Properties of Frame-Difference Signals Generated by Moving Images

The properties of the frame-difference signals arising from updated "moving" areas and nonupdated "stationary" areas in conditional replenishment interframe encoders are examined. Expressions for the correlation functions and power density spectra of these signals are developed assuming an infinite image field undergoing uniform linear motion. These expressions are modified so as to include the effect of camera integration. Experimentally obtained power spectra are in good agreement with those predicted. Three-dimensional frame-difference correlation functions are evaluated using a realistic image correlation function. The properties of the frame-difference correlation functions in directions parallel and perpendicular to the direction of movement, and in the temporal direction are delineated. It is shown that the correlation function of the frame-difference signal arising from temporally uncorrelated noise is fundamentally different in updated areas compared with nonupdated areas.