US 7,558,160 B2
Demodulation of a focusing error signal during a focus search for a lens focusing control in an optical disc system
Ainobu Yoshimoto, Milpitas, Calif. (US); Hyun-Gyu Jeon, Pleasanton, Calif. (US); and Yuan Zheng, Newark, Calif. (US)
Assigned to LSI Corporation, Milpitas, Calif. (US)
Filed on Jun. 14, 2005, as Appl. No. 11/152,554.
Prior Publication US 2006/0280104 A1, Dec. 14, 2006
Int. Cl. G11B 7/00 (2006.01)
U.S. Cl. 369—44.11  [369/53.23] 15 Claims
OG exemplary drawing
 
2. A method for demodulating a focusing error signal in an optical disc system, comprising the steps of:
(A) generating a beam strength signal and said focusing error signal;
(B) sampling said beam strength signal and said focusing error signal at an appropriate sampling rate;
(C) removing a static offset from said beam strength signal and said focusing error signal;
(D) calibrating a peak-to-peak value of said beam strength signal and said focusing error signal;
(E) 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
(F) 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.