Control system for ion projection printing and the like

Abstract

A print engine including a two-dimensional matrix print head is operated by data signals from a raster image processor through a distributed digital controller having a master controller and a plurality of separate controllers each for a separate set of elements along one of the dimensions of the array, specifically the finger control electrodes of an ion projection printing head. The elements along the other dimension of the array (the RF electrodes of the ion projection head) are controlled by the master controller which also controls the timing of writing of the pixel data signals into memories associated with each of the distributed controllers and the timing of the readout of the pixel data to the finger control electrodes in synchronism with the activation of the RF electrodes and the movement of a medium on which the image is printed so as to print portions of each line in sequence (interleaving dots representing pixels on each line) to form the image on the medium. The pixel data is in the form of digital grey-scale data words representing the grey scale or density of the pixels. The distributed controllers have counters which are preset by the grey-scale data words and deliver pulses of duration (a pulse width modulated output) which varies the density or grey scale of the dots.