| 摘要 |
PURPOSE:To simplify the constitution and the control, by providing a movable yoke in a wide magnetic gap and providing a driving coil for an optical head in a narrow magnetic gap part formed with this movable yoke. CONSTITUTION:A magnetic circuit 22 is formed which has comparatively wide magnetic gaps 21 extending in the direction of the radius of a disc-shaped recording medium (which is not shown in figure) and is closed in the terminal in the direction of the radius, and movable yokes 23 having a length required for inducing electromagnetic force in respective driving coils are arranged in magnetic gaps 21. Partially narrow gaps 24 are formed, and AFC driving coils 25 for an optical head, ATC driving coils 26, and ASC driving coils 27 are provided in relation to these movable yokes 23. Movable yokes 23 move in accordance with the movement of the optical head in the direction of the radius to secure always magnetic fields crossing coils 25-27. Thus, a high magnetic flux density is obtained easily, and the constitution and the control are simplified. |
