Patent ID: 7035187

Claim:
A method for providing slice levels of a slice level signal adapted to an optical system, wherein the slice levels of the slice level signal are used to slice an RFRP (RF ripple) signal, the method comprising: in response to a track-crossing operation, entering a first mode to generate the slice level signal having a first-mode slice level by using a predetermined slice level in a beginning when the optical system starts to perform the track-crossing operation for reading data until about a first time that is determined with respect to a low-pass filter; entering a second mode from about the first time to generate the slice level signal having a second-mode slice level by feeding the RFRP signal into the low-pass filter, wherein the first time indicates when the low-pass filter has caught variations of the RFRP (RF ripple) signal; and in response to the track-on command, entering a third mode to generate the slice level signal having a third-mode slice level according to an average value derived from the RFRP signal.