Patent ID: 8319812

Claim:
An image forming apparatus comprising: a photosensitive member; a light source configured to emit a light beam for irradiating the photosensitive member; a rotary polygon mirror configured to deflect the emitted light beam such that the light beam scans on the photosensitive member; a control unit configured to control a rotational speed of the rotary polygon mirror to correspond to each of a plurality of rotational speeds; an image data generating unit configured to generate image data corresponding to each of the plurality of rotational speeds; and a signal generating unit configured to generate a drive signal of driving the light source based on a clock signal of a predetermined frequency and the generated image data, wherein the image data generating unit generates the image data corresponding to the each of the plurality of rotational speeds, such that a width of an image area in a scanning direction in which the light beam scans the photosensitive member in a case where the rotary polygon mirror is controlled to rotate at a first rotational speed and a width of the image area in the scanning direction in a case where the rotary polygon mirror is controlled to rotate at the second rotational speed which is lower than the first rotational speed are identical with each other.