Patent ID: 6267467
Filing Date: 2001-07-31
Classification: B41J,G06K

Abstract:
A printing apparatus that prints images by forming dots on a print medium, comprising:a print head that includes a plurality of dot formation elements configured to form dots on the print medium;a main scanning drive section that drives at least one of the print head and the print medium for a main scan;a head drive section that, during the main scan, causes at least a portion of the plurality of dot formation elements to form dots;a sub-scanning drive section that, upon a completion of each main scan, drives at least one of the print head and the print medium for a sub-scan; anda controller configured to control the main scanning drive section, the head drive section, and the sub-scanning drive section;wherein:the print head including a first dot formation element array and a second dot formation element array;the first dot formation element array including a plurality of color dot formation element groups arranged in the sub-scanning direction and configured to form dots with color inks, each of the plurality of color dot formation element groups including an equal number of first dot formation elements;the second dot formation element array including a plurality of second dot formation elements arranged parallel to the first dot formation element array and configured to form black dots;the plurality of second dot formation elements disposed at same sub-scanning positions as the first dot formation elements included in the plurality of color dot formation element groups;the controller being configured to use, during a color printing, a number N of the first dot formation elements of each color dot formation element group, N being an integer greater than 1, to form dots on the print medium, and to use j sets of the second dot formation elements included in the second dot formation element array, j being a second integer greater than 0, each set of second dot formation elements comprised of N dot formation elements, to form black dots;one set of the N second dot formation elements being disposed at same sub-scanning positions as the N first dot formation elements for a specific color ink, the one set of the N second dot formation elements and the N first dot formation elements for a specific color ink being used in a same main scanning pass to form black dots and color ink dots of the specific color ink on the same scanning lines;the controller being programmed to control the main scanning drive section and the sub-scanning drive section such that, with respect to each ink,(i) one cycle of sub-scans, which is repeated during printing, includes k.times.s sub-scans, k being an integer greater than 1 and representing a pitch of the dot formation elements expressed as a number of dots in the sub-scanning direction, s being an integer greater than zero and representing a number of main scans performed to form dots on each raster line,(ii) an offset F after each said k.times.s sub-scans assumes every value from 0 to k-1 each s times with a sub-scan feed amount L in the one cycle, the offset F being a remainder of a division of .SIGMA.L by k, .SIGMA.L being a sum of each said sub-scan feed amount L, each said sub-scan feed amount L being an integer expressed as a number of dots, and(iii) an average sub-scan feed amount L for the k.times.s sub-scans in the one cycle is equal to .SIGMA.L/(k.times.s).