Patent ID: 8064809

Claim:
An image forming apparatus comprising: an endless belt type transfer member configured to carry an image formed with developer of a plurality of colors; a drive roller configured to drive the endless belt type transfer member by rotating while contacting the endless belt type transfer member; a first detection unit configured to detect a mark provided on the endless belt type transfer member; a second detection unit configured to detect the mark at a position different from the position of the first detection unit in a conveyance direction of the endless belt type transfer member; and a correction unit configured to correct a conveyance speed of the endless belt type transfer member using a difference between respective times at which the first detection unit and the second detection unit detect the mark, wherein the first detection unit and the second detection unit are located such that an interval between respective positions at which the first detection unit and the second detection unit detect the mark is an integral multiple of a perimeter of the drive roller.