一种光栅型成像光谱仪光学系统设计

 成像光谱仪是一种“图谱合一”的光学遥感仪器。从光栅型成像光谱仪的使用要求出发，利用Zemax软件设计了一种光栅型成像光谱仪光学系统。其中，前置望远物镜采用反射式结构，传统的卡塞格林结构在主次镜均采用非球面时校正像差的能力依然有限，设计时采用改进后的卡塞格林结构对像差进行校正，最终设计的望远镜头传函在50 lp/mm处达到0.5，场曲控制在0.078以内，且不存在畸变。针对光谱成像系统通常采用的基于平面光栅的Czerny-Turner结构由于像差校正能力有限、成像质量较差不能满足仪器的使用要求。采用基于凸面光栅的光谱成像系统，该系统结构紧凑、可实现宽波段内像差的同时校正。最终设计的光谱成像系统光谱分辨率<5 nm，MTF在50 lp/mm时升至0.75。将前置望远物镜与光谱成像系统根据匹配原则进行组合优化后光栅型成像光谱仪系统点列图RMS半径随波长的变化均小于0.2，波长的80%的能量集中在Φ6 μm范围内，波长各视场在特征频率50 lp/mm处的光学传递函数均大于0.5。整个光学系统具有结构简单、像差校正能力强、结构尺寸较小的优点。

Optical system design of grating-based imaging spectrometer

Imaging spectrometer is a kind of optical remote sensing instruments which combining image with spectrum. Grating-based imaging spectrometer has a wide range of applications because of concise principle, stable performance, and nature of the technology. This article designs a kind of grating-based imaging spectrometer optical system using ZEMAX. The fore optic adopts reflection structure, aiming at the issue that the traditional Cassegrain structure has limited ability of aberration correction and makes system processing complex when both the primary and secondary mirror all use aspheric surface, this design adopts the improved Cassegrain structure for aberration correction. The transfer function of final fore optic is 0.5 at 50 lp/mm, the field curvature is less than 0.078 and there is no distortion .The Czerny-Turner structure based on plane grating that the spectral imaging system usually adopts has low spectral resolution, and the image quality is so bad as not to meet the requirement of the instrument. So the spectral imaging system based on convex grating is used, it has compact structure, strong ability to correct aberrations and high spectral resolution. The final spectral resolution is less than 5 nm, MTF is 0.75 at 50 lp/mm.According to the principle of matching, the grating-based imaging spectrometer is achieved by combinatorial optimization of the fore optic and spectral imaging system. The RMS radius of spot diagram of the spectrometer is always less than 0.2 with the change of wavelength, 80% of the wavelength energy concentrates in Φ6 μm and the MTF is greater than 0.5 at 50 lp/mm over the whole FOV.The entire optical system is characterized by simple structure ,good capability of aberration correction and small size.