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AssigneeKoninklijke Philips Electronics N.V.
InventorJosephus J. M. Braat
Estimating the term…
A device scans an optical record carrier having optically detectable marks along a track. The device includes a radiation source for emitting a radiation beam, an objective system for guiding the radiation beam to the record carrier, and a radiation-sensitive detection system for receiving radiation from the record carrier. The detection system includes at least two detectors on both sides of a dividing line. Each detector has an output for providing a detector signal. An electronic circuit forms a focus error signal from the detector signals. The electronic circuit determines a time or phase difference between corresponding parts of the detector signals relating to passage of the radiation beam over patterns of the marks having a spatial frequency in a first range and in a different, second range, and forms a focus error signal in dependence on the time or phase difference.
An optical record carrier for being scanned by an optical system having a predetermined spatial cut-off frequency and having an information layer in which information is stored in optically readable marks arranged in tracks, wherein at predetermined parts along the tracks a first pattern of marks and a second pattern of marks are located, the first pattern having a spatial frequency in a range from 0.14 to 0.2 times the cut-off frequency and the second pattern having a spatial frequency in a range from 0.35 to 0.5 times the cut-off frequency.
A method for scanning an optical record carrier comprising optically detectable marks along a track, the method comprising:
A method for scanning an optical record carrier comprising optically detectable marks along a track, the method comprising:
Dependencies are inferred from the claim text.