Most existing forward looking infrared systems (FLIRs) are based on parallel scanning of the object by rotating a mirror across a vector detector which has a relatively small number of elements (typically 60 - 180). In order to get a good picture, it is necessary to fill all the lines of the display with information which has been achieved from a small number of elements. The benefits of this line filling (multiplication) operation which is an interpolation process is to increase overall system magnification hence improving the modulation transfer function (MTF) of the eye and the display. This process also allows the display of the image without geometric distortion on a pleasant, not too high, picture width to height ratio (aspect ratio). Concerning the MTF of the display, the line multiplication operates in two ways. It increases the MTF by scaling down the display Gaussian point spread function width due to increased magnification but, as we shall show, also decreases the MTF because after the line filling process, the image is composed of several sub-images each of which includes a different set of display lines. The MTF of each of these sub-images may be decreased and the sub-images themselves, their line of sight, may be shifted one to the other. In this work we shall quantify the resolution loss that had not been considered previously in terms of explicit MTF which can be grouped together with other system MTFs in performance simulation. We shall also describe artifacts which might appear as a result of line multiplications in imaging of time-varying scene. KEYWORDS: IR imaging, display MTF, Interpolation

Date Published: 8 September 1995
PDF: 10 pages
Proc. SPIE 2552, Infrared Technology XXI, (8 September 1995); doi: 10.1117/12.218207

Published in SPIE Proceedings Vol. 2552:
Infrared Technology XXI
Bjorn F. Andresen; Marija Strojnik, Editor(s)