设计了一种基于衍射元件的长焦距中波红外连续变焦光学系统,焦距为70~800 mm,11.4倍连续变焦。该系统采用二次成像技术,具有100%冷光阑效率,公差分配合理,没有冷反射和鬼像。在空间频率16 lp/mm处,所有焦段的MTF值均大于0.5。采用衍射元件,提高了光学系统的像质,减小了光学系统的体积和重量,采用凸轮变焦,光机结构紧凑、重量轻。

A middle infrared long-focus continuous zoom optical system was designed based on diffractive element, whose zoom ratio was 11.4×, and it could realize 70~800 mm continuous zoom. The optical system met 100% cold shield efficiency through reimaging technology, and it had reasonable tolerances and no cold reflection and ghost images. The modulation transfer function was above 0.5 in all focal distance at the spatial frequency of 17 lp/mm. The optical system used a diffractive element to improve image quality and reduce the volume and weight. And the mechanical structure which was zoomed by cam was designed in compact structure and light weight.