Patent ID: 7551192

Claim:
An optical beam scanning apparatus comprising: a light source configured to emit an optical beam; a control unit configured to control the light source to emit the optical beam according to image data; a deflecting unit configured to deflect the optical beam in a main scanning direction; a detecting unit configured to detect deflected optical beam on a main scanning line; a first correcting unit configured to correct a main scanning magnification; and a second correcting unit configured to correct the main scanning magnification, wherein, when an error is not detected in a count value based on a scanning time of the optical beam, the first correcting unit includes a clock generator configured to generate a lighting control clock for the light source based on the count value, the second correcting unit includes a clock-phase changing unit configured to change a phase of the lighting control clock by a unit of 1/n, where n is a positive integer equal to or larger than two, and the main scanning magnification is corrected by a combination of correction by the first correcting unit and correction by the second correcting unit.