Patent ID: 7720180
Filing Date: 2010-05-18
Classification: G11B

Abstract:
1. A tracking error detection method usable in a Differential Phase Detection (DPD) system of an optical disc device, the system comprising: converting a first analog radio frequency (RF) signal, a second analog RF signal, a third analog RF signal, and fourth analog RF signal into a first digital signal, a second digital signal, a third digital signal, and a fourth digital signal, wherein a phase difference between the first and second analog RF signals varies corresponding to a tracking error from an optical pickup, and wherein a phase difference between the third and fourth analog RF signals varies corresponding to the tracking error from the optical pickup; monitoring the sign of each digital value for each sampling interval for the first digital signal, the second digital signal, the third digital signal, and the fourth digital signal; determining times for each zero crossing with a predetermined approximation formula when there is a change of sign between consecutive digital values for each of the first and second digital signals; determining times for each zero crossing with the predetermined approximation formula when there is a change of sign between consecutive digital values for each of the third and fourth digital signals; determining time differences between corresponding zero crossings of the first and second RF signals; determining time differences between corresponding zero crossings of the third and fourth RF signals; and generating a synthetic digital tracking error signal based at least in part on the time differences between corresponding zero crossings of the first and second RF signals and the time differences between corresponding zero crossings of the third and fourth RF signals by: