Inkjet printer and ejection timing correction method

An ejection timing correction method used in an inkjet printer including a first outlet row and a second outlet row that are arranged in a predetermined movement direction, for correcting ejection timing of said second outlet row with respect to ejection timing of said first outlet row,

• said inkjet printer including:
• a head that ejects fine droplets of ink toward a base material;
• and
• a movement mechanism that moves said base material in said movement direction relative to said head,
• wherein said head includes said first outlet row and said second outlet row, each including a plurality of outlets arranged with a fixed outlet pitch in a direction that intersects said movement direction, and
• each outlet in said second outlet row is disposed between each pair of adjacent outlets in said first outlet row with respect to a width direction perpendicular to said movement direction,
• said ejection timing correction method comprising the steps of:
• a) with said movement mechanism, moving said base material in said movement direction relative to said head;
• b) with said head, recording uniform images in a plurality of check regions, each being a region of a predetermined size on said base material, according a predetermined rule, said step b) being performed in parallel with said step a);
• c) specifying a maximum density check region that has a maximum dot area rate in the uniform image, out of said plurality of check regions;
• and
• d) correcting ejection timing of said second outlet row with respect to ejection timing of said first outlet row based on said maximum density check region,
• wherein under said predetermined rule, assuming that a plurality of dots arranged in said width direction is taken as a dot row in the uniform image in each check region, a combination of a first dot row formed with said first outlet row and a second dot row formed with said second outlet row while being spaced apart from said first dot row in said movement direction is repeatedly arranged with a fixed pitch in said movement direction, and when the uniform image is recorded in said each check region, a distance that is obtained by changing a reference distance, which is half said pitch, by a set shift amount is assigned as a distance between said first dot row and said second dot row, said set shift amount being progressively changed for said plurality of check regions,
• in said plurality of check regions, an overlapping area of said first dot row and said second dot row varies depending on an actual shift amount of a distance between said first dot row and said second dot row from said reference distance, and
• in said step d), said ejection timing of said second outlet row is corrected based on a set shift amount corresponding to said maximum density check region.