Dual-band small spectral imaging system based on double slits

Abstract

The invention relates to a dual-band small spectral imaging system based on double slits, and the system is characterized in that a slit incident plane controls the incidence of light, and obtains incident light; after incident light is transmitted by the plano-convex lens, a first transmission light beam is obtained; the concave spherical reflector converges an incident first transmission light beam and generates and reflects a convergent light beam; the convex spherical reflection grating receives the reflected convergent light beam, generates a monochromatic divergent light beam and reflects the monochromatic divergent light beam to the concave spherical reflection mirror; the positive meniscus lens transmits the light beam reflected by the concave spherical reflector to obtain a second transmission light beam; the dichroscope converges the second transmission light beam, generates visible, near-infrared and short-wave infrared light beams, and reflects the visible, near-infrared and short-wave infrared light beams to a first image surface and a second image surface for imaging; wherein the direction of the inner concave surface of the concave spherical reflector is opposite to the direction of incident light; the outer convex spherical surface direction of the convex spherical surface reflection grating is the same as the direction of incident light; the mirror surface normal of the dichroscope and the optical axis of the incident light form an acute angle. The device is compact in structure, small in size, light in weight and easy to machine, install and adjust.

Description

Technical Field

[0001] The invention relates to the technical field of spectral imaging, and in particular to a small-sized dual-band spectroscopic imaging system based on double slits. Background Art

[0002] As an advanced optical remote sensing device, imaging spectrometer integrates the functions of target area imaging and spectral feature capture, and has been widely used in military reconnaissance, crop growth monitoring, biomedical diagnosis and other military and commercial application fields. With the rapid progress of modern aerospace technology and UAV technology, the aerospace field has put forward more stringent requirements for detection payloads: not only pursuing high-resolution detection capabilities in a wide spectral range, but also emphasizing the compact design and lightweight manufacturing of instruments to adapt to the strict restrictions of flight platforms on payload volume and mass. Therefore, the imaging spectrometers carried by aircraft are constantly being optimized and innovated in the direction of higher resolution, smaller size and lighter mass to meet the growing demand for wide spectral band and miniaturized detection.

[0003] The core components of the spectral imaging system include the front objective lens and the spectroscopic imaging system. Among them, the selection of the spectroscopic element has a decisive influence on the complexity, volume, quality and overall performance of the imaging spectrometer. Therefore, it is crucial to match the spectroscopic technology according to the technical requirements of the specific application. Among the many spectroscopic elements, filters, prisms and gratings are particularly commonly used, especially prisms and gratings, which dominate the design of spectrometers due to their superior performance. Plane prisms have attracted attention for their advantages in enhancing the signal-to-noise ratio of the system, but their dispersion nonlinearity and the additional aberrations introduced limit their scope of application. In contrast, curved prisms (proposed by Fery) have won favor in the optical design community due to their unique dispersion and imaging capabilities, but their large size and heavy mass are not conducive to the miniaturization and lightweighting of the system. In addition, for plane gratings, in order to avoid introducing large aberrations, they must be placed in the collimated light path for spectrometry, which not only complicates the light path design, but also reduces the compactness of the structure.

[0004] In the prior art, the document “Design of a compact wide-spectrum double-channel prism imaging spectrometer with freeform surface” (published in Applied Optics, 57(31), 2018) discloses a spectroscopic imaging system based on an Offner structure and a curved dispersion prism, and introducing a freeform surface. The system separates the large-aperture reflector in the initial Offner structure into two small-aperture reflectors, adds variables such as deviation and tilt angle as degrees of freedom, and introduces a freeform surface at the position of the convex spherical reflector, thereby improving the correction capability of the system's off-axis aberration. However, since the system introduces too many optical elements, it has the problems of high design complexity, large system volume, heavy mass, and high difficulty in processing and assembly, making it unsuitable for civilian use. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the shortcomings of the prior art, such as complex optical path design, insufficient structural compactness, excessive volume, excessive weight, and difficulty in processing and assembly.

[0006] In order to solve the above technical problems, the first aspect of the present invention provides a dual-band small spectroscopic imaging system based on double slits, comprising: The slit incident plane is used to control the light incidence and obtain the incident light; a plano-convex lens, used for receiving and transmitting the incident light to obtain a first transmitted light beam; a concave spherical reflector, used for converging the incident first transmitted light beam, generating a convergent light beam, and reflecting the convergent light beam; A convex spherical reflection grating is used to receive the reflected convergent light beam, generate monochromatic divergent light beams of different wavelengths and reflect them to the concave spherical reflector; A positive meniscus lens, used for transmitting the light beam reflected by the concave spherical reflector and obtaining a second transmitted light beam; a dichroic mirror, configured to converge the second transmitted light beam to generate a visible and near-infrared light beam and a short-wave infrared light beam, and reflect the visible and near-infrared light beam and the short-wave infrared light beam; A first image plane, used for receiving the visible and near-infrared light beams and forming an image; A second image plane, used for receiving the short-wave infrared light beam and forming an image; The inner concave surface of the concave spherical reflector is in the opposite direction to the incident light; the outer convex spherical surface of the convex spherical reflection grating is in the same direction as the incident light; and the mirror normal of the dichroic mirror forms an acute angle with the optical axis of the incident light.

[0007] In one embodiment of the present invention, a mirror normal of the dichroic mirror forms an acute angle with the optical axis of the incident light, and the acute angle is 45°.

[0008] In one embodiment of the present invention, the plano-convex lens and the positive meniscus lens are arranged vertically to form a lens combination, and the convex spherical reflection grating is located between the lens combination and the concave spherical reflector.

[0009] In one embodiment of the present invention, the first transmitted light beam converges at a non-repeating area of ​​the concave spherical reflector, and the concave spherical reflector reflects the converged light beam to a non-repeating area of ​​the convex spherical reflection grating.

[0010] In one embodiment of the present invention, the concave spherical reflector and the convex spherical reflective grating are coaxial and concentric structures.

[0011] In one embodiment of the present invention, the aperture stop of the optical imaging system is located at the convex spherical reflection grating.

[0012] In one embodiment of the present invention, the slit incident plane, the first image plane and the second image plane are located on the same side of the axis of the spectroscopic imaging system.

[0013] A second aspect of the present invention provides a dual-band small-scale spectroscopic imaging method based on double slits, comprising: The incident light is transmitted through the slit incident plane and converged to the concave spherical reflector through the plano-convex lens to obtain a converging beam; The convergent light beam is reflected by the concave spherical reflector to the convex spherical reflective grating to obtain a monochromatic divergent light beam with a different wavelength. The monochromatic divergent light beam is reflected by the concave spherical reflector again, and then reflected by the concave spherical reflector to the positive meniscus lens, and is transmitted through the positive meniscus lens to obtain a second transmitted light beam. The second transmitted light beam converges on the dichroic mirror to obtain a visible and near-infrared light beam and a short-wave infrared light beam, and the visible and near-infrared light beams are reflected to the first image plane, and the short-wave infrared light beam is reflected to the second image plane; the visible and near-infrared light beams are imaged on the first image plane, and the short-wave infrared light beam is imaged on the second image plane.

[0014] A third aspect of the present invention provides an imaging spectrometer, comprising the above-mentioned dual-band small spectroscopic imaging system based on double slits.

[0015] A fourth aspect of the present invention provides an aircraft, comprising the above-mentioned imaging spectrometer.

[0016] The above technical solution of the present invention has the following beneficial effects compared with the prior art: The present invention discloses a dual-band small spectroscopic imaging system based on double slits, which uses the slit incident plane to control the light incidence, realizes the common optical path of the spectroscopic imaging system, and increases the aberration correction capability of the system. In the optical path design, a convex spherical grating is introduced as a spectroscopic element to realize spectroscopic, and a plano-convex lens and a positive meniscus lens are selected, which can effectively improve the system's correction capability for spectral distortion and ensure the accuracy and stability of the imaging results. At the same time, a dichroic mirror is introduced to realize the separation of light beams of different bands, and finally image them to different image planes, so as to realize the simultaneous acquisition of spectral information in the visible and near-infrared and part of the short-wave infrared bands in a single push-scan process. The spectroscopic imaging system provided by the present invention not only has a simple optical path design, compact structure, small size and light weight, but is also easy to process and assemble, and has strong stability.

[0017] In addition, the coaxial and concentric structure of the concave spherical reflector and the convex spherical reflection grating, as well as the upper and lower arrangement of the plano-convex lens and the positive meniscus lens (i.e., the upper and lower arm structure on the optical path), this compact structure not only realizes the flexible configuration of the double slits, but also significantly broadens the band range of spectral imaging, while ensuring the dual advantages of high spatial resolution and spectral resolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings.

[0019] Figure 1 It is a structural schematic diagram of a dual-band small-sized spectroscopic imaging system based on double slits in a preferred embodiment of the present invention; Figure 2 A ray tracing point diagram of a dual-band small-scale spectroscopic imaging system based on double slits in a preferred embodiment of the present invention; Figure 3 The MTF curve diagram of the transfer function of a dual-band small spectroscopic imaging system based on double slits in a preferred embodiment of the present invention; Figure 4 This is a curve diagram of the enclosed energy concentration of a dual-band small spectroscopic imaging system based on double slits in a preferred embodiment of the present invention.

[0020] Explanation of the reference numerals in the specification: 1. slit incident plane; 2. plano-convex lens; 3. concave spherical reflector; 4. convex spherical reflection grating; 5. positive meniscus lens; 6. dichroic mirror; 71. first image plane; 72. second image plane. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0022] Embodiment 1

[0023] Reference Figure 1 As shown, an embodiment of the present invention provides a dual-band small spectroscopic imaging system based on double slits, comprising: The slit incident plane 1 is used to control the incident light and obtain the incident light; A plano-convex lens 2, used for receiving and transmitting incident light to obtain a first transmitted light beam; The concave spherical reflector 3 is used to converge the incident first transmitted light beam, generate a convergent light beam, and reflect the convergent light beam; The convex spherical reflection grating 4 is used to receive the reflected convergent light beam, generate monochromatic divergent light beams of different wavelengths and reflect them to the concave spherical reflector 3; The positive meniscus lens 5 is used to transmit the light beam reflected by the concave spherical reflector 3 and obtain a second transmitted light beam; a dichroic mirror 6, for converging the second transmitted light beam, generating a visible and near-infrared light beam and a short-wave infrared light beam, and reflecting the visible and near-infrared light beam and the short-wave infrared light beam; The first image plane 71 is used to receive visible and near-infrared light beams and form images; The second image plane 72 is used to receive the short-wave infrared light beam and form an image; The inner concave surface of the concave spherical reflector 3 is in the opposite direction to the incident light; the outer convex spherical surface of the convex spherical reflection grating 4 is in the same direction as the incident light; and the mirror normal of the dichroic mirror 6 forms an acute angle with the optical axis of the incident light.

[0024] The embodiment of the present invention provides a dual-band small spectroscopic imaging system based on double slits, which uses the slit incident plane 1 to control the incident light, realizes the common optical path of the spectroscopic imaging system, and increases the aberration correction capability of the system. In the optical path design, a convex spherical grating is introduced as a spectroscopic element to realize spectroscopic, and a plano-convex lens 2 and a positive meniscus lens 5 are selected, which can effectively improve the system's correction capability for spectral distortion and ensure the accuracy and stability of the imaging result. In addition, a dichroic mirror 6 is introduced to realize the separation of light beams of different bands, and finally image them to different image planes, so as to obtain spectral information in the visible and near-infrared and partial short-wave infrared bands in a single push-scan process. The spectroscopic imaging system provided by the embodiment of the present invention not only has a simple optical path design, compact structure, small size and light weight, but is also easy to process and assemble, and also has strong stability.

[0025] Specifically, in terms of structure, the plano-convex lens 2, the concave spherical reflector 3, the convex spherical reflection grating 4, the positive meniscus lens 5 and the dichroic mirror 6 have a common optical path and an approximately concentric structure; the dichroic mirror 6 is placed at an angle, and its mirror normal is at an acute angle with the optical axis of the incident light, and the acute angle is preferably 45°; the plano-convex lens 2 and the positive meniscus lens 5 are arranged up and down to form a lens combination, and the position of the convex spherical reflection grating 4 is preferably located between the lens combination and the concave spherical reflector 3; the slit incident plane 1, the first image plane 71 and the second image plane 72 are located on the same side of the axis of the spectroscopic imaging system, the concave spherical reflector 3 and the convex spherical reflection grating 4 are coaxial and concentric structures, and the aperture stop of the spectroscopic imaging system is located at the convex spherical reflection grating 4. Among them, the slit incident plane 1 can control the incidence of light, improve spectral resolution, optimize spectral measurement, and reduce background interference and background noise. In this embodiment, the slit incident plane 1 includes two independent slits. The design of the double incident slits can realize the common optical path of the system and improve the aberration correction capability of the system. According to the incident direction of the light, the optical elements in the embodiment of the present invention are the plano-convex lens 2, the concave spherical reflector 3, the convex spherical reflective grating 4, the positive meniscus lens 5 and the dichroic mirror 6.

[0026] In the embodiment of the present invention, the coaxial and concentric structure of the concave spherical reflector 3 and the convex spherical reflection grating 4, as well as the upper and lower arrangements of the plano-convex lens 2 and the positive meniscus lens 5 (i.e., the upper and lower arm structure on the optical path), this compact structure not only realizes the flexible configuration of the double slits, but also significantly broadens the band range of spectral imaging, while ensuring the dual advantages of high spatial resolution and spectral resolution.

[0027] Specifically, in the optical element, the plano-convex lens 2, the concave spherical reflector 3, the convex spherical reflection grating 4, and the positive meniscus lens 5 are all composed of standard spherical surfaces. The surface shapes of the optical elements are all designed as standard spherical surfaces, which reduces the difficulty and cost of lens processing and also has the advantages of small size and light weight, and has practical application value. The curvature radius of the first spherical surface and the second spherical surface of the plano-convex lens 2, the concave spherical reflector 3, the convex spherical reflection grating 4, and the positive meniscus lens 5 are R 22 , R3, R4, R 51 , R 52 , the value range of each curvature radius satisfies -851≤R 22 ≤-848, -96≤R3≤-93, -48≤R4≤-46, 189≤R 51 ≤192 and 165.5≤R 52 ≤168.5, any value within this range can be selected according to actual needs. For example, R 22 The options are -851, -850, -849.1, -848, etc.; R3 can be selected as -96, -95.5, -93, etc.; R4 can be selected as -48, -47.5, -46, etc.; R 51You can choose 189, 191.5, 192, etc.; R 52 The options are 165.5, 166, 168.5, etc. In terms of optical element materials, when selecting the materials of the plano-convex lens 2, the concave spherical reflector 3, the convex spherical reflective grating 4, the positive meniscus lens 5, and the dichroic mirror 6, multiple factors need to be considered, including optical performance, mechanical strength, thermal stability, chemical stability, and cost, etc. In practical applications, trade-offs and selections can be made according to specific needs.

[0028] Specifically, the object-side numerical aperture of the spectroscopic imaging system provided in the embodiment of the present invention is NA, and its value range satisfies 0.095≤NA≤0.12, and any value within this value range can be selected according to actual needs, such as 0.095, 0.1, 0.12, etc. The tube length is L, and its value range satisfies 85mm≤L≤110mm, and any value within this value range can be selected according to actual needs, such as 85 mm, 90 mm, 110 mm, etc.

[0029] Specifically, in the imaging process of the spectroscopic imaging system provided in the embodiment of the present invention, the optical system is an off-axis three-mirror system, and the two incident light beams pass through two independent slits on the slit plane respectively and emit, and are transmitted through the plano-convex lens 2 and then converged and incident on the concave spherical reflector 3, and then reflected by the concave spherical reflector 3 to the convex spherical reflection grating 4, and the light beams are dispersed by the grating and divided into monochromatic divergent light beams of different wavelengths, and are incident on the concave spherical reflector 3 again; then they are reflected to the positive meniscus lens 5, and are transmitted through the meniscus lens and converged on the dichroic mirror 6; the dichroic mirror 6 is placed at an angle of 45° relative to the optical axis, and it transmits the light in the visible and near-infrared bands of 400~1000nm while reflecting the light in the partial short-wave infrared band of 1000~1700nm, and converges the two light beams in the optical path on the first image plane 71 and the second image plane 72 respectively, so as to realize the simultaneous acquisition of spectral information and spatial information of visible and near-infrared and partial short-wave infrared in the target area. The first transmitted light beam transmitted through the plano-convex lens 2 converges on the non-repeating area (i.e., different areas) of the concave spherical reflector 3, and the concave spherical reflector 3 reflects the converged light beam to the non-repeating area (i.e., different areas) of the convex spherical reflection grating 4.

[0030] The embodiment of the present invention innovatively uses a convex spherical grating to replace the second convex spherical reflector in the Offner relay system, which cleverly balances the needs of aberration correction and high-resolution imaging. At the same time, since the Offner structure of the system automatically corrects the third-order astigmatism and field curvature of the system, only the fifth-order astigmatism remains. To this end, the lens is introduced and applied to the initial structure, that is, the two lenses are placed at the upper and lower arms of the Offner structure respectively. By adding variables, the system is further optimized to ensure a better aberration correction capability, and the system can simultaneously perform spectroscopic imaging on two parallel slits. Among them, in terms of spectral quality control, the spectral line bending and color distortion in the visible and near-infrared bands at the first image plane 71 are controlled within 2.7μm; and in part of the short-wave infrared band at the second image plane 72, the spectral line bending and color distortion are also accurately controlled to not exceed 4.0μm. This spectral characteristic lays a solid foundation for subsequent spectral calibration work, and also greatly facilitates the reconstruction and processing of spectral images, and improves the accuracy and efficiency of data processing. In addition, before the outgoing light beam converges, a semi-transparent and semi-reflective dichroic mirror 6 is introduced to separate the light of different wavelengths and finally converge them to different image planes, so that the system can obtain wide-band spectral information in a single push scan.

[0031] Exemplarily, in the embodiment of the present invention, the length of the two slits is preferably 10 mm, the vertical distance between the upper and lower slits is 5 mm, the optical tube length TOTR <95 mm, NA = 0.11; the working band is 400-1700 nm, covering the visible and near-infrared and part of the short-wave infrared bands, and its spectral resolution is better than 1.5 nm in the working band, and the dispersion linearity is good; when the spectroscopic imaging system provided by the embodiment of the present invention is installed on an electric turntable to perform push-scan imaging on the target area, the number of spectral channels obtained by the system in the visible and near-infrared bands is 198, and the number of spectral channels obtained in the part of the short-wave infrared band is 162. The curvature radius, thickness, air gap, refractive index and Abbe number parameters of the preferred plano-convex lens 2, concave spherical reflector 3, convex spherical reflection grating 4 and positive meniscus lens 5 are shown in Table 1.

[0032] Table 1 Parameter information of optical components

[0033] The ray tracing point diagram of the light entering the spectroscopic imaging system provided in this embodiment can be referred to as Figure 2 . Figure 2In part (a), the root mean square radius of the spot diagram of each field of view corresponding to the five wavelengths of 400nm, 550nm, 700nm, 850nm and 1000nm is less than 3.5μm, and the geometric radius of the spot diagram is less than 7.0μm; in part (b), the root mean square radius of the spot diagram of each field of view corresponding to the five wavelengths of 1000nm, 1175nm, 1350nm, 1525nm and 1700nm is less than 3.5μm, and the geometric radius of the spot diagram is less than 6.7μm. From the results, it can be seen that the imaging quality is good in the working band of 400~1700nm.

[0034] The MTF curves of the transfer functions on the image plane corresponding to each field of view of the spectroscopic imaging system provided in this embodiment can be referred to as Figure 3 . Figure 3 In (a), (b) and (c), the MTF curve values ​​of each field of view with working wavelengths of 400nm, 700nm and 1000nm are shown at the first image plane 71. As can be seen from (a), (b) and (c), when the cutoff frequency is 36Lp / mm, the MTF values ​​of each field of view with wavelengths of 400nm (a), 700nm (b) and 1000nm (c) are all greater than 0.78. Figure 3 In (d), (e) and (f), the MTF curve values ​​of each field of view with working wavelengths of 1000nm (d), 1350nm (e) and 1700nm (f) are shown at the second image plane 72. As can be seen from (d), (e) and (f), when the cutoff frequency is 25Lp / mm, the MTF values ​​of each field of view with wavelengths of 1000nm (d), 1350nm (e) and 1700nm (f) are all greater than 0.70. The results of (a), (b), (c), (d), (e) and (f) are all close to the diffraction limit, and the curves are relatively smooth, indicating that the lens has clear and uniform imaging and has good imaging quality in the full band and full field of view.

[0035] Furthermore, the energy concentration curves of the spectroscopic imaging system provided in this embodiment at wavelengths of 700nm and 1350nm can be referred to Figure 4 . Figure 4 Part (a) is the circled energy concentration curve at a wavelength of 700nm. Figure 4 Part (b) is the circled energy concentration curve at 1350nm wavelength. From the figure, it can be seen that more than 80% of the energy at the two wavelengths is concentrated in the Airy disk range, and the energy is relatively concentrated.

[0036] The spectroscopic imaging system provided by the embodiment of the present invention, after the correction of the aberrations related to the spectroscopic and field of view, not only has the characteristics of wide coverage band, high spatial and spectral resolution and common optical path, but also has the advantages of small size and light weight. At the same time, it has good imaging quality and is suitable for practical fields such as unmanned aerial vehicle hyperspectral detection, and has broad application prospects.

[0037] Embodiment 2

[0038] Based on the same inventive concept, this embodiment provides a dual-band small spectroscopic imaging method based on double slits, and the principle of solving the problem is similar to the dual-band small spectroscopic imaging system based on double slits provided in Example 1, and the repeated parts are not repeated here.

[0039] The embodiment of the present invention provides a dual-band small-scale spectroscopic imaging method based on double slits, comprising: The incident light is transmitted through the slit incident plane 1, passes through the plano-convex lens 2 and converges to the concave spherical reflector 3 to obtain a convergent beam; The convergent light beam is reflected by the concave spherical reflector 3 to the convex spherical reflective grating 4 to obtain a monochromatic divergent light beam of different wavelengths. The monochromatic divergent light beam is reflected by the concave spherical reflector 3 again, and then reflected by the concave spherical reflector 3 to the positive meniscus lens 5, and transmitted through the positive meniscus lens 5 to obtain a second transmitted light beam. The second transmitted light beam converges on the dichroic mirror 6 to obtain a visible and near-infrared light beam and a short-wave infrared light beam, and the visible and near-infrared light beam is reflected to the first image plane 71, and the short-wave infrared light beam is reflected to the second image plane 72; the visible and near-infrared light beams are imaged on the first image plane 71, and the short-wave infrared light beam is imaged on the second image plane 72.

[0040] Embodiment 3

[0041] This example provides an imaging spectrometer, including a double-slit based dual-band small spectroscopic imaging system provided in the first embodiment.

[0042] Embodiment 4

[0043] This example provides an aircraft, including an imaging spectrometer provided in Example 3.

[0044] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A dual-band small spectroscopic imaging system based on double slits, characterized in that: include: The slit incident plane is used to control the light incidence and obtain the incident light; a plano-convex lens, used for receiving and transmitting the incident light to obtain a first transmitted light beam; a concave spherical reflector, used for converging the incident first transmitted light beam, generating a convergent light beam, and reflecting the convergent light beam; A convex spherical reflection grating is used to receive the reflected convergent light beam, generate monochromatic divergent light beams of different wavelengths and reflect them to the concave spherical reflector; A positive meniscus lens, used for transmitting the light beam reflected by the concave spherical reflector and obtaining a second transmitted light beam; a dichroic mirror, configured to converge the second transmitted light beam to generate a visible and near-infrared light beam and a short-wave infrared light beam, and reflect the visible and near-infrared light beam and the short-wave infrared light beam; A first image plane, used for receiving the visible and near-infrared light beams and forming an image; A second image plane, used for receiving the short-wave infrared light beam and forming an image; The inner concave surface of the concave spherical reflector is in the opposite direction to the incident light; the outer convex spherical surface of the convex spherical reflection grating is in the same direction as the incident light; and the mirror normal of the dichroic mirror forms an acute angle with the optical axis of the incident light.

2. A dual-band small spectroscopic imaging system based on double slits according to claim 1, characterized in that , the mirror normal of the dichroic mirror forms an acute angle with the optical axis of the incident light, and the acute angle is 45°.

3. A dual-band small spectroscopic imaging system based on double slits according to claim 1, characterized in that The plano-convex lens and the positive meniscus lens are arranged up and down to form a lens combination, and the convex spherical reflection grating is located between the lens combination and the concave spherical reflector.

4. The dual-band small spectroscopic imaging system based on double slits according to claim 1, characterized in that: The first transmitted light beam converges at the non-repeating area of ​​the concave spherical reflector, and the concave spherical reflector reflects the converged light beam to the non-repeating area of ​​the convex spherical reflection grating.

5. The dual-band small spectroscopic imaging system based on double slits according to claim 1, characterized in that: The concave spherical reflector and the convex spherical reflective grating are coaxial and concentric structures.

6. The dual-band small spectroscopic imaging system based on double slits according to claim 1, characterized in that , the aperture stop of the optical imaging system is located at the convex spherical reflection grating.

7. The dual-band small spectroscopic imaging system based on double slits according to claim 1, characterized in that: The slit incident plane, the first image plane and the second image plane are located on the same side of the diaphragm of the spectroscopic imaging system.

8. A dual-band small-scale spectroscopic imaging method based on double slits, characterized in that: include: The incident light is transmitted through the slit incident plane and converged to the concave spherical reflector through the plano-convex lens to obtain a converging beam; The convergent light beam is reflected by the concave spherical reflector to the convex spherical reflective grating to obtain a monochromatic divergent light beam with a different wavelength. The monochromatic divergent light beam is reflected by the concave spherical reflector again, and then reflected by the concave spherical reflector to the positive meniscus lens, and is transmitted through the positive meniscus lens to obtain a second transmitted light beam. The second transmitted light beam converges on the dichroic mirror to obtain a visible and near-infrared light beam and a short-wave infrared light beam, and the visible and near-infrared light beams are reflected to the first image plane, and the short-wave infrared light beam is reflected to the second image plane; the visible and near-infrared light beams are imaged on the first image plane, and the short-wave infrared light beam is imaged on the second image plane.

9. An imaging spectrometer, characterized in that: A small dual-band spectroscopic imaging system based on double slits as described in any one of claims 1 to 7.

10. An aircraft, characterized in that: An imaging spectrometer comprising the method of claim 9.

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