Synchronous light detector for optical scanning apparatus

摘要

A synchronous light detector for an optical scanning apparatus comprises a cylindrical lens 14 and a light-receiving device 15. The cylindrical lens 14 is disposed between an imaging lens 8 of the optical scanning apparatus and the light-receiving device 15 so as to have a generator direction parallel to a scanning direction of a light beam. The light-receiving surface of the light-receiving device 15 is disposed at a position shifted from a paraxial image point P in the direction orthogonal to the scanning plane of the light beam by a predetermined distance DELTA along the optical axis direction of the light-receiving device 15 when the deflecting point of the light beam caused by a polygon mirror 6 is taken as an object point. As a consequence, the synchronous signal of the optical scanning can be detected correctly even when there is a flaw or dirt on the light-receiving surface.