Patent ID: 7988251
Filing Date: 2011-08-02
Classification: G06K

Abstract:
1. A method of printing from a printhead comprising a nozzle array for forming an image bitmap as ink drops on a print medium, said nozzle array being arranged substantially along a vertical advance direction of the print medium relative to the printhead, said nozzle array having a height of Z nozzles through which ink is ejected onto the print medium, said image bitmap being arranged in a pixel grid defining a series of vertically extending adjacent pixel columns and a series of horizontally extending raster lines, said adjacent pixel columns being horizontally spaced apart by a pixel column spacing, d, wherein raster lines are printed in a plurality of printing passes, each printing pass corresponding to one swath printed on said print medium, said method comprising the steps of: a) virtually dividing said nozzle array having an height of Z nozzles in at least one first nozzle section and at least one second nozzle section, wherein said at least one first nozzle section comprises a number of nozzles smaller than the number of nozzles of the second nozzle section; b1) providing N print masks associated to said at least one first nozzle section and to said at least one second nozzle section governing the deposition of the ink drops on the print medium, each of said N print masks being associated to one swath and being defined as a mask grid of first mask elements corresponding to pixel locations enabled for printing and second mask elements corresponding to pixel locations disabled from printing, said mask grid being arranged as a series of vertically extending adjacent mask columns and a series of horizontally extending mask rows, said vertically extending mask columns comprising enabling mask columns comprising the first mask elements and disabling mask columns consisting essentially of the second mask elements; b2) providing input image data corresponding to the image bitmap to be printed in said plurality of printing passes; c) providing said N print masks associated to said at least one first nozzle section and to said at least one second nozzle section for printing said input image, each of said print masks being defined as mask grid arranged in a N series of vertically extending adjacent mask columns and a series of Z horizontally extending mask rows, said series of mask rows being divided in at least two adjacent mask sections, a first mask section and a second mask section corresponding to said at least one first nozzle section and to said at least one second nozzle section respectively wherein the mask rows of said at least one second mask section are arranged spaced from one another by N−1 adjacent second mask elements and the mask rows of said at least one first nozzle section are arranged spaced from one another by 2N−1 adjacent second mask elements within the same mask row; d) performing an interleaving logical operation on said masked image data comprising removing the masked data columns of said masked image data essentially consisting of disabled pixel locations so as to create print image data arranged in a two-dimensional data array defined as a series of print data columns containing pixel locations enabled for printing; e) printing said first swath based on said print image data by providing a sequence of trigger signals having a time interval between signals of Δt for initiating firing of the nozzle array as said printhead moves horizontally over said print medium along a scan direction at an average printhead speed of N·d/Δt to deposit ink drops onto pixel columns containing enabled pixel locations; f) advancing the print medium relative to the printhead along a vertical advance direction substantially orthogonal to the scan direction; and g) continuing printing of the swaths repeating the requirements of steps b) to f) until said pixel grid has been printed on said print medium.