利用多层表面微结构提高DOE宽波段衍射效率

Improving diffraction efficiency of DOE in wide waveband application by multilayer micro-structure

针对单层衍射光学元件的不足,介绍了一种新型的多层衍射光学元件,通过层叠多个具有不同材料色散特性与相位高度的单层表面微结构,增加元件相位分布函数中的可变因子,实现波段内各波长光波的等效相位调制等于或接近2-的整数倍,双层衍射光学元件在0.4～0.8μm可见光波段的理论衍射效率可以达到96%以上。利用双层衍射光学元件替代萤石透镜校正混合光学系统的二级光谱,设计并制作了一套长焦距物镜,并利用系统调制传递函数评价了多层衍射光学元件衍射效率,测试结果表明衍射效率在整个设计波段内以较高的数值平均分布。

According to the disadvantage of single layer diffractive optical element（DOE）,a new DOE is introduced.More than two layers of stratified microstructures of different phase heights and dispersive materials are taken into the configuration to increase variable factors of the phase distribution function of multilayer DOE.By controlling the phase modulation of wide waveband to approximate to integer times of 2π,the diffraction efficiency of a double-layer DOE can be greater than 96% in 0.4~0.8 μm visual band.As substitute for fluorite lens,a double-layer DOE is used in a long focal-length apochromatic objective lens.The modulation transfer function（MTF） of this hybrid optical system is suggested for evaluating diffraction efficiency of the multilayer DOE.The results show the diffraction efficiency has a wide and symmetrical distribution in the whole waveband.