基于谐衍射透镜成像理论和变焦系统原理，采用轴向移动式变换视场，同时引入谐衍射透镜，实现了红外谐衍射双波段双视场光学系统的设计。对设计结果进行了像质评价。设计与分析结果表明，该系统使用5片透镜在双波段实现了40~80 mm两档变焦，满足100%冷光阑效率。在3.7~4.3 μm中波红外波段，系统奈奎斯特频率处调制传递函数(MTF)值大于0.5；在8.7~11 μm长波红外波段，系统奈奎斯特频率处MTF值大于0.3。该成像系统具有双波段、高分辨率、体积小、结构简单等特点。

On the basis of harmonic diffractive element theory and zoom theory, a dual-band and dual-field infrared optical system employing harmonic diffractive element is designed. The optical configuration is based on the axial motion of a lens group along the optical axis for changing field of view. The image quality evaluation are listed. Evaluation results show that the system has five lens and realizes a zoom of 40~80 mm in dual-band, which satisfing 100% cold shield efficiency. The modulaiton transform function value is over 0.5 at the Nyquist frequency for the waveband of 3.7~4.3 μm and over 0.3 at the Nyquist frequency for the waveband of 8.7~11 μm. The system is characterized by dual-band, high resolution, miniaturization and simple structure.