采用多层衍射元件是实现宽波段高衍射效率的有效方法，设计了一个含双层衍射元件-30 ℃~70 ℃消热差系统。通过合理选择衍射面的基底材料，优化衍射表面的浮雕深度，设计出红外宽波段高衍射效率的消热差光学系统。设计结果表明，在整个设计温度范围内，该光学系统成像质量良好，光学传递函数在16 lp/mm时均在0.6以上。

A multi-layer diffractive optical element can improve the diffraction efficiency in wide waveband. An athermalized system with dual-layer diffractive optical element is designed, which works at temperatures ranging from -30 ℃~+70 ℃. By reasonable choosing the substrate material, and optimizing the relief depth of diffraction plane, a LWIR athermalized optical system with dual-layer diffractive element is designed. Experimental results show that the designed optical system can achieve a high imaging quality, and the modulation transfer function is higher than 0.6 at 16 lp/mm in the designed temperature range.