Patent ID: 7667868

Claim:
An optical scanning device comprising: a plurality of light sources that are modulation-driven, each of which is made a common light source; a deflecting unit having a plurality of tiers of multi-facet reflecting mirrors on a common rotation axis; a light flux splitting unit that splits beams from the common light source and makes the split beams incident on mutually different tiers of reflecting mirrors of the deflecting unit; a plurality of surfaces to be scanned; a scanning optical system that guides the beams made to scan from the deflecting unit to the surfaces to be scanned; and light-receiving units that detect beams made to scan by the deflecting unit, so that the beams split from the common light source scan mutually different surfaces, wherein the mutually different tiers of multi-facet reflecting mirrors is shifted from each other in terms of angles in a rotating direction, and the following conditions are satisfied: θ/2<2π /M−φ, and θ/2−φ, and θ/2<2α wherein θ: Angle of view including beams that reach the light-receiving units α: Average incidence angle on the reflecting mirror at an effective scanning width φ: Angle shift in a rotating direction between the different tiers of multi-facet reflecting mirrors M: Number of faces of the multi-facet reflecting mirror.