Patent ID: 8167412

Claim:
A dot position measurement method comprising: a line pattern formation step of recording dots continuously by a plurality of recording elements of a recording head while performing relative movement between the recording head and a recording medium in such a manner that a measurement line pattern including a plurality of lines of rows of the dots respectively corresponding to the plurality of recording elements is formed on the recording medium; a reading step of reading the measurement line pattern formed on the recording medium with an image reading apparatus in a state where a longitudinal direction of the plurality of lines of the measurement line pattern are directed to a sub-scanning direction of the image reading apparatus and a reading resolution in the sub-scanning direction of the image reading apparatus is lower than a reading resolution in a main scanning direction of the image reading apparatus in such a manner that an electronic image data indicating a read image of the measurement line pattern is acquired; a region allocating step of allocating a plurality of averaging regions where an image signal on the read image is averaged in terms of the sub-scanning direction, to different positions in terms of the sub-scanning direction of each of line blocks, each line block including the lines arranged in the main scanning direction; an average profile image forming step of averaging the image signal in terms of the sub-scanning direction in each of the plurality of averaging regions that have been allocated to the different positions and creating average profile images for positions in terms of the main scanning direction; an edge position determination step of determining positions of both edges of each of the lines according to the average profile images; an averaging region position determination step of determining positions of the lines in the plurality of averaging regions according to the determined positions of the both edges; and a line block position determination step of determining positions of the lines in the line blocks according to the positions of the lines in the plurality of averaging regions determined according to the average profile images corresponding to the plurality averaging regions respectively.