Digital focus and tracking servo system
First Claim
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1. A method of controlling a position of an optical pick-up unit, comprising:
- calculating an error signal from digitized signals received from detectors in an optical pick-up unit mounted on an actuator arm;
adding an offset value to the error signal to form a biased error signal;
digitally amplifying the biased error signal to form an amplified signal;
digitally filtering a pre-filtered signal related to the amplified signal to form a filtered signal; and
driving the actuator arm in response to a digital control signal related to the filtered signal to control the position of the optical pick-up unit.
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Abstract
A digital servo system for controlling tracking or focus in an optical disk driver is presented. A servo system according to the present invention includes an optical pick-up with detectors providing optical signals, an analog processor receiving the optical signals and providing a digital signal, and digital processors receiving the digital signal and providing a control signal that controls the position of the optical pick-up unit. The digital processor executes an algorithm that calculates an error signal, provides amplification and biasing to the error signal, provides filtering for the error signal, and computes the control signal. The error signal can be the focus error signal or the tracking error signal.
8 Citations
22 Claims
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1. A method of controlling a position of an optical pick-up unit, comprising:
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calculating an error signal from digitized signals received from detectors in an optical pick-up unit mounted on an actuator arm;
adding an offset value to the error signal to form a biased error signal;
digitally amplifying the biased error signal to form an amplified signal;
digitally filtering a pre-filtered signal related to the amplified signal to form a filtered signal; and
driving the actuator arm in response to a digital control signal related to the filtered signal to control the position of the optical pick-up unit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 18, 19, 20, 21)
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15. A servo system according to the present invention, comprising:
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at least one detector positioned in an optical pick-up unit, the at least one detector including optical detector elements, the optical pick-up unit being mounted on an actuator arm that controls a position of the optical pick-up unit;
an analog processor coupled to the optical detector elements of the at least one detector and providing digitized signals related to signals from the optical detector elements;
at least one digital processor coupled to receive the digitized signals and provide a control signal; and
a driver coupled to receive the control signal and control the actuator, wherein the at least one digital processor executes a servo algorithm that calculates an error signal from the digitized signals, adds an offset value to the error signal to form a biased error signal, amplifies the biased error signal to form an amplified signal, filters a pre-filtered signal related to the amplified signal to form a filtered signal, and calculates the control signal from the filtered signal.
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22. A system for controlling an optical pick-up unit in an optical drive, comprising:
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means for obtaining signals from an optical pick-up unit;
means for supplying a digitized signal;
means for calculating a control signal from the digitized signal;
means for controlling the position of the optical pick-up unit in response to the control signal.
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Specification
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Current AssigneeRPX Corporation
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Original AssigneeDPHI Incorporated
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InventorsKadlec, Ron J., Wach, Hans B., Watt, Charles R., Turner, Christopher J.
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Granted Patent
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Time in Patent OfficeDays
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Field of Search
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US Class Current369/44.29
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CPC Class CodesG11B 7/0941 Methods and circuits for se...
