Granted Patent B2

US 6,882,603 · App. 09/950,410 · Granted Apr 19, 2005

Abstract

Claims (34)

1. A method of detecting a tracking skate condition, comprising:

receiving a tracking error signal;

obtaining the absolute value of the tracking error signal;

filtering the absolute value of the tracking error signal with a low-pass filter to obtain a filtered signal;

comparing the filtered signal with a threshold value;

counting the number of times that the filtered signal exceeds the threshold value to obtain a count; and

indicating the tracking skate condition when the count exceeds a maximum value.

2. The method of claim 1 , further including

comparing the filtered signal with a second threshold value;

counting the number of times that the filtered signal exceeds the second threshold value to obtain a second count; and

indicating a second skate condition when the count exceeds a second maximum value.

3. The method of claim 2 , wherein the threshold exceeds the second threshold.

4. The method of claim 3 , wherein the skate condition indicates a tracking open condition.

5. The method of claim 3 , wherein the second skate condition enables an anti-skate algorithm, the anti-skate algorithm allowing a tracking servo to close when the tracking error signal is at a stable slope on a tracking error signal curve.

6. The method of claim 1 , wherein filtering the absolute value includes filtering with a second order low pass filter.

7. A servo system, comprising:

an optical pick-up unit;

an analog processor coupled to receive signals from detectors in the optical pick-up unit and provide digital signals;

at least one processor coupled to receive the digital signals, the processor calculating a control signal; and

a driver coupled to control the position of the optical pick-up unit in response to the control signal,

wherein the at least one processor executes an algorithm that

calculates a tracking error signal from the digital signals,

obtains the absolute value of the tracking error signal,

filters the absolute value of the tracking error signal with a low-pass filter to obtain a filtered signal,

compares the filtered signal with a threshold value,

counts the number of times that the filtered signal exceeds the threshold value to obtain a count, and

indicates a tracking skate condition when the count exceeds a maximum value.

8. The system of claim 7 , wherein the algorithm further includes

comparing the filtered signal with a second threshold value;

counting the number of times that the filtered signal exceeds the second threshold value to obtain a second count; and

indicating a second skate condition when the count exceeds a second maximum value.

9. The system of claim 8 , wherein the second skate condition enables an anti-skate algorithm, the anti-skate algorithm allowing a tracking servo to close when the tracking error signal is at a stable slope.

10. The system of claim 7 , wherein the skate condition indicates a tracking open condition.

11. The system of claim 7 , wherein the filter is a second order low pass filter.

Assignments (8)