Correcting variations in ink discharge velocity in a printer by printing a test pattern and adjusting a printing position shift

A printing apparatus, having scanning means for reciprocally scanning a printhead, for performing printing on a printing medium by discharging ink from said printhead while scanning said printhead by said scanning means, comprising:

• test pattern printing means for test-printing a plurality of patterns, wherein the plurality of patterns are patterns printed by changing a printhead scanning speed;
• selection means for selecting one of the plurality of patterns;
• memory means for storing information on an ink discharge velocity from said printhead corresponding to a printhead scanning speed used for test-printing the pattern selected by said selection means;
• calculation means for calculating a correction amount for correcting a printing position shift when printing on a printing medium is performed by discharging ink from said printhead, based on a pattern selected from the plurality of patterns by said selection means;
• and
• printing means for performing actual printing while performing correction based on the correction amount calculated by said calculation means,
• wherein said calculation means calculates the correction amount, based on the information stored by said memory means, and
• said test pattern printing means test-prints by controlling ink discharge from the printhead according to the changed printhead scanning speed.

A computer program product executable in a computer for correcting a printing position shift when printing on a printing medium is performed by discharging ink from a printhead while reciprocally scanning the printhead, comprising:

• a test printing process code for causing an inkjet printer to test-print a plurality of patterns, wherein the plurality of patterns are patterns printed by changing a printhead scanning speed;
• a selection process code for selecting one of the plurality of printed patterns;
• a storage process code for storing information on an ink discharge velocity from the printhead used for test-printing the selected pattern after performing said selection process into a memory;
• and
• a calculation process code for calculating a correction amount for correcting the printing potion shift, based on the selected pattern,
• wherein said calculation process calculates the correction amount, based on the information stored in the memory, and
• said test-printing process code causes test-printing to be performed by controlling ink discharge from the printhead according to the changed printhead scanning speed.