Patent ID: 7372479

Claim:
An image forming apparatus for forming images with an electrophotographic system, said image forming apparatus comprising: a laser drive unit configured to control a laser light; a polygon mirror configured to reflect the laser light; a polygon mirror drive unit including a polygon motor and configured to rotate said polygon mirror; an electric power supply unit configured to supply electric power to the polygon mirror drive unit; a polygon motor operation condition signal generating device configured to generate an operation condition signal in accordance with an operation condition of the polygon motor; a first pulse signal generating device configured to generate a first pulse signal having a prescribed level and frequency when the electric power supply unit stops supplying power; a second pulse signal generating device configured to generate a second pulse signal based on the polygon motor operation condition signal and the first pulse signal; and an error occurrence determining device configured to determine which one of the polygon mirror drive unit and the electric power supply unit is in an abnormal condition based on the second pulse signal.