Patent ID: 8111278

Claim:
An image forming apparatus which performs an exposure of a plurality of line images concurrently, by scanning an image carrier with a plurality of light beams in a main scanning direction and simultaneously drives the image carrier in a sub scanning direction which is perpendicular to the main scanning direction, the image forming apparatus comprising: a plurality of light sources to generate the plurality of light beams, which are driven to emit the plurality of light beams corresponding to image data; a polygon mirror configured to deflect the plurality of light beams emitted from the plurality of light sources in a main scanning direction; and a control section which determines an image formation speed and changes a combination of a number of light sources to be used for a drive to emit the plurality of light beams and a number of polygon mirror use-surfaces used for a scanning with the light beams in the main scanning direction, based on the determined image formation speed, wherein the control section controls so that, in cases where a plurality of combinations of light sources to be used for a drive to emit the plurality of light beams and a number of polygon mirror use-surfaces used for a scanning with the light beams in the main scanning direction exist to the same image formation speed, priority is given to the change of the number of polygon mirror use-surfaces.