具有非罗兰圆结构的太阳极紫外正入射宽波段成像光谱仪光学设计

Concave grating imaging spectrometers operating at conventional Rowland circle mounting have excellent on-axis imaging performances. However, such spectrometers have been found to possess poor off-axis imaging performances as a result of the existence of large off-axis grating aberrations, which are not suitable for spatial and spectral imaging under a large off-axis field of view (FOV) and a broad band. Based on the aberration correction theory of toroidal varied line-space gratings operating at non-Rowland circle mounting, we designed a solar extreme ultraviolet (EUV) normal-incidence imaging spectrometer with a large off-axis FOV and a broad band. Specifically, this instrument can provide excellent imaging with high spatial and spectral resolutions for EUV spectroscopic observations of the solar corona and transition region. Besides, the instrument has only two reflective surfaces with periodic SiC/Al multilayer coating, which minimizes the loss of photon flux in the EUV band and improves the transmission efficiency of the instrument greatly. Finally, this unprecedented spectrometer, with an aperture of 100 mm and the operating bands of 4047 nm, 5360 nm, and 6673 nm, achieves a spatial resolution and a spectral resolution better than 0.55" and 30×10^-4 nm respectively, providing ultrahigh resolution imaging over the off-axis FOV of 18' along the slit.