Design of cooled infrared switch-zoom optical system with long effective focal length based on R-C system

Based on the R-C system a cooled infrared swith-zoom optical system with long effective focal length is designed.The initial parameters are calculated and the components' focal power is deduced.Secondary imaging structure is adopted,and relay lens is used to match the cold stop.Zoom is realized by switching the relay lens of the short focal length system and the long focal length system.The optimized design of optical system aberration is made.The optimized imaging results of the long effective focal length optical system and the short effective focal length optical system at different field of view are presented,and the modulation transfer functions within 0.8 field of view at 17 lp / mm of spatial frequency are greater than 0.4.Finally,corresponding precision analysis of the main structure is made and the results show that the structure is rational and the imaging quality is good.The optical system can meet actual requirement.