A hyperspectral spaceborne optical imaging system

Abstract

The present invention discloses a hyperspectral spaceborne optical imaging system, comprising: a grating primary mirror, a spectral focusing imaging system, a slit or a coding plate, and a spectral unfolding system; wherein, the slit or the coding plate is arranged at the primary image plane of the spectral focusing imaging system; the +1st order or -1st order diffracted light generated by the diffraction of the incident light by the grating primary mirror passes through the spectral focusing imaging system as parallel light to form a primary image at the slit or the coding plate, and the primary image passes through the spectral unfolding system to form a secondary image at the secondary image plane of the spectral unfolding system. The present invention meets the subsequent spaceborne requirements for large-aperture and ultra-large-aperture optical imaging spectrometers.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical system design, and particularly relates to a hyperspectral space optical imaging system. Background Art

[0002] With the increasing application requirements in the field of space remote sensing, new performance requirements are put forward for imaging spectroscopy systems. With the continuous increase in the number of spectra, this not only increases the design difficulty of the optical system itself. In particular, traditional spectrometer systems, including dispersive spectrometers, narrowband tunable filter imaging spectrometers, imaging Fourier transform spectrometers, and tomographic imaging spectrometers, are restricted by imaging systems and space launch space, as well as factors such as optical system material preparation, processing technology, and launch capacity. Using traditional imaging methods may not be able to meet the subsequent space requirements for large-aperture and ultra-large-aperture optical imaging spectrometers. Summary of the Invention

[0003] The technical problem solved by the present invention is: overcoming the deficiencies of the prior art, and providing a hyperspectral space optical imaging system that meets the subsequent space requirements for large-aperture and ultra-large-aperture optical imaging spectrometers.

[0004] The object of the present invention is achieved by the following technical solutions: A hyperspectral space optical imaging system includes: a grating primary mirror, a spectral focusing imaging system, a slit or encoding plate, and a spectral unfolding system; wherein, the slit or encoding plate is arranged at the primary image plane of the spectral focusing imaging system; the +1st order or -1st order diffracted light generated by the diffraction of incident light by the grating primary mirror passes through the spectral focusing imaging system as parallel light to form a primary image at the slit or encoding plate, and the primary image passes through the spectral unfolding system to form a secondary image at the secondary image plane of the spectral unfolding system.

[0005] In the above hyperspectral space optical imaging system, the spectral focusing imaging system includes a second reflector, a third reflector, and a fourth reflector; wherein, the +1st order or -1st order diffracted light passes through the second reflector, the third reflector, and the fourth reflector in sequence as parallel light to form a primary image at the slit or encoding plate.

[0006] In the above hyperspectral space optical imaging system, the spectral unfolding system includes a sixth reflector, a seventh reflector, a dispersion grating, and an eighth reflector; wherein, the primary image passes through the sixth reflector, the seventh reflector, the dispersion grating, and the eighth reflector in sequence to form a secondary image.

[0007] In the above hyperspectral spaceborne optical imaging system, the radius of curvature of the third mirror is smaller than that of the second mirror, the radius of curvature of the fourth mirror is larger than that of the third mirror and smaller than that of the second mirror; the distance from the grating main mirror to the second mirror is greater than the distance from the second mirror to the third mirror; the distance from the second mirror to the third mirror is equal to the distance from the third mirror to the fourth mirror; the distance from the fourth mirror to the slit or encoding plate is greater than the distance from the second mirror to the third mirror.

[0008] In the above hyperspectral spaceborne optical imaging system, the radius of curvature of the sixth mirror is larger than that of the seventh mirror dispersion grating, the radius of curvature of the seventh mirror dispersion grating is smaller than that of the eighth mirror, and the radius of curvature of the eighth mirror is smaller than that of the sixth mirror; the distance from the sixth mirror to the seventh mirror dispersion grating is greater than the distance from the seventh mirror dispersion grating to the eighth mirror; the distance from the eighth mirror to the secondary image plane of the spectral unfolding system is greater than the distance from the sixth mirror to the seventh mirror dispersion grating.

[0009] In the above hyperspectral spaceborne optical imaging system, the radius of curvature of the grating main mirror is infinite, the thickness of the grating main mirror is 30 mm, the line density of the grating main mirror is 1740 lp / mm, the distance from the grating main mirror to the spectral focusing imaging system is 11180 mm, and the clear aperture of the grating main mirror is 3000×20000 mm.

[0010] In the above hyperspectral spaceborne optical imaging system, the radius of curvature of the second mirror is -53700 mm, the distance from the second mirror to the third mirror is 1279.3 mm, the clear aperture of the second mirror is 3000×3000 mm, and the distance from the grating main mirror to the second mirror is 11180 mm.

[0011] In the above hyperspectral spaceborne optical imaging system, the radius of curvature of the third mirror is -13750 mm, the distance from the third mirror to the fourth mirror is 1279.3 mm, and the clear aperture of the third mirror is 2600×2600 mm.

[0012] In the above hyperspectral spaceborne optical imaging system, the radius of curvature of the fourth mirror is -17470 mm, the distance from the fourth mirror to the slit or encoding plate is 2166.6 mm, and the clear aperture of the third mirror is 3600×3600 mm.

[0013] In the above hyperspectral spaceborne optical imaging system, the radius of curvature of the sixth mirror is 2120 mm, the distance from the sixth mirror to the dispersion grating of the seventh mirror is 1023 mm, and the clear aperture of the sixth mirror is 590×590 mm.

[0014] In the above hyperspectral spaceborne optical imaging system, the radius of curvature of the dispersion grating of the seventh mirror is 1067.4 mm, the line density of the dispersion grating of the seventh mirror is 145 lp / mm, the distance from the dispersion grating of the seventh mirror to the eighth mirror is 990.4 mm, and the clear aperture of the dispersion grating of the seventh mirror is 192×192 mm.

[0015] In the above hyperspectral spaceborne optical imaging system, the radius of curvature of the eighth mirror is 2086.5 mm, the distance from the eighth mirror to the secondary image plane of the spectral unfolding system is 2113.3 mm, and the clear aperture of the eighth mirror is 590×403 mm.

[0016] The present invention has the following beneficial effects compared with the prior art:

[0017] (1) The entire hyperspectral spaceborne optical imaging system of the present invention meets the subsequent space requirements for large-aperture and extra-large-aperture optical imaging spectrometers;

[0018] (2) The present invention effectively utilizes the advantages of diffraction grating spectral imaging technology, simultaneously completes dispersion and imaging, is a unique spectrometer with axial dispersion, perfectly combines high resolution and high spectral resolution, and the hyperspectral resolution can reach 0.05 nm. Therefore, the finally obtained spectral resolution is better than that of traditional imaging spectral systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0020] Figure 1 is a schematic diagram of the hyperspectral spaceborne optical imaging system provided by an embodiment of the present invention;

[0021] Figure 2 is a schematic diagram of the diffraction optical path of the grating main mirror of the hyperspectral spaceborne optical imaging system provided by an embodiment of the present invention;

[0022] Figure 3 is a schematic diagram of the spectral focusing imaging system provided by an embodiment of the present invention;

[0023] Figure 4It is a schematic diagram of the spectral unfolding system provided by an embodiment of the present invention. Detailed implementation manners

[0024] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be completely conveyed to those skilled in the art. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0025] Figure 1 It is a schematic diagram of the hyperspectral spaceborne optical imaging system provided by an embodiment of the present invention. As Figure 1 shown, the system includes: a grating primary mirror 1, a spectral focusing imaging system, a slit or encoding plate 5, and a spectral unfolding system; wherein,

[0026] The slit or encoding plate 5 is disposed at the primary image plane of the spectral focusing imaging system;

[0027] The +1st order or -1st order diffracted light generated by the diffraction of the incident light by the grating primary mirror 1 passes through the spectral focusing imaging system as parallel light to form a primary image at the slit or encoding plate 5, and the primary image passes through the spectral unfolding system to form a secondary image at the secondary image plane of the spectral unfolding system.

[0028] As Figure 3 shown, the spectral focusing imaging system includes a second mirror 2, a third mirror 3, and a fourth mirror 4; wherein, the +1st order or -1st order diffracted light passes through the second mirror 2, the third mirror 3, and the fourth mirror 4 in sequence as parallel light to form a primary image at the slit or encoding plate 5.

[0029] As Figure 4 shown, the spectral unfolding system includes a sixth mirror 6, a seventh mirror dispersion grating 7, and an eighth mirror 8; wherein, the primary image passes through the sixth mirror 6, the seventh mirror dispersion grating 7, and the eighth mirror 8 in sequence to form a secondary image.

[0030] As Figure 2 shown, the grating primary mirror 1 is a plane grating. The light is diffracted by the grating, and the generated +1st order diffracted light exits as parallel light, and its exit angle is 80 degrees, which is determined by the slit pitch of the grating. Since the diffraction exit angle of the grating primary mirror 1 can achieve an 80° exit, the overall axial dimension of the system is greatly compressed, and the dimension is reduced to 1 / 6 of the original system, which is beneficial to the lightweight and miniaturized design of optical imaging and reduces the cost of the optical system.

[0031] The radius of curvature of the grating primary mirror 1 is infinite, the thickness of the grating primary mirror 1 is 30 mm, the line density of the grating primary mirror 1 is 1740 lp / mm, the distance from the grating primary mirror 1 to the second mirror 2 is 11180 mm, and the clear aperture of the grating primary mirror 1 is 3000×20000 mm.

[0032] The radius of curvature of the second mirror 2 is -53700 mm, the distance from the second mirror 2 to the third mirror is 1279.3 mm, and the clear aperture of the second mirror 2 is 3000×3000 mm.

[0033] The radius of curvature of the third mirror 3 is -13750 mm, the distance from the third mirror 3 to the fourth mirror is 1279.3 mm, and the clear aperture of the third mirror 3 is 2600×2600 mm.

[0034] The radius of curvature of the fourth mirror 4 is -17470 mm, the distance from the fourth mirror to the slit or encoding plate 5 is 2166.6 mm, and the clear aperture of the fourth mirror 4 is 3600×3600 mm.

[0035] The slit or encoding plate 5 is located at the position of the primary real image; if slit pushbroom spectral imaging is adopted, a slit is placed at the position of the primary real image, and the system is used to pushbroom the target to obtain spectral data; if snapshot computational spectral imaging is adopted, an encoding plate is placed at the position of the primary real image, and spectral data is obtained at one time by means of computational solution.

[0036] Specifically, the snapshot computational spectral imaging method is based on the sparse reconstruction theory. An observation matrix that is not correlated with the transform basis is adopted to project the high-dimensional signal onto a low-dimensional space, and the original high-dimensional signal is reconstructed and restored through optimization and solution. That is, in the implementation process, light passes through the encoding plate (2D space) to perform amplitude modulation on the three-dimensional data (1D spectrum + 2D space). After the three-dimensional data is dispersed by the grating, it is received by the detector, and the area array detector obtains spatial-spectral aliased data. Through the solution of the prior information of the encoding plate, the three-dimensional aliased data is sparsely reconstructed to obtain two-dimensional (1D spectrum + 2D space) data.

[0037] The radius of curvature of the sixth mirror 6 is 2120 mm, the distance from the sixth mirror 6 to the seventh mirror dispersion grating is 1023 mm, and the clear aperture of the sixth mirror 6 is 590×590 mm.

[0038] The radius of curvature of the seventh mirror dispersion grating 7 is 1067.4 mm, the line density of the seventh mirror dispersion grating 7 is 145 lp / mm, the distance from the seventh mirror dispersion grating 7 to the eighth mirror is 990.4 mm, and the clear aperture of the seventh mirror dispersion grating 7 is 192×192 mm.

[0039] The radius of curvature of the eighth mirror 8 is 2086.5 mm, the distance from the eighth mirror 8 to the image plane is 2113.3 mm, and the clear aperture of the eighth mirror 8 is 590×403 mm.

[0040] Working principle: A grating is used as the primary mirror. Through satellite pushbroom or area array imaging, according to the different imaging positions in different fields of view, the spectral information and imaging information of the same ground object are detected with high precision, and the scenes within the field of view are hyper-spectrally imaged to achieve simultaneous spectral splitting and imaging at one time. At the same time, the principle of reverse grating diffraction is adopted, and the +1 / -1 diffraction exit angles can be used to achieve an 80° exit, greatly compressing the overall axial size of the system, which helps to realize the lightweight and miniaturized design of optical imaging.

[0041] After the light passes through the grating primary mirror, it propagates in a straight line between the mirrors. The parameters of each optical element are shown in the following table:

[0042]

[0043] The working spectral band of the system of the present invention is 450 - 850 nm, the finite focal length is 13 m, and the full field of view angle is 18.7°×1.6°.

[0044] In this embodiment, when the satellite orbital altitude is 500 km, the hyperspectral spaceborne optical imaging system in this embodiment can achieve the technical indicators of a ground resolution of 0.5 m and a spectral resolution of 0.05 nm.

[0045] In the present invention, the photon shot noise of the spectral signal is relatively small. Because this kind of noise only comes from a few spectral channels adjacent to the measured spectral band, while in the traditional Fourier transform imaging spectrometer, photon shot noise will be generated in its entire spectral band; when the fifth encoding plate is used for the primary image position in the present invention, compared with the conventional dispersive spectrometer, its advantage is that the entire input aperture can collect light, improving the utilization rate of the light flux, and the light flux can be increased by more than 4 times; the present invention effectively utilizes the advantages of the diffraction grating spectral imaging technology, simultaneously completes dispersion and imaging, and is a unique axially dispersive spectrometer, perfectly combining high resolution and high spectral resolution, and the hyperspectral resolution can reach 0.05 nm. Therefore, the finally obtained spectral resolution is better than that of the traditional imaging spectrometer.

[0046] Although the present invention has been disclosed above with preferred embodiments, it is not used to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention without departing from the spirit and scope of the present invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention all belong to the protection scope of the technical solution of the present invention.

Claims

1. A hyperspectral spaceborne optical imaging system, characterized in that Comprising: A grating primary mirror (1), a spectral focusing imaging system, a slit or a coding plate (5), and a spectral unfolding system; wherein, The slit or the coding plate (5) is disposed at the primary image plane of the spectral focusing imaging system; The +1st order or -1st order diffracted light generated by diffraction of the incident light by the grating primary mirror (1) passes through the spectral focusing imaging system as parallel light to form a primary image on the slit or the coding plate (5), and the primary image passes through the spectral unfolding system to form a secondary image at the secondary image plane of the spectral unfolding system; The spectral focusing imaging system includes a second mirror (2), a third mirror (3), and a fourth mirror (4); wherein, The +1st order or -1st order diffracted light passes through the second mirror (2), the third mirror (3), and the fourth mirror (4) in sequence as parallel light to form a primary image on the slit or the coding plate (5); The spectral unfolding system includes a sixth mirror (6), a seventh mirror dispersion grating (7), and an eighth mirror (8); wherein, The primary image passes through the sixth mirror (6), the seventh mirror dispersion grating (7), and the eighth mirror (8) in sequence to form a secondary image; The radius of curvature of the third mirror (3) is less than the radius of curvature of the second mirror (2), the radius of curvature of the fourth mirror (4) is greater than the radius of curvature of the third mirror (3) and the radius of curvature of the fourth mirror (4) is less than the radius of curvature of the second mirror (2); The distance from the grating primary mirror (1) to the second mirror (2) is greater than the distance from the second mirror (2) to the third mirror (3); The distance from the second mirror (2) to the third mirror (3) is equal to the distance from the third mirror (3) to the fourth mirror (4); The distance from the fourth mirror to the slit or the coding plate (5) is greater than the distance from the second mirror (2) to the third mirror (3); The radius of curvature of the sixth mirror (6) is greater than the radius of curvature of the seventh mirror dispersion grating, the radius of curvature of the seventh mirror dispersion grating is less than the radius of curvature of the eighth mirror (8), and the radius of curvature of the eighth mirror (8) is less than the radius of curvature of the sixth mirror (6); The distance from the sixth mirror (6) to the seventh mirror dispersion grating (7) is greater than the distance from the seventh mirror dispersion grating (7) to the eighth mirror; the distance from the eighth mirror (8) to the secondary image plane of the spectral unfolding system is greater than the distance from the sixth mirror (6) to the seventh mirror dispersion grating (7).

2. The hyperspectral spaceborne optical imaging system according to claim 1, wherein: The radius of curvature of the grating primary mirror (1) is infinity, the thickness of the grating primary mirror (1) is 30 mm, the line density of the grating primary mirror (1) is 1740 lp / mm, the distance from the grating primary mirror (1) to the spectral focusing imaging system is 11180 mm, and the clear aperture of the grating primary mirror (1) is 3000×20000 mm.

3. The hyperspectral spaceborne optical imaging system according to claim 1, wherein: The radius of curvature of the second mirror (2) is -53700 mm, the distance from the second mirror (2) to the third mirror (3) is 1279.3 mm, the clear aperture of the second mirror (2) is 3000×3000 mm, and the distance from the grating primary mirror (1) to the second mirror (2) is 11180 mm; The radius of curvature of the third mirror (3) is -13750 mm, the distance from the third mirror (3) to the fourth mirror (4) is 1279.3 mm, and the clear aperture of the third mirror (3) is 2600×2600 mm.

4. The hyperspectral spaceborne optical imaging system according to claim 1, wherein: The radius of curvature of the fourth mirror (4) is -17470 mm, the distance from the fourth mirror to the slit or encoding plate (5) is 2166.6 mm, and the clear aperture of the fourth mirror (4) is 3600×3600 mm.

5. The hyperspectral spaceborne optical imaging system according to claim 1, characterized in that: The radius of curvature of the sixth mirror (6) is 2120 mm, the distance from the sixth mirror (6) to the seventh mirror dispersion grating is 1023 mm, and the clear aperture of the sixth mirror (6) is 590×590 mm.

6. The hyperspectral spaceborne optical imaging system according to claim 1, characterized in that: The radius of curvature of the seventh mirror dispersion grating (7) is 1067.4 mm, the line density of the seventh mirror dispersion grating (7) is 145 lp / mm, the distance from the seventh mirror dispersion grating (7) to the eighth mirror is 990.4 mm, and the clear aperture of the seventh mirror dispersion grating (7) is 192×192 mm; The radius of curvature of the eighth mirror (8) is 2086.5 mm, the distance from the eighth mirror (8) to the secondary image plane of the spectral unfolding system is 2113.3 mm, and the clear aperture of the eighth mirror (8) is 590×403 mm.

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