Symmetry Properties of Halftone Images II: Accounting for Ink Opacity and Dot Sharpness

Abstract

Previous work has shown that tone reproduction characteristics of halftone images can be modeled with knowledge of the probability function P00, for light to reflect from the paper between the halftone dots after having entered the paper between thehalftone dots. In the current report, experimental measurements of the micro-reflectance, Rp, of the paper between the dots is measured as a function of dot area fraction, F, and used with the model to calculate experimental values for P00 versus F. It is then shown that the model can be modified to account for inks that have significant scattering. The model is shown to fit data on halftones printed with electrophotography toner which is highly opaque. In addition, the model is further modified to account for the effects of the non-sharpness of the edges of halftone dots. Using both of these effects, the model is shown to fit well with measured data from a variety of AM and FM halftones printed at different resolutions with different colorants. In addition, the model is shown to fit experimental data on the tone reproduction characteristics of a ontinuous tone, electrophotographic, office copy machine.