Hyperspectral imaging low-distortion large-image-plane object image double-telecentric spectrometer and implementation method

Abstract

The invention provides a hyperspectral imaging low-distortion large-image-plane object image double-telecentric spectrometer and an implementation method. The implementation method comprises the following steps: establishing a spectrograph object image space double-telecentric theoretical model, namely establishing three sub-models of spectrum bending-telecentricity, spectrum distortion-telecentricity and astigmatism-telecentricity; based on the theoretical model, corresponding parameter relations between the telecentric and spectrograph field diaphragm, the meniscus lens, the primary / secondary reflector and the convex grating are given, and rapid design of initial structure parameters of the spectrograph is given. The novel spectrograph with the characteristics of large field of view, low astigmatism, low spectral distortion and low spectral lateral deviation is successfully designed through the method, the inherent problem that dispersion and distortion of the spectrograph are nonlinearly and sharply increased along with the increase of the field of view is solved, and the dispersion and distortion are fundamentally changed close to a constant under the condition of the large field of view; a traditional empirical design method based on optical design software is converted into an initial structure accurate analysis design method based on a telecentric theoretical model.

Description

Technical Field

[0001] The invention belongs to the technical field of optical instruments, and relates to a spectrometer and a design implementation method, and in particular to an implementation method of a high-spectral imaging, low-distortion, large-image-surface, object-image double-telecentric spectrometer. Background Art

[0002] Hyperspectral imaging technology can simultaneously obtain the geometric, radiation and spectral information of the target, enriching the dimension of cognitive targets, achieving a leap from macro to micro, and forming a unique advantage in material "fingerprint" identification. It has shown great application potential in energy resource exploration, environmental disaster monitoring, agricultural and forestry remote sensing, greenhouse gas monitoring, urban surveys, etc. Hyperspectral imaging technology was included in the "100 Major Innovation Breakthroughs for the Future" catalog released by the European Union in 2021, and is considered to be one of the disruptive technologies that may have a major impact on the global economy.

[0003] As one of the core optical components in hyperspectral imaging technology, the spectrometer decomposes the light reflected or radiated by the object into spectral information of different wavelengths, and combines it with the imaging system to obtain the complete spectral curve of each spatial pixel, thereby achieving classification and identification of different objects. The high spectral resolution of the spectrometer can accurately capture the absorption, reflection or transmission characteristics of the material to each wavelength of light. These spectral characteristics can reflect the physical and chemical properties of the material. These data can be further processed and used for tasks such as material classification, component identification and defect detection.

[0004] Since the end of the last century, the world has been competing to develop hyperspectral imaging technology. At present, there are more than 30 hyperspectral satellites in orbit, under research and in planning. However, due to the narrow width of the ground survey and insufficient spectral accuracy, the timeliness of hyperspectral detection data is low and the application effect is poor, which cannot meet the commercialization and practical popularization of satellite-borne hyperspectral remote sensing instruments. The reason is that the traditional imaging design method based on the three-level aberration theory only focuses on geometric dispersion and geometric astigmatism, while the spectral distortion and spectral lateral deviation used to measure the quantitative accuracy level of the hyperspectral imaging system are weakened or even ignored, resulting in low precision in the two dimensions of the hyperspectral data space spectrum, bringing about the abnormal phenomenon of "different spectra for the same object, and the same spectrum for different objects". If low dispersion, low spectral distortion, and low spectral lateral deviation are taken into account to achieve high imaging quality, the traditional spectrometer can only achieve a narrow linear field of view, and its field of view "cannot be made longer or wider".

[0005] In 2000, the U.S. EO-1 satellite Hyperion hyperspectral camera realized an Offner spectrometer structure based on a convex grating in orbit, with a linear field of view of about 15 mm (Folkman MA, Pearlman J, Liao LB, et al. EO-1 / Hyperion hyperspectral imager design, development, characterization, and calibration [J]. Hyperspectral Remote Sensing of the Land and Atmosphere, 2001, 4151: 40-51.). The inventor realized an Offner structure convex grating spectrometer in 2002 (Shen Beijun, Liu Baoli, Liu Yinian, et al. Catadioptric convex grating imaging optical system: CN02136154.1 [P]. CN1391090A [2025-02-04].), which can better control image quality, spectral distortion, and spectral curvature within a 20 mm field of view. Beyond this range, image quality, spectral distortion, and spectral lateral deviation deteriorate sharply. This has become a bottleneck that restricts the further expansion of the field of view of satellite-borne hyperspectral detection at home and abroad. The inventor first introduced a new Offner spectrometer structure in 2011 (Yang Bo. Research on optical technology of wide-band hyperspectral imaging [D]. Graduate School of the Chinese Academy of Sciences, 2011.), and based on traditional aberration theory and optical software such as ZEMAX, the object-image double telecentric design idea was first applied to the design of a 60mm ultra-large field of view convex grating spectrometer. In 2018, the world's first wide-band hyperspectral camera (AHSI) was put into orbit (Liu YN, Sun DX, Hu XN, et al. The advanced hyperspectral imager: Aboard China's GaoFen-5 satellite [J]. IEEE Geoscience and Remote Sensing Magazine, 2019, 7(4): 23-32.), while maintaining the same spectral range (0.4μm~2.5μm) and spatial resolution (30m) as the mainstream international satellite-borne hyperspectral cameras, the bandwidth has been increased from the internationally common 30km to 60km, the spectral distortion is close to 0.1 pixel, the lateral deviation of the spectrum is less than 1nm, and the accuracy has reached the international best. It is unanimously recognized by domestic and foreign experts and scholars as a typical example of high-quantitative hyperspectral detection and is of milestone significance.

[0006] Subsequently, Jia. C. Zhu et al. studied the astigmatism expression of the new Offner spectrometer structure with large field of view, low spectral distortion and low spectral lateral deviation, and proved that the new Offner spectrometer has a larger astigmatism-free field of view than the conventional Offner spectrometer from the perspective of astigmatism elimination (Zhu Jiacheng, Shen Weimin. Compact astigmatism-free long slit spectrometer optical system [J]. Journal of Infrared and Millimeter Waves, 2019, 38(4):7.). X. Prieto studied the spectrometer structures of two Offner plus meniscus lenses, and confirmed the large field of view and high image quality capabilities of the new Offner spectrometer from the perspective of aberration elimination (Prieto-Blanco X, de la Fuente R. Compact Offner–Wynne imaging spectrometers [J]. OpticsCommunications, 2014, 328: 143-150.). However, none of them gave the theoretical model of double telecentricity of the object and image, the corresponding initial structure design method and the constraints of engineering application. Summary of the invention

[0007] The present invention provides a method for realizing a high-spectral imaging, low-distortion, large-image-surface object-image double-telecentric spectrometer, comprising the establishment of a spectrometer object-image double-telecentric theoretical model and a method for quickly designing initial structural parameters of the spectrometer based on the theoretical model, so as to realize a novel spectrometer with large field of view, high image quality, and extremely low spectral distortion and lateral deviation characteristics.

[0008] A theoretical model of double telecentricity of the object and image side of a spectrometer is established. The theoretical model consists of three sub-models: "spectral curvature-telecentricity", "spectral distortion-telecentricity" and "astigmatism-telecentricity". Among them, the "spectral curvature-telecentricity" model explains the mapping relationship between spectral curvature (e) and object side telecentricity (a) and image side telecentricity (b), the "spectral distortion-telecentricity" model explains the mapping relationship between spectral distortion (d) and object side telecentricity (a) and image side telecentricity (b), and the "astigmatism-telecentricity" model explains the mapping relationship between astigmatism (c) and object side telecentricity (a) and image side telecentricity (b). The specific relationship is as follows: The “spectral curvature-telecentricity” model (e-ab) is: ; The spectral distortion-telecentricity model (d-ab) is: ; The astigmatism-telecentricity model (c-ab) of the spectrometer is: ; in, is the object telecentricity, with clockwise as the positive direction; is the image telecentricity, with the counterclockwise direction as the positive direction; ( x o ,y o ) is the object point coordinate, ( x i ,y i ) are the image point coordinates, R 2 is the radius of curvature of the convex grating, m is the diffraction order, g is the line density of the convex grating, λ is the wavelength; Astig is the astigmatism of the spectrometer; α o is the incident azimuth angle of the chief ray of the spectrometer, α i is the main light emission azimuth of the spectrometer, with clockwise being the positive direction; CO is the distance from the object point of the spectrometer to the common center of curvature of each mirror.

[0009] Based on the above theoretical model combined with the low distortion large image area object image double telecentric spectrometer engineering implementation, the implementation parameters of the spectrometer must satisfy the following formula: ; in, is the object telecentricity, is the image telecentricity, ( x o ,y o ) are the object point coordinates, The spectrometer is from the central field of view position of the slit to the edge field of view position, λ is the wavelength, λ 1 ~λ n is the working band range of the spectrometer, λ 1 is the starting wavelength, λ n is the ending wavelength.

[0010] Based on the flat sagittal field curvature condition of the telecentricity-astigmatism model, the slit is located on the plane XCY which is perpendicular to the optical axis and passes through the common curvature center of each optical surface (the slit is parallel to the x-axis, and any point on the slit is z o The coordinates are zero, where z o is the Z coordinate of the object point, and the distance between the slit and the common curvature center C is y o).

[0011] The basic idea of ​​the method for quickly acquiring the initial structure is to first establish the distance between the telecentricity of the object-image square (a, b) and the off-axis distance of the spectrometer field stop ( y o1 , y o2 )、The radius of curvature of the meniscus lens( R 1 ，R 2 )、Main reflector curvature radius( R 3 ), radius of curvature of the secondary reflector ( R 4 ) and the radius of curvature of the convex grating ( R 2 ), and then screen the initial structural parameters that meet the telecentricity requirements based on the relationship, and finally determine the initial structural parameters of spectrometer 2 R 1 、R 2 、R 3 、R 4 and the off-axis distance of the slit y o1 , y o2 . The specific process of determining the initial structure includes steps S51 to S57. Among them, S51 is to obtain the first input parameter and the second input parameter, S52 is to obtain the intermediate parameter according to the first input parameter and the second input parameter, S53 is to solve the object space telecentric model and the image space telecentric model, S54 is to obtain the initial structure parameters, S55 is to determine whether the initial structure corresponding to the initial structure parameters blocks light, S56 is to determine whether the initial structure meets the requirements of engineering application spectrum detection, and S57 is to output the initial structure parameters and establish the initial structure of the spectrometer when the judgment conditions of S55 and S56 are met.

[0012] The present invention first obtains a first curved surface distribution and a second curved surface distribution based on the theoretical model. The first curved surface distribution is the curved surface distribution of the structural parameters of the meniscus lens and the primary reflector along the two-dimensional rectangular field of view when forming object telecentricity, and its structural parameter curve function is: ; in, k 13 =2, others k 1i =1, n 12 =n ,other n 1i =1;k 22 =2, others k 2j =1, n 21 = n ,other n 2j =1; CO is the distance from the object point of the spectrometer to the common curvature center of each mirror ; The second curved surface distribution is the curved surface distribution of the structural parameters of the meniscus lens and the secondary reflector along the two-dimensional rectangular field of view when forming image telecentricity, and the structural parameter curve function is: ; in, k 14 =2, k 13 =0Other k 1i =1, n 12 = n ,other n 1i =1; k 22 =2, others k 2j =1, n 21 = n ,other n 2j =1; CI is the distance from the image point of the spectrometer to the common curvature center of each mirror: ; is the object telecentricity, is the image telecentricity, ( x o ,y o ) is the object point coordinate, n is the refractive index of the meniscus lens, m is the diffraction order, g is the line density of the convex grating, λ is the wavelength, R 1 is the radius of curvature of the front surface of the meniscus lens, R 2 is the radius of curvature of the convex grating, R 3 is the radius of curvature of the primary reflector, R4 is the radius of curvature of the secondary reflector, where R 1 , R 3 To determine the structural parameters of the object telecentricity, R 1 , R 4 It is the structural parameter that determines the telecentricity of the image.

[0013] In the present invention, the functional relationship between the object telecentricity and the structural parameters of the meniscus lens and the main reflector is: ; in, Object-side telecentricity adjustment factor introduced for meniscus lens: ; is the incident angle of the object principal ray on the front surface of the lens: ; is the angle of incidence of the object-side principal ray on the front surface of the lens: ; is the incident angle of the object principal ray on the rear surface of the lens: ; is the angle of incidence of the object-side principal ray on the rear surface of the lens: ; is the incident angle of the object principal ray on the primary reflector: ; is the incident angle of the object-side principal ray on the grating: ; The functional relationship between the image-side telecentricity and the structural parameters of the meniscus lens and the secondary reflector is: ; in, Image-side telecentricity adjustment factor introduced for meniscus lens: ; is the angle of incidence of the image-side chief ray on the front surface of the lens: ; is the incident angle of the image-side chief ray on the front surface of the lens: ; is the angle of incidence of the image-side principal ray on the rear surface of the lens: ; is the incident angle of the image-side chief ray on the rear surface of the lens: ; is the incident angle of the image-side chief ray at the secondary reflector: ; is the incident angle of the image-side chief ray on the grating: .

[0014] Adding constraints of telecentricity deviation and telecentricity deviation change rate to the first curved surface and the second curved surface distribution to obtain initial structural parameters of the spectrometer 2 that meet the requirements of object-side telecentricity and image-side telecentricity R 1 、R 2 、R 3 、R 4 and the off-axis distance of the slit y o1 , y o2 . The first curved surface distribution and the second curved surface distribution are profiled along the direction along the slit and the direction perpendicular to the slit to obtain a profile curve; finally, parameters corresponding to a curve whose flatness is less than a flatness threshold are selected from the profile curve as initial structural parameters of the spectrometer. The constraints on the telecentricity deviation and the rate of change of the telecentricity deviation of the present invention include: the telecentricity deviation of the spectrometer is less than the maximum telecentricity deviation corresponding to the engineering distortion requirement, and the rate of change of the telecentricity deviation is 0 when the telecentricity deviation is maximum, and the telecentricity deviation is 0 when the rate of change of the telecentricity deviation is maximum.

[0015] The maximum telecentricity deviation corresponding to the engineering distortion requirement of the present invention is: ; ; in, is the object telecentricity, is the image telecentricity, ( x o ,y o ) is the object point coordinate, is the length of the slit, (x i ,y i ) are the image point coordinates, R 2 is the radius of curvature of the convex grating, m is the diffraction order, g is the line density of the convex grating, λ is the wavelength, λ 1 ~λ n is the working band range of the spectrometer, λ 1 is the starting wavelength, λ n is the ending wavelength, d is the pixel size of the spectral channel.

[0016] The present invention first obtains the initial structural model of the distortion-eliminating spectrometer through a double telecentric path. The initial structure obtained in this way has extremely low distortion and low dispersion. Since it is difficult for the dispersion to converge at one time in the case of a large image surface and a large relative aperture, the engineering distortion requirement is used to expand the dispersion convergence range and relax the distortion constraint, so that the dispersion converges quickly, and finally achieves the effect of a low-distortion large image surface.

[0017] In the implementation method, the initial parameter selection for expanding the traditional spectrometer line field of view to a large rectangular field of view is: Realize a long-line field-of-view spectrometer, taking Implement a large rectangular field of view spectrometer, where is the slit length or rectangular field length, R 2 is the grating curvature radius, F# is the F number of the system, h is the width of the rectangular field of view.

[0018] When the large rectangular field of view of the spectrometer is set as a parallel double slit, the small array detector can be constructed as a large array detector for hyperspectral use, wherein the horizontal direction of the double slits is: the double slits are intermittently distributed and overlapped with each other, and the overlap length is Depends on the deviation angle of size and meets , the number of overlapping pixels is , the number of horizontal slits , the length of each "intermittent" slit ,in is a double slit interval, d is the pixel size of the spectral channel, the drift angle is the angle between the satellite flight direction and the vertical direction of the slit, is the total number of spatial objects, is the number of pixels in the detector space dimension; vertical direction is: the distance between the two slit positions ,in , is the number of spectral channels, , It is the distance from the edge of the detector to the edge after packaging. The minimum required spacing for the detector splicing process; , is the number of pixels in the detector spectral dimension. The small array detectors are arranged in a triangular shape, and different rows of the detectors strictly coincide with the images of different wavelengths formed by the slit on the image side of the spectrometer in sequence.

[0019] The large rectangular field of view of the spectrometer is set to a spacing of L v The first slit uses the +2nd or -2nd order of the grating to adjust the wavelength. λ 1 ~λ n For spectroscopic imaging, the second slit uses a grating +1 or -1 level for wavelength 2 λ 1 ~2λ n For spectroscopic imaging, the sum of the width Nd of the spectral array detector and the installation distance △L of the two detector chips is less than the slit spacing. L v And is larger than the single slit spectral dispersion width h spec , the spectral range of the spectrometer can be changed from λ 1 ~λ n To 2 λ 1 ~2λ n Widen.

[0020] The large rectangular field of view of the spectrometer is set to parallel double slits or multiple slits, and the diffraction order of the spectrometer is the same. For a moving target, the trajectory and speed of the moving target can be obtained by using the position and elapsed time on the field of view of different slits. If the signals of the same target on N multiple slits are superimposed, the signal-to-noise ratio of the target can be improved. The use of multiple slits can improve target detection in many aspects, but is not limited to this.

[0021] The present invention has the following beneficial effects: As mentioned above, the present invention proposes a spectrometer object-image double telecentricity theoretical model, which is the first time to systematically analyze and optimize the key parameters in the design of complex spectrometers through theoretical models. Under the guidance of this theoretical model, the initial structural parameters of the spectrometer are further determined, and an innovative spectrometer with large field of view, high image quality, and extremely low spectral distortion and lateral deviation characteristics is successfully designed. With its superior performance, this spectrometer breaks through the technical bottleneck of traditional spectrometers that are difficult to balance between large field of view and high precision, and opens up a new path for the design of high-performance spectrometers.

[0022] In addition, the present invention adopts for the first time an implementation method for rapid design of the initial structural parameters of the spectrometer with object-side and image-side dual telecentricity as the core. By reconstructing the quantitative relationship between the telecentric design and the optical structure parameters, the traditional complex aberration optimization problem is transformed into a simple parameter solving problem. The initial structure obtained by this method has extremely low spectral distortion and lateral deviation characteristics, and only requires simple subsequent optimization to meet the needs of high-precision engineering design. More importantly, this method innovatively solves the problem of nonlinear increase in spectrometer dispersion and distortion with the increase of field of view, and achieves the invariance of spectral distortion and lateral deviation close to a constant under large field of view conditions. This groundbreaking innovation breaks the traditional technical limitations of the length and width of the field of view of the spectrometer, provides theoretical support for the engineering application of wide-spectrum and wide-width satellite-borne hyperspectral imagers, and lays the foundation for the development of satellite-borne wide-spectrum and wide-width hyperspectral imaging.

[0023] Furthermore, the solution provided by the present invention can solve the technical difficulties in designing a rectangular field of view spectrometer under the conditions of small F number, low distortion and high image quality. On the one hand, the large rectangular field of view spectrometer provides a feasible solution for the application of small array pin-shaped spliced ​​detectors in satellite-borne large-width hyperspectral payloads. This technological breakthrough not only significantly improves the engineering efficiency of satellite-borne hyperspectral instruments, but also successfully shortens the research and development cycle of wide-spectrum and wide-width satellite-borne hyperspectral payloads by 5 to 10 years, accelerates the realization of ultra-wide-width, highly quantitative and highly accurate satellite-borne hyperspectral remote sensing detection technology, and provides important technical guarantees for future on-orbit remote sensing detection and resource monitoring. Furthermore, the large rectangular field of view of the spectrometer is set as a parallel double slit or multiple slits, and the spectral range can be widened several times under different grating diffraction orders. Under the same grating diffraction order, the trajectory and speed of the moving target can be obtained, or the signal-to-noise ratio of the static target can be improved several times. Through the solution provided by the present invention, the design of the spectrometer has achieved a leapfrog development from theoretical innovation to engineering application. The results have important scientific value and engineering significance, support the on-orbit application of satellite-borne wide-spectrum and wide-width hyperspectral cameras, and significantly promote technological progress in remote sensing, environmental monitoring, resource exploration and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Shown is a schematic diagram of an application scenario of the present invention.

[0025] Figure 2 Shown is an example diagram of the linear field of view, low distortion and large image surface effect of the spectrometer and the object-image double telecentric model provided by the present invention.

[0026] Figure 3 Shown is an example diagram of the rectangular field of view, low distortion and large image surface effect of the spectrometer and the object-image double telecentric model provided by the present invention.

[0027] Figure 4 Shown is an example diagram of the rectangular field of view expansion spectrum effect of the spectrometer and the object-image double telecentric model provided by the present invention.

[0028] Figure 5 Displayed is the theoretical model of telecentricity of the object-image side of the spectrometer provided by the present invention and an example diagram of parameters.

[0029] Figure 6 Shown is a schematic diagram of the multi-slit parallel imaging principle of the present invention.

[0030] Figure 7 Shown is a schematic diagram of the trajectory fitting and speed calculation principle of the present invention.

[0031] Figure 8 Shown is an example diagram of the slit positions provided in the present invention.

[0032] Fig. 9 , Fig.10 and Fig.11 Shown is an example diagram of the variation of telecentricity with field of view for materials with different refractive indices simulated in the present invention.

[0033] Fig.12 Shown are exemplary diagrams of the three-dimensional distribution of the object-space telecentricity and image-space telecentricity with the rectangular field of view for different wavelengths fitted in the present invention.

[0034] Fig.13 Shown are exemplary diagrams of the changes in the object-image telecentricity, distortion, and astigmatism of the double slits simulated in the present invention as a function of the slit length.

[0035] Fig.14 Shown are exemplary diagrams of the changes in the object-image telecentricity, distortion, and astigmatism of the double slits simulated in the present invention as a function of the slit length.

[0036] Fig.15 Shown is a flow chart for obtaining the initial structural model of a low-distortion large-image-surface spectrometer in the present invention.

[0037] Fig.16 An example diagram showing a curve whose flatness is less than a flatness threshold obtained in the present invention.

[0038] Fig.17 and Fig.18Shown are the first curved surface distribution and the second curved surface distribution in the present invention, as well as cross-sectional curve diagrams obtained by sectioning the first and second curved surface distributions from a direction perpendicular to the slit and from the direction of the slit, respectively.

[0039] Fig.19 and Fig. 20 Shown are the spot diagrams of the single-slit and double-slit spectrometers in the present invention respectively.

[0040] Fig.21 The diagram shows an example of how the present invention changes the nonlinear increase in dispersion and distortion to a nearly constant value.

[0041] Component number description 2: Spectrometer; 21: field diaphragm with slits; 22: Meniscus lens; 23: Main reflector; 24: secondary reflector; 25: Convex grating. DETAILED DESCRIPTION

[0042] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the features in the following contents can be combined with each other without conflict.

[0043] It should be noted that the illustrations provided in the following content are only used to illustrate the basic concept of the present invention in a schematic manner. Therefore, the illustrations only show the components related to the present invention rather than being drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0044] Before further describing the present invention in detail, the nouns and terms involved in the present invention are explained. The nouns and terms involved in the present invention are applicable to the following interpretations: <1> Telecentricity: Telecentricity is when the principal ray enters or exits parallel to the optical axis.

[0045] <2> Object-side telecentricity: When the aperture stop is on the back focal plane of the optical system, the entrance pupil is at infinity, and the chief ray enters the optical system parallel to the optical axis or perpendicular to the object plane, it is object-side telecentricity.

[0046] <3> Image-side telecentricity: When the aperture stop is on the front focal plane of the optical system, the exit pupil is at infinity, and the chief ray is parallel to the optical axis or perpendicular to the image plane, it is image-side telecentricity.

[0047] <4> Telecentricity deviation: Telecentricity deviation refers to the degree to which light deviates from the telecenter, and is expressed by the deviation angle between the main light of the imaging beam and the direction of the optical axis.

[0048] <5> Telecentricity deviation change rate: refers to the rate of change of telecentricity deviation with field of view.

[0049] As one of the core optical components in hyperspectral imaging technology, spectrometers have been widely used in many scenarios. Figure 1 In the shown satellite-borne hyperspectral imaging scene, the spectrometer can be installed on a satellite platform for fine spectral and spatial information detection of surface targets from space. The present invention provides a method for realizing a hyperspectral imaging low-distortion large image surface object image dual telecentric spectrometer. It should be noted that low distortion and large image surface need to be achieved at the same time in order to ensure high-quality wide-spectrum and wide-width imaging. At present, the maximum image surface spatial dimension of the hyperspectral imaging spectrometer on orbit internationally is about 30mm-40mm, the spectral dimension is less than 20mm, and the distortion is less than 0.2 pixels. The specific values ​​of large image surface and low distortion can be determined according to actual needs. For example, in some implementations, it can be considered that the diagonal of the image surface reaches 50mm as a large image surface, and the distortion is less than or equal to 0.2 pixels as low distortion, but the present invention is not limited to this.

[0050] See also Figures 2 to 7 ,like Figure 2 , Figure 3 , Figure 4 and Figure 5 As shown, the spectrometer 2 includes a field stop 21 with a slit, a meniscus lens 22, a primary reflector 23, a secondary reflector 24, and a convex grating 25. The spectrometer object-image double telecentricity theoretical model consists of three sub-models: "spectral curvature-telecentricity", "spectral distortion-telecentricity" and "astigmatism-telecentricity". The "spectral curvature-telecentricity" model explains the mapping relationship between e and a, b, the "spectral distortion-telecentricity" model explains the mapping relationship between d and a, b, and the "astigmatism-telecentricity" model explains the mapping relationship between c and a, b. Figure 2 As shown, the spectrometer 2 can realize an ultra-long single slit field of view. Figure 3 As shown, the large image plane of the spectrometer 2 can be used for the zigzag stitching of small array detectors. Figure 4 As shown, the large image plane of the spectrometer 2 can be used for hierarchical sub-imaging of the spectrum, thereby expanding the spectral range. Figures 2 to 4The slit in the spectrometer 2 shown is a single slit or a double slit, but the present invention is not limited thereto. In some other implementations, the slit may also be two or more slits. Figure 5 Shown is an example diagram of the theoretical model and parameters of the object-image telecentricity of the spectrometer in the present invention. Figure 6 Shown is a schematic diagram of the multi-slit parallel imaging principle of the present invention. Figure 7 The diagram shows the principle diagram of trajectory fitting and velocity calculation in the present invention, where the horizontal axis is wavelength in nm and the vertical axis is spectral radiance in W / m 2 / sr / μm.

[0051] like Figure 8 As shown in the figure, the flat sagittal curvature condition is set based on the telecentricity-astigmatism model. The slit is located on the plane XCY which is perpendicular to the optical axis and passes through the common curvature center of each optical surface (the slit is parallel to the x-axis, and any point on the slit is z o The coordinates are zero, where z o is the Z coordinate of the object point, and the distance between the slit and the common curvature center C is y o ), in this way, it can be ensured that the spectrometer 2 achieves low astigmatism and flat field curvature.

[0052] In the present invention, the design idea of ​​the spectrometer 2 includes: exploring the effect of different refractive index materials on the change of the object telecentricity of the spectrometer with the field of view, such as Figures 9 to 11 As shown. As the reflector radius evolves from 1.95, 2 to 2.45 times the convex grating radius, the refractive index greater than 1.3 will give the spectrometer a larger telecentric range compared to a refractive index of 1 (traditional Offner spectrometer), and spectrometer 2 can be used in an extremely wide spectral range from ultraviolet to very long waves. After the correction lens is introduced into the traditional Offner spectrometer, the starting wavelength λ 1 = 1.0 μm to end wavelength λ n =2.5μm change in object-image telecentricity. The introduction of the correction lens maintains a wider range of object-space telecentricity and image-space telecentricity along the slit direction. With a suitable reflector structure, it can also significantly reduce the chromatic aberration caused by diffraction while maintaining the object-image telecentricity of the matrix field of view. Fig.12 The structural parameters of the spectrometer are shown. R 1=0.827, R 3=2.12, R 4=2.10, the object telecentricity and image telecentricity when the starting wavelength is 1.0μm, the central wavelength is 1.7μm, and the ending wavelength is 2.5μm follow the three-dimensional distribution surface of the rectangular field of view. The telecentricity range of the spectrometer is maintained within a convex grating radius. Beyond this limit, the telecentricity of the spectrometer increases dramatically with the nonlinearity of the field of view. Fig.13 and Fig.14 For the first time, the nonlinear variation of distortion and astigmatism with field of view is demonstrated from the perspective of telecentricity calculation. It is analyzed that the purpose of the next design is to achieve telecentricity of the object and image in a large field of view.

[0053] Fig.15 The flowchart of the method for realizing the low-distortion large-image-surface double-telecentric spectrometer provided by the present invention is shown. In the present invention, the initial structural parameters of the spectrometer 2 include R 1 、R 2 、R 3 、R 4 , y o1 , y o2 , as well as F# .like Fig.15 As shown, when the slits are double slits, the process of determining the initial structural parameters includes the following steps S51 to S57.

[0054] S51, obtaining a first input parameter and a second input parameter, wherein the first input parameter is a fixed value in the whole process, and the second input parameter is a variable value.

[0055] The first input parameter includes the slit length , system F number F# , convex grating order m , spectral resolution △ λ , spectral channel pixel size d And double slit interval These parameters can be set according to actual needs or experience, and the present invention does not limit their specific values.

[0056] The second input parameter includes the radius of curvature of the convex grating 25 R 2 , the line density of the convex grating 25 g and the refractive index of the lens at the operating wavelength n(λ) . R 2 and g The volume envelope of the spectrometer 2 and the diffraction efficiency of the convex grating 25 can be comprehensively selected and meet the following conditions: ; .

[0057] S52, obtaining an intermediate parameter according to the first input parameter and the second input parameter, wherein the intermediate parameter includes the off-axis distance of the slit 1 yo1 and the off-axis distance of slit 2 y o2 ,in y o1 and y o2 The following conditions are met: ; .

[0058] S53, solving the object-side telecentric model and the image-side telecentric model to obtain the normalized structural parameters of the object-side telecentricity ( R 1o , R 3 ) and the normalized structural parameter of the image-side telecentricity ( R 1i , R 4 ),right R 1o and R 1i Taking the average value, we get R 1 .in R 1o is obtained by passing through the object's telecentricity R 1 The numerical value of R 1i is obtained by passing through the image square R 1i The numerical value of .

[0059] The process of solving the object-image telecentric model may include: First, according to the above-mentioned spectrometer object and image side double telecentricity theoretical model, when the object side and image side of the spectrometer 2 are made double telecentric to eliminate the large field of view distortion of the spectrometer 2, the first surface distribution and the second surface distribution are obtained. The first surface distribution is the surface distribution of the structural parameters of the meniscus lens 22 and the primary reflector 23 along the two-dimensional rectangular field of view when the object side telecentricity is formed, and the second surface distribution is the surface distribution of the structural parameters of the meniscus lens 22 and the secondary reflector 24 along the two-dimensional rectangular field of view when the image side telecentricity is formed.

[0060] Then, under the constraints of the telecentric deviation and the rate of change of the telecentric deviation, the first curved surface distribution and the second curved surface distribution are profiled in the direction along the slit and in the direction perpendicular to the slit to obtain a profile curve.

[0061] Finally, from the object telecentric profile curve, the curve parameters whose flatness is less than the flatness threshold within the designed field of view are searched to obtain the normalized structural parameters of the object telecentricity ( R 1o , R3 ). The design field of view range can be determined according to actual needs. From the image-side telecentric profile curve, search for curve parameters whose flatness is less than the flatness threshold within the design field of view range to obtain the normalized structural parameters of the image-side telecentric ( R 1i , R 4 ). Fig.16 Shown is an example diagram of a curve selected in the present invention.

[0062] S54, obtaining initial structural parameters, including R 1 、R 2 、R 3 、R 4 , y o1 , y o2 , as well as F# .

[0063] S55: If the initial structure corresponding to the initial structure parameters blocks light, adjust y o1 And jump to step S52, otherwise go to step S56. Adjust y o1 For example, the method is to y o1 = y o1 +△1, and the adjusted y o1 The requirement of no total reflection should be met. △1 is the adjustment step length, and the specific value can be set according to actual needs.

[0064] S56, determine whether the initial structure meets the engineering application map detection requirements, if yes, execute step S57, otherwise adjust R 2 And jump to step S51. Adjust R 2 For example, the method is to R 2 = R 2 +△2, and the adjusted R 2 The processing conditions and the volume requirements of the spectrometer should be met at the same time. △2 is the adjustment step size, and the specific value can be set according to actual needs.

[0065] S57, output initial structure parameters and establish the initial structure of the spectrometer.

[0066] After the initial structural parameters of the spectrometer 2 are obtained, the requirements for distortion can be appropriately relaxed to balance the relationship between distortion and image quality, thereby optimizing the structure of the spectrometer 2 to achieve the best performance required by the engineering.

[0067] It should be noted that when the slit is a single slit, the process of obtaining the initial structural parameters of the spectrometer 2 is the same as Fig.15 Similar, except that the process does not involve y o2 In order to save space in the specification, no further description is given here.

[0068] In the present invention, the theoretical model includes a spectral curvature-telecentricity model of the spectrometer 2 , a spectral distortion-telecentricity model of the spectrometer 2 , and an astigmatism-telecentricity model of the spectrometer 2 .

[0069] The spectral curvature-telecentricity model of spectrometer 2 can be expressed as: ; in, is the object telecentricity, is the image telecentricity, ( x o ,y o ) is the object point coordinate, ( x i ,y i ) are the image point coordinates, R 2 is the radius of curvature of the convex grating 25, m is the diffraction order, g is the line density of the convex grating 25, λ is the wavelength.

[0070] The spectral distortion-telecentricity model of spectrometer 2 can be expressed as: .

[0071] The astigmatism-telecentricity model of spectrometer 2 can be expressed as: ; in, Astig is the astigmatism of spectrometer 2, α o is the incident azimuth of the chief ray of spectrometer 2, α i is the main light emission azimuth of spectrometer 2, is the object telecentricity, is the image telecentricity, CO is the distance from the object point of spectrometer 2 to the common center of curvature of each mirror.

[0072] According to the above spectral curvature-telecentricity model, spectral distortion-telecentricity model and astigmatism-telecentricity model, the high quantitative realization parameters of the spectrometer 2 that meet the requirements of large field of view, high image quality, low spectral distortion and low spectral lateral deviation can be determined as follows: ; in, is the object telecentricity, is the image telecentricity, ( x o ,y o ) are the object point coordinates, is the position of the spectrometer 2 from the center field of view of the slit to the edge field of view, ( x i ,y i ) are the image point coordinates, λ is the wavelength, λ 1 ~λ n is the working band range of spectrometer 2, λ 1 is the starting wavelength, λ n is the ending wavelength.

[0073] When the object is telecentric, the structural parameter curve function of the meniscus lens 22 and the main reflector 23 is: ; in, k 13 =2, others k 1i =1, n 12 =n ,other n 1i =1; k 22 =2, others k 2j =1, n 21 = n ,other n 2j =1; CO is the distance from the object point of the spectrometer to the common center of curvature of each mirror: ; When the image is telecentric, the structural parameter curve function of the meniscus lens 22 and the secondary reflector 24 is: ; in, k14 =2, k 13 =0Other k 1i =1, n 12 = n ,other n 1i =1; k 22 =2, others k 2j =1, n 21 = n ,other n 2j =1; CI is the distance from the image point of the spectrometer to the common curvature center of each mirror: ; is the object telecentricity, is the image telecentricity, ( x o ,y o ) are the object point coordinates, n is the refractive index of the meniscus lens 22, m is the diffraction order, g is the line density of the convex grating 25, λ is the wavelength, R 1 is the radius of curvature of the front surface of the meniscus lens 22, R 2 is the radius of curvature of the convex grating 25, R 3 is the curvature radius of the main reflector 23, R 4 is the radius of curvature of the secondary reflector 24, where R 1 , R 3 To determine the structural parameters of the object telecentricity, R 1 , R 4 In the present invention, the structural parameters for determining the image telecentricity can be The corresponding structural parameter curve function is used to obtain the first surface distribution. The corresponding structural parameter curve function is used to obtain the second surface distribution.

[0074] The main light azimuth of spectrometer 2 α i for: ; in,( x o ,y o ) is the object point coordinate, m is the diffraction order, g is the line density of the convex grating 25, λ is the wavelength, R 2 is the radius of curvature of the convex grating 25 .

[0075] In the present invention, the constraints of telecentric deviation and telecentric deviation change rate include: determining the maximum allowed telecentric deviation according to the application requirements of high- and medium-quantitative atlas in engineering applications, and constraining the telecentric deviation and telecentric deviation change rate at the same time, so that the telecentric deviation of the system is less than the maximum telecentric deviation corresponding to the engineering distortion requirement, and when the telecentric deviation is the largest, the telecentric deviation change rate is 0, and when the telecentric deviation change rate is the largest, the telecentric deviation is 0. The engineering distortion requirement is used to expand the dispersion convergence interval, relax the distortion constraint, make the dispersion converge quickly, and finally achieve the effect of low distortion and large image surface.

[0076] The maximum telecentricity deviation corresponding to the engineering distortion requirement is: ; ; in, is the object telecentricity, is the image telecentricity, ( x o ,y o ) is the object point coordinate, is the slit length, ( x i ,y i ) are the image point coordinates, R 2 is the radius of curvature of the convex grating 25, m is the diffraction order, g is the line density of the convex grating 25, λ is the wavelength, λ 1 ~λ n is the working band range of spectrometer 2, λ 1 is the starting wavelength, λ n is the ending wavelength, d is the pixel size of the spectral channel, and the flatness threshold is 0.2 d .

[0077] In order to expand the traditional spectrometer linear field of view to a large rectangular field of view, the implementation process can be Realize a long-line field-of-view spectrometer, taking A large rectangular field of view spectrometer is realized. l is the slit length or rectangular field length, R 2 is the grating curvature radius, F# is the F number of the system, h is the width of the rectangular field of view.

[0078] The present invention can construct a small array detector into a large array detector for hyperspectral use, and the large rectangular field of view of the spectrometer is set as a parallel double slit. The horizontal direction of the double slit is: the double slits are intermittently distributed and overlapped with each other, and the overlap length is Depends on the deviation angle of size and meets , the number of overlapping pixels is , the number of horizontal slits , the length of each "intermittent" slit ,in is a double slit interval, d is the pixel size of the spectral channel, the drift angle is the angle between the satellite flight direction and the vertical direction of the slit, express The minimum value of express The maximum value of is the total number of spatial objects, is the number of pixels in the detector space dimension. The vertical direction of the double slits is: the distance between the two slits ,in , is the number of spectral channels, , It is the distance from the edge of the detector to the edge after packaging. The minimum required spacing for the detector splicing process; , is the number of pixels in the detector spectral dimension. The small array detectors are arranged in a triangular shape, and different rows of the detectors strictly coincide with the images of different wavelengths formed by the slit on the image side of the spectrometer in sequence.

[0079] The present invention can set the large rectangular field of view of the spectrometer to a spacing of The first slit (Slit1) uses the +2nd or -2nd order of the grating to adjust the wavelength. λ 1 ~λ n The second slit (Slit2) uses a grating +1 or -1 level for wavelength 2 λ 1 ~2λ n For spectroscopic imaging, the sum of the width Nd of the spectral array detector and the installation distance △L of the two detector chips is less than the slit spacing. , and is larger than the single slit spectral dispersion width , the spectral range of the spectrometer is realized by λ 1 ~λ n To 2 λ 1 ~2λ n Widen.

[0080] The present invention can set the large rectangular field of view of the spectrometer to parallel double slits or multiple slits, and the diffraction order of the spectrometer is the same. For a moving target, the position and elapsed time on the field of view of different slits can be used to obtain the trajectory and speed of the moving target. N The signal superposition of the same target on multiple slits can improve the signal-to-noise ratio of the target The use of multiple slits can improve target detection in many ways.

[0081] The solution provided by the present invention will be introduced below through two specific cases. The first case can realize a 300mm ultra-long line field of view low-distortion spectrometer, and the second case can realize a 240mm×32mm double-slit large rectangular field of view low-distortion spectrometer. It should be noted that the contents in these cases are only used to illustrate the solution of the present invention, and they do not limit the scope of protection of the present invention in any way. Table 1 shows the indicators and performance parameters of the spectrometers in the two cases.

[0082] Table 1. Example of spectrometer indicators and performance parameters

[0083] Table 2 shows the simulation results of two spectrometer cases. As shown in Table 2, the spectrometer provided by the present invention can have an ultra-long slit field of view of 300 mm and a large rectangular field of view of 240 mm × 32 mm. The image quality is shown in Tables 3 and 4. The spectral distortion is controlled within 0.2 pixels, and the lateral deviation of the spectrum is less than 0.1 △ λ , the dispersion is close to the diffraction limit, and the spot diagrams of the single-slit and double-slit spectrometers are as follows: Fig.17 and Fig.18As shown, the dispersion is about 1 / 3 of the pixel. Among them, RMS (Root Mean Square) represents the root mean square value of the distance between the imaging point of the actual optical system and the ideal image point, and is used to quantify the dispersion of the optical system. The larger the value, the more significant the aberration and the worse the image quality. MTF (Modulation Transfer Function) is used to describe the contrast transfer capability of the optical system for different spatial frequencies. The higher the curve, the stronger the ability to resolve details and the clearer the imaging. Smile (spectral curvature) is used to indicate the deviation of the slit monochromatic image in the dispersion direction as the slit becomes longer. Keystone (spectral distortion) is used to indicate the deviation of the spectral curve of the slit object element in the spatial position direction as the dispersion of different wavelengths. As shown Fig.19 , Fig. 20 and Fig.21 As shown, the present invention has made a major breakthrough by creatively transforming the dramatic increase of dispersion and distortion nonlinearity into a nearly constant value, breaking the bottleneck that the field of view of the spectrometer cannot be extended or widened.

[0084] It should be noted that the present invention is not limited to a single slit or a double slit, but can also be used for a rectangular field of view composed of multiple slits. The present invention is not limited to short-wave infrared of 1 μm-3 μm, but can also be used for other bands including ultraviolet, visible, and very long waves.

[0085] Table 2. Telecentricity calculation and optimized structural parameters of the spectrometer

[0086] Table 3. Image quality of the spectrometer in Case 1

[0087] Table 4. Image quality of the spectrometer in Case 2

[0088] In summary, the present invention proposes a telecentric realization model of a spectrometer, and for the first time systematically analyzes and optimizes the key parameters in the design of a complex spectrometer through a theoretical model. Under the guidance of this theoretical model, the initial structural parameters of the spectrometer were further determined, and an innovative spectrometer with a large field of view, high image quality, and extremely low spectral distortion and lateral deviation characteristics was successfully designed. With its superior performance, the spectrometer has broken through the technical bottleneck of traditional spectrometers that are difficult to balance between a large field of view and high precision, and has opened up a new path for the design of high-performance spectrometers.

[0089] In addition, the present invention adopts for the first time a spectrometer design method with object-side and image-side dual telecentricity as the core. By reconstructing the quantitative relationship between telecentricity design and optical structure parameters, the traditional complex aberration optimization problem is transformed into a simple parameter solving problem. The initial structure obtained by this method has extremely low spectral distortion and lateral deviation characteristics, and only simple subsequent optimization is required to meet the needs of high-precision engineering design. More importantly, this method innovatively solves the problem of nonlinear increase in spectrometer dispersion and distortion with the increase of field of view, and achieves the invariance of spectral distortion and lateral deviation close to a constant under large field of view conditions. This groundbreaking innovation breaks the traditional technical limitations of the length and width of the field of view of the spectrometer, provides theoretical support for the engineering application of wide-spectrum and wide-bandwidth satellite-borne hyperspectral imagers, and lays the foundation for the development of satellite-borne hyperspectral, wide-spectrum and wide-bandwidth imaging.

[0090] Furthermore, the solution provided by the present invention can solve the technical difficulties of rectangular field spectrometer design under the conditions of small F number, low distortion and high image quality. On the one hand, the large rectangular field spectrometer provides a feasible solution for the application of small array pin-shaped spliced ​​detectors in satellite-borne large-width hyperspectral payloads. This technological breakthrough not only significantly improves the engineering efficiency of satellite-borne hyperspectral instruments, but also successfully shortens the research and development cycle of wide-spectrum and wide-width satellite-borne hyperspectral payloads by 5 to 10 years, accelerates the realization of ultra-wide-width, highly quantitative and highly accurate satellite-borne hyperspectral remote sensing detection technology, and provides important technical guarantees for future on-orbit remote sensing detection and resource monitoring. Furthermore, the large rectangular field of view of the spectrometer is set as a parallel double slit or multiple slits, and the spectral range can be widened several times under different grating diffraction orders. Under the same grating diffraction order, the trajectory and speed of the moving target can be obtained, or the signal-to-noise ratio of the static target can be improved several times. Through the solution provided by the present invention, the design of the spectrometer has achieved a leapfrog development from theoretical innovation to engineering application. The results have important scientific value and engineering significance, support the on-orbit application of satellite-borne wide-spectrum and wide-width hyperspectral cameras, and significantly promote technological progress in remote sensing, environmental monitoring, resource exploration and other fields.

[0091] The above contents are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with the art may modify or alter the above contents without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for realizing a high-spectral imaging low-distortion large-image-surface object-image double-telecentric spectrometer, characterized in that: The implementation method includes: establishing a double telecentric theoretical model of the spectrometer object and image, quickly designing the initial structural parameters of the spectrometer based on the theoretical model, and determining the corresponding parameter relationship between the field stop with a slit, a meniscus lens, a primary reflector, a secondary reflector and a convex grating included in the spectrometer.

2. The implementation method according to claim 1, characterized in that: The method for quickly designing the initial structural parameters of the spectrometer comprises: determining the initial structural parameters of the spectrometer R 1 、R 2 、R 3 、R 4 and the off-axis distance of the slit y o1 , y o2 ,in, R 1 is the radius of curvature of the front surface of the meniscus lens, R 2 is the radius of curvature of the convex grating, R 3 is the radius of curvature of the primary reflector, R 4 is the radius of curvature of the secondary reflector; the process of determining the initial structure of the spectrometer comprises: S51, obtaining a first input parameter and a second input parameter; S52, acquiring an intermediate parameter according to the first input parameter and the second input parameter; S53, solving the object-side telecentric model and the image-side telecentric model; S54, obtaining the initial structural parameters; S55, determining whether the initial structure corresponding to the initial structure parameter blocks light; S56, determining whether the initial structural parameters meet the engineering application map detection requirements; S57, when the judgment conditions of S55 and S56 are met, the initial structure parameters are output to establish the initial structure of the spectrometer.

3. The implementation method according to claim 1, characterized in that: The theoretical models include a "spectral curvature-telecentricity" model, a "spectral distortion-telecentricity" model and a "astigmatism-telecentricity" model.

4. The implementation method according to claim 3, characterized in that: The spectral curvature-telecentricity model is: ； The spectral distortion-telecentricity model is: ； The astigmatism-telecentricity model of the spectrometer is: ； in, is the object telecentricity, with clockwise as the positive direction; is the image telecentricity, with the counterclockwise direction as the positive direction; ( x o ,y o ) is the object point coordinate, ( x i ,y i ) are the image point coordinates, R 2 is the radius of curvature of the convex grating, m is the diffraction order, g is the line density of the convex grating, λ is the wavelength; Astig is the astigmatism of the spectrometer; α o is the incident azimuth angle of the chief ray of the spectrometer, α i is the main light emission azimuth of the spectrometer, with clockwise being the positive direction; CO is the distance from the object point of the spectrometer to the common center of curvature of each mirror.

5. The implementation method according to claim 1, characterized in that: The implementation parameters of the spectrometer satisfy the following formula: ； in, is the object telecentricity, is the image telecentricity, ( x o ,y o ) are the object point coordinates, The spectrometer is from the central field of view position of the slit to the edge field of view position, λ is the wavelength, λ 1 ~λ n is the working band range of the spectrometer, λ 1 is the starting wavelength, λ n is the ending wavelength.

6. The implementation method according to claim 1, characterized in that: The slit is located on a plane perpendicular to the optical axis and passing through the common center of curvature of each optical surface. z o The coordinate is zero, and the slit is parallel to the x-axis, and the distance from the common curvature center C is y o .

7. The implementation method according to claim 1, characterized in that: The implementation method further includes: obtaining a first curved surface distribution and a second curved surface distribution based on the theoretical model, wherein the first curved surface distribution is a curved surface distribution of structural parameters of the meniscus lens and the primary reflector along a two-dimensional rectangular field of view when object-side telecentricity is formed, and the structural parameter curve function is: ； in, k 13 =2, others k 1i =1, n 12 =n ,other n 1i =1; k 22 =2, others k 2j =1, n 21 = n ,other n 2j =1; CO is the distance from the object point of the spectrometer to the common center of curvature of each mirror: ； The second curved surface distribution is the curved surface distribution of the structural parameters of the meniscus lens and the secondary reflector along the two-dimensional rectangular field of view when forming image telecentricity, and the structural parameter curve function is: ； in, k 14 =2, k 13 =0Other k 1i =1, n 12 = n ,other n 1i =1; k 22 =2, others k 2j =1, n 21 = n ,other n 2j =1; CI is the distance from the image point of the spectrometer to the common curvature center of each mirror: ； is the object telecentricity, is the image telecentricity, ( x o ,y o ) are the object point coordinates, n is the refractive index of the meniscus lens, m is the diffraction order, g is the line density of the convex grating, λ is the wavelength, R 1 is the radius of curvature of the front surface of the meniscus lens, R 2 is the radius of curvature of the convex grating, R 3 is the radius of curvature of the primary reflector, R 4 is the radius of curvature of the secondary reflector, R 1 , R 3 To determine the structural parameters of the object telecentricity, R 1 , R 4 It is the structural parameter that determines the telecentricity of the image.

8. The implementation method according to claim 7, characterized in that: The functional relationship between the object telecentricity and the structural parameters of the meniscus lens and the main reflector is: ； in, The object-side telecentric adjustment factor introduced for the meniscus lens is: ； is the incident angle of the object principal ray on the front surface of the lens: ； is the angle of incidence of the object-side principal ray on the front surface of the lens: ； is the incident angle of the object principal ray on the rear surface of the lens: ； is the angle of incidence of the object-side principal ray on the rear surface of the lens: ； is the incident angle of the object principal ray on the primary reflector: ； is the incident angle of the object-side principal ray on the grating: ； The functional relationship between the image-side telecentricity and the structural parameters of the meniscus lens and the secondary reflector is: ； in, The image-side telecentricity adjustment factor introduced for the meniscus lens is: ； is the angle of incidence of the image-side chief ray on the front surface of the lens: ； is the incident angle of the image-side chief ray on the front surface of the lens: ； is the angle of incidence of the image-side principal ray on the rear surface of the lens: ； is the incident angle of the image-side chief ray on the rear surface of the lens: ； is the incident angle of the image-side chief ray at the secondary reflector: ； is the incident angle of the image-side chief ray on the grating: 。 9. The implementation method according to claim 7, characterized in that: The implementation method further includes: under the constraints of telecentric deviation and telecentric deviation change rate, sectioning the first curved surface distribution and the second curved surface distribution in a direction along the slit and a direction perpendicular to the slit to obtain a profile curve; selecting parameters corresponding to a curve whose flatness is less than a flatness threshold from the profile curve as initial structural parameters of the spectrometer; The constraints on the telecentricity deviation and the rate of change of the telecentricity deviation include: the telecentricity deviation of the spectrometer is less than the maximum telecentricity deviation corresponding to the engineering distortion requirement, and the rate of change of the telecentricity deviation is 0 when the telecentricity deviation is maximum, and the telecentricity deviation is 0 when the rate of change of the telecentricity deviation is maximum.

10. The implementation method according to claim 9, characterized in that: The maximum telecentricity deviation corresponding to the engineering distortion requirement is: ； ； in, is the object telecentricity, is the image telecentricity, ( x o ,y o ) are the object point coordinates, is the length of the slit, ( x i ,y i ) are the image point coordinates, R 2 is the radius of curvature of the convex grating, m is the diffraction order, g is the line density of the convex grating, λ is the wavelength, λ 1 ~λ n is the working band range of the spectrometer, λ 1 is the starting wavelength, λ n is the ending wavelength, d is the pixel size of the spectral channel.

11. The implementation method according to claim 10, characterized in that: The engineering distortion requirement is used to expand the diffusion convergence range, relax the distortion constraint, make the diffusion converge quickly, and finally achieve the effect of low distortion and large image surface.

12. The implementation method according to any one of claims 1 to 11, characterized in that: The implementation method expands the traditional spectrometer line field of view to a large rectangular field of view. Realize a long-line field-of-view spectrometer, taking Implement a large rectangular field of view spectrometer, where is the slit length or rectangular field length, R 2 is the radius of curvature of the convex grating, F# is the F number of the system, h is the width of the rectangular field of view.

13. The implementation method according to any one of claims 1 to 11, characterized in that: The implementation method structures the small array detector into a large array detector for hyperspectral use, and the large rectangular field of view of the spectrometer is set as a parallel double slit; The horizontal direction of the double slits is: the double slits are distributed intermittently and overlapped with each other, and the overlap length is Depends on the deviation angle of size and meets , the number of overlapping pixels is , the number of horizontal slits , each "intermittent" slit length ,in is a double slit interval, d is the pixel size of the spectral channel, the drift angle is the angle between the satellite flight direction and the vertical direction of the slit, is the total number of spatial objects, is the number of pixels in the detector space dimension; The vertical direction of the double slits is: the distance between the two slits ,in , is the number of spectral channels, , It is the distance from the edge of the detector to the edge after packaging. The minimum required spacing for the detector splicing process; , is the number of pixels in the detector spectral dimension; The small array detectors are arranged in a triangular shape, and different rows of the detectors strictly coincide with the images of different wavelengths formed by the slit on the image side of the spectrometer in sequence.

14. The implementation method according to any one of claims 1 to 11, characterized in that: The implementation method sets the large rectangular field of view of the spectrometer to a spacing of L v The first slit uses the +2nd or -2nd order of the grating to adjust the wavelength. λ 1 ~λ n The second slit uses a grating +1 or -1 level for wavelength 2 λ 1 ~2λ n For spectroscopic imaging, the sum of the width Nd of the spectral array detector and the installation distance △L of the two detector chips is less than the slit spacing L v And is larger than the single slit spectral dispersion width h spec , in order to realize the spectrometer spectral range from λ 1 ~λ n To 2 λ 1 ~2λ n Widen.

15. The implementation method according to any one of claims 1 to 11, characterized in that: The implementation method sets the large rectangular field of view of the spectrometer to parallel double slits or multiple slits, and the diffraction order of the spectrometer is the same; For a moving target, the trajectory and speed of the moving target can be obtained by using the position and elapsed time on different slit fields of view; If N The signal superposition of the same target on multiple slits can improve the signal-to-noise ratio of the target times; The use of multiple slits can improve target detection in many aspects.

16. A spectrometer, characterized in that: The spectrometer is realized by the method according to any one of claims 1 to 15.

Images