Charge deposition print head and method of printing

Abstract

A print head has a matrix array of charge generating loci defined by crossings of a first set of electrodes which are parallel to each other and extend across the region to be printed and a second set of electrodes that extend obliquely across the first electrodes so that the crossings are closely spaced lattice points. The charge deposited by a lattice point varies with the position of the first electrode defining the point, but the electrodes are arranged so charge carriers are generated or gated for projection onto a latent imaging member with local charge dot uniformity. In one embodiment of the invention, there are an odd number of first electrodes, and the second electrodes are arranged such that when electrodes are actuated, pairs of adjacent dots are deposited by pairs of lattice points having complementary variations in charge. As viewed or measured along the print line, each pair of deposited dots has a substantially uniform level of charge, and doubling and extreme discontinuities do not occur. The second electrodes may overlap in a cross scan direction to interleave their deposited charge dots. Alternatively, using zig-zag but non-overlapping electrodes, each electrode may deposit a continuous uninterrupted sequence of dots while still achieving a uniform regional charge distribution. In another aspect, the second electrodes include first and second subsets of electrodes having a different pitch defining two sets of charge loci at lattice points slightly shifted in the cross-scan direction to interleave strong dots with weak dots without doubling. This embodiment includes print heads with an even number of first electrodes without introducing aliasing patterns of charge density.