Patent ID: 7558160

Claim:
An apparatus for demodulating a focusing error signal in an optical disc system comprising: means for generating a beam strength signal and said focusing error signal; means for sampling said beam strength signal and said focusing error signal at an appropriate sampling rate; means for removing static offset from said beam strength signal and said focusing error signal; means for calibrating a peak-to-peak value of said beam strength signal and said focusing error signal; means for determining an appropriate phase to (i) demodulate said focusing error signal and (ii) calculate a vertical position of a lens in relation to said optical disc; and means for entering into a first phase when said beam strength signal is greater than a beam strength threshold (BST) and a threshold value of the difference between said beam strength signal and an absolute value of said focusing error signal is greater than an absolute value of the difference between said beam strength signal and said absolute value of said focusing error signal.