Patent ID: 7619796

Claim:
An optical scanning device comprising: a laser light source that emits a light beam; a coupling lens that couples the light beam; an aperture having an aperture opening that transmits a predetermined portion of the light beam; a phase optical element that changes a phase of a portion of the light beam coupled by the coupling lens including a center of the light beam; a deflecting unit that deflects the light beam transmitted through the aperture for scanning; and a scanning lens that focuses the light beam deflected by the deflecting unit into a beam spot on a scanning surface, wherein the phase optical element has a function of increasing a light intensity of a side-lobe of the scanning beam near the scanning surface, the aperture opening is set to satisfy 0.03≦( SR−SA )/ SR≦ 0.20 where SR is area of a rectangle circumscribing the aperture opening and SA is area of the aperture opening, and the function of the phase optical element and the aperture expand a depth allowance of the beam spot.