| 摘要 |
PROBLEM TO BE SOLVED: To surely match the optical axis of a light beam with the optical axis of an optical element by constituting an optical element holder so that its neutral point is always positioned in the vicinity of the magnetic pole boundary of a second magnetic field generating part in the range movable along the axis without a neutral point holding magnetic circuit. SOLUTION: Magnetic poles of focusing permanent magnets 106a, 106b and tracking permanent magnets 109a-109d are arranged lineally symmetrically relative to a surface P, whereby overlapping of magnetic attraction to both magnetic bodies becomes constant, a switching voltage to the arrow A and a switching voltage to the arrow B are set to the same value, and switching directional dependency is reduced to a driving voltage. And even if either of optical elements 103a or 103b is selected, the total sum of magnetic attraction exerting on the magnetic bodies 111a, 111b is not changed, a magnetic spring constant is not also changed, and always a stable frequency characteristic is maintained. Therefore, a circuit scale for controlling the device is also reduced because of being controlled by one servo circuit.
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