| 摘要 |
PURPOSE:To suppress the motion of a rotary polygon mirror except in its rotating direction and to improve the accuracy of optical scanning by fitting the rotary polygon mirror to a sleeve at an axial position opposite the pattern of a couple of dynamic pressure generating grooves cut symmetrically in the outer periphery of a fixed shaft. CONSTITUTION:The rotary polygon mirror 9 is fitted directly to the sleeve 1 fitted onto the fixed shaft 7 at the axial position opposite the pattern of the couple of dynamic pressure generating grooves 22 cut symmetrically in the outer periphery of the fixed shaft 7, and a thrust bearing 2 which has dynamic pressure generating grooves is provided with an end part of the center internal wall 15a of a cup-shaped case 15 where the fixed shaft 7 is fitted and fixed and the opposite surface of the sleeve 1 from the surface where an upper lid 21 is fitted. The rotary polygon mirror 9 can be pivoted with high rigidity by fluid dynamic pressure operation in the radial direction, axial direction, and swing direction. Consequently, the scanning speed irregularity and right- angled deflection of the optical scanning by the rotary polygon mirror are reducible. |
