Research on secondary colour optical dot gain model in electrostatic digital colour printings

摘要

Screening dot is the basic printing element to reproduce continuous image and to form the printing image. Printing quality depends on the transfer quality of the screening dot. It is important to control the dot gain, sharpening, deformation, doubling and slur. In practice, some specific quality control techniques are used to monitor the screening dot variation. For dot gain control technique, multi-colour scales are often used to investigate dot gain or tone change. This article aims to investigate the secondary colour dot gain in electrostatic digital printing, by considering dot gain of the colour scales, Cyan, Magenta, Yellow, Blue, Red and Green. The relations between secondary colour dot gain and primary colour dot gain are studied. Three primary colour scales, Cyan, Magenta, Yellow, and three secondary colour scales, Blue, Red and Green, are designed from 2 % to 90 %. The colour scales are output by electrostatic colour press and measured by spectrophotometer. The dot gain of the secondary colour scales is modelled according to the dot gain rules of the primary colour scales using multiple linear regression method. The results illustrate that the dot gain of secondary colour changes with the dot gain of primary colour scales synchronously, and that further research is needed to make for dot gain compensation and printing process control.