Patent ID: 8210645

Claim:
An image forming apparatus comprising: a recording head configured to form a pattern on a recording medium; a main scanning unit configured to change a relative position between the recording head and the recording medium in a main scanning direction perpendicular to an auxiliary-scanning direction; an auxiliary-scanning unit configured to change a relative position between the recording head and the recording medium in the auxiliary-scanning direction; and a processing unit configured to control the printing head, the main scanning unit and the auxiliary-scanning unit to form rows of dots extending in the main-scanning direction and columns of dots extending in the auxiliary-scanning direction using a plurality of partially overlapping main scans, wherein, when there is no scanning error, in a non-overlapping area, adjacent rows and columns of dots are at uniform grid locations, and in an overlapping area, adjacent rows are offset, in the auxiliary-scanning direction, by a distance smaller than a distance between adjacent columns, wherein dots in adjacent rows appear in alternating columns, and dots in adjacent columns appear in alternating rows.