| 摘要 |
A method, apparatus, and medium for determining actuator signals for focusing a laser on a label surface of an optical disc. A plurality of virtual angular sectors are defined on the label surface. A single rotation of the disc is performed. During the rotation, the focus of the laser is sinusoidally swept from a baseline once per sector. During the rotation, a SUM signal indicative of a degree of focus of the laser on the label surface is measured at a plurality of angular positions of each sector. The actuator signals are derived from the measured SUM signals.
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