Patent ID: 8731418

Claim:
An image forming apparatus, comprising; a rotatable belt used to form an image on a recording medium; a detection unit configured to detect, at a detecting position, an object to be detected on the belt; a cartridge including a photosensitive drum and configured to be attachable to and detachable from a main body of the apparatus independently of the belt; and an openable and closable member configured to be openable and closable relative to the main body of the apparatus to attach and detach the cartridge to and from the main body of the apparatus, wherein the detection unit is movable between a retracted position, which is outside of a space used for attachment and detachment of the cartridge, and the detecting position, and wherein, when the detection unit is at the detecting position, at least a part of the detection unit is located in the space used for attachment and detachment of the cartridge, and, when the detection unit is at the retracted position, at least a part of the detection unit is located in a space that is formed by opening the openable and closable member relative to the main body of the apparatus.