利用红外双波段成像能够获得更多的信息，从而提高探测和识别能力。将多层衍射光学元件应用到红外双波段光学系统中，可以校正色差、简化结构。讨论了多层衍射光学元件的成像特性，相比于单层衍射光学元件，多层衍射光学元件可在宽波段范围内获得高衍射效率，给出了多层衍射光学元件设计方法。基于此，设计了一种红外双波段混合成像光学系统。其中，双层衍射光学元件在3.7~4.8 μm和7.7~9.5 μm工作波段上的衍射效率达98.5%以上。仿真结果表明，系统像质良好，满足要求。

The detection and recognition capability can be improved by using infrared dual-band imaging to obtain more information.The application of multi-layer Diffractive Optical Elements (DOEs) in infrared dual-band optical system can correct the chromatic aberration and simplify the system structure.Compared with the single-layer DOEs,the multi-layer DOEs have higher diffraction efficiency in wide wave bandwidths.In this paper,the imaging characteristics of multi-layer DOEs are presented,and the design method is given.Based on which,an infrared dual-band hybrid diffractive-refractive optical system is designed.The diffraction efficiency of the double-layer DOE is higher than 98.5% in the working bands of 3.7 to 4.8 μm and 7.7 to 9.5 μm.The simulation result shows that the system has fine imaging quality,and the performance meets the optical system requirements.