Raster in scanned imagery can be suppressed to improve visual observation of image detail. In the work reported here this is accomplished by optimal choice of the scanning spot and/or by optimal smoothing. Both techniques are based on selection of a Wiener filter. The optimal spot is shown to extend only over two scan lines, for scenes with 1 /f2 power spectra. The filter is designed to be used in an incoherent imaging system. It is constrained to a phase-only approximation of the optimum complex filter to avoid reducing light level in the optical system. Experimental results demonstrate the effectiveness of the filter design.
Robert A. Gonsalves,
Philip S. Considine,
"Spot Shaping and Incoherent Optical Smoothing for Raster Scanned Imagery," Optical Engineering 15(1), 150164 (1 February 1976). https://doi.org/10.1117/12.7971911