| 摘要 |
The invention relates to an optical drive for e.g. CD, DVD, HD-DVD or BD disks. A radial servomechanism controls the radial position of a laser beam in response to a push pull signal (PP). The radial servomechanism has an amplifier (VGA, 55) with a variable gain (G). The drive contains wobble signal detection means (51, 52, 53) so as to provide an amplitude (WA) of the wobble signal from the push pull signal (PP). Transition detection means (54) assesses if the focused radiation beam is or has been exposed to a change in a local optical environment on the optical carrier, such a read- write transition. In case of a transition, the radial servo gain (G) is adjusted in dependence of a ratio (r) of a wobble amplitude (WA_ b) just before said transition to a wobble amplitude (WA_ a) just after said transition so as to obtain a substantially constant radial bandwidth of the radial servomechanism. |
