In an optical scanning apparatus, the shape of a sub-scanning section of a transmissive imaging optical element on which a light beam subjected to scanning and deflected by a deflecting surface of an optical deflector is incident twice, the tilt angle of a reflective optical element disposed in an optical...http://www.google.co.uk/patents/US8149477?utm_source=gb-gplus-sharePatent US8149477 - Optical scanning apparatus and image forming apparatus including the same
