Thermal/structural/optical Integrated Analysis And Thermal Design Of Infrared Imaging System

With the continuous progress of infrared technology, more and more infraredimaging systems are applied to various fields such as military, aerospace andindustry. People also raise higher demand for its image quality. For the infraredimaging systems based on ground, thermal environment is the main factor affectingits image quality. Therefore, studying the thermal distribution of an infrared imagingsystem in actual conditions, analyzing the impact which caused by this distributionand designing the cooling system particularly will greatly help to improve theperformance of the infrared imaging system.The thermal distribution of the infrared imaging system is simulated with theuse of integrated Thermal/Structural/Optical (TSO) technique at designing andworking conditions. Simulation’s accuracy is better than4.5%after comparing withactual temperature of the infrared imaging system tested under designing condition.Based on the result of thermal analysis，several factors are considered which willaffect image quality. These factors include the change of optical elements’ positioncaused by the distortion of mechanical elements, the distortion of optical lensescaused by gradient temperature distribution and the change of infrared materials’character caused by temperature shift. System image quality is remarked in eachcondition after inputting all factors into optical design software. The conclusion isthat temperature shift causes both change of infrared materials’ characteristic andequal distortion of optical elements’ shape which lead optical system unfocusedwhile gradient temperature distribution causes unequal distortion of opticalelement’s shape which introduces aberrations. Aberrations still exist after focus thesystem.According to the result analyzed by integrated TSO technology, cooling systemshould be designed to reduce both system’s gradient temperature distribution andtemperature shift. After comparing the refinements brought by several thermalcooling methods, the conception of distributed cooling system was applied. Protowas manufactured and assembled after calculated the detailed parameter andoptimized the distributions of cooling units. The highest temperature of the infraredimage system reduced16.25℃at designing condition when distributed cooling system was turned on. Further more study showed that distributed cooling systemalso helped to prevent the temperature gradient distribution and aberration caused byit at each condition.