正入射通常不能反映成像衍射光学元件的实际工作状态,斜入射才是其普遍工作状态。建立了斜入射时三层衍射光学元件的衍射效率与入射角度关系的表达式。针对入射方向、两侧基底材料以及中间介质材料这三个影响因素,分析了三层衍射光学元件的衍射效率随入射角度的变化关系。结果表明,光线从正谐衍射元件端入射时,对应的衍射效率随入射角度增大下降得比较缓慢。组成三层衍射光学元件两侧谐衍射元件基底材料的阿贝数差值越大,衍射效率随入射角度增大下降得越缓慢。中间介质材料的选取由三层衍射光学元件工作时的入射角度范围决定。该分析方法和结论适用于可见光、红外等光学系统中的三层衍射光学元件。

Normal incidence cannot fully reflect the working condition of diffractive optical elements (DOEs) for imaging. However, oblique incidence can reflect their general working condition. The relationship between the diffraction efficiency and the incident angle is established for triple-layer diffractive optical elements (TLDOEs). For the three influencing factors, such as the determination of incident direction, the selection of the substrate materials on both sides and the selection of medium materials, the relationship between the diffraction efficiency and the incident angle is simulated and analyzed for TLDOEs. The results show that the diffraction efficiency decreases slowly with the increase of incident angle when the light is incident from the positive harmonic diffractive element (HDE). The larger of the difference of abbe number for the substrate materials of TLDOEs is, the more slowly of the corresponding diffraction efficiency decreases with the increase of incident angle. The selection of the medium material is decided by the incidence angle range of TLDOEs. The analysis method and conclusions are applicable to the visible or infrared TLDOEs.