| 摘要 |
PROBLEM TO BE SOLVED: To prevent an electromagnetic force from lowering and to obtain superior servo characteristics as well as recording and reproducing characteristics by structuring a part of the yoke constituting a magnetic circuit, with the magnetic material similar to or different from that of the yoke. SOLUTION: A magnetic circuit is designed to have a structure in which a cold rolled steel plate (SPCC) with a thickness of 0.6 mm for example is adhered to the outer side face of the yoke 60 which is, integrally formed into a shape including an attaching part, using a thin plate yoke material 1 made of an SPCC with a thickness of 0.15 mm for example. A magnet to be used is 0.9 mm thick for example, and the width of the magnetic circuit is about 35 mm. With such a structure, the yoke 60 can be manufactured by bending which has a high mass-productivity, and the electromagnetic force is prevented from lowering; also, using a magnetic flux distribution in the inside and the periphery of the magnetic circuit, the operating center of the electromagnetic force can be made to coincide with the center of gravity of the moving part consisting of an objective lens/lens holder 52, focus coil 53, tracking coil 54, etc.
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