| 摘要 |
PURPOSE:To attain the rotation with less fluctuation with a light weight and small sized device, by providing fixedly plural magnetic poles having alternately an N and an S pole under a collar of a magnetic substance and scanning a screen with a reflecting light of a rotary polygon mirror having plural reflecting planes. CONSTITUTION:The plural magnetic poles having alternately an N and an S magnetic pole fixed under a collar 10b being a magnetic substance yoke are provided to a field magnet 11 in an annulus shape. Further, the rotary polygon mirror 12 forms a flat square shape having four reflecting planes 12a. Further, an open angle of conductor sections 6a, 6b contributing to a radial generating torque in an electromagnetic coil 6 is formed as almost (2n-1) times (where n>=1) of the width of the magnetic poles of the magnet 11, e.g., as open angle width almost equal to a magnetic pole end of the magnet, and coil groups are provided at an equal interval so as not to be overlapped with each other. Further, each coil 6 is provided with one position detecting element 8 and the element 8 is provided in a cavity section 9 in the frame of the coil 6. |
