| 摘要 |
PROBLEM TO BE SOLVED: To more efficiently attain high speed of a movable part by suppressing reduction of the driving force and to realize such high speed at low cost with a simple magnetic circuit structure. SOLUTION: An objective lens driving unit 2 is composed of a lens holder 4 that is freely displaceable in the Z- and Y-axis direction with an objective lens 3 held, a track coil 7 having a Z-axis directional part in which an electric current flows in the Z-axis direction coincidental to the optical axis direction of the objective lens, and a focus coil having a Y-axis directional part in which an electric current flows in the Y-axis direction. A unit 1 for forming a magnetic flux circuit consists of a magnet 11 that comes close to the Z- and Y-axis directional parts to form a magnetic flux turning to the X-axis direction and a magnetic path forming body 13. The magnetic path forming body 13 forms a part for guiding a magnetic path in the Y-axis direction, a part that guides, to the Y-axis direction, the magnetic flux turning to the Y- and Z-axis directions on the side of the magnet 11.
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