Hewlett-packard Company

Warangkana Tepmongkol

Jerry Yeeming Chung

Compensation for pixel aberrations in a laser printer is accomplished by selecting pixels to be augmented, and providing additional optical energy to the selected pixels. In one embodiment, the pixels are selected by selecting pixels in combinations in which required pixel augmentation is indicated. The additional optical energy may be applied at the sub-pixel level so that a threshold of energy depletion on an optical photoreceptor (OPR) is not reached where image development would occur. The energy applied at the sub-pixel level results in enhancement of the selected pixels at an adjacent pixel location.

Dot enhancement for laser imagers

In its basic aspects, the present invention uses a 3.times.3 data window to examine and to convert data in a 2.times.-resolution enhancement. Data is altered from a linear 2.times.-expansion method if and when the 3.times.3 data meets four criteria that determines the frequency content of the original 3.times.3 data window subset. The criteria are deterministic of whether a random pattern--such as in a graphical artwork figure--or a logical frequency domain pattern--namely text characters, numbers, or the like--are being printed. The method is particularly useful in dot matrix, or bit mapped, printing and the like. The data smoothing method is employed only after it is determined that a logical frequency domain pattern is being analyzed.

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Boise, ID, United States of America

Warangkana Tepmongkol