Patent ID: 8558860

Claim:
An image forming apparatus comprising: a light source configured to emit a light beam; a photosensitive member; a brushless motor comprising: a stator in which a plurality of coils are placed; and a rotor in which a plurality of magnets are placed; a rotary polygon mirror, which is configured to be rotated by the brushless motor, and which is configured to periodically deflect the light beam emitted from the light source to form scanning lines on the photosensitive member; an energization switching unit configured to turn on and off energizations of the coils; a voltage detecting unit configured to output a detection signal based on induced voltages generated in the coils by rotation of the rotor; a motor controlling unit configured to control the turning on and off of the energizations by the energization switching unit based on the detection signal; an electric component that operates during formation of the scanning lines; an initial position detecting unit configured to detect an initial position of the rotor that is a stop position at which the rotor is stopped before the motor controlling unit starts a rotation control of the brushless motor; and a power supply controlling unit which, in a detecting period in which the initial position of the rotor is detected by the initial position detecting unit, is configured to reduce an amount of electric power supplied to the electric component to less than an amount of electric power supplied to the electric component in a period of the formation of scanning lines after the detecting period, wherein, in the detecting period, the motor controlling unit is configured to increase an upper limit of an amount of electric power supplied to each of the coils higher than in the period of the formation of scanning lines.