Hybrid gray level-spatial frequency pseudocolour encoding with phase filters

Abstract An optical filtering system which allows gray level pseudocolouring of different spatial frequency bands, so resulting in a hybrid gray level-spatial frequency pseudocolour encoding, is described. For such purpose, phase filters of appropriate shape, size and thickness are introduced in the Fourier plane of a polychromatic processor. The theoretical analysis and some experimental results are presented, showing the use of this hybrid gray level-spatial frequency encoder for image enhancement and analysis.