| 摘要 |
PROBLEM TO BE SOLVED: To realize a stable focus servo even if a reaction force against acting force to an objective lens holder is generated, and to aiming at a miniaturized actuator with a simplified constitution. SOLUTION: When an acting force generation source which consists of a focusing coil 6 and a magnetic circuit 8 generates the acting force for displacing the objective lens holder 3 in a focusing direction of an optical disk, a flat spring 9 supports the magnetic circuit 8 so that the magnetic circuit 8 can rotate around an optional point O, as the center, of the flat spring 9, by the reaction force. A relationship of a=I/Mh stands, where M is the mass of the magnetic circuit, I is the moment of inertia around the center of gravity of the magnetic circuit, a is the distance between the center of gravity of the magnetic circuit 8 and an acting line in the direction of the acting force, and h is the distance between the center of rotation O for the flat spring 9 and the center of gravity of the magnetic circuit 8. In this case, even if the acting force may be a dynamic force, for example, sine wave oscillation exciting force or the like, the flat spring 9 deforms statically, and the excitation of oscillation thereof is securely suppressed even if oscillation of the magnetic circuit 8 is excited by the reaction force.
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