Design Of Compact Medium-wave Infrared Imaging System

Infrared imaging system is an important optical system that can be widely applied in various domains,such as target detection,information acquirement,accordingly it occurs the new demands for the infrared system,like a compact dimension,athermal,etc.In this paper,we designed a compact infrared imaging system based upon the above demands.The system consists of three parts of shield,Casey Grain system and relay lenses.The system adopts the structural type with the combination of Casey Grain system and relay lenses.The distance between the second reflective mirror and the cold stop is less than 47 mm,which makes the system compact enough.While realizing the compact design of the medium-wave infrared optical system,the matching of the cold shield of the infrared detector in the refrigeration system is realized,and the system can react the 100% cold shield efficiency.Due to the serious impact of temperature on the infrared system,the initial structure of the optical system is calculated by the theoretical deduction of athermalization and achromatism,which is then optimized by Zemax software.Finally,athermalization analysis of the system is conducted.The wavelength range is 3.7-4.8?m,the field of view is 3°,the values of Modulation Transfer Function(MTF)are all larger than 0.4 at the spatial frequency 17lp/mm in the full field of view,and the system can keep a good image quality within the temperature range of-40?~+50?.