| 摘要 |
A scanning optical apparatus includes a light source, a deflecting element for deflecting and reflecting a beam emitted from the light source, and a scanning optical element for focusing the beam deflected by the deflecting element, on a surface to be scanned. The scanning optical element includes a plurality of optical elements. A shape in a main scanning direction of at least one surface out of optical surfaces of the plurality of optical elements is an aspheric shape. An optical element having a largest power in a sub scanning direction on the optical axis out of the plurality of optical elements is located on the deflecting element side with respect to a middle point in an optical-axis direction between the deflecting element and the surface to be scanned. The optical element having the largest power in the sub scanning direction has two optical surfaces. Where phiS1 represents a power in the sub scanning direction of the optical element having the largest power in the sub scanning direction and phiS1X a power of an optical surface having a smaller power in the sub scanning direction out of the two optical surfaces of the optical element having the largest power in the sub scanning direction, the powers phiS1 and phiS1X satisfy phiS1X<0.2xphiS1.
|
