| 摘要 |
<p>The scanning head has an objective (5) focussing the optical beam into the surface of the recording disc, its position corrected continuously via an electromagnetic positioning drive, to maintain track alignment. The objective mounting (7) has a movable annular permanent magnet (200) coaxial to the optical axis, with axially opposed magnetic poles, cooperating with fixed coils (204,205,206) to control the displacement of the objective mounting (7). At least three coil sets (204,205,206) each have a segment coil (204A,205A,206A,) and a second coil (204B,205B,206B) lying between the active parts of the segment coil (204A,205A,206A).</p> |
