含有双层谐衍射元件的红外双波段光学系统消热差设计

The Design of Infrared Dual-band Athermalized Optical System with Double-layer Harmonic Diffractive Element

用投影无热差图和双层衍射元件选玻璃的原则，选择了适用红外双波段消热差、消色差的玻璃组合．为提高衍射效率，基于双层衍射元件衍射效率表达式研究了双层谐衍射元件的结构优化，给出了优化方法．利用双层谐衍射元件设计的折衍混合双波段光学系统视场角10°，F#为2，有效焦距115mm．系统在3．4～4．2um和8～11um两个工作波段的衍射效率均达到90％以上；-40～100℃温度范围内，中心视场的调制传递函数值变化最大为0．09、边缘视场的调制传递函数值变化最大为0．13．

For satisfying the requirements of the achromatism and athermalism, the infrared materials are selected based on the projective athermal chart and the requirement of the double-layer diffractive element. To improve the diffraction efficiency, the double-layer HDE structure is investigated and the optimization procedure is given based on the equation of diffraction efficiency of the double layer diffractive element. An infrared diffractive refractive hybrid dual-band optical system with 10° field of view is designed. The effective focal length is 115 mm,while the F number is 2.0. The variation of the MTF is less than 0.09 for the centre field of view for the bands 3.4-4.2 um and 8-11 um in the range -40-100℃ ,and it is 0.13 for the marginal field of view. The optical system attains the athermal and achromatic purposes, and it performs perfectly. Particularly,the high diffraction efficiency and the high image quality in -40- 100℃, make the system satisfy the requirements in military and space applications.