根据光学补偿变焦距理论, 基于红外中波制冷型320×240焦平面探测器, 设计了31×光学补偿式红外步进变焦光学系统。该光学系统工作波长范围为3 μm～5 μm, 光学系统的F#和探测器相匹配, 恒定为4, 冷屏效率100%, 焦距范围430 mm~12.867 mm。采用3种光学材料和非球面对光学系统进行优化设计, 对7个视场严格校正了像差, 各个视场的MTF曲线均接近衍射极限, 获得了良好的像质。

According to the optical compensation theory, a 31× infrared step zoom optical system was designed based on 320×240 cooled mid-wave infrared (MWIR) focal plane array (FPA) detector. Its operation wavelength range was 3 μm~5 μm, F number was 4, cold stop efficiency was 100%, and focal length range was 430 mm~12.867 mm. The step zoom optical system was optimized by adopting three kinds of optical materials and aspheric surface. Aberrations of seven fields of view (FOVs) were strictly corrected, the MTF of each FOV was close to diffraction limit, and the image quality was good.