Design of LWFIR Zoom Optical System with Large Relative Aperture

A high-speed uncooled infrared zoom optical system in the spectrum 8-12μm region is designed.The system is a simple structure with four parts and five pieces lens;the rear fixed unit is composed of two lenses,the rest are only one lens.The effective focal length ranges from 50mm to 200mm.The relative aperture is 1∶1. The zoom cam curve shape and data are given by zpl which is can be applied to two-ariable-unit zoom system,in this way the requirement of defocus was satisfied at some focal length.Image quality evaluation result shows that the MTF is higher than 0.4 in all field of view at the spatial frequency 20 lp/mm.