Color printing using a vertical nozzle array head

A method of printing images by forming dots on a print medium using a print head including a first array including a plurality of dot formation element groups, each group comprising first dot formation elements configured to form color dots, and a second array including a plurality of second dot formation elements configured to form black dots, the first and second arrays arranged parallel along the sub-scanning direction, the first and second dot formation elements arranged at same sub-scanning positions in the sub-scanning direction, comprising steps of:

• sub-scanning said print medium, comprising
• repeating a sub-scan cycle including scanning k×s sub-scans and offsetting F after each said k×s sub-scans with a sub-scan feed amount L, wherein:
• k is 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 is an integer greater than zero and representing a number of main scans performed to form dots on each raster line,
• F assumes every value from 0 to k−1 s times and is a remainder of a division of ΣL by k,
• ΣL is a sum of each said sub-scan feed amount L,
• each said sub-scan feed amount L is an integer expressed as a number of dots, and
• an average sub-scan feed amount L for the k×s sub-scans in the one cycle is equal to ΣL/(k×s);
• each of said scanning k×s sub-scans step comprising main scanning said print medium including
• selecting a number N of first dot formation elements from each dot formation element group, N being an integer greater than 1,
• selecting j sets of the second dot formation elements, j being an integer greater than zero and each of j sets including N second dot formation elements, and
• printing using one set of the j sets and the number N of first dot formation elements of a specific color in said main scanning step.

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 scanning;
• 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;
• and
• a 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 color printing, a number N of the first dot formation elements of each color dot formation element groups, N being an integer greater than 1, to form dots on the print medium, and to use a number M of the second dot formation elements included in the second dot formation element array to form black dots, M being a second integer greater than N and equal to an integral multiple of N;
• the controller further being configured to execute overlap printing during color printing, said controller configured to form intermittent dots using a number (M-N) of the second dot formation elements at pixels on a same scanning line during a main scan pass and to form all dots on the same scanning line during plural said main scan passes.

A method of printing images by forming dots on a print medium using a print head including a first array including a plurality of dot formation element groups, each group comprising first dot formation elements configured to form color dots, and a second array including a plurality of second dot formation elements configured to form black dots, the first and second arrays arranged parallel along the sub-scanning direction, the first and second dot formation elements arranged at same sub-scanning positions in the sub-scanning direction, comprising steps of:

• selecting a number N of first dot formation elements from each dot formation element group, N being an integer greater than 1;
• selecting a number M of the second dot formation elements, M being a second integer greater than N and equal to an integral multiple of N;
• and
• overlap printing including forming intermittent pixels using a number (M−N) second dot formation elements in said same main scanning pass while forming all pixels on the same scanning line using plural said main scanning passes.