Patent ID: 8379313

Claim:
An optical scanning apparatus comprising: two light source units configured to emit a plurality of light beams; a deflecting unit having a deflection surface and configured to deflect and scan the plurality of light beams with the same deflection surface; two imaging optical systems configured to form images of the light beams emitted from the two light source units and deflected by the same deflection surface of the deflecting unit, the images being formed on two surfaces to be scanned each corresponding to one of the two light source units; and a beam splitter disposed between the deflection surface and the two surfaces to be scanned so as to straddle the light beams emitted from the two light source units and deflected by the same deflection surface of the deflecting unit; wherein the beam splitter serves as a composite element including first and second reflective surfaces and including first, second, third and fourth transmissive surfaces integrated therein, wherein a light beam that reaches a surface to be scanned located at a position physically far from the deflection surface of the deflecting unit passes through the first transmissive surface and the second transmissive surface of the beam splitter in this order, and a light beam that reaches a surface to be scanned located at a position physically close to the deflection surface of the deflecting unit passes through the third transmissive surface, the first reflective surface, the second reflective surface, and the fourth transmissive surface of the beam splitter in this order, and wherein an optical path between the first reflective surface and the second reflective surface for the light beam reaching the surface to be scanned located at the position physically close to the deflection surface of the deflecting unit intersects with an optical path between the first transmissive surface and the second transmissive surface for the light beam reaching the surface to be scanned located at the position physically far from the deflection surface of the deflecting unit in a sub-scanning cross section in the beam splitter.