Lexmark International, Inc.

George Peter Olson

Gregory Lawrence Ream

Douglas Anthony Able

Thomas Campbell Wade

Cyrus Bradford Clarke

Daniel George Mlejnek

Mark Edwin Kirtley Lund

An improved EP printer will automatically compensate for printer output darkness shift over the usage life of one or more components of the print engine. In many EP print engines, the printer output darkness without correction will gradually change as the components are used, and typically, the darkness will increase to an extent that is perceptible. The printer output darkness can be controlled using a EP operating point that changes certain operating parameters, such as the laser diode current, the duty cycle of the video data signals driving the laser diode, and other voltage parameters including the charge roller voltage, or the developer bias voltage. It is desirable to make adjustments over the usage life of these components, so as to maintain the initial printer output darkness throughout the life of the major system components. The adjustments can occur at periodic intervals based upon a metric that includes one or more of the following parameters: number of pels produced, number of pages printed, number of cycles of one or more components of the print engine, and/or the consumption of toner in grams. The adjustment information can be provided as look-up tables, or in the form of transfer functions. If look-up tables are used, the adjustment control algorithm could be one that interpolates between periodically-adjusted usage values stored in the look-up tables. Since many EP process cartridges tend to print darker rather than lighter over the life usage of that process cartridge, the present invention will accomplish two important goals by utilizing the methodology described above; not only will the printer output darkness be maintained at a substantially constant value, but the actual number of pels printed and pages printed will be increased by use of the same quantity of toner stored within the replaceable process cartridge.

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Lexington, KY, United States of America

George Peter Olson