present invention;

[0024] Figure 2This is a spectral imaging footprint diagram generated under wide field-of-view dispersion according to an embodiment of the present invention;

[0025] Figure 3 This is an MTF (modulation transfer function) curve of an embodiment of the present invention at a wavelength of 4800nm;

[0026] Figure 4 This is an MTF curve of an embodiment of the present invention at a wavelength of 4500nm;

[0027] Figure 5 This is an MTF curve of an embodiment of the present invention at a wavelength of 4200nm;

[0028] Figure 6 This is an MTF curve of an embodiment of the present invention at a wavelength of 3900nm;

[0029] Figure 7 This is an MTF curve of an embodiment of the present invention at a wavelength of 3700nm;

[0030] Figure 8 This is an MTF curve of the front objective lens group in an embodiment of the present invention;

[0031] Figure 9 This is the MTF curve of the Dyson spectral spectrometer group at a wavelength of 4800nm ​​in an embodiment of the present invention;

[0032] Figure 10 This is the MTF curve of the Dyson spectral spectrometer group at a wavelength of 4500 nm in an embodiment of the present invention;

[0033] Figure 11 This is the MTF curve of the Dyson spectral spectrometer group at a wavelength of 4200nm in an embodiment of the present invention;

[0034] Figure 12 This is an MTF curve of the Dyson spectral spectrometer group at a wavelength of 3900 nm in an embodiment of the present invention;

[0035] Figure 13 This is an MTF curve of the Dyson spectral spectrometer group at a wavelength of 3700 nm in an embodiment of the present invention;

[0036] Figure 14 This is an MTF curve diagram of the relay lens group in an embodiment of the present invention; Explanation of reference numerals:

[0037] 1-Front objective lens group, 101-Primary reflecting mirror, 102-Secondary reflecting mirror, 103-First front objective lens, 104-Second front objective lens;

[0038] 2-Dyson spectral beam splitter group, 201-plane reflection grating, 202-folding mirror, 203-first lens, 204-second lens, 205-third lens;

[0039] 3-Relay lens group, 301-Fourth lens, 302-Fifth lens, 303-Sixth lens;

[0040] 4 - Cold screen; 501 - Primary image plane; 502 - Secondary image plane; 503 - Image plane. Detailed Implementation

[0041] The present invention will be further described below with reference to the accompanying drawings and exemplary embodiments.

[0042] Reference Figure 1 A slitless mid-wave infrared spectroscopy system based on a Dyson improved concentric structure includes a front objective lens group 1, a Dyson spectral beam splitter group 2, and a relay lens group 3. The front objective lens group 1 has an image-side telecentric pupil, the relay lens group 3 has an object-side telecentric pupil, and the Dyson spectral beam splitter group 2 has both object-side and image-side telecentric pupils, meaning that each lens group satisfies the pupil matching principle.

[0043] The front objective lens group 1 is used to focus the wide field-of-view infrared beam radiated by the target onto the primary image plane 501. The front objective lens group 1 includes a primary reflector 101, a secondary reflector 102, a first front objective lens 103, and a second front objective lens 104 arranged sequentially along the optical path. The wide field-of-view infrared beam radiated by the target passes sequentially through the primary reflector 101, the secondary reflector 102, the central through-hole on the primary reflector 101, the first front objective lens 103, and the second front objective lens 104, and is then focused onto the primary image plane 501.

[0044] The parameters of the primary mirror 101, secondary mirror 102, first front objective lens 103, and second front objective lens 104 are shown in Table 1.

[0045] Table 1

[0046]

[0047] The primary reflector 101 has a parabolic surface with negative optical power, and the secondary reflector 102 has a hyperboloid surface with negative optical power. The first front objective lens 103 is a biconvex lens with positive optical power, and its incident surface is an aspheric surface containing an even-order 8th order. The second front objective lens 104 is a biconcave lens with negative optical power, and its incident surface is an aspheric surface containing an even-order 8th order. The first front objective lens 103 converges light rays, while the second front objective lens 104 diverges light rays. The use of an aspheric surface design corrects aberrations, optimizes the optical path, and improves the overall imaging performance of the infrared optical system.

[0048] The distances between the reflecting surface of the primary mirror 101 and the reflecting surface of the secondary mirror 102, the reflecting surface of the secondary mirror 102 and the incident surface of the first front objective lens 103, the incident surface of the first front objective lens 103 and the exit surface, the exit surface of the first front objective lens 103 and the incident surface of the second front objective lens 104, the incident surface of the second front objective lens 104 and the exit surface, and the exit surface of the second front objective lens 104 and the primary image plane 601 are 294.31, 405.31, 9.4, 7.48, 6.8, and 81.55 mm, respectively.

[0049] The first front objective lens 103 and the second front objective lens 104 are made of ZnSe and ZnS, respectively. The two infrared materials ZnSe and ZnS are matched to correct primary aberrations and combined with higher-order aspherical surfaces to correct higher-order aberrations, thereby improving the imaging quality. The first front objective lens 103 and the second front objective lens 104 are used to achieve image-side telecentric design.

[0050] The centerline obstruction ratio of the primary reflector 101 and the secondary reflector 102 is 0.35.

[0051] The Dyson spectral beam splitter group 2 is used to spectrally split the wide-field infrared beam focused on the primary image plane 501 by the front objective lens group 1 to obtain an infrared spectral beam, and then focus it onto the secondary image plane 502. The Dyson spectral beam splitter group 2 includes a first lens 203, a second lens 204, a third lens 205, a plane reflection grating 201, and a folding mirror 202. The wide-field infrared beam focused by the front objective lens group 1 passes sequentially through the first surface (the side away from the second lens 204) and the second surface of the first lens 203, the first surface and the second surface of the second lens 204, and the first surface and the second surface of the third lens 205, and is then projected onto the plane reflection grating 201. The plane reflection grating 201 performs spectral splitting and reflection, and then passes again through the second and first surfaces of the third lens 205, the second and first surfaces of the second lens 204, the second and first surfaces of the first lens 203, and the folding mirror 202 to focus it onto the secondary image plane 502, and then expands along the dispersion direction wavelength.

[0052] The first lens 203 is a lens with positive optical power that bends towards the plane reflection grating 201, and the first surface is an aspheric surface containing even-order 10; the second lens 204 is a lens with positive optical power that bends towards the plane reflection grating 201; the third lens 205 is a lens with negative optical power that bends towards the plane reflection grating 201, contains even-order 8 double-sided aspheric surfaces, and the plane reflection grating 201 is a plane reflection blazed grating with a scribe line width of 40 μm.

[0053] The parameters of the first lens 203, the second lens 204, and the third lens 205 are shown in Table 2.

[0054] Table 2

[0055]

[0056] The distances between the first and second surfaces of the first lens 203, the second surface of the first lens 203 and the first surface of the second lens 204, the first and second surfaces of the second lens 204, the second surface of the second lens 204 and the first surface of the third lens 205, the first and second surfaces of the third lens 205, and the second surface of the third lens 205 and the secondary image plane 502 are 13.9, 50.24, 13.5, 1.68, 11.84, and 183.55 mm, respectively.

[0057] The first lens 203, the second lens 204, and the third lens 205 are made of Ge, Si, and Ge, respectively. The two infrared materials Ge and Si are matched to correct primary aberrations, and higher-order aspherical surfaces are added to the surface of Ge to correct higher-order aberrations, thereby achieving a dual telecentric design for both the object and image sides.

[0058] The Dyson spectral beam splitter group 2 achieves "optical path multiplexing" of the incident beam and the outgoing beam, with a magnification of -1x.

[0059] The relay lens group 3 is used to image the infrared spectral beam focused on the secondary image plane 502 by the Dyson spectral beam splitter group 2 onto the image plane 503. The relay lens group 3 includes a fourth lens 301, a fifth lens 302, and a sixth lens 303 arranged sequentially along the optical path.

[0060] The fourth lens 301 is a lens bent towards the image plane 503 and has positive optical power. The fifth lens 302 is a lens bent towards the image plane 503, containing an 8th-order even-order double-sided aspherical surface, and has negative optical power. The sixth lens 303 is a lens with positive optical power. The infrared spectral beam separated by the Dyson spectral beam splitter group 2 passes sequentially through the fourth lens 301, the fifth lens 302, and the sixth lens 303 to be imaged at the image plane 503. Simultaneously, the exit pupil of the relay lens group 3 (the system's exit pupil) is aligned with the cold screen 4 of the infrared detector, satisfying 100% cold stop efficiency. The image plane 503 is used to coincide with the target surface of the infrared detector, and the magnification of the relay lens group 3 is -0.5x.

[0061] The parameters of the fourth lens 301, the fifth lens 302, and the sixth lens 303 are shown in Table 3.

[0062] Table 3

[0063]

[0064]

[0065] The distances between the incident and exit surfaces of the fourth lens 301, the distances between the exit surface of the fourth lens 301 and the incident surface of the fifth lens 302, the distances between the incident and exit surfaces of the fifth lens 302, the distances between the exit surface of the fifth lens 302 and the incident surface of the sixth lens 303, and the distances between the incident and exit surfaces of the sixth lens 303 are 12.65, 3.05, 9.08, 13.5, and 12.5 mm, respectively.

[0066] The fourth lens 301, the fifth lens 302, and the sixth lens 303 are made of Si, Ge, and Si, respectively. The two infrared materials Ge and Si are matched to correct primary aberrations, and higher-order aspherical surfaces are added to the surface of Ge to correct higher-order aberrations, thereby achieving object-side telecentric design.

[0067] The front objective lens group 1, the Dyson spectral beam splitter group 2, and the relay lens group 3 meet the pupil matching principle, ensuring the effective utilization of the pupils of each lens group, and each lens group is modularly designed.

[0068] The infrared detector used is a cooled HgCdTe detector with an operating wavelength of 3.7–4.8 μm. The number of the cold screen 4 is 2, the distance between the cold screen 4 and the target surface is 20.47 mm, the pixel size is 15 μm × 15 μm, and the target surface size is 9.6 mm × 7.68 mm (M × N).

[0069] The slitless mid-wave infrared spectral imaging system based on the improved Dyson concentric structure has a focal length of 600mm, an aperture of 300mm, an imaging field of view of 9.6mm × 7.68mm (M × N), a working spectral band of 3.7μm to 4.8μm, a spectral resolution better than 10nm, and uses a planar reflective blazed grating with a grating line width of 40μm. This invention is compatible with planar reflective blazed gratings with grating line widths > 40μm, can adapt to various grating line widths, achieves spectral expansion in a wide field of view, and ensures that spectral line curvature and color distortion do not exceed 10μm. The modular design of each lens group results in good imaging performance, a compact system structure, simple assembly, easy system integration, and excellent overall imaging performance.

[0070] Figure 2 This is a spectral footprint diagram of dispersion generated in an embodiment of the present invention. In the diagram, x corresponds to different imaging fields of view, and y corresponds to different wavelengths. It can be seen that the spectral lines of dispersion expansion are straight with good linearity under different wavelength bands and the spectral lines generated under different imaging fields of view are straight with good linearity, that is, the spectral line curvature and color distortion are very small, and the spectral dispersion performance is better. Figures 3 to 7The figures show the MTF curves for each wavelength in the embodiments of the present invention. At a spatial frequency of 331 p / mm, the meridional / sagittal MTF of the maximum off-axis field of view in each band and field of view is better than 0.41, approaching the diffraction limit. The spectral line curvature and chromatic aberration are both better than 10 μm, with small spectral aberrations, resulting in good spectral imaging quality and clear infrared spectral lines unfolded at various wavelengths in a wide field of view. The present invention has a simple and compact structure, with an overall efficiency of better than 50%. Each lens group adopts a modular design, which is easy to integrate, and the assembly process is simple and controllable, making it highly valuable for engineering applications.

[0071] Figure 8 This is an MTF curve of the front objective lens group 1 in an embodiment of the present invention. Figures 9-13 This is an MTF curve of the Dyson spectral spectrometer group 2 in an embodiment of the present invention at various wavelengths. Figure 14 This is the MTF curve of relay lens group 3 in this embodiment of the invention. At a spatial frequency of 331p / mm, the meridional / sagittal MTF of the maximum off-axis field of view of the front objective lens group 1 is better than 0.22, the meridional / sagittal MTF of the maximum off-axis field of view of the Dyson spectroscopic beam splitter group 2 at each band and at each field of view is better than 0.26, and the meridional / sagittal MTF of the maximum off-axis field of view of the relay lens group 3 is better than 0.58. The MTF of each lens group is close to the diffraction limit, and the imaging quality of each lens group is good.

Claims

1. A slitless mid-wave infrared spectroscopy system based on a Dyson improved concentric structure, characterized in that: It includes a front objective lens group (1), a Dyson spectral beam splitter group (2), and a relay lens group (3); The front objective lens group (1) is used to focus the wide field-of-view infrared beam radiated by the target onto the primary image plane (501). The front objective lens group (1) has the characteristic of telecentric pupil on the image side, including a primary reflector (101), a secondary reflector (102), a first front objective lens (103), and a second front objective lens (104) arranged sequentially along the optical path. The wide field-of-view infrared beam radiated by the target passes sequentially through the primary reflector (101), the secondary reflector (102), the central through hole on the primary reflector (101), the first front objective lens (103), and the second front objective lens (104) before being focused onto the primary image plane (501). The Dyson spectral beam splitter group (2) is used to spectrally split the wide-field infrared beam focused on the primary image plane (501) by the front objective lens group (1) to obtain an infrared spectral beam, and focus it onto the secondary image plane (502); the Dyson spectral beam splitter group (2) has the characteristic of object-side and image-side telecentric pupils, including a first lens (203), a second lens (204), a third lens (205), a plane reflection grating (201) and a folding mirror (202); the wide-field infrared beam focused by the front objective lens group (1) passes through the first lens (203), the second lens (204) and the third lens (205) in sequence, and is then projected onto the plane reflection grating (201) for spectral splitting and reflection, and then passes through the third lens (205), the second lens (204), the first lens (203) and the folding mirror (202) in sequence to focus it onto the secondary image plane (502), and is expanded along the dispersion direction wavelength; The relay lens group (3) is used to focus the infrared spectral beam of the Dyson spectral beam splitter group (2) onto the secondary image plane (502) and image it onto the image plane (503). The relay lens group (3) has the characteristic of telecentric pupil, including a fourth lens (301), a fifth lens (302), and a sixth lens (303) arranged sequentially along the optical path. The infrared spectral beam separated by the Dyson spectral beam splitter group (2) is imaged onto the image plane (503) by the fourth lens (301), the fifth lens (302), and the sixth lens (303) in sequence. The exit pupil of the relay lens group (3) is used to coincide with the cold screen (4) of the infrared detector, and the image plane (503) is used to coincide with the target surface of the infrared detector.

2. The slitless mid-wave infrared spectroscopy system based on a Dyson improved concentric structure according to claim 1, characterized in that: The first lens (203) is a lens with positive optical power, which is bent towards a plane reflection grating (201), and the side away from the second lens (204) is a high-order aspherical surface containing even-order 10; the second lens (204) is a lens with positive optical power, which is bent towards a plane reflection grating (201); the third lens (205) is a lens with negative optical power, which is bent towards a plane reflection grating (201), contains a high-order double-sided aspherical surface containing even-order 8; and the plane reflection grating (201) is a plane reflection blazed grating.

3. The slitless mid-wave infrared spectroscopy system based on a Dyson improved concentric structure according to claim 2, characterized in that: The materials of the first lens (203), the second lens (204), and the third lens (205) are Ge, Si, and Ge, respectively.

4. A slitless mid-wave infrared spectroscopy system based on a Dyson improved concentric structure according to any one of claims 1 to 3, characterized in that: The primary reflector (101) has a parabolic surface with negative optical power, the secondary reflector (102) has a hyperboloid surface with negative optical power, the first front objective (103) is a biconvex lens with positive optical power and its incident surface is an aspheric surface containing even-order 8; the second front objective (104) is a biconcave lens with negative optical power and its incident surface is an aspheric surface containing even-order 8.

5. A slitless mid-wave infrared spectroscopy system based on a Dyson improved concentric structure according to claim 4, characterized in that: The materials of the first front objective lens (103) and the second front objective lens (104) are ZnSe and ZnS, respectively.

6. The slitless mid-wave infrared spectroscopy system based on a Dyson improved concentric structure according to claim 5, characterized in that: The centerline obstruction ratio of the primary reflector (101) and the secondary reflector (102) is 0.

35.

7. The slitless mid-wave infrared spectroscopy system based on a Dyson improved concentric structure according to claim 4, characterized in that: The fourth lens (301) is a lens that bends toward the image plane (503) and has positive optical power; the fifth lens (302) is a lens that bends toward the image plane (503), contains an 8th even-order double-sided high-order aspherical surface, and has negative optical power; and the sixth lens (303) is a lens with positive optical power.

8. A slitless mid-wave infrared spectroscopy system based on a Dyson improved concentric structure according to claim 7, characterized in that: The fourth lens (301), the fifth lens (302), and the sixth lens (303) are made of Si, Ge, and Si, respectively.

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