Laser scanning unit having a noise reducing portion

摘要

A laser scanning unit includes an emitting portion for emitting laser beams, a deflecting portion having a plurality of mirror surfaces at its side portions to deflect the laser beams upon a predetermined position of a pickup surface by rotation of a predetermined speed, and a pickup portion for scanning the laser beams deflected by the deflecting portion into the pickup surface. A rotative noise reducing portion is formed at a plurality of edges formed by the plurality of adjacent mirror surfaces of a polygon mirror which acts as the deflecting portion. Preferably, the rotative noise reducing portion includes at least one air groove at the portion where the mirror surfaces connect, so as to be formed around the edges of the mirrors. Thus, it is possible to reduce the pressure difference between the mirror surfaces with the air groove, thereby reducing noise during rotation of the polygon mirror.