A Study On Color Halftone Spectral Model Based On Spectral Analysis

In order to reduce the metamerism caused by the colorimetric reproduction, people pay more and more attention to the spectral reproduction. The model of the Spectral-Based Printer Characterization ,namely color model to map reflectance spectra of the printer output image to the input digital counts of inks, has been focused on in recent years. Lots of halftone color models have been applied at present, such as Neugebauer model(N),Yule-Nielsen model(YN), Clapper-Yule model(C-Y) and Williams–Clapper model, but only the Yule-Nielsen modified Spectral Neugebauer model(YNSN) is used widely in actual application. This paper mainly discusses the printer characterization based on the YNSN spectral model.In the YNSN model, although the modified n-value takes optical dot gain into account ,this model neglects the dot gain caused by ink spreading and interaction between ink and paper. This paper improves the YNSN model wihh physical considerations , that is EYNSN spectral model. Firstly, considering the different ink superposition conditions in the stochastic screens,rotated screens and dot-on-dot screens, we establish dot gain functions model of ink spreading between effective dot area coverage and theoretical area coverage,also,considering spectrum redundancy of pure and chromatic black and restrictions on the amount of inks, this EYNSN model is extended to the near-infrared domain ,namely IRYNSN model referred to as the ink spreading and near-infrared enhanced Yule-Nielsen modified Spectral Neugebauer model. At the same time , according to the fact of the phenomenon that not all superposition conditions are useful and the ink spreading curves on solid black do not improve the accuracy of model, we therefore propose halftone black model relying on a reduced set of ink spreading equations. Finally, the paper presents IREYNAN model to spectral-based characterization of ink-jet color printers and definition of a large number of parameters using genetic algorithms,then show spectral accuracy in terms of mean root mean squared error .Our method has practical significance and is convenient with LUT approaches.