为满足高光谱傅里叶变换光谱仪对高光谱分辨率、小畸变、像面光谱辐照度均匀、高信噪比以及仪器轻量化小型化的要求,设计了空间外差光谱仪成像光学系统。基于傅里叶变换的空间外差光谱仪空间干涉的特点和对成像系统缩放比、畸变等要求,依据干涉图调制度分析了最恶劣面形改变条件下对干涉仪元件面形误差的要求,并采用前后镜组匹配实现了双远心成像系统的设计。设计结果表明: 该光学结构可避免调焦产生的成像系统缩放比改变,有效视场内畸变量<0.1%,传递函数在38.5 lp/mm处物面所有点全视场范围≥0.60。依据仪器视场角对滤光片安装位置和精度提出要求,并对成像系统进行杂散光和照度均匀性分析提出有效抑制杂散光的措施和方法。系统设计满足了空间外差光谱仪对成像的要求,实现了照度均匀、低畸变、离焦情况下缩放比保持不变等。

To meet the commands of Spatial Heterodyne Spectrometer(SHS) based on Fourier Transform that are high spectral resolution, minimum distortion, homogeneous illumination, high signal to noise ratio and the limited resources of volume and weight, an imaging optical system of SHS was designed. According to the characteristic of spatial interference in SHS, the interferogram on the location plane of the fringes near the gratings was imaged onto the detector with a specific magnification, which determined the spectral resolution and the band width of SHS. For the case of SHS in which magnification was the limit factor, the constant magnification could be obtained by use of the match of fore lens and rear lens to achieve a telecentric optical system. The imaging optical system actually contained a spread of optical elements from grating to detector, and hence, the diffracted wavefront error of gratings and RMS change in wavefront error of beam splitter and field widened wedges in interferometer would decrease the modulation efficiency. The imaging optical system offered the constant magnification, and it is apparent that even minor change in the position of FPA have a slight effect on the spectral resolution and band width, furthermore, the maximum distortion decreases to less than 0.1% over the field of view. The theoretical Modulation Transfer Function (MTF) is high than 0.60 at the spatial frequency in cycles per mm of 38.5 over the entire defined format. Based on the analysis of stray light, uniformly illumination and the ability of field widened of interferometer contained in the imaging optical system, a tolerance sensitivity analysis to determine the worst tilted error of the filter is performed. The optical system has well suited to SHS applications that require high spectral resolution and high modulation efficiency over a relative narrow spectral band.