基于双波段系统的多层衍射光学元件(MLDOE)的带宽积分衍射效率(PIDE),建立其与入射角度和基底材料关系的数学模型,提出一种双波段斜入射多层衍射光学元件基底材料的选择方法,并通过该方法选择出双波段多层衍射光学元件基底材料的最佳组合方案。方法的提出以及数学模型的建立,解决了光线斜入射时基底材料选择不当导致多层衍射元件衍射效率和带宽积分衍射效率下降的问题,为多层衍射元件在多波段和宽波段系统中的应用提供理论指导。依据该方法,设计了适用于中波红外3.7~4.8 μm(MWIR)和长波红外7.7~9.5 μm(LWIR) 双波段的多层衍射光学元件,并利用该衍射元件设计了10倍中长波折衍混合双波段红外变焦系统。结果表明,该系统在中波红外奈奎斯特频率处的调制传递函数(MTF)均大于0.52,在长波红外奈奎斯特频率处的MTF均大于0.35。

In this study, a mathematical model of the relationship between the bandwidth integral diffraction efficiency (PIDE) and the incident angle with the substrate material of a multilayer diffractive optical element (MLDOE) for a two-band system is established. A method for selecting a double-band oblique incident MLDOE substrate material is proposed; this method selects the best base material combination of the dual-band MLDOE. The proposed method and the mathematical model solve the problem in which the improper selection of the substrate material leads to a decrease in the diffraction efficiency and bandwidth integral diffraction efficiency of the MLDOE when light is obliquely incident. In addition, the method provides theoretical guidance for the application of MLDOE in multi-band and wide-band systems. According to the method, an MLDOE suitable for a medium wave infrared (MWIR) of 3.7-4.8 μm and a long wave infrared (LWIR) of 7.7-9.5 μm is designed, and a 10× hybrid zoom lens is designed using the diffraction element for the dual-band. The results show that the modulation transfer function (MTF) of the system at the Nyquist frequency of the MWIR is greater than 0.52 and the MTF at the Nyquist frequency of the LWIR is greater than 0.35.