OPTICAL SCANNER AND IMAGE FORMING APPARATUS

摘要

PROBLEM TO BE SOLVED: To provide an optical scanner which copes with changes in light quantity or diameter of a light spot due to vignetting of a light beam to be caused by a deflection reflection surface.SOLUTION: An optical scanner includes an aperture element 7 formed on an optical path leading from a light source 1 to an optical deflector 3. A luminous flux diameter in a main-scanning direction of a light beam made incident on a deflection reflection surface of the optical deflector is smaller than a length in the main-scanning direction of the deflection reflection surface. When a peripheral part in a deflection range of the light beam to be deflected by the optical deflector 3 is scanned, a part of the light beam to be made incident on the deflection reflection surface is not reflected toward a scanned surface. The aperture element 7a gradually decreases an aperture width in a sub-scanning direction from a central part in the main-scanning direction of an aperture part toward at least one peripheral part. A part of the light beam which is not reflected toward the scanned surface includes a light flux portion passing through the at least one peripheral part in the main-scanning direction of the aperture part of the aperture element.