Abstract
Common dispersive-type spectroscopic instruments include prism-type and grating-type, usually using a single dispersive element. The continuous imaging band is always limited by the dispersion angle. When it is necessary to image two wavebands with an ultra-spectral resolution that are far apart, the imaging is difficult due to the large diffraction angle. To broaden the spectral coverage of the imaging spectrometer, in this paper, we propose a dual-gratings imaging spectrometer with two independently rotating gratings. In this proposed system, two very far apart wavelength bands can be imaged in the adjacent areas by adjusting the angle of the dual gratings. This greatly expands the spectral coverage of the imaging spectrometer. Currently, the only application area considered for this instrument is solar applications. In this article, we present the optical system of the dual-gratings imaging spectrometer, illustrate several advantages of the new structure, and discuss new problems caused by the dual-gratings, which are referred to as overlap between two spectra and double image offset. We deduced the calculation process of the dual grating rotation angle, the relationship between the final acquired image and the slit, the relationship between the angle change between the dual gratings and the double image offset, and the relationship between the MTF upper limit reduction and the spatial frequency. This article also summarizes the shortcomings of this structure and studies the applicable fields under these shortcomings. At last, we simulate a dual-gratings imaging spectrometer system, compare this scheme with two traditional schemes, and conclude that this instrument has certain practical significance.
Highlights
An imaging spectrometer is an instrument that is used in hyperspectral imaging and imaging spectroscopy to acquire a spectrally-resolved image of an object or scene [1]
In the case of using the same grating, two imaging spectrometers with the same spectral resolution designed according to the traditional scheme can obtain the nearly same parameters as the dual-grating system, and the system volume can be 0.028 m3 according to the simulation, which is almost twice that of the dual-grating system
Our main objective is to address the limited spectral range of the conventional imaging spectrometers, which are limited by the dispersion angle
Summary
An imaging spectrometer is an instrument that is used in hyperspectral imaging and imaging spectroscopy to acquire a spectrally-resolved image of an object or scene [1]. Xue’s work uses this structure in a planar grating imaging spectrometer, but his structure divides the field of view into two parts and cannot be connected to common imaging systems. In this paper, this structure is applied to the planar grating imaging spectrometer to expand the system’s spectral coverage and ensure high spectral resolution. The light passing through the slit is converted into collimated light by the mirror and exits at different dispersion angles after passing through the grating The main advantages of the E-F structure imaging spectrometer are its simple assembly and high-quality images
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