Granted Patent B2

US 6,898,164 · App. 09/950,444 · Granted May 24, 2005

Abstract

Claims (60)

1. A method of closing tracking in a tracking servo system, comprising:

determining a track crossing rate, the track crossing rate being indicative of the speed of an optical pick-up unit relative to an optical medium;

comparing the track crossing rate with a threshold value;

when the track crossing rate is less than the threshold value, closing a tracking servo loop by enabling a tracking servo algorithm; and

reducing a rotation rate of the optical media if the track crossing rate is not below the threshold value within a predetermined period of time.

2. A method of closing tracking in a tracking servo system, comprising:

determining a track crossing rate, the track crossing rate being indicative of the speed of an optical pick-up unit relative to an optical medium;

comparing the track crossing rate with a threshold value;

when the track crossig rate is less than the threshold value, closing a tracking servo loop by enabling a tracking servo algorithm; and

enabling a low frequency integrator in the tracking servo loop after a first time delay from enabling the tracking servo loop.

3. A method of closing tracking in a tracking servo system, comprising:

determining a track crossing rate, the track crossing rate being indicative of the speed of an optical pick-up unit relative to an optical medium;

comparing the track crossing rate with a threshold value;

when the track crossing rate is less than the threshold value, closing a tracking servo loop by enabling a tracking servo algorithm; and

enabling a TES sample integrity test after a second time delay from enabling the tracking servo loop.

4. A method of closing tracking in a tracking servo system, comprising:

determining a track crossing rate, the track crossing rate being indicative of the speed of an optical pick-up unit relative to an optical medium;

comparing the track crossing rate with a threshold value;

when the track crossing rate is less than the threshold value, closing a tracking servo loop by enabling a tracking servo algorithm;

delaying for a first time period after enabling the tracking servo loop and enabling a low frequency integrator; and

delaying for a second time period after enabling the tracking servo loop and enabling a tracking error signal integrity test;

wherein the second time period is longer than the first time period.

5. A method of closing tracking in a tracking servo system, comprising:

determining a track crossing rate, the track crossing rate being indicative of the speed of an optical pick-up unit relative to an optical medium;

comparing the track crossing rate with a threshold value; and

when the track crossing rate is less than the threshold value, closing a tracking servo loop by enabling a tracking servo algorithm,

the tracking servo algorithm further including:

a TES offset, the TES offset adding an offset value to the tracking error signal derived from the optical signals received from the optical pick-up unit;

a TES gain amplifier, the TES gain amplifier amplifying an offset signal output from the TES offset;

filters receiving an amplified signal from the TES offset and providing a tracking control signal;

a driver receiving the tracking control signal and controlling an actuator arm to move the optical pick-up unit relative to the optical medium.

6. A tracking servo system, comprising:

an optical pick-up unit with optical detectors providing optical signals, the optical pick-up unit being mounted on an actuator arm which positions the optical pick-up unit over an optical media;

at least one digital to analog converter that receives signals related to the optical signals from the optical pick-up unit and provides digitized optical signals;

at least one processor that receives digitized signals related to the digitized optical signals and provides a control signal;

decimation filters coupled between the at least one digital to analog converter and the at least one processor; and

a driver that receives the control signal and controls the actuator arm,

the at least one processor executes an algorithm that,

determines a track crossing rate, the track crossing rate being indicative of the speed of an optical pick-up unit relative to an optical medium,

compares the track crossing rate with a threshold value, and

when the track crossing rate is less than the threshold value, closes a tracking servo loop by enabling the tracking servo system.

7. The system of claim 6 , wherein the at least one processor determines the track crossing rate by

computing a tracking error signal from the digitized signals;

determining the time period between zero crossings of the tracking error signal.

8. A tracking servo system, comprising:

means for receiving signals from an optical pick-up unit;

means for calculating a track crossing rate;

means for enabling a tracking servo algorithm when the track crossing rate is below a threshold;

means for applying a control signal from the tracking servo algorithm to an actuator arm controlling the position of the optical pick-up unit, thereby closing a tracking servo loop;

means for enabling an integrator in the tracking servo algorithm; and

means for enabling a tracking error signal sample integrity test in the tracking servo algorithm.

9. The method of claim 1 , wherein determining the track crossing rate includes:

obtaining a tracking error signal;

measuring a time period between zero crossings in the tracking error signal;

determining the track crossing rate from the time period.

10. The method of claim 9 , wherein obtaining the tracking error signal includes:

receiving optical signals from at least one optical detector in the optical pick-up unit, the at least one optical detector including two outside elements and an center element; and

calculating the normalized difference between the optical signals from the two outside elements for each of the at least one optical detector.

11. The system of claim 6 , further including a preamplifier coupled between the

optical pick-up unit and the at least one digital to analog converter.

Assignments (10)