In this study, a technique which enhances image contrast using differentials of radiances being measured from successively over-lapping footprints is discussed. One of the immediate advantages of this approach is to improve spatial resolution when the practical size limitation of detectors is reached. When diffraction is considered, radiometric accuracy at the higher spatial frequencies is decreased even though edge response (boundary crossing sharpness) will improve. For instance, an imager system based on this principle could have a primary aperture no larger than 30 cm diameter yet be capable of resolving a ground footprint as small as 2 m from a 780 km altitude.
Honctsuk H. Kim,
Gregory C. Elman,
"Differential Imaging System", Proc. SPIE 1153, Applications of Digital Image Processing XII, (30 January 1990); doi: 10.1117/12.962355; https://doi.org/10.1117/12.962355