Data Products Corporation

Hitachi Koki Imaging Solutions, Inc.

Said Zandian

Leo J Rheingold

James Estrada

A multi-level printer is controlled to selectively enhance each pel, based on an error diffusion process. However, each channel (e.g., RGB red, green and blue color channels; Lab luminance, red direction and blue direction channels; or other suitable channel division) is processed individually according to a suitable kernel to provide a multi-color image. The printer is capable of providing a plurality of 'actual' levels of enhancement to a pel for any particular channel. The 'desired' image defines a 'desired' level of enhancement for each pel in each channel. Correlation bins are defined for each actual level of enhancement for associating each 'desired' level of enhancement for each pel in each channel with an actual level of enhancement. An error value based upon the selected actual level of enhancement and the desired level of enhancement is diffused to the neighboring pels according to a kernel. Also, the order of processing individual pels and the error diffusion matrix are both reversed for each subsequent line of pels. It has been found that each one and various combinations of these features significantly improves image clarity, sharpness and tone continuity.

Color imaging

A bi-level printer is controlled to selectively enhance each pel, based on an error diffusion process. However, each channel (e.g., RGB red, green and blue color channels; Lab luminance, red direction and blue direction channels; or other suitable channel division) is processed individually according to a suitable kernel to provide a multi-color image. In addition, an individual 'threshold' level (by which the 'actual' state of enhancement of a pel is determined) is calculated for each color channel, based on the minimum and maximum enhanced levels of all of the pels in the 'desired' image. Also, the order of processing individual pels and the error diffusion matrix are both reversed for each subsequent line of pels. It has been found that each one and various combinations of these features significantly improves image clarity, sharpness and tone continuity.

A method and apparatus for printing an image on a printing medium with phase change ink, the printing medium providing a printing area composed of a plurality of parallel pixel rows extending in a first direction, with a uniform spacing, p, between pixel rows in a second direction perpendicular to the first direction, with each row being made up of a plurality of elemental pixel areas. Printing is effected with a print head having at least one set of N nozzles for projecting drops of phase change ink onto the printing area, N being an integer and the nozzles having a uniform spacing, in a direction corresponding to the second direction when the print head faces a printing area, equal to s.multidot.p, s being an integer smaller than N and greater than unity, and relative movement is effected between the printing medium and the print head such that there are successive relative movements in the first direction while drops of phase change ink are projected onto respective pixel areas; and, in alternation with the successive movements in the first direction, there are stepwise relative movements in the second direction such that each stepwise movement in the second direction has an amplitude equal to an integral number multiple of p, which number is not equal to s, and the sum of the amplitudes of every two successive movements in the first direction is less than the product of N, s and p.

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Agoura, CA, United States of America

Said Zandian