Colorspan Corporation

John Patrick Novotny

Robert Anthony Laumeyer

Lawrence J Lukis

Paul R Erickson

David H Bennefeld

Neill Arthur Johnson

An ink on demand type ink jet head energization system is provided to drive ink out of a nozzle in the head. The head contains at least one nozzle for discharging ink. The power applied to the nozzle is modified to include a noise component. By providing a driving voltage which varies between firings, the head produces ink droplets which differ in size between firings. Preferably, the voltage is randomly or pseudo-randomly varied over a range of from 50 to 100% of maximum voltage, and a new voltage is provided for each successive firing of the head. This variation of drive voltage produces ink dots which randomly vary in size at a rate too dense to be perceived by a viewer, and successfully reduces perceived artifacts in the printed output.

Ink jet printer with artifact-reducing drive circuit

The present invention relates to the a method usable in the field of printing, and in particular to a method of characterizing a drum-based digital print engine so that each of a plurality of ink droplets propelled toward a common picture element location, or pixel, of a print media coupled to an exterior surface of a rotating drum member precisely reaches the same pixel location irregardless of slight variations in portions of the surface of the drum. In a preferred embodiment, a drum based printing system contains eight print heads mounted on an axially driven carriage assembly and arranged in two rows of four such that no two print heads prints upon a common print swath at any given time, and each row of print heads is further oriented rotationally around a portion of the circumference of the drum member. All print heads operate relatively independently of fixed firing locations, and instead operate based on a first firing printing head so that each subsequent print heads fire only after a predetermined delay due simply to its rotational and axial displacement from the first print head. Slight variations in the surface of the drum and non concentric alignment of a rotation sensor coupled to the axis of rotation of the drum are compensated during initial assembly of the print engine. In one embodiment, this technique allows implementation of effective and simple calibration process for a four hundred nozzle wide format ink jet digital print engine during printing by an end user.

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Burnsville, MN, United States of America

John Patrick Novotny