Patent ID: 7310291

Claim:
A method of producing a tracking error signal using optical detection signals generated by at least two optical detectors positioned along each of two lines diagonal to a track center, the method comprising: summing the optical detection signals generated by the at least two optical detectors positioned along the each of two lines diagonal to the track center to produce summation signals; binarizing each of the summation signals; phase locking to generate respective clock signals synchronized with each of the binarized outputs, wherein the phase locking comprises generating a first clock signal and phase locking each of the binarized outputs with the first clock signal to generate the respective clock signals; dividing the first clock signal when the output tracking error signal is inverted according to the first clock signal being outside the range of the phase locking; detecting a phase difference between the synchronized clock signals; and low-pass filtering the detected phase difference to output the tracking error signal.