| 摘要 |
A scanning optical apparatus includes: an incident optical system which is disposed in an optical path between a light source unit and a deflection unit, and includes an optical element for making a light flux emitted from the light source unit enter a deflection surface of the deflection unit with an oblique angle in a sub scanning section; and a positional regulation member for holding the optical element having an x reference surface for performing positional regulation of the optical element in an optical axis direction and a z reference surface for performing positional regulation of the optical element in a sub scanning direction. The optical element is held by a casing so that the x reference surface and the z reference surface contact with the positional regulation member of the casing. The principal ray of the light flux outgoing from the optical element satisfies a conditional equation (1).
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