Spatial filtering and image positive-negative reversal.
A generalized analysis of spatial filtering of object transparencies modulated by (TV) raster lines has been developed from which various particular cases and also the limits and approximations of the processes appear naturally. It can be seen that the positive-negative reversal of the filtered image depends upon the nature of the modulating lines (opaque or clear) and also on the order of the Fourier spectrum that forms the image. The same analysis (one dimensional) can also explain, in principle, the behavior of the filtered images from half-tone transparencies. The experimental results reported support the analysis.
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Roychoudhuri
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Malacara