Extended focus control
AssigneeKoninklijke Philips Electronics N.V.
InventorsHendrik Josephus Goossens, Frank Cornelis Penning
Life of this patent
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Abstract
An apparatus for scanning a track on a record carrier has a head (41) for providing a beam of radiation and generating at least one sensor signal. The device has a focusing unit for controlling a focusing element to maintain an in-focus position for generating a focused spot on the track. The sensor signal is converted into a displacement signal by a multitude of piecewise converters (42, 43, 44), each converter converting a range of the sensor signal values into a position signal, and selection means (46) for selecting one of the position signals as the displacement signal based on an estimated displacement.
Claims14
Device for scanning a track on a record carrier via a beam of radiation, the track comprising marks representing information, the device comprising
- a head (22) for providing the beam and generating at least one sensor signal, the head comprising
- a focusing element,
- a focusing unit (25) for controlling the focusing element (34) to maintain an in-focus position for generating a focused spot on the track in dependence on a displacement signal based on the sensor signal,
- the displacement signal being indicative of a displacement of the focusing element with respect to an in-focus position, the sensor signal having overlapping ranges of sensor signal values for different ranges of the displacement,
- wherein
- a multitude of piecewise converters (42,43,44), each converter converting a range of the sensor signal values into a first, second and third position signal, and
- selection means (46) for comparing the first, second and third position signals with an estimated displacement signal and for selecting one of the first, second or third position signals as the displacement signal based on an estimated displacement.
Method of scanning a track on a record carrier via a beam of radiation, the track comprising marks representing information, the method comprising
- generating at least one sensor signal,
- controlling a focusing element to maintain an in-focus position for generating a focused spot on the track in dependence on a displacement signal based on the sensor signal, the displacement signal being indicative of a displacement of the focusing element with respect to an in-focus position, the sensor signal having overlapping ranges of sensor signal values for different ranges of the displacement,
- converting a multitude of ranges of the sensor signal values into a multitude of position signals,
- comparing the multitude of position signals with an estimated displacement signal;
- and
- selecting one of the position signals as the displacement signal based on said comparison.
Device for scanning a track on a record carrier via a beam of radiation, the track comprising marks representing information, the device comprising
- a head (22) for providing the beam and generating at least one sensor signal, the head comprising
- a focusing element,
- a focusing unit (25) for controlling the focusing element (34) to maintain an in-focus position for generating a focused spot on the track in dependence on a displacement signal based on the sensor signal,
- the displacement signal being indicative of a displacement of the focusing element with respect to an in-focus position, the sensor signal giving overlapping ranges of sensor signal values for different ranges of the displacement,
- wherein
- a multitude of piecewise converters (42, 43, 44), each converter a range of the sensor signal values into a first, second and third position signal, and
- selection means (46) for comparing the first, second and third position signals with an estimated displacement signal and for selecting one of the first, second or third position signals as the displacement signal based on an estimated displacement,
- wherein the selection means (46) comprises an estimator (47) for determining the estimated displacement based on previous values of the displacement signal, and
- wherein the estimator (47) calculates as the estimated displacement y=(2z2−1)/z3;
- z−1 indicating a delay unit in digital signal processing.
Dependencies are inferred from the claim text.