Patent ID: 7817926

Claim:
An image forming apparatus comprising: an image forming apparatus main body including an image forming unit that forms an image on a sheet, a detachable main body sheet feeding tray that holds the sheet and a sheet feeding unit that feeds the sheet from the main body sheet feeding tray toward the image forming unit; an optional sheet feeding device that is capable of being added on a lower side of the main body and feeds the sheet toward the image forming unit, the optional sheet feeding device having a first detector capable of detecting whether or not the main body sheet feeding tray is attached to a proper position; and a controller that controls operations of the image forming apparatus main body and the optional sheet feeding device based on a detection result of the first detector; wherein a portion of the main body sheet feeding tray constitutes a portion of a transport path of the sheet which extends from the optional sheet feeding device to the image forming unit when the main body sheet feeding tray is attached to the proper position, and wherein the first detector comprises a light emitting element and a light receiving element; and a shutter that is protrusively disposed on the main body sheet feeding tray and shuts an optical path extending from the light emitting element to the light receiving element when the main body sheet feeding tray is attached to the proper position; and further comprising a second detector capable of detecting that the optional sheet feeding device is added and capable of detecting that the optional sheet feeding device is not added.