Coalescence constraints for inkjet print mask optimization

A print mask is a unique way of controlling the firing sequence of nozzles in inkjet printing. It is desirable to design a print mask which maximizes throughput while maintaining desired image quality. This can be formulated as an optimization problem where the objective is to maximize throughput by minimizing printing time subject to image quality constraints under uncertainties and variations in the printing process. Coalescence is an important image quality artifact. This paper outlines the development of a coalescence model, which can be used as an image quality constraint in finding an optimal print mask. The proposed coalescence model computes the probability of coalescence as a function of time between two adjacent drops. Monte Carlo simulation is used based on experimentally obtained distributions of model parameters. Given an acceptable coalescence probability the minimum printing time between adjacent drops can be determined, which translates to a minimum distance between pixels in a print mask that can be printed on the same pass.