三级次太阳极紫外窄波段无狭缝成像光谱仪光学设计

Optical Design of 3-Order Solar Extreme Ultraviolet Narrowband Slitless Imaging Spectrometer

对太阳进行光谱成像观测是太阳物理和空间天气研究的重要数据来源。在极紫外波段对动态的太阳大气进行光谱成像观测面临着严峻挑战。传统的狭缝式成像光谱仪受瞬时视场的限制,必须通过耗时的推扫才能获取二维日面图像,系统不具有高时间分辨率,无法捕获太阳过渡区域和日冕的快速演化过程。尽管极紫外成像仪能够实现大二维视场和高时间分辨率的观测,但却无法获取光谱分辨率信息。本文基于像差校正的椭球面变线距光栅,提出了一款新型无狭缝成像光谱仪,该系统同时工作在三个光栅衍射级次(m=-1,0,1)上,这样的新颖设计不需要任何元件的机械运动,单次快照便可同时获得三幅视场为20 arcmin×20 arcmin的极紫外窄波段(29.4〜31.4 nm)太阳日面图像,该仪器的时间分辨率高且视场大。不发生色散的0级次系统相当于一台极紫外成像仪,可以直接获得高分辨率空间信息(0.6 arcsec);发生色散的±1级次图像携带有空间和光谱的混叠信息,类似于计算层析成像原理。通过数据反演算法,可以从三个级次的图像中提取高分辨率的光谱信息(0.0035 nm)。

The observation of solar spectral imaging provides an importance data source for solar physics and space weather research.However,it faces a serious challenge from the dynamic solar atmosphere in the extreme ultraviolet(EUV)band.Only by time-consuming push-broom imaging can the traditional slit-type imaging spectrometer acquire 2D images of the solar disk due to a limited instantaneous field of view(FOV).Moreover,its system is unable to capture the rapid evolution of the solar transition region and corona since it does not have a high time resolution.Although an EUV imager can observe at a large 2D FOV and high time resolution,it cannot get the spectral resolution.For this reason,relying on the aberration-corrected elliptical varied line-space(EVLS)grating,we proposed a new slitless imaging spectrometer in this paper,which can simultaneously work in three diffraction orders(m=-1,0,or+1).Besides,three EUV narrowband(29.4-31.4 nm)images of the solar disk with a FOV of 20 arcmin×20 arcmin can be obtained in a single snapshot without the mechanical motion of any component,which demonstrates the high time resolution and large FOV of our instrument.Additionally,the zero-order system without spectral dispersion,equivalent to an EUV imager,can directly obtain high-resolution spatial information(0.6 arcsec).In contrast,the images from the zb 1-order systems with spectral dispersion carry spatial and spectral overlapping information,which is similar to the imaging principle of computed tomography.High resolution spectral information(0.0035 nm)can be extracted from the 3-order images by a data inversion algorithm.