Patent ID: 8600248

Claim:
An image forming apparatus comprising: a belt; a plurality of photosensitive units configured to contact the belt are disposed at a predetermined interval in a transportation direction of the belt and transfer marks for image adjustment to the belt, images of different colors being respectively formed on the plurality of photosensitive units; an exposure unit configured to expose the photosensitive units by light so that the marks are disposed at the same interval on the belt; a detector configured to detect the marks transferred to the belt; and an image adjustment unit configured to perform an image adjustment based on a detection result of the detector, wherein a width and an interval of the marks in the transportation direction are set based on a width of a contact area between the belt and each photosensitive unit in the transportation direction so that a mark of at least one color does not exist in all contact areas of the belt contacting with the plurality of photosensitive units.