Patent ID: 6050675
Filing Date: 2000-04-18
Classification: B41J

Abstract:
A method for operating an ink jet printer having a platen on which a printing medium is arranged, a printhead in proximity to the platen, said print head comprising a plurality of nozzles for ejecting ink onto the printing medium, means for moving the print head in a first direction across the printing medium and means for moving the printing medium in a second direction which is substantially perpendicular to the first direction, said method comprising the steps of:a) depositing a swath of N bands of ink required for forming desired markings on the printing medium in several passes of the print head across said printing medium, wherein N is an integer value, said depositing, during one pass, including the substeps of:(i) controlling ink election from subsets of nozzles of said plurality of nozzles so that only a first subset of said nozzles is activated, such that during said one pass of the printhead, a first amount of ink that is a fraction of total ink required to form the desired markings is ejected from said first subset of nozzles in a first band of the print head, whose position relative to the platen results in errors of placement of ink dots on the printing medium, and(ii) further controlling ejection of ink from a second subset of said subsets of nozzles in a second band of said N bands so that a second amount of ink that is greater than said first amount of ink is ejected therefrom, where resulting errors of placement of ink dots on the printing medium are smaller than for the first band;b) moving the printing medium in the second direction between passes of the printhead by an amount that is less than a width of a swath; andc) repeating steps a)(i) and a)(ii) during another pass to overprint ink dots in said bands.