| 摘要 |
PURPOSE:To attain stable operation in a focus drive system and a radial drive system by projecting upward one end of an optical head base, providing an objective lens to the projected part, projecting downward the other end of the optical head base, to attain weight balance to the turning shaft. CONSTITUTION:A lens holder 11 has a projection 13 projected upward partly and the projection 13 causes weight unbalancing, but since the other side is projected downward,the dynamic balance is attained by placing the center of gravity to nearly the midpoint between the upper and lower directions of the lens holder 11. Since a focus coil 17 and a radial coil 18 are provided to the center of gravity of the lens holder 11, the center of gravity is placed at a point at which the electromagnetic operating point is nearly made constant. When the center of gravity point and the electromagnetic operating point are nearly made coincident, the vertical movement and turning of the lens holder 11 are attained stably, the sub resonance at the servo band is prevented when an external vibration is exerted attended therewith and stable operation is obtained. |
