| 摘要 |
PURPOSE:To reduce windage loss in a rotary polygonal mirror and to attain power saving and fast rotation by separating by sealing between the rotating room of the rotary polygonal mirror of a sealed type optical deflecting system and bearing space, and applying low pressure to the room of the rotary polygonal mirror. CONSTITUTION:A permeable fixed shaft 8 on which plural dynamic pressure generating grooves (e), (f) are engraved is arranged in the center of the bottom of a case 4, and a stator yoke 6 in the neighborhood of an inner wall, respectively, and a hollow rotary shaft 3 equipped with plural air reservior grooves (j) is out-fitted in the fixed shaft 8 keeping a micro gap (s), and also, a magnetic fluid sealing part A is provided at the bottom part of the hollow rotary shaft 3, and in addition to that, a magnet ring on the bottom of the sealing part A is set as the receiving plane of a thrust lower magnet ring, and furthermore, a magnet 5 for rotary driving is arranged at the outer periphery of the hollow rotary shaft 3 conforming to the rotary polygonal mirror 2 and the stator yoke 6, and a cover 9 in which an air draw-out hole 7 and a laser beam input/output window 16 are provided is mounted closely covering the hollow rotary shaft 3. |
