An image forming apparatus for forming images with an electrophotographic system. The image forming apparatus includes a laser drive unit configured to control a laser light, and an image data transfer control unit configured to control image data from to the laser drive unit. The apparatus also includes a polygon mirror configured to reflect laser light from the electrophotographic system, a polygon mirror drive unit including a motor configured to rotate the polygon mirror, and a power supply level detecting unit configured to detect a voltage level of power supplied to the polygon mirror drive unit by an electric power supply unit. The image data transfer control unit is configured to provide any width and any number of a first pulse signal indicating a state when power supply is cut off to the polygon mirror drive unit.