Patent ID: 6527359
Filing Date: 2003-03-04
Classification: B41J

Abstract:
A printing apparatus that carries out bidirectional, reciprocating main scan to effect printing on a printing medium, the printing apparatus comprising:a print head having a nozzle group that ejects ink droplets to record dots on the printing medium; a memory that stores a correction value, the correction value being used to correct misalignment of recording positions in a main scanning direction on a forward pass and a backward pass of the main scan; and a positional misalignment correction unit that corrects, using the correction value, the misalignment of recording positions in the main scanning direction occurring in bidirectional printing, wherein the correction value is determined according to correction information that represents a favorable correction state selected based on a positional misalignment test pattern, the positional misalignment test pattern including a rear test sub-pattern and a front test sub-pattern printed at different positions shifted in a sub-scanning direction, the front test sub-pattern being printed with a front nozzle sub-group on the printing medium on a selected one of the forward pass and the backward pass of the main scan of the print head, the front nozzle sub-group being not an entirety but part of the nozzle group and including nozzles located in a relatively forward section of the nozzle group in the sub-scanning direction, the front nozzle sub-group being selected to eject a first identical color ink, the rear test sub-pattern being printed with a rear nozzle sub-group on the printing medium on the other of the forward pass and the backward pass of the main scan of the print head, the rear nozzle sub-group being not the entirety but part of the nozzle group and including nozzles located in a relatively backward section of the nozzle group in the sub-scanning direction, the rear nozzle sub-group being selected to eject a second identical color ink, wherein at least one nozzle in the rear nozzle sub-group is not in the front nozzle sub-group, and at least one nozzle in the front nozzle sub-group is not in the rear nozzle sub-group, and the relatively forward and backward sections respectively cover a same range in the sub-scanning direction.