In general, image qualities are extremely sensitive to the change of the refractive index of IR(infrared) optic systems due to the temperature variation. When IR optic systems are included in dynamic lookout systems which experience in flight with a large temperature variation environment (from -35℃ to 72℃), the refractive index change must be compensated to distinguish objects. This dissertation deals with a movement sensitive passive autofocusing method, which acts to elimate defocus effects of continuously moving IR optic systems. In general, when movement of the optic system exists, the passive autofocusing method has problems obtaining a clear image. In this study, the image search algorithm, more specifically, the block matching algorithm and the gradient based method, is implemented into the passive autofocusing method to compensate for the refractive index change of continuously moving IR optic system. This study attempted to reduce search errors, which may be induced by the changing definition of images when image search methods are used simultaneously with passive autofocusing. Experimental results demonstrate that the image search algorithm implemented into the passive autofocusing method was capable of compensating for changing refractive index in IR optic systems.
