TILTED DEFLECTION ELECTRODE METHOD AND APPARATUS FOR LIQUID DROP PRINTING SYSTEMS

A liquid drop (i.e. ink jet) printing system is disclosed of the type wherein many parallel drop streams are continuously generated. Selected drops from each stream are deflected laterally to address the multiple pixels of a segment of a raster image scan line. The scan line segments addressed by each stream collectively compose a full scan line of a raster image. The drops are deflected by electrostatic fields tilted relative to the scan line to compensate for drop placement errors due to the relative motion between a target and the drop generator. The tilted fields are created in the spaces between interleaved teeth of two electrode members resembling garden rakes. The teeth are triangular, in cross-section at least partially, to tilt the fields. In addition, a drop collection gutter is positioned adjacent each tooth of one of the rake members. The gutter collects drops from adjacent streams not intended for marking a target. The drops within adjacent streams are swept in opposite directions. The alternately tilted (clockwise and counterclockwise) deflection fields and the appropriate sweep direction are selected for a given target direction of travel. The rake members move apart during start up and shut down of the drop streams.