Patent ID: 8477171

Claim:
An image forming apparatus comprising: a light source configured to emit a light beam; a light-source driving unit configured to drive the light source; a photosensitive member that comprises an image forming region; a determining unit configured to determine a level of a rotation speed of the photosensitive member; a scanner unit configured to expose the photosensitive member by deflecting the light beam emitted from the light source by a deflecting unit; a sensor configured to receive the light beam and output a detection signal; and a control unit configured to control the image forming apparatus based on the detection signal output from the sensor, wherein when the determining unit determines that the rotation speed is low, the light-source driving unit is configured: to drive the light source to emit the light beam when a deflecting direction of the light beam is oriented toward the sensor; and not to drive the light source to emit the light beam when the deflecting direction of the light beam is oriented toward the image forming region, wherein an intensity of the light beam emitted from the light source is configured to vary according to a current supplied to the light source, wherein the light-source driving unit is configured to supply: a first current configured to drive the light source to emit a light beam having a first intensity for exposing the photosensitive member with an intensity of greater than or equal to a predetermined exposure amount; and a second current configured to drive the light source to emit a light having a second intensity for exposing the photosensitive member with an intensity of less than the predetermined exposure amount, wherein when the deflecting direction of the light beam is oriented toward the sensor, the light-source driving unit is configured to supply the first current to the light source, wherein when the determining unit determines that the rotation speed of the photosensitive member is high, the light-source driving unit is configured to constantly supply the second current as a bias current to the light-source driving unit, and wherein when the determining unit determines that the rotation speed of the photosensitive member is low, the light-source driving unit is configured to stop supplying the bias current to the light source and to make a timing at which the light source is supplied with the first current faster than a timing at which the first current is supplied when the rotation speed of the photosensitive member is high.