Patent ID: 7880947

Claim:
An adjusting method for an illuminated position in an optical scanning apparatus, the optical scanning apparatus comprising: a plurality of light source units; a common deflection unit for deflecting for scanning a plurality of light beams emitted from the plurality of light source units; and a plurality of imaging optical units each comprising at least one imaging optical element and at least one light beam reflection unit which are disposed in optical path of the light beam deflected for scanning on a deflection surface of the common deflection unit, and image the light beam on a surface to be scanned, the adjusting method comprising rotating the light beam reflection unit, in a sub scanning direction, which is disposed optically closest to the surface to be scanned in an optical path in which a largest number of the light beam reflection units are disposed among the optical paths of the plurality of light beams guided to the plurality of surfaces to be scanned, to thereby adjust the illuminated position of the light beam, which illuminates the surface to be scanned, on the surface to be scanned in the sub scanning direction, and eccentrically parallelizing the imaging optical element, in the sub scanning direction, which is disposed optically closest to the surface to be scanned among the at least one imaging optical element in the optical paths other than the optical path in which the largest number of the light beam reflection units are disposed, to thereby adjust the illuminated position of the light beam on the surface to be scanned in the sub scanning direction, wherein the following condition is satisfied, 0.5×φ_all≦φ_adj≦2×φ_all, wherein the optical paths others than the optical path in which the largest number of the light beam reflection units are disposed, φ_adj represents a power of the imaging optical element disposed optically closest to the surface to be scanned on an optical axis within a sub scanning section among the at least one imaging optical element, and φ_all represents a power of all of the at least one imaging optical element disposed in the same optical path on the optical axis within the sub scanning section.