星载高光谱成像仪光学系统的选择与设计

摘要

对几台国内外典型的星载高光谱成像仪所采用的光学系统结构进行了分析,阐述了棱镜色散、光栅色散、傅里叶变换3种主流高光谱成像仪分光方式的结构原理和优缺点.根据宽波段、小型化的研究目标,设计了一个全反射式高光谱成像仪光学系统.该系统由离轴非球面三反射镜望远成像系统和两个Offner凸光栅光谱成像系统组成,通过改变两个光谱成像系统的变倍比来实现两种探测器的匹配.给出的该系统的详细设计结果显示,光学系统128个谱段的调制传递函数均达到0.6以上,畸变＜0.44%,谱线弯曲＜0.03%.实验结果表明,选定的全反射式光学系统满足小型化星载高光谱成像仪的技术要求,有效降低了仪器的体积和质量,通过加大光学系统的相对孔径弥补了光栅衍射效率低的缺点.%A proper optical system is selected for a compact, wide waveband spaceborne hyperspectral imager by comparing with existing optical systems applied to spaceborne hyperspectral imagers. Firstly, the advantages and disadvantages of optical systems for the hyperspectral imagers are discussed. Then, the principle and characteristics of three spectralsplittering methods with a prism, a grating or FT(Fourier Transform) as dispersion elements are compared and analyzed. Finally, based on the research objective of a hyperspectral imager, a reflective optical system is chosen. The system is composed of an offaxis ThreeMirror Anastigmatic(TMA) telescope and two Offner convex grating spectrometers. By changing the magnification of two spectral imaging systems, two array detectors with different pixel sizes can be matched. The detailed design results are presented,which indicate that the Modulation Transfer Function (MTF) of 128 wavebands from 400 nm to 2 500 nm is all over 0.6, distortion is less than 0.44% and the spectral bend(smile) is less than 0.03%. The chosen reflective optical system can satisfy the technical requirements of the compact spaceborne hyperspectral imager and can efficiently decrease the volume and weight. By enlarging the relative aperture of the optical system, the low diffraction efficiency of gratings can be compensated.