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ADAPTIVE HALFTONING FOR ARRAY INK JET PRINTING

IP.com Disclosure Number: IPCOM000025545D
Original Publication Date: 1986-Feb-28
Included in the Prior Art Database: 2004-Apr-04
Document File: 2 page(s) / 91K

Publishing Venue

Xerox Disclosure Journal

Abstract

For ink jet and similar processes which require accurate single pixel rendition, the class of adaptive algorithms, like the Floyd technique for digital halftoning, performs well and are particularly resistant to the type of drop placement errors experienced by such processes. The process information given to this algorithm describes the density increase produced by blackening a pixel on the recording medium with a droplet, given the black pixels present in the neighborhood. Excellent prints have been produced using this technique over a wide range of process conditions, The major defect, and one that would become critical in subtractive color processes, is the signature of the nozzle plate in ink jet printing systems. In continuous stream ink jet array printing, each nozzle prints a narrow stripe down the page as it moves thereby. Sensors and control electronics insure the abutment of these regions. The size of the droplets from each nozzle IS

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XEROX DISCLOSURE JOURNAL

ADAPTIVE HALFTONING FOR ARRAY INK JET PRINTING

Peter A. Crean

Proposed ClassLf ication
U.S. CI. 346/1.1 Int. CI. Gold 9/00

For ink jet and similar processes which require accurate single pixel rendition, the class of adaptive algorithms, like the Floyd technique for digital halftoning, performs well and are particularly resistant to the type of drop placement errors experienced by such processes. The process information given to this algorithm describes the density increase produced by blackening a pixel on the recording medium with a droplet, given the black pixels present in the neighborhood. Excellent prints have been produced using this technique over a wide range of process conditions, The major defect, and one that would become critical in subtractive color processes, is the signature of the nozzle plate in ink jet printing systems. In continuous stream ink jet array printing, each nozzle prints a narrow stripe down the page as it moves thereby. Sensors and control electronics insure the abutment of these regions. The size of the droplets from each nozzle IS

sufficiently uniform so that solid black regions are perceived to have the same density. For regions of partial coverage, droplet size variations of a few percent are visible, and for color images, the perceivable limit is finer.

Accordingly, it 1s necessary to compensate for the measured array characteristics in creating the digital halftone image, so that they do not appear as visible defects in the print. In particular, when the adaptive halftone algorithm decides to print a droplet, it projects the local density increase produced by the actual nozzle covering that part of the page. Thus, the bit map produced will, when printed on the target printer, render the tonal content of the digital origi...