Patent ID: 7978987

Claim:
An image forming apparatus comprising: an image forming portion having a rotator and being configured to form an image on at least one of said rotator and a recording medium traveling with rotation of said rotator; a storage portion configured to store change characteristics information relevant to correction parameters corresponding to phase points of said rotator; a designating portion configured to sequentially designate said correction parameters based on said change characteristics information; a correcting portion configured to correct an image forming position on said at least one of said rotator and said recording medium based on the correction parameter designated by said designating portion; a detecting portion configured to detect when said rotator has reached a detecting phase point; a determining portion configured to determine, based on a time when said detecting portion detects said detecting phase point of said rotator, whether a current phase of said rotator corresponds to a gradual phase point at which said correction parameter changes at a rate equal to or lower than a predetermined value; and a shifting portion configured to shift a designation by said designating portion to the correction parameter corresponding to said gradual phase point when said determining portion determines that the current phase of said rotator corresponds to said gradual phase point.