Spectral Color Prediction by Advanced Physical Modelling of Toner, Ink and Paper, with Application to Halftoned Prints

摘要

A new spectral color prediction model for prints is presented, which is based on the combination of ray-tracing, Mie scattering and Monte Carlo simulation. The wavelength dependent radiation transfer properties of ink or toner are determined by means of physically modelling the ingredients. The resin is described using optical constants, whereas the dyes use an absorption coefficient, and fluoresent re-emission probabilities. The scattering and absorption properties of pigments are described by the Mie theory, using realistic optical constants and particle size distributions. Knowing the radiation transfer properties of the used materials, geometric objects like dots or layers are illuminated by a light source with adjustable spectral and directional characteristics. The angle and wavelength dependent reflectance and transmittance are obtained. The simulated reflection spectra agree well with measured data. Finally we combine printed patterns with a paper model containing scattering and fluorescent properties. In this way reflection spectra of printed samples are modelled succesfully. The chosen approach is unique and more powerful than standard methods like Kubelka-Munk. Former difficult aspects of color prediction like surface gloss, angle-dependent scattering and fluorescence of dyes are an intrinsic outcome of this new model. The model is appropriate to make an accurate color prediction of halftoned prints.