Patent ID: 7657196

Claim:
An image forming apparatus comprising: an image carrier on which a toner image is formed; an endless belt member that is supported by a plurality of supporting rollers, such that a belt supporting area is an area that is supported by one of the plurality of supporting rollers; a transfer unit that transfers the toner image formed on the image carrier onto a surface of the endless belt member; an optical sensor that detects at least one of the toner image and a toner adhesion amount per unit area in the toner image based on a change of an optical characteristic on the surface of the endless belt member; a control unit that performs a predetermined process based on a detection result obtained by the optical sensor; and a sensor moving unit that moves the optical sensor between a first position and a second position that is different from the first position, wherein when the optical sensor is disposed in the second position, one of a recording member on which the toner image is to be recorded and a predetermined member that is moved by a driving unit is temporarily disposed in the first position and occupies a same location as occupied by the optical sensor when the optical sensor is in the first position, the optical sensor is configured to obtain the detection result when the optical sensor is disposed in the first position by the sensor moving unit, and the first position is disposed opposite of the belt supporting area.