Tracking and focus servo system with error signal inverse non-linearity calibration

1. A method of providing operating parameters for a digital servo system of an optical disk drive, comprising:

selecting an error signal offset for a digital servo system from a set of error signal offset values;

determining an error signal gain value corresponding to the error signal offset such that a loop gain of the digital servo system is approximately unity; and

storing the error signal gain value in a look-up table.

2. The method of claim 1 , wherein the loop gain is measured at a cross-over frequency.

3. The method of claim 1 , further including

calibrating a second error signal gain in a second digital servo system; and

storing the second error signal gain in the look-up table.

4. The method of claim 3 , further including

calibrating a second error signal offset in the second digital servo system; and

storing the second error signal offset in the look-up table.

5. The method of claim 4 , further including

calibrating a second loop gain in the second digital servo system; and

storing the second loop gain in the look-up table.

6. The method of claim 5 , further including

calibrating a cross-coupling parameter between the digital servo system and the second digital servo system; and

storing the cross-coupling parameter in the look-up table.

7. The method of claim 6 , wherein the digital servo system is a focus servo system and the second digital servo system is a tracking servo system.

8. A method of calibrating inverse non-linearity in a focus servo system and a tracking servo system, comprising:

selecting a focus error signal offset value from a set of offset values;

calibrating a focus error signal gain corresponding to the focus error signal offset; and

storing the focus error signal gain in a look-up table,

wherein, during operation of the focus servo system, the focus servo system looks up the focus error signal gain corresponding to the focus error signal offset in the look-up table.

9. The method of claim 8 , wherein calibrating the focus error signal gain includes adjusting the focus error signal gain until a loop gain of the focus servo system is approximately unity.

10. The method of claim 9 , wherein adjusting the focus error signal gain includes measuring the loop gain of the focus servo system at a cross-over frequency.

11. The method of claim 10 , wherein the cross-over frequency is about 1.5 kHz.

12. The method of claim 8 , further including

calibrating a tracking error signal gain corresponding to the focus error signal offset; and

storing the tracking error signal gain in the look-up table.

13. The method of claim 12 , further including

calibrating a tracking error signal offset corresponding to the focus error signal offset; and

storing the tracking error signal offset in the look-up tables.

14. The method of claim 13 , further including

calibrating a tracking loop gain corresponding to the focus error signal offset; and

storing the tracking loop gain in the look-up table.

15. The method of claim 14 , wherein calibrating the tracking loop gain includes measuring the tracking loop gain at a tracking cross-over frequency.

16. The method of claim 15 , wherein the tracking cross-over frequency is about 1.8 kHz.

17. The method of claim 14 , further including

calibrating a tracking error signal to focus error signal crosstalk parameter; and

storing the crosstalk parameter in the look-up table.

18. An optical disk drive, 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 at least one processor calculating control signals; and

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

wherein the at least one processor executes an algorithm that selects a focus error signal offset value from a set of offset values, calibrates a focus error signal gain corresponding to the focus error signal offset,

stores the focus error signal gain in a look-up table, calibrates a tracking error signal gain corresponding to the focus error signal offset;

calibrates a tracking error signal offset corresponding to the focus error signal offset;

calibrates a tracking loop gain corresponding to the focus error signal offset; and

stores the tracking error signal gain, the tracking error signal offset, and the tracking loop gain in the look-up table.