Patent ID: 8223416
Filing Date: 2012-07-17
Classification: G02B

Abstract:
1. A scanning optical apparatus comprising: a plurality of individually modulated light sources; a first optical element configured to convert light emitted from each of the plurality of light sources into a beam of light; a second optical element configured to convert beams of light having passed through the first optical element into linear images extending in a main scanning direction; a deflecting mirror configured to deflect the beams of light having passed through the second optical element in the main scanning direction; and a third optical element configured to convert the beams of light having been deflected by the deflecting mirror into spot-like images to be focused on a scanned surface, the third optical element being a single lens having a pair of opposite lens surfaces each having an optical axis, each of the pair of opposite lens surfaces having a curvature in a sub-scanning direction varying continuously from a position corresponding to the optical axis thereof outward in the main scanning direction in such a manner that MTF values in a sub-scanning direction of an image formed on the scanned surface vary less with image height, wherein MTF is a modulated transfer function, the values of which represent resolutions of the image, and wherein a curvature of the third optical element in the sub-scanning direction varies such that a maximum MTF value MTF where β max =cos −1 (0.5*λ*u/NA), β min =cos −1 (0.55*λ*u/NA), in which u indicates a spatial frequency determined for a dot pitch on the scanned surface, NA indicates a numerical aperture in the sub-scanning direction of the third optical element, and λ indicates a wavelength of light emitted from each of the plurality of light sources.