| 摘要 |
PROBLEM TO BE SOLVED: To provide a small-sized brushless motor detecting the rotational position of a rotor magnet precisely and a light deflector utilizing the brushless motor. SOLUTION: In a dynamic pressure air bearing polygon scanner 1, a rotor 14 fixed with a polygon mirror 9 is rotatably supported by a dynamic pressure bearing, and a flange 10 is fitted to the rotor 14 which is always supported in the axial direction with magnetic force by means of a magnetic bearing to permit a brushless motor 20 to drive the rotation of the rotor 14. A rotor magnet 13 is fitted to the inner-periphery surface of the lower end of the flange 10, a stator core 16 with a coil winding 17 is disposed in the internal-diameter direction of the flange 10, and a Hall element 19 is disposed in the external- diameter direction of the flange 10 so as to put the flange 10 therebetween. It is thus possible to prevent a magnetic field by the excitation of the coil winding 17 from having an adverse effect upon the Hall element 19 as noise, thereby detecting the position of the rotor magnet 13 by means of the Hall element 19 with high precision and stability.
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