Patent ID: 6882601

Claim:
A method of controlling the position of an optical pick-up unit over an optical media, comprising: calculating a control signal in response to digitized optical signals received from the optical pick-up unit; detecting periodic variations in the control signal; forming a new control signal by adding the periodic variations into the control signal; and controlling a position of the optical pick-up unit in response to the new control signal; said detecting periodic variations in the control signal including mixing the control signal with sin(ωt) to form a sin signal; mixing the control signal with cos(ωt) to form a cosine signal; accumulating the sin signal over a number of cycles to form an accumulated sin signal; accumulating the cosine signal over the number of cycles to form an accumulated cosine signal; integrating the accumulated sin signal to form a sine coefficient; and integrating the accumulated cosine signal to form a cosine coefficient.