| 摘要 |
The present invention relates to an optical system for reproducing and/or recording on optical record carrier. The system includes light providing means for providing at least: 1) a main beam for reading information, and 2) a plurality of auxiliary beams for radial tracking; a first (A), a second (B) and a third (C) auxiliary beam. The optical record carrier has readable effects arranged in tracks ( 2, 12 ) in one or more spiral(s), the spiral(s) being separated by one or more guard band(s) ( 5, 15 ). The optical system performs radial tracking from the reflected light of 1) the first auxiliary beam (A), the first auxiliary beam being positioned in a first guard band, and 2) the second (B) and third auxiliary beam (C). The second auxiliary beam is positioned on a first track (I), and the third auxiliary beam (C) is positioned on a second track (II) and on opposite side of the first guard band ( 5, 15 ) relative to the second auxiliary beam (B). The optical system provides improved radial tracking on the above-mentioned carrier format.
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