Patent ID: 7471434

Claim:
An optical scanning device comprising: a common light source that is driven by a modulation; a deflecting unit including a plurality of polyhedral reflection mirrors provided in a multiple stages with a common rotation axis; a beam splitting unit that splits a beam emitted from the common light source and outputs split beams to the reflection mirrors in different stages; and a common photodetecting unit that detects a plurality of beams scanned by the reflection mirrors in different stages, and generates a synchronization detection signal based on detected beams, wherein the split beams respectively scan different scanning target surfaces, the reflection mirrors make a predetermined angle θ1 in a direction of rotation of the reflection mirrors, and when time between two consecutive synchronization detection signals on a time line generated by the common photodetecting unit is ti, where i is a positive integer equal to or smaller than number of the split beams, at least one of ti is different from others.