| Nowadays, infrared systems have been widely applied in many affairs. Insome special cases, such as when we have to search and track the target, step-zoomsystem will be used. With the rapid development of technology, infrared detector hasmade great progress in recent years. For its’ higher resolution and responsespeed，cooling detector has been used in many infrared thermal imaging systems toget clear images, which causes a series of problems, such as the narcissus effect, coldshielding eiffciency as well as athermalization, which makes the optical designprocess much harderSome certain optical measure instalment is used to trace and measure the trailof missile. IRST optical system is an important part of it. Firstly this paper gave ageneral look at the advantage and development of infrared thermal imagingtechnology. Then in chapter2it introduced some knowledge of infrared radiation，and showed the relationship between infrared radiation and medium wave, and thendetermined optical parameters of the infrared system. In chapter3it focused on theconcepts and basic types of zoom optical system, and gave some detail analysis ofthe step-zoom system. In order to minimize the bad effect to image quality caused byenvironmental temperature, three kinds of athermalization has been discussed in thepaper, and the step-zoom optical system designed in chapter was put intoathermalization analysis, so that they can endure the temperature changes and havegood image quality during-40。C?+60。C. Finally, in chapter5，it gave the notionand generating conditions of narcissus. The article analysed the effect of cold reflection by two parameters named YNI and I/Ibar. Narcissus analysis was done tothe axial motion zoom system, and effective measures were put forward to controlthe cold reflect effect. |
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