Patent ID: 8369726

Claim:
An image forming apparatus that forms a toner image on an endless belt driven by a driving roller, the apparatus comprising: a detector that detects light from the endless belt or the toner image formed on the endless belt; a measurement unit that measures a moving amount of a surface of the endless belt when the driving roller rotates once based on a result of the detection by the detector; a first acquiring unit that acquires, based on the result of the detection by the detector, first waveform data of an image-formed surface of the endless belt that is used to form an image; a second acquisition unit that acquires, based on the result of the detection by the detector, second waveform data of the image-formed surface of the endless belt that is used to form an image, the second waveform data including at least part of the first waveform data; and a correction unit that corrects the first waveform data and the second waveform data based on the moving amount of the surface of the endless belt measured by the measurement unit.