Focus detection in a digital focus servo system
DC
First Claim
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1. A method of detecting focus in an optical disk drive, comprising:
- providing a digital signal processor configured to receive digitized versions of optical sensor signals from an optical pickup unit and form a focus error signal (FES) from the digitized versions, the digital signal processor configured with a digital servo algorithm that multiplies FES with an FES gain to provide a modified FES signal, the digital servo algorithm processing the modified FES signal to control focus in the optical disk drive;
obtaining a sum signal of the digitized versions;
obtaining a threshold value based upon the modified FES signal;
determining if the sum signal is below the threshold value; and
indicating a focus open condition if the sum signal is below the threshold value.
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Abstract
A system for determining whether a focus servo system is in focus or out of focus (i.e. open) is disclosed. A sum signal can be compared with a threshold value. If the sum signal is below the threshold value, then a focus open condition (i.e., out-of-focus) can be indicated. In some embodiments, a focus open condition is indicated where the sum signal remains below the threshold value for a predetermined period of time.
69 Citations
6 Claims
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1. A method of detecting focus in an optical disk drive, comprising:
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providing a digital signal processor configured to receive digitized versions of optical sensor signals from an optical pickup unit and form a focus error signal (FES) from the digitized versions, the digital signal processor configured with a digital servo algorithm that multiplies FES with an FES gain to provide a modified FES signal, the digital servo algorithm processing the modified FES signal to control focus in the optical disk drive;
obtaining a sum signal of the digitized versions;
obtaining a threshold value based upon the modified FES signal;
determining if the sum signal is below the threshold value; and
indicating a focus open condition if the sum signal is below the threshold value. - View Dependent Claims (2, 3, 4)
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5. A focus servo system, comprising:
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an optical pick-up unit mounted on an actuator arm, the optical pick-up unit being positioned over an optical media;
at least one analog to digital converter that digitizes signals received from detectors in the optical pick-up unit;
at least one processor coupled to receive versions of the digitized signals from the at least one analog to digital converter and to calculate a focus error signal (FES) from the versions, the at least one processor executing a digital servo algorithm that multiplies FES with an FES gain to provide a modified FES signal, the digital servo algorithm processing the modified FES signal to control focus in the optical disk drive; and
wherein the at least one processor executes software that, obtains a threshold value based upon the modified FES signal, computes a sum signal from the versions of the digitized signals, determines if the sum signal is below the threshold value, and indicates a focus open condition if the sum signal is below the threshold value. - View Dependent Claims (6)
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Specification
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Litigation Data
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Current AssigneeRPX Corporation
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Original AssigneeDPHI Acquisitions, Inc.
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InventorsKadlec, Ron J., Watt, Charles R.
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Primary Examiner(s)Miller, Brian E.
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Assistant Examiner(s)Agustin, Peter Vincent
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Application NumberUS09/950,394Publication NumberTime in Patent Office1,541 DaysField of Search369/53.28, 369/44.29, 369/53.34, 369/53.35, 369/44.25US Class Current369/53.28CPC Class CodesG11B 7/0908 for focusing only G11B7/092...G11B 7/0946 specially adapted for opera...G11B 7/0948 specially adapted for detec...
