Patent ID: 7050209

Claim:
A scanning optical apparatus, comprising: light source means; a first optical element that converts a light flux emitted from the light source means; a second optical element that converts the light flux emitted from the first optical element into a longitudinal linear image in a main scanning direction; a deflection element that scanningly deflects the light flux emitted from the second optical element; a third optical element that guides the light flux deflected by the deflection element to a surface to be scanned; a synchronous detection element that obtains a synchronous signal; and a fourth optical element that guides the light flux deflected by the deflection element to the synchronous detection element, wherein in a case where a point at which a principal ray traveling toward a scanning center on the surface to be scanned is deflected by the deflection element is assumed as a deflection point, an optical path from an exit surface of the second optical element to the deflection point of the deflection element is longer than an optical path from the deflection point to an incident surface of the fourth optical element.