Method and device for retrieving information from an optical record carrier at various reading speeds
AssigneeKoninklijke Philips Electronics N.V.
InventorsJohannes H.M. Spruit, Bas Feddes, Jacob G. Nijboer, Paul Weijenbergh
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Abstract
The present invention is related to a method and a reading device (1) for retrieving information from an optical record carrier (10) in which the read power level of a radiation beam (3) for scanning the optical record carrier is set in dependence on the read-out speed. The invention is also related to a record carrier for use with such a method and a reading device.
Claims9
A method of retrieving information from an optical record carrier (10) comprising the steps of:
- setting a power level of a radiation beam to a predetermined read power level,
- scanning the record carrier by the radiation beam (3),
- detecting a reflected radiation beam reflected from the record carrier, and
- retrieving the information from the reflected radiation beam (9),
- characterized in that
- the power level of the radiation beam is set in dependence on a read-out speed to a read power level of
- ((1−α)+α√{square root over (n)})•PN
- where α is a predetermined parameter with 0.2<α<0.8, and PN is a read power level at a nominal read-out speed, and n is the actual read-out speed divided by the nominal read-out speed.
A reading device (1) for retrieving information from an optical record carrier (10) comprising
- a radiation source (2) for generating a radiation beam (3),
- a setting means (6) for setting a power level of the radiation beam to a predetermined read power level,
- a scanning means (5, 7) for scanning the record carrier by the radiation beam,
- a detector (4) for transferring a reflected radiation beam (9), said reflected radiation beam reflected from the record carrier, into an electrical signal (13), and
- a decoding means (8) for retrieving the information from said electrical signal,
- characterized in that
- the setting means is arranged for setting the power level of the radiation beam in dependence on a read-out speed to a read power level of
- ((1−α)+α√{square root over (n)})•PN
- where α is a predetermined parameter with 0.2<α<0.8, and PN is a read power level at a nominal read-out speed, and n is the actual read-out speed divided by the nominal read-out speed.
Optical record carrier as claimed in 8 comprising multiple information layers, wherein said area comprises patterns of optically detectable marks and of spaces between the marks representing values of the parameter α for each of the information layers.
Dependencies are inferred from the claim text.