| 摘要 |
PROBLEM TO BE SOLVED: To obtain a scanning optical apparatus which is compact and suitable for high-definition printing, by appropriately setting the shape of an fθlens. SOLUTION: In a scanning optical apparatus, a luminous flux emitted from a light source means causes to form an image linearly in a main scanning direction on the deflecting surface of a deflecting element via a first optical element and a second optical element, and a plurality of luminous fluxes deflected with deflected element causes to form the image into a spot-like shape on a surface to be scanned via a third optical element, wherein the third optical element is construted by at least two lens faces, and a principal plane position in the on-axis subscanning direction on the optical axis makes the principal plane position in the off-axis subscanning direction closer to the position of the surface to be scanned by allowing curvatures of the two lens faces in a subscanning direction to be consecutively varied from the on-axis toward the off-axis, so that the change of an f-number in the subscanning direction caused by the image height of the luminous flux made incident on the surface to be scanned is restrained. COPYRIGHT: (C)2006,JPO&NCIPI |
