| 摘要 |
PROBLEM TO BE SOLVED: To perform highly accurate image formation by reducing the windage loss of a polygon mirror on which plural laser beams are made incident. SOLUTION: For a dynamic pressure air bearing type polygon scanner 30, a fixing shaft 33 is inserted inside the hollow of a rotary sleeve 37, the fixed flange 38 of a magnetic bearing rotation part 39 and a polygon mirror 40 are fixed to the rotary sleeve 37 and they constitute a rotating body 45. The magnetic bearing rotation part 39 is inserted inside a permanent magnet assembly 34 buried inside the upper end recessed part of the fixing shaft 33 and the fixing shaft 33 floats and supports the rotary sleeve 37 in a shaft direction by the magnetic bearing rotation part 39 and the permanent magnet assembly 34 and turns a contact surface with the rotary sleeve 37 to a dynamic pressure air bearing surface and supports the rotary sleeve 37 in a radial direction by the dynamic pressure of air when the rotary sleeve 37 is rotated. Mirror surface parts 40a and 40b and a non mirror surface part 40c are formed at the polygon mirror 40, the non mirror surface part 40c is formed in a diameter smaller than the mirror surface parts 40a and 40b, weight is reduced and the windage loss at the time of high speed rotation is reduced. Thus, the high speed rotation is stably performed with low vibration and the highly accurate image formation is performed. |
