双层衍射光学元件在微光夜视物镜中的应用

Application of Low-Light Night-Vision Objective Lens with Double-Layer Diffractive Optical Element

将衍射光学元件（DOE）应用于微光镜头的设计中，可以达到减少体积和重量的目的。衍射光学元件不同于传统透镜的负色散性质，可以很好地校正色差。单层衍射光学元件的衍射效率只能在某一波长处达到100%，其他波长处衍射效率下降明显，双层衍射光学元件则在整个工作波段内不同波长处都有较高的衍射效率。基于此，设计了一个使用双层衍射光学元件的微光夜视物镜系统。双层衍射光学元件在0.65-0.9 μm工作波段内衍射效率达98%以上，系统总长为60 mm，系统焦距为25 mm，F数为1.2，全视场为40°。仿真结果表明系统的像质良好，40 lp/mm处的调制传递函数大于0.5。

The design of low-light lens with diffractive optical element （DOE） can reduce the volume and weight of lens. DOE can correct aberrations well in virtue of its negative diffusion performance that is different from traditional lenses. The diffraction efficiency of a single-layer DOE can reach 100% only at a specific wavelength, and obviously decreases with the change of wavelength. The double-layer DOE has higher diffraction efficiency at any wavelength in the entire working band. A low-light night-vision objective lens system with double-layer DOEs is designed based on the excellent performance of double-layer DOEs. The diffraction efficiency of the double-layer DOE is higher than 98% in the working band from 0.65 μm to 0.9 μm. The length of the system is 60 mm, the field of view is 40°, the F number is 1.2, and the focal length is 25 mm. The simulation result shows that the system has fine imaging quality, and the modulation transfer function value is greater than 0.5 at the spatial frequency of 40 lp/mm.