Hewlett-Packard Company

John T Eaton

Jason M Quintana

George Barbehenn

Carl Eric Thomsen

The present invention provides a method for compensating for the velocity variation in an ink-jet pen by dynamically varying the ink drop firing timing as a function of pen velocity. This makes it possible to print while the pen is accelerating or decelerating without affecting image quality. Scanning velocity change compensation is dynamically and continuously updated at a rate equal to or greater than an encoder edge rate. Further, the present invention provides a method for improving ink drop positioning accuracy across a print media scan by compensating for the change in ink-drop flight time as printhead-to-paper distance changes. Ink drop flight time error is dynamically compensated such that a fired droplet of ink hits its intended target pixel without any appreciable error.

Method and apparatus for compensating for variations in printhead-to-media spacing and printhead scanning velocity in an ink-jet hard copy apparatus

In thermal inkjet printing, an energy source supplies voltage pulses to a set of resistors in a printhead. The resistors are not necessarily equal-valued. The subset of energized resistors changes from pulse to pulse as a function of the printable data. As the subsets vary, resulting in a varying load on the energy source, this causes undesirable variations in the energy supplied to individual resistors, even when a regulated source is used, because of residual impedances in the source and wiring. The invention compensates for such energy variations, using information about which subset of resistors is to be energized during a pulse. By determining the electrical load presented by the subset, and by referring to a predetermined relation between the load value and the voltage drop in the residual impedances, the invention maintains nominally constant energy in individual pulsed resistors by an appropriate adjustment of the pulse width.

Reducing energy variations in thermal inkjet printers

A battery charge level monitor for a computing system is presented. The monitor stores a value representing the charge stored in a battery. The value is varied to take into account battery charge depletion resulting from operations by the computing system, and to take into account charge added to the battery by a recharger. An operator can access the value through computer commands or by automatic display of the value by the computing system.

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Vancouver, WA, United States of America

John T Eaton