Shadow pulse compensation of an ink jet printer

Abstract

In an electrostatic ink jet printer, all nozzles of a printhead are spaced generally the same distance from a moving paper print substrate. Three voltage levels are selectively applied to each nozzle of the printhead. As the paper moves past the printhead, a bias voltage Vb is applied to all nozzles which have a static protruding meniscus which shape is determined by a balance between the internal pressure, surface tension, and bias voltage. When the paper arrives at a print row, nonprinting nozzles have a shadow voltage pulse Vs, the 'shadow pulse,' applied thereto, and printing nozzles have a higher magnitude print pulse Vp applied thereto. The magnitude of the shadow pulse Vs causes an additional excursion of the ink meniscus to form at each non-printing nozzle. The higher magnitude of print pulse Vp causes an ink filament to move from a printing nozzle to the paper. The time duration of each print pulse is varied in accordance with an ink density parameter up to a range that is determined by the duration of the shadow pulse. The electrostatic field difference between nonprinting and printing nozzles (Vp-Vs) is of a low magnitude that inhibits ink filament deflection and ink volume differences due to crosstalk between nozzles.