Lasermaster Corporation

Colorspan Corporation

David H Bennefeld

Danny James Vatland

Paul R Erickson

John M Gilbert

John Patrick Novotny

Jonathan D Elliot

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

A thermal printer includes a thermal print head having a plurality of heating elements for printing dots. A source of drive pulses operates respective heating elements. Each drive pulse is modulated to provide first and second periods of the drive pulse to selectively energize the respective heating element, the first and second periods defining a selected energy level. A memory stores the modulated drive pulses and supplies respective modulated drive pulses to the respective heating elements. A measuring circuit measures a heating factor of each heating element and provides a correction factor for each heating element based on the respective measured heating factor. The correction factors are combined to the respective drive pulses to alter the first and second periods, thereby reducing variations in dots due to differences in the heating factors of the heating elements.

Heating control for thermal printers

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Ramsey, MN, United States of America

David H Bennefeld