| 摘要 |
PURPOSE: To facilitate handling of the device and to reduce the cost of equipment and also to shorten the tact time by constituting a focusing coil and a tracking coil out of wire materials having the same wire diameter. CONSTITUTION: A coil bobbin 12 of the biaxial actuator 10 is constituted in such manner that its centroid is positioned on the objective lens 11b side. That is, only to an inner yoke 15a of a yoke 15 a magnet 16 is fitted. A sufficient magnetic circuit can be formed by the yoke 15, a yoke bridge 17 and the magent 16 of the inner yoke 15a, whereas a magnet 16a can be omitted. As the result, the controid G1 is made to coindide with the vicinity of a force point of the focusing coil 12b and the tracking coil 12c to reduce the weight of a movable part. Thus, the coil 12b of the bobbin 12 can be miniaturized in size and reduced in weight. Consequently, sincee the coils 12b and 12c can be small in resistance, the number of winding turns is reduced. Therefore, as to the coil 12c, a wire material having the same wire diameter as a winding wire of the coil 12b can be used for this winding wire, for example, a relatively large wire diamter of abont 0.07ϕ.
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