| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that fluctuation of driving torque generated by a motor comprising a driving magnet and an iron core coil causes the inter-dot pitch fluctuation of a beam that is scanned on a photoreceptor or the like by the rotation of a polygon mirror. SOLUTION: The optical deflector includes a polygon mirror in which a plurality of reflection faces are formed having an effective scanning area to be scanned by a beam, and a motor which is composed of a driving magnet and an iron core coil for rotatably driving the polygon mirror. In this optical deflector, assuming that the number of the reflection faces is P (P is an even number≥4), the variation of the inter-dot pitch of the beam to be scanned on a photoreceptor or the like is minimized, by setting the number of the magnetic poles of the driving magnet to nP (n is a natural number) and by setting a difference of angle to roughly 90°/nP or roughly 270°/nP between the starting position of beam scanning in the effective scanning area and the boundary position of the N pole and the S pole constituting the magnetic poles. COPYRIGHT: (C)2007,JPO&INPIT |
