| 摘要 |
An optical disc is rotated using a spindle motor of an optical disc device, at no more than 600 revolutions per minute (RPM). The spindle motor has at least three coil groups, where each coil group has one or more coils. While the optical disc is rotating, at least one of the coil groups generates a back electromagnetic force (EMF) signal. The back EMF signal is used to determine marking positions on the optical disc. An optical beam is used to mark the optical disc at the determined marking positions.
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