Hyperspectral Imaging Low-Distortion Large-Image-Plane Object-Image Double-Telecentric Spectrometer and Implementation Method

Abstract

The present invention provides a hyperspectral imaging spectrometer with a large image plane, low distortion, and object-image double telecentricity, as well as a realization method thereof. The realization method includes the establishment of a theoretical model for object-image double telecentricity of the spectrometer, namely, the establishment of three sub-models: "spectral bending - telecentricity", "spectral distortion - telecentricity", and "astigmatism - telecentricity". Based on this theoretical model, the corresponding parameter relationships between telecentricity and the field stop, meniscus lens, primary / secondary mirrors, and convex grating of the spectrometer are given, and a rapid design of the initial structural parameters of the spectrometer is provided. Through this method, a new type of spectrometer with characteristics of large field of view, low astigmatism, low spectral distortion, and low spectral lateral deviation is successfully designed, solving the inherent problem that the dispersion and distortion of the spectrometer increase non-linearly with the increase of the field of view, achieving a fundamental change that the dispersion and distortion approach constants under large field of view conditions, and transforming the traditional empirical design method based on optical design software into an accurate analytical design method for the initial structure based on the telecentricity 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 Hyperion hyperspectral camera on the US EO-1 satellite achieved an Offner spectrometer structure based on a convex grating in orbit, with a line-of-sight field of about 15 mm (Folkman M A, Pearlman J, Liao L B, 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 achieved an Offner-structured convex grating spectrometer in 2002 (Shen Beijun, Liu Baoli, Liu Yannian, et al. Catadioptric convex grating imaging optical system: CN02136154.1[P]. CN1391090A[2025-02-04]). Within a 20-mm field of view, better control can be obtained for image quality, spectral distortion, and spectral curvature. Beyond this range, the image quality, spectral distortion, and spectral lateral deviation deteriorate sharply. This has become a bottleneck restricting the further expansion of the field of view of spaceborne hyperspectral detection at home and abroad. The inventor first introduced a new Offner spectrometer structure in 2011 (Yang Bo. Research on wide-field hyperspectral imaging optical technology[D]. Graduate University of the Chinese Academy of Sciences, 2011.). Based on traditional aberration theory and optical software such as ZEMAX, the design concept of object-image double telecentricity was first applied to the design of a 60-mm ultra-wide-field convex grating spectrometer. In 2018, the world's first wide-spectrum and wide-field hyperspectral camera (AHSI) was applied in orbit (Liu Y N, Sun D X, Hu X N, et al. The advanced hyperspectral imager: Aboard China's GaoFen-5 satellite[J]. IEEE Geoscience and Remote Sensing Magazine, 2019, 7(4): 23-32.). On the premise that the spectral range (0.4 μm - 2.5 μm) and spatial resolution (30 m) are the same as those of international mainstream spaceborne hyperspectral cameras, the swath width was increased from the generally 30 km internationally to 60 km. The spectral distortion is close to 0.1 pixel, and the spectral lateral deviation is less than 1 nm. The accuracy reaches the international best. It is unanimously recognized by domestic and foreign experts and scholars as a typical example of high-quantification hyperspectral detection and has milestone significance.

[0006] After that, Jia. C. Zhu et al. studied the astigmatism expression of the above-mentioned new Offner spectrometer structure with large field of view, low spectral distortion, and low spectral lateral deviation, and proved from the perspective of astigmatism elimination that the new Offner spectrometer has a larger astigmatism-free field of view compared with the conventional Offner spectrometer (Zhu Jiacheng, Shen Weimin. Optical system of compact anastigmatic long slit spectrometer[J]. Journal of Infrared and Millimeter Waves, 2019, 38(4):7.). X. Prieto studied two spectrometer structures of Offner plus meniscus lenses, and confirmed the large field of view and high image quality ability of the new Offner spectrometer from the perspective of aberration correction (Prieto-Blanco X, de la Fuente R. Compact Offner–Wynne imaging spectrometers[J]. Optics Communications, 2014, 328: 143-150.). However, neither of them gave the object-image double telecentric theoretical model, the corresponding initial structure design method, and the engineering application constraints. Summary of the Invention

[0007] The present invention provides a method for realizing a high-spectral imaging spectrometer with low distortion and large image plane and object-image double telecentricity, including the establishment of an object-image double telecentric theoretical model of the spectrometer and a method for quickly designing the initial structure parameters of the spectrometer based on this theoretical model, which is used to realize a new spectrometer with the characteristics of large field of view, high image quality, extremely low spectral distortion, and lateral deviation.

[0008] The establishment of an object-image double telecentric theoretical model of a spectrometer, the theoretical model consists of three sub-models: "spectral curvature - telecentricity", "spectral distortion - telecentricity", and "astigmatism - telecentricity". Among them, the "spectral curvature - telecentricity" model describes the mapping relationship between spectral curvature (e), object-side telecentricity (a), and image-side telecentricity (b), the "spectral distortion - telecentricity" model describes the mapping relationship between spectral distortion (d), object-side telecentricity (a), and image-side telecentricity (b), and the "astigmatism - telecentricity" model describes the mapping relationship between astigmatism (c), object-side telecentricity (a), and image-side telecentricity (b). The specific relational expressions are as follows:

[0009] The "spectral curvature - telecentricity" model (e - ab) is:

[0010] ;

[0011] The spectral distortion - telecentricity model (d - ab) is:

[0012] ;

[0013] The astigmatism - telecentricity model (c - ab) of the spectrometer is:

[0014] ;

[0015] Among them, is the object-space telecentricity, with the clockwise direction being the positive direction; is the image-space telecentricity, with the counterclockwise direction being the positive direction; ( x o ,y o ) is the object point coordinate, ( x i ,y i ) is the image point coordinate, R 2 is the radius of curvature of the convex grating, m is the diffraction order, g is the groove density of the convex grating, λ is the wavelength; Astig is the astigmatism of the spectrometer; α o is the azimuth angle of the chief ray incident on the spectrometer, α i is the azimuth angle of the chief ray exiting the spectrometer, with the clockwise direction being the positive direction; CO is the distance from the object point of the spectrometer to the common center of curvature of each mirror.

[0016] Based on the above theoretical model and combined with the engineering implementation of a low-distortion large-image-plane object-image double-telecentric spectrometer, the implementation parameters of the spectrometer need to satisfy the following formula:

[0017] ;

[0018] Among them, is the object-space telecentricity, is the image-space telecentricity, ( x o ,y o ) is the object point coordinate, is the distance from the central field position to the edge field position of the spectrometer from the slit, λ is the wavelength, λ 1 ~λ n is the working wavelength range of the spectrometer, λ 1 is the starting wavelength, λ n is the ending wavelength.

[0019] Based on the condition of the tangential field curvature - 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 the z o coordinate of any point on the slit is 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 ).

[0020] The basic idea of the method for quickly obtaining the initial structure is to first establish the parameter relationships between the object - space and image - space telecentricities (a, b) and the off - axis distances of the spectrometer field stop ( y o1 , y o2 ), the curvature radius of the meniscus lens ( R 1 ，R 2 ), the curvature radius of the primary mirror ( R 3 ), the curvature radius of the secondary mirror ( R 4 ), and the curvature radius of the convex grating ( R 2 ). Then, according to these relationships, the initial structure parameters that meet the telecentricity requirements are screened, and finally, the initial structure parameters of the spectrometer 2 R 1 、R 2 、R 3 、R 4 and the off - axis distance of the slit y o1 , y o2 are determined. 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 telecentricity model and the image - space telecentricity model, S54 is to obtain the initial structure parameters, S55 is to judge whether there is light blocking in the initial structure corresponding to the initial structure parameters, S56 is to judge whether the initial structure meets the requirements of the 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.

[0021] The present invention first obtains the first surface distribution and the second surface distribution based on the above - mentioned theoretical model. The first surface distribution is the surface distribution of the structural parameters of the meniscus lens and the primary mirror when the object - space telecentricity is formed, and its structural parameter curve function is:

[0022] ;

[0023] Among them, k 13 = 2, and others k 1i = 1, n 12 =n and others n 1i = 1; k 22 = 2, and others k 2j = 1, n 21 = n and others n 2j = 1; CO is the distance from the object point of the spectrometer to the common curvature center of each mirror

[0024] ;

[0025] The second surface distribution is the surface distribution of the structural parameters of the meniscus lens and the secondary mirror when forming an image-side telecentricity with respect to the two-dimensional rectangular field of view, and its structural parameter curve function is:

[0026] ;

[0027] Among them, k 14 = 2, k 13 = 0 and others k 1i = 1, n 12 = n and others n 1i = 1; k 22 = 2 and others k 2j = 1, n 21 = n and others n 2j = 1; CI is the distance from the image point of the spectrometer to the common curvature center of each mirror:

[0028] ;

[0029] is the object-side telecentricity, is the image-side telecentricity, (x o ,y o ) are the coordinates of the object point, n is the refractive index of the meniscus lens, m is the diffraction order, g is the grating 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 main reflector, R 4 is the radius of curvature of the secondary reflector, where, R 1 、 R 3 are the structural parameters determining the object-space telecentricity, R 1 、 R 4 are the structural parameters determining the image-space telecentricity.

[0030] In the present invention, the functional relationship between the object-space telecentricity and the structural parameters of the meniscus lens and the main reflector is:

[0031] ;

[0032] Wherein, is the object-space telecentricity adjustment factor introduced by the meniscus lens:

[0033] ;

[0034] is the incident angle of the object-space chief ray on the front surface of the lens:

[0035] ;

[0036] is the exit angle of the object-space chief ray on the front surface of the lens:

[0037] ;

[0038] is the incident angle of the object-space chief ray on the rear surface of the lens:

[0039] ;

[0040] is the exit angle of the object-space chief ray on the rear surface of the lens:

[0041] ;

[0042] is the incident angle of the object-space chief ray on the primary mirror:

[0043] ;

[0044] is the incident angle of the object-space chief ray on the grating:

[0045] ;

[0046] The functional relationship between the image-space telecentricity and the structural parameters of the meniscus lens and the secondary mirror is:

[0047] ;

[0048] wherein, is the image-space telecentricity adjustment factor introduced by the meniscus lens:

[0049] ;

[0050] is the exit angle of the image-space chief ray on the front surface of the lens:

[0051] ;

[0052] is the incident angle of the image-space chief ray on the front surface of the lens:

[0053] ;

[0054] is the exit angle of the image-space chief ray on the rear surface of the lens:

[0055] ;

[0056] is the incident angle of the image-space chief ray on the rear surface of the lens:

[0057] ;

[0058] is the exit angle of the image-space chief ray on the secondary mirror:

[0059] ;

[0060] is the exit angle of the image-space chief ray on the grating:

[0061] .

[0062] Add constraints on the telecentric deviation and the change rate of the telecentric deviation to the distributions of the first surface and the second surface, and obtain the initial structural parameters of the spectrometer 2 that meet the requirements of object-space telecentricity and image-space telecentricity. R 1 、R 2 、R 3 、R 4 and the off-axis distance of the slit y o1 , y o2 . Obtain profile curves from the distributions of the first surface and the second surface in the direction along the slit and the direction perpendicular to the slit; finally, select the parameters corresponding to the curves with flatness less than the flatness threshold from the profile curves as the initial structural parameters of the spectrometer. The constraints on the telecentric deviation and the change rate of the telecentric deviation in the present invention include: the telecentric deviation of the spectrometer is less than the maximum telecentric deviation corresponding to the engineering distortion requirement, and the change rate of the telecentric deviation is 0 when the telecentric deviation is the largest, and the telecentric deviation is 0 when the change rate of the telecentric deviation is the largest.

[0063] The maximum telecentric deviation corresponding to the engineering distortion requirement in the present invention is:

[0064] ;

[0065] ;

[0066] wherein, is the object-space telecentricity, is the image-space telecentricity, ([[]]ID=35] x o ,y o ) is the object point coordinate, is the length of the slit, ([[]]ID=42] x i ,y i ) is the image point coordinate, R 2 is the radius of curvature of the convex grating, m is the diffraction order, g is the groove density of the convex grating, λ is the wavelength, λ 1 ~λ n is the working wavelength range of the spectrometer, λ 1 is the starting wavelength, λ n ​​is the end wavelength, d is the spectral channel pixel size.

[0067] In the present invention, an initial structural model of an anamorphic spectrometer is first obtained 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 in one go under the conditions of a large image plane and a large relative aperture, the engineering distortion requirement is used at this time to expand the dispersion convergence interval and relax the distortion constraint, so that the dispersion converges quickly, and finally the effect of a large image plane with low distortion is achieved.

[0068] In the implementation method, the initial parameters for expanding the line field of view of a traditional spectrometer to a large rectangular field of view are selected as: take To implement a long-line field of view spectrometer, take To implement a large rectangular field of view spectrometer, where is the slit length or the length of the rectangular field of view, R 2 is the grating curvature radius, and F# is the F-number of the system, h is the width of the rectangular field of view.

[0069] When the large rectangular field of view of the spectrometer is set as parallel double slits, a small area array detector can be configured as a large area array detector for hyperspectral use. The horizontal direction of the double slits is: the double slits are discontinuously distributed and overlap with each other between the discontinuities. The overlap length depends on the magnitude of the drift angle and satisfies , the number of overlapping pixels is , the number of discontinuities of the horizontal slits , the length of each "discontinuous" slit , where is the double slit interval, d is the spectral channel pixel size, and the drift angle is the angle between the satellite flight direction and the vertical direction of the slit, is the total number of ground objects in the spatial dimension, is the number of detector pixels in the spatial dimension; the vertical direction is: the distance between the positions of the two slits , where , is the number of spectral channels, , is the margin from the outermost effective pixel to the edge after detector packaging, is the minimum required interval for the detector splicing process; , is the number of detector pixels in the spectral dimension. The small area array detectors are arranged in a triangular pattern, and different rows of the detectors are strictly coincident with the images of different wavelengths formed by the slits in the image space of the spectrometer in sequence.

[0070] Set the large rectangular field of view of the spectrometer to a spacing ofL 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.

[0071] 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.

[0072] The present invention has the following beneficial effects:

[0073] As mentioned above, the present invention proposes a spectrometer object-image double telecentricity theoretical model, which is the first time that the key parameters in the design of complex spectrometers are systematically analyzed and optimized 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.

[0074] In addition, for the first time in the present invention, an implementation method for rapidly designing the initial structural parameters of a spectrometer with object space and image space double telecentricity as the core is adopted. By reconstructing the quantitative relationship between telecentric 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 the characteristics of extremely low spectral distortion and lateral deviation, and only simple subsequent optimization is required to meet the requirements of high-precision engineering design. More importantly, this method innovatively solves the problem that the dispersion and distortion of the spectrometer increase non-linearly with the increase of the field of view, and realizes the invariance that the spectral distortion and lateral deviation are close to constants under large field of view conditions. This breakthrough innovation breaks the traditional technical limitations of the field of view length and width of the spectrometer, provides theoretical support for the engineering application of wide-spectrum and wide-field spaceborne hyperspectral imagers, and also lays a foundation for the development of spaceborne wide-spectrum and wide-field hyperspectral imaging.

[0075] Furthermore, the solution provided by the present invention can solve the technical problems in the design of 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 area array pinhole-shaped spliced detectors in spaceborne wide-field hyperspectral payloads. This technological breakthrough not only significantly improves the engineering efficiency of spaceborne hyperspectral spectrometers, but also successfully shortens the R & D cycle of wide-spectrum and wide-field spaceborne hyperspectral payloads by 5 - 10 years, accelerates the realization of ultra-wide-field, high quantification, and high-precision spaceborne hyperspectral remote sensing detection technology, and provides an important technical guarantee for future on-orbit remote sensing detection and resource monitoring. Further, by setting the large rectangular field of view of the spectrometer as parallel double slits or multiple slits, the spectral range can be broadened several times under different grating diffraction orders, the trajectory and speed of moving targets can be obtained under the same grating diffraction order, or the signal-to-noise ratio of static targets can be increased several times. Through the solution provided by the present invention, the development of spectrometer design has achieved a leap from theoretical innovation to engineering application, and its results have important scientific value and engineering significance, supporting the on-orbit application of spaceborne wide-spectrum and wide-field hyperspectral cameras, and significantly promoting the technological progress in the fields of remote sensing, environmental monitoring, resource exploration, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 It shows a schematic diagram of an application scenario of the present invention.

[0077] Figure 2 It shows an example diagram of the line field of view with low distortion and large image plane effect of the spectrometer and the object-image space double telecentric model provided by the present invention.

[0078] Figure 3 It shows an example diagram of the rectangular field of view with low distortion and large image plane effect of the spectrometer and the object-image space double telecentric model provided by the present invention.

[0079] Figure 4Shown 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.

[0080] 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.

[0081] Figure 6 Shown is a schematic diagram of the multi-slit parallel imaging principle of the present invention.

[0082] Figure 7 Shown is a schematic diagram of the trajectory fitting and speed calculation principle of the present invention.

[0083] Figure 8 Shown is an example diagram of the slit positions provided in the present invention.

[0084] Figure 9 , Figure 10 and Figure 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.

[0085] Figure 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.

[0086] Figure 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.

[0087] Figure 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.

[0088] Figure 15 Shown is a flow chart for obtaining the initial structural model of a low-distortion large-image-surface spectrometer in the present invention.

[0089] Figure 16 An example diagram showing a curve whose flatness is less than a flatness threshold obtained in the present invention.

[0090] Figure 17 and Figure 18 Shown 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.

[0091] Figure 19 and Figure 20 Shown are the spot diagrams of the single-slit and double-slit spectrometers in the present invention respectively.

[0092] Figure 21It is an exemplary diagram showing that the present invention transforms the sharp increase in dispersion and distortion non-linearity into an almost constant value.

[0093] Description of Component Labels

[0094] 2: Spectrometer;

[0095] 21: Field diaphragm with slit;

[0096] 22: Meniscus lens;

[0097] 23: Primary mirror;

[0098] 24: Secondary mirror;

[0099] 25: Convex grating. Detailed Implementation Manner

[0100] The following uses specific specific examples to illustrate the implementation manner of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, without conflict, the features in the following content can be combined with each other.

[0101] It should be noted that the diagrams provided in the following content only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components during actual implementation. The type, quantity, and ratio of each component during actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0102] Before further elaborating on 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 explanations:

[0103] <1> Telecentric: Telecentric means that the chief ray is incident or exits parallel to the optical axis.

[0104] <2> Object-side telecentric: When the aperture stop is located on the rear 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, which is the object-side telecentric.

[0105] <3> Image-side telecentric: When the aperture stop is located on the front focal plane of the optical system, the exit pupil is at infinity, and the chief ray exits parallel to the optical axis or perpendicular to the image plane, which is the image-side telecentric.

[0106] <4>Telecentric deviation: The telecentric deviation refers to the degree of deviation of light from telecentricity, which is represented by the deviation angle between the chief ray of the imaging beam and the optical axis direction.

[0107] <5>Rate of change of telecentric deviation: It refers to the rate of change of telecentric deviation with respect to the field of view.

[0108] As one of the core optical components in hyperspectral imaging technology, spectrometers have been widely used in many scenarios. For example, in Figure 1 the shown spaceborne hyperspectral imaging scenario, the spectrometer can be installed on a satellite platform to detect fine spectral and spatial information of surface targets from space. The present invention provides a method for realizing a high-spectral imaging low-distortion large-image-plane object-image double-telecentric spectrometer. It should be noted that low distortion and a large image plane need to be achieved simultaneously to ensure high-quality wide-spectrum wide-field imaging. Currently, the maximum image-plane spatial dimension of the spaceborne hyperspectral imaging spectrometers in orbit internationally is about 30 mm - 40 mm, the spectral dimension is less than 20 mm, and the distortion is less than 0.2 pixels. The specific values of the large image plane and low distortion can be determined according to actual requirements. For example, in some implementation manners, it can be considered that the diagonal of the image plane reaches 50 mm for a large image plane, and the distortion is less than or equal to 0.2 pixels for low distortion, but the present invention is not limited thereto.

[0109] Please refer to Figures 2 to 7 , as Figure 2 , Figure 3 , Figure 4 and Figure 5 shown, the spectrometer 2 includes a field stop 21 with a slit (Slit), a meniscus lens 22, a primary mirror 23, a secondary mirror 24, and a convex grating 25. The object-image double-telecentric theoretical model of the spectrometer consists of three sub-models: "spectral curvature - telecentricity", "spectral distortion - telecentricity", and "astigmatism - telecentricity". Among them, the "spectral curvature - telecentricity" model elaborates on the mapping relationship between e and a, b, the "spectral distortion - telecentricity" model elaborates on the mapping relationship between d and a, b, and the "astigmatism - telecentricity" model elaborates on the mapping relationship between c and a, b. As Figure 2 shown, the spectrometer 2 can achieve an ultra-long single-slit field of view. As Figure 3 shown, the large image plane of the spectrometer 2 can be used for the character-shaped splicing of small area array detectors. As Figure 4 shown, the large image plane of the spectrometer 2 can be used for hierarchical sub-imaging of the spectrum, thereby expanding the spectral range. It should be noted that in the spectrometer 2 shown in Figures 2 to 4 , the slit is a single slit or a double slit, but the present invention is not limited thereto. In some other implementation manners, the slit can also be a multi-slit with two or more slits. Figure 5 Shows the object-image telecentric theoretical model and parameter example diagram of the spectrometer in the present invention. Figure 6 Shows the parallel imaging principle diagram of multi-slits in the present invention.Figure 7 Shown is the schematic diagram of trajectory fitting and velocity calculation in the present invention. Here, the abscissa is the wavelength with the unit of nm, and the ordinate is the spectral radiance with the unit of W / m 2 / sr / μm.

[0110] As Figure 8 shown, based on the telecentricity-astigmatism model, the conditions of the flat arc field curvature are set. The slit is located on the plane XCY that 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 the z o coordinate of any point on the slit is 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 ), and in this way, it can be ensured that the spectrometer 2 achieves low astigmatism and flat field curvature.

[0111] In the present invention, the design idea of the spectrometer 2 includes: exploring the variation of the object-space telecentricity of the spectrometer with the field of view for different refractive index materials, as Figures 9 to 11 shown. As the radius of the mirror evolves from 1.95, 2 to 2.45 times the radius of the convex grating, compared with the refractive index equal to 1 (traditional Offner spectrometer), a refractive index greater than 1.3 will enable the spectrometer to have a larger telecentric range, and the spectrometer 2 can be applicable to an extremely wide spectral range from ultraviolet to very long wave. After introducing a correction lens into the traditional Offner spectrometer, from the starting wavelength λ 1 = 1.0 μm to the ending wavelength λ n = 2.5 μm, the variation of the object-space and image-space telecentricity, the introduction of the correction lens enables a larger range of object-space telecentricity and image-space telecentricity to be maintained along the slit direction. With a suitable mirror structure, it is also possible to significantly reduce the chromatic aberration caused by diffraction while maintaining the object-space and image-space telecentricity of the matrix field of view. Figure 12 Shows the three-dimensional distribution surface of the object-space telecentricity and image-space telecentricity with respect to the rectangular field of view when the structural parameters R 1 = 0.827, R 3 = 2.12, R 4 = 2.10, the starting wavelength is 1.0 μm, the central wavelength is 1.7 μm, and the ending wavelength is 2.5 μm for the spectrometer. The telecentric range of the spectrometer is maintained within the range of one convex grating radius, and beyond this limit, the telecentricity of the spectrometer increases non-linearly with the field of view. Figure 13 And Figure 14 for the first time show the non-linear variation law of distortion and astigmatism with the field of view from the perspective of telecentric calculation. Analyzing from this, the purpose of the next design is to achieve object-space and image-space telecentricity for a large field of view.

[0112] Figure 15Shown is a flowchart of the implementation method of a low-distortion large-image-plane object-image double telecentric spectrometer provided by the present invention. 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 , and F# . As Figure 15 shown, when the slit is a double slit, the process of determining the initial structural parameters includes the following steps S51 to S57.

[0113] S51, obtain a first input parameter and a second input parameter. Among them, the first input parameter is a fixed value throughout the process, and the second input parameter is a variable value.

[0114] The first input parameter includes the slit length , the system F-number F# , the convex grating order m , the spectral resolution Δ λ , the spectral channel pixel size d and the double slit interval . These parameters can be set according to actual needs or experience, and the present invention does not limit their specific values.

[0115] The second input parameter includes the radius of curvature R 2 of the convex grating 25, the line density g of the convex grating 25, and the refractive index n(λ) of the lens at the working wavelength. R 2 and g can be selected by considering the volume envelope of the spectrometer 2 and the diffraction efficiency of the convex grating 25, and satisfy the following conditions:

[0116] ;

[0117] .

[0118] S52, obtain intermediate parameters according to the first input parameter and the second input parameter. The intermediate parameters include the off-axis distance y o1 of the first slit and the off-axis distance y o2 of the second slit, where y o1 and yo2 Meet the following conditions:

[0119] ;

[0120] .

[0121] S53, solve the object-side telecentric model and the image-side telecentric model to obtain the normalized structural parameters of the object-side telecentric ( R 1o , R 3 ), and the normalized structural parameters of the image-side telecentric ( R 1i , R 4 ). Take the average of R 1o and R 1i to obtain R 1 . Among them, R 1o is the value of R 1 obtained when passing through the object-side telecentric, R 1i is the value of R 1i obtained when passing through the image-side telecentric.

[0122] The process of solving the object-image-side telecentric model may include:

[0123] First, according to the above object-image-side double telecentric theoretical model of the spectrometer, when the object-side and image-side double telecentrics of the spectrometer 2 are made to achieve the elimination of large-field distortion of the spectrometer 2, obtain the first surface distribution and the second surface distribution. The first surface distribution is the surface distribution of the structural parameters of the meniscus lens 22 and the main mirror 23 with the two-dimensional rectangular field of view when forming the object-side telecentric, and the second surface distribution is the surface distribution of the structural parameters of the meniscus lens 22 and the secondary mirror 24 with the two-dimensional rectangular field of view when forming the image-side telecentric.

[0124] Then, under the constraints of the telecentric deviation and the change rate of the telecentric deviation, perform cross-sections on the first surface distribution and the second surface distribution from the direction along the slit and the direction perpendicular to the slit to obtain cross-section curves.

[0125] Finally, from the object-side telecentric cross-section curve, search for the curve parameters with flatness less than the flatness threshold within the designed field of view to obtain the normalized structural parameters of the object-side telecentric ( R 1o , R 3). Among them, the designed field of view range can be determined according to actual requirements. From the image-side telecentric cross-sectional curve, search for the curve parameters within the designed field of view range where the flatness is less than the flatness threshold to obtain the normalized structural parameters of the image-side telecentric ( R 1i , R 4 ). Figure 16 It is shown as an example diagram of a curve selected in the present invention.

[0126] S54, obtain the initial structural parameters, including R 1 、R 2 、R 3 、R 4 , y o1 , y o2 , and F# .

[0127] S55, if there is light blocking in the initial structure corresponding to the initial structural parameters, then adjust y o1 and jump to step S52, otherwise execute step S56. The method of adjusting y o1 is, for example, to make y o1 = y o1 +△1, and the adjusted y o1 should meet the requirement of no total reflection. Among them, △1 is the adjustment step size, and the specific value can be set according to actual requirements.

[0128] S56, determine whether the initial structure meets the detection requirements of the engineering application spectrum. If it meets, execute step S57, otherwise adjust R 2 and jump to step S51. The method of adjusting R 2 is, for example, to make R 2 = R 2 +△2, and the adjusted R 2 should simultaneously meet the processing conditions and the volume requirements of the spectrometer. Among them, △2 is the adjustment step size, and the specific value can be set according to actual requirements.

[0129] S57, output the initial structural parameters and establish the initial structure of the spectrometer.

[0130] After obtaining the initial structural parameters of the spectrometer 2, the requirement 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 project.

[0131] 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 similar to Figure 15 that, except that this process does not involve y o2 , and for the sake of saving space in the specification, it will not be elaborated here.

[0132] In the present invention, the above theoretical models include the spectral bending - telecentricity model of the spectrometer 2, the spectral distortion - telecentricity model of the spectrometer 2, and the astigmatism - telecentricity model of the spectrometer 2.

[0133] The spectral bending - telecentricity model of the spectrometer 2 can be expressed as:

[0134] ;

[0135] Wherein, is the object - side telecentricity, is the image - side telecentricity, ([[]] x o ,y o o ) is the object - point coordinate, ([[]] x i ,y i i ) is the image - point coordinate, R 2 is the radius of curvature of the convex grating 25, m is the diffraction order, g is the groove density of the convex grating 25, λ is the wavelength.

[0136] The spectral distortion - telecentricity model of the spectrometer 2 can be expressed as:

[0137] .

[0138] The astigmatism - telecentricity model of the spectrometer 2 can be expressed as:

[0139] ;

[0140] Wherein, Astig is the astigmatism of the spectrometer 2, α o is the incident azimuth angle of the chief ray of the spectrometer 2, α i is the exit azimuth angle of the chief ray of the spectrometer 2, is the object - side telecentricity, is the image - side telecentricity,CO is the distance from the object point of the spectrometer 2 to the common curvature center of each mirror.

[0141] According to the above spectral curvature - telecentricity model, spectral distortion - telecentricity model, and astigmatism - telecentricity model, the high - quantitative implementation 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 are:

[0142] ;

[0143] Among them, is the object - side telecentricity, is the image - side telecentricity, ([[]] x o ,y o ) are the object - point coordinates, is the range from the central field - of - view position to the edge field - of - view position of the spectrometer 2 from the slit, ([[]] x i ,y i ) are the image - point coordinates, λ is the wavelength, λ 1 ~λ n is the working wavelength range of the spectrometer 2, λ 1 is the starting wavelength, λ n is the ending wavelength.

[0144] The structural - parameter curve functions of the meniscus lens 22 and the main mirror 23 in the case of object - side telecentricity are:

[0145] ;

[0146] Among them, k 13 = 2, and others k 1i = 1, n 12 =n , and others n 1i = 1; k 22 = 2, and others k 2j = 1, n 21 = n , and others n 2j = 1; CO is the distance from the object point of the spectrometer to the common curvature center of each mirror:

[0147] ;

[0148] When the image space is telecentric, the structural parameter curve function of the meniscus lens 22 and the secondary mirror 24 is:

[0149] ;

[0150] Wherein, k 14 = 2, k 13 = 0 for others k 1i = 1, n 12 = n for others n 1i = 1; k 22 = 2 for others k 2j = 1, n 21 = n for others n 2j = 1; CI is the distance from the image point of the spectrometer to the common curvature center of each mirror:

[0151] ;

[0152] is the object space telecentricity, is the image space telecentricity, ( x o ,y o ) is the object point coordinate, n is the refractive index of the meniscus lens 22, m is the diffraction order, g is the groove density of the convex grating 25, λ is the wavelength, R 1 is the curvature radius of the front surface of the meniscus lens 22, R 2 is the curvature radius of the convex grating 25, R 3 is the curvature radius of the primary mirror 23, R 4 is the curvature radius of the secondary mirror 24, wherein, R 1 R 3 are the structural parameters determining the object space telecentricity, R 1 R 4 ​​To determine the structural parameters of the image-space telecentricity. In the present invention, the first surface distribution can be obtained according to the above corresponding structural parameter curve function, and the second surface distribution can be obtained according to the above corresponding structural parameter curve function.

[0153] The azimuth angle of the chief ray exiting the spectrometer 2 α i is:

[0154] ;

[0155] where, ( x o ,y o ) are the object point coordinates, 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.

[0156] In the present invention, the constraints on the telecentric deviation and the telecentric deviation change rate include: determining the maximum allowable telecentric deviation degree according to the high-quantification atlas application requirements in engineering applications, and simultaneously constraining the telecentric deviation and the telecentric deviation change rate 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 and relax the distortion constraint, so that the dispersion converges quickly, and finally achieves the effect of low distortion and large image plane.

[0157] The maximum telecentric deviation corresponding to the engineering distortion requirement is:

[0158] ;

[0159] ;

[0160] where, is the object-space telecentricity, is the image-space telecentricity, ( x o ,y o ) are the object point coordinates, 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 the 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 .

[0161] is to expand the line field of view of the traditional spectrometer to a large rectangular field of view. During the implementation process, to implement a long-line field of view spectrometer, take to implement a large rectangular field of view spectrometer. Among them, l is the slit length or the length of the rectangular field of view, 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.

[0162] In the present invention, a small area array detector can be configured as a large area array detector for hyperspectral use, and the large rectangular field of view of the spectrometer is set as parallel double slits. The horizontal direction of the double slits is: the double slits are discontinuously distributed and overlap with each other between the discontinuities. The overlap length depends on the magnitude of the drift angle and satisfies , the number of overlapping pixels is , the number of discontinuities of the horizontal slits , the length of each "discontinuous" slit , among which is the double slit interval, d is the pixel size of the spectral channel, and the drift angle is the angle between the satellite flight direction and the vertical direction of the slit, represents the minimum value of, represents the maximum value of, is the total number of ground objects in the spatial dimension, is the number of pixels of the detector in the spatial dimension. The vertical direction of the double slits is: the distance between the positions of the two slits , among which , is the number of spectral channels, , is the margin from the outermost effective pixel to the edge after the detector is packaged, is the minimum required interval for the detector splicing process; , is the number of pixels in the spectral dimension of the detector. The small area array detectors are arranged in a pin shape, and different rows of detectors are strictly coincident with the images of different wavelengths formed by the slit in the image space of the spectrometer in sequence.

[0163] The present invention can set the large rectangular field of view of the spectrometer as parallel double slits with a spacing of where the first slit (Slit1) uses the +2 or -2 order of the grating to disperse the wavelength λ 1 ~λ n and the second slit (Slit2) uses the +1 or -1 order of the grating to perform spectroscopic imaging on the wavelength 2 λ 1 ~2λ n The sum of the width Nd of the spectral dimension area array detector and the installation spacing △L of the two detector chips is less than the slit spacing and greater than the spectral dispersion width of a single slit to achieve the broadening of the spectral range of the spectrometer from λ 1 ~λ n to 2 λ 1 ~2λ n .

[0164] The present invention can set the large rectangular field of view of the spectrometer as parallel double slits or multiple slits, and the diffraction orders of the spectrometer are the same. For a moving target, the trajectory and speed of the moving target can be obtained by using the positions and passing times of the target on different slit fields of view. If the signals of the same target on N multiple slits are superimposed, the signal-to-noise ratio of the target can be increased by times. The use of multiple slits can improve the detection of the target in many aspects.

[0165] The following will introduce the solutions provided by the present invention through two specific cases. The first case can achieve a spectrometer with a 300 mm ultra-long line of sight and low distortion, and the second case can achieve a spectrometer with a 240 mm × 32 mm double-slit large rectangular field of view and low distortion. It should be noted that the content in these cases is only used to illustrate the solutions of the present invention and does not limit the protection scope of the present invention in any way. Table 1 shows the indicators and performance parameters of the spectrometers in these two cases.

[0166] Table 1. Example table of spectrometer indicators and performance parameters

[0167]

[0168] 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 spectral lateral deviation is less than 0.1△ λ , the dispersion is close to the diffraction limit. The spot diagrams of the single-slit and double-slit spectrometers are respectively as Figure 17 and Figure 18 shown, and the dispersion is about 1 / 3 pixel. Among them, RMS (Root Mean Square) represents the root mean square value of the distance between the imaging points of the actual optical system and the ideal image points, 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 ability of the optical system to different spatial frequencies. The higher the curve, the stronger the ability to resolve details and the clearer the imaging. Smile (spectral bending) is used to represent the deviation of the slit monochromatic image in the dispersion direction as the slit gets longer, and Keystone (spectral distortion) is used to represent the deviation of the spectral curve of the slit object element in the spatial position direction with the dispersion of different wavelengths. As Figure 19 , Figure 20 and Figure 21 shown, the present invention has made a major breakthrough in uniquely changing the non-linear sharp increase of dispersion and distortion into almost constant, breaking the bottleneck that the field of view of spectrometers cannot be made long or wide.

[0169] It should be noted that the present invention is not limited to a single slit or a double slit, and can also be used for a rectangular field of view composed of multiple slits. The present invention is not limited to the short-wave infrared of 1 μm - 3 μm, and can also be used for other bands including ultraviolet, visible, and very long waves.

[0170] Table 2. Telecentric calculation structural parameters and optimized structural parameter table of the spectrometer

[0171]

[0172] Table 3. Image quality table of the spectrometer in Case 1

[0173]

[0174] Table 4. Image quality table of the spectrometer in Case 2

[0175]

[0176] 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.

[0177] 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.

[0178] 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.

[0179] The above is only an illustrative description of the principles and effects of the present invention, and is not intended to limit the present invention. Any person familiar with this technology can modify or change the above content without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should 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 comprises: establishing a double telecentric theoretical model of the spectrometer object-image side, 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, wherein: 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 includes: S51, obtaining a first input parameter and a second input parameter; S52, obtaining an intermediate parameter according to the first input parameter and the second input parameter; S53, solving an object-side telecentric model and an image-side telecentric model; S54, obtaining the initial structure parameters; S55, judging whether the initial structure corresponding to the initial structure parameters has light blocking; S56, judging whether the initial structure parameters meet the requirements of engineering application spectrum detection; S57, when the judgment conditions of S55 and S56 are met, outputting the initial structure parameters and establishing the initial structure of the spectrometer; The theoretical models include a "spectral curvature-telecentricity" model, a "spectral distortion-telecentricity" model and an "astigmatism-telecentricity" model; The way of solving the object-side telecentric model and the image-side telecentric model in the design method is to obtain a first curved surface distribution and a second curved surface distribution based on the theoretical model, wherein 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 the 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, with clockwise as the positive direction, is the image telecentricity, with the counterclockwise direction as the positive direction, ( 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 , 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.

2. The implementation method according to claim 1, characterized in that: The spectral curvature-telecentricity model is: ； The spectral distortion-telecentricity model is: ； The astigmatism-telecentricity model of the spectrometer is: ； in,( x i ,y i ) are the image point coordinates, 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.

3. The implementation method according to claim 1, characterized in that: The implementation parameters of the spectrometer satisfy the following formula: ； in, The spectrometer is from the central field of view position of the slit to the edge field of view position, λ 1 ~λ n is the working band range of the spectrometer, λ 1 is the starting wavelength, λ n is the ending wavelength.

4. 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 .

5. The implementation method according to claim 1, 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: 。 6. The implementation method according to claim 1, 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.

7. The implementation method according to claim 6, characterized in that: The maximum telecentricity deviation corresponding to the engineering distortion requirement is: ； ； in, is the length of the slit, 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.

8. The implementation method according to claim 7, 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.

9. The implementation method according to any one of claims 1 to 8, 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, F# is the F number of the system, h is the width of the rectangular field of view.

10. The implementation method according to any one of claims 1 to 8, 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.

11. The implementation method according to any one of claims 1 to 8, 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.

12. The implementation method according to any one of claims 1 to 8, 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.

13. A spectrometer, characterized in that: The spectrometer is realized by the method according to any one of claims 1 to 12.

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