Patent ID: 7825947

Claim:
An optical scanning device, comprising: an optical deflector configured to scanningly deflect a light beam emitted from light source means; and an imaging optical system configured to image the light beam scanningly deflected by a deflecting surface of said optical deflector, upon a scan surface; wherein the light beam incident on the deflecting surface of said optical deflector is incident perpendicularly on the deflecting surface, in a sub-scan section, wherein the light beam incident on the deflecting surface of said optical deflector is incident with an angle with respect to an optical axis of said imaging optical system, in a main-scan section, wherein, along a light path between said optical deflector and the scan surface, there are a transmission type imaging optical element constituting said imaging optical system and a reflection type optical element, which are disposed in this order from said optical deflector, wherein, when in the sub-scan section the angle defined between a principal ray of a light beam reflected by said reflection type optical element and a normal to said reflection type optical element is denoted by θ, a condition θ<45 degrees is satisfied, and wherein, in the sub-scan section, said transmission type imaging optical element is disposed so that, to avoid interference with a light path reflected by said reflection type optical element, a contour central line of said transmission type imaging optical element is positioned at one side of a principal ray of the light beam incident on said transmission type imaging optical element which side is remote from the light path reflected by said reflection type optical element.