Patent ID: 7755822

Claim:
A multibeam optical scanning device comprising: a plurality of light sources that respectively emit a plurality of light beams; a collimating lens that collimates the light beams; an aperture that shapes the light beams output from the collimating lens; a cylinder lens that focuses the light beams to form a plurality of line images each elongated in a main scanning direction and separated in a sub scanning direction near a deflecting reflection surface of a light deflecting unit that deflects the light beams focused by the cylinder lens; a scanning optical system that focuses the light beams deflected by the light deflecting unit into a plurality of beam spots separated in the sub scanning direction on a scanning surface to scan the scanning surface simultaneously with the beam spots; and a phase adjusting element that performs phase adjustments of wavefronts of the light beams to expand a depth allowance without substantially increasing a beam spot size of each of the beam spots on the scanning surface.