极紫外光谱观测和诊断是研究太阳大气基本物理过程的最重要手段之一。 但因为波长短, 很多可见光仪器的设计方案不再适用, 且极紫外观测只能在太空中开展。 国际上现有卫星上的太阳极紫外成像仪和光谱仪都有各自的不足, 比如极紫外成像仪不能获得高光谱分辨率的谱线信息; 狭缝式光谱仪通过扫描可得到活动区域的信息, 但扫描时间过长, 对于研究剧烈变化的太阳活动有很大的局限性。 这些不足制约了对日冕物质抛射（CME）和耀斑等太阳活动的高精度观测及对其机理的研究: 无法看到CME在内日冕的加速过程, 而且无法将可见光看到的CME现象同极紫外看到的日面源区直接联系; 缺少观测目标的视向速度信息, 难以识别CME的触发过程。 采用多级衍射成像方式的一种新型太阳极紫外成像仪, 除实现传统极紫外成像仪功能外, 还可以在太阳活动变化过程中同步获得全日面各区域的光谱信息。 新型成像仪可以得到高光谱分辨率数据, 用于反演低日冕的等离子体视向速度, 获得全日面的速度分布, 与同时得到的高空间分辨率图像相结合, 可以识别太阳活动现象对应的物质运动, 为空间科学研究提供数据; 因为没有狭缝和运动部件, 可以实现对大视场的太阳活动区域的高时间分辨率成像, 有利于捕捉日面活动的快速变化。 新型成像仪采用无狭缝光谱分光成像的设计理念, 即同一时间把一定光谱带宽的信息记录到一个二维的图像上, 此过程可以看成是从某一个角度将空间和光谱数据立方体投影到一个面上, 然后再利用反演得到空间分辨图像和光谱信息。 多级光谱成像的光学设计与传统光谱仪最大的不同是其不存在逐行扫描的狭缝, 这使得其能够同时获得大视场内太阳的空间信息和光谱信息。 因为极紫外波段的特殊性, 以及本仪器面向卫星遥感应用, 不可能像可见光波段或者医用CT机一样实现很多衍射级的同时成像。 因此, 新型极紫外成像仪光学系统由反射镜、 色散光栅和五个探测器组成, 入射的太阳极紫外辐射经过光栅色散后分别由五个级次的探测器接收, 其中四个探测器分部接收±1和±2衍射级图像, 另外一个接收0级图像。 空间信息可以直接从0级图像得到, 而光谱信息则需要根据五个级次成像的反演结果得出。 介绍了光学系统的设计以及反演算法, 并分析了反演算法的误差。 光路基于变间距光栅设计, 可实现空间分辨率1.8 arcsec·pixel-1, 光谱分辨率7.8×10-3 nm·pixel-1, 同时减小了体积和重量, 适合空间应用。

Extreme Ultraviolet (EUV) spectroscopic observation is one of the most important approaches in diagnosing the basic physical phenomena in the solar atmosphere. However, the designs of many instruments used for visible wavelengths cannot be applied for EUV because of its much shorter wavelength. Conventional solar EUV imagers and spectrographs have their own limitations: Where as we cannot get spectral information from a EUV imager, it takes too long time for a single slit spectrometer to scan an area, which makes it difficult to catch the dynamics of highly transient solar activities. These limitations make the high resolution observation of solar activities and the research of its mechanism very difficult. We cannot observe the acceleration process of CME (coronal mass ejections) in inner coronal and cannot connect the CME observed by visible light with the activity area observed by EUV directly. Moreover, we cannot get the line-of-sight velocity of the solar activities, so it is difficult to find the source area of CME. In this paper, we present the design of a new type of solar EUV spectral imager with extra high spectral resolution. It can get the full-disk EUV image of the Sun with additional information on spectral line profile. So we can get the line-of-sight velocity of plasma in low coronal and the velocity map of the full coronal disk. Combining the spatial and spectral information, we can identify the movement corresponding to the configuration evolvement of the plasma. Because there is no slit and movement assembly, the imager can get high temporal resolution data of the whole solar disk to capture the rapidly transformation of solar activities. The new imager adopts a kind of slitless spectral imaging design, which means to project a narrow band spectrum data from different angle to a plate detector and invert to get the spatial image and spectral information. The biggest difference between the multi-order spectral imaging and the traditional spectrograph is that there is no scanning slit in former. These give the new imager the advantage which can get the spatial and spectral information in a wide field of view simultaneously. Considering the limitations of the EUV band and space application, it is impossible to get many orders image like the medical CT or telescopes response to visible light. Based on the multi-order imager principle, we proposed a five-order spectrograph. The optical system of the new imager consists of a reflect mirror, a grating and five CCD detectors. The dispersed lights after the grating are received by five detectors. Four detectors receive ±1 and ±2 orders of diffraction, and another one receives 0 order image with spatial resolution information. The spectral information can be obtained by inversion with five orders spectral images. The paper introduces the design of the optical system based on a varied line space (VLS) grating and the inversion algorithm, which will improve the instrument efficiency and image qualitywith limited volume and weight. The spatial resolution will be 1.8 arcsec·pixel-1 and the spectral resolution will be 7.8×10-3 nm·pixel-1. With this technology, we can get the full solar disk velocity map aswell as the intensity map simultaneously, which is suitable for space application.