Abstract

When an object (target) is illuminated by an electromagnetic field, the energy it scatters to a given observation point depends upon its geometry and material characteristics, the conditions of illumination (angle of incidence, polarization, frequency(ies), etc.) and the medium through which the field propagates. It is intuitively obvious, and demonstrated by analysis and measurement, that the scattered field (which will also contain, in general, interference and/or noise energy) has impressed or encoded on it information about the target which might somehow be extracted for purposes of: 1) detection (i.e., is there a target?); 2) classification (determine whether the target belongs to a class of interest); 3) recognition (if in the class of interest, which one of that class is it?) and 4) imaging or inversion (reconstruct the target's geometry and/or material properties).*

© 1983 Optical Society of America