Spectral analysis and minimization of moire patterns in color separation
Undesired moire patterns may appear in color printing for various reasons. One of the most important reasons is interference between the superposed halftone screens of the different primary colors, due to an improper alignment of their frequencies or orientations. We explain the superposition moire phenomenon using a spectral model that is based of Fourier analysis. After examining the basic case of cosinusoidal grating superpositions we advance, step by step, through the cases of binary gratings, square grids, and dot screens, and discuss the implications on moires between halftone screens in color separation. Then, based on these results, we focus on the moire phenomenon from a different angle , the dynamic point of view: We introduce the noire parameter space and show how changes in the parameters of the superposed layers vary the moire patterns in the superposition. This leads us to an algorithm for moire minimization that provides stable moire-free screen combinations for color separation.