Effect of system point spread function, apparent size, and detector instantaneous field of view on the infrared image contrast of small objects

Prediction of the performance of IR sensor systems in the detection and classification of features in an image requires estimation of the sensor signals produced by a given feature (source) and the background in the image. This process includes estimation of the effects that the detector, the scanning system (if used), and the optical system have on the performance of the system in a specified environment. The analysis of sensor performance takes into account the emission characteristics of the source and background and often assumes an extended source. For some tasks, the apparent size of a source, as well as the emission characteristics, must be taken into account in determining the scene contrast produced by the source. This requirement to account for the apparent size of a source arises as a result of the reduction in image contrast of a source of small apparent size due to optical blurring caused by the formation of the image. An analysis of the effect of apparent source size, the detector instantaneous field of view, and optical blurring on the image contrast produced by imaging IR sensor systems is presented.