为对比分析不同光栅常数下Offner光栅和Dyson光栅光谱仪的性能差异, 推导了两种光谱仪结构的衍射角公式, 获得其衍射特点, 并在F数为2.5, 工作波段为8~12 μm, 光谱分辨率15.6 nm, 光栅常数分别为100 μm、50 μm下, 借助ZEMAX软件对这两种结构进行了优化设计。结果表明: 较大光栅常数下, 两者都能理想成像, Offner光谱仪体积约为Dyson的7倍, 质量约为Dyson的1/13; 较小光栅常数下, Dyson光谱仪仍可理想成像, 而Offner必须加入二次非球面镜并进行离轴, 才能满足系统对像质及光谱分辨率的要求, 此时, Offner光谱仪体积约为Dyson的7倍, 重量约为Dyson的1/11。设计结果表明, 两种同心结构在加工难易度、体积、重量方面各有优劣, 在光谱仪选型工作中, 可根据具体情况进行取舍。

Performance differences between Offner convex grating imaging spectrometer and Dyson concave grating imaging spectrometer, both with concentric structure, was analyzed under different grating constants. The diffraction angle expressions of the two spectrometers were obtained, and their diffraction characteristics were acquired. Both of the spectrometers were designed and analyzed by ZEMAX, under F number of 2.5, spectral rage of 8-12 μm, spectral resolution of 15.6 nm, and grating constants of 100 μm and 50 μm. The two structures could both meet the system requirements using spherical mirrors in the case of a higher grating constant. Offner′s volume is 7 times larger than Dyson′s, and Offner′s weight is about Dyson′s 1/13. When grating constant turned lower, Dyson could still meet the requirements just with spherical mirrors, while Offner must adopt aspherical mirrors and make an off-axis design for the requirements. The Offner′s volume is 7 times larger than Dyson′s, and Offner′s weight is about Dyson′s 1/11. The results show that Offner form and Dyson form have advantages and disadvantages in the aspect of operability of machining, volume, and weight. In the selection of spectrometer, the choice should be made depending on the specific application requirements.