| 摘要 |
PURPOSE:To uniform the angle of reflection of a laser beam in the subscanning direction by supporting nonmagnetic journal parts of a shaft on plural bearings consisting of electromagnets and magnetic fluid, and correcting the tilt angle of the shaft by the control of a magnetic field and the characteristics of the magnetic fluid. CONSTITUTION:When a detection signal is supplied from a rotation position detecting mechanism 27 to a control part 32, a control part 32 judges which reflecting surface of a polygon mirror 13 is within a specific rotation range and receives an angle signal 34 regarding the tilt angle of the reflecting surface from the storage part 33. Then, the control part 32 supplies a control signal 35 for placing the reflecting surface in a specific state to an electromagnet driving circuit 36, and consequently a driving signal 37 corresponding to the control signal 35 is supplied to four electromagnets 23 and 24 of bearings 19 and 20 to vary the magnetic field established by the respective electromagnets 23 and 24 and also vary the tilt angle of the shaft 12, so that said reflecting surface of the polygon mirror 13 is corrected into the specific state. |
