Adaptive Methods for the Halftone Improvement in Conventional Screening Techniques

Non-periodic dot placement of the variety of so-called FM screening techniques results in greater NSR of the grey scale rendition and, hence, in lower printability as compared with a prevailing in commercial use regular halftone pattern. From the other hand, the finite screen ruling of the periodic halftones limits the definition of a printed image keeping it over a century, since the times of the halftoning invention, about ten times inferior to that of the plate making and printing processes. Nevertheless, the digital picture processing of today provides the facility to selectively modify the geometry of the microdot placement in a periodic screen pattern in accordance with the local image area content. That improves the picture sharpness and definition while preserving the printability (grey scale rendition) of a halftone structure for the stationary image area. Our patented adaptive screening approaches provided on the basis of the normal and excessive volumes of an input pictorial data are described here with comparison to the other high frequency filtration techniques and screening error corrections.