Patent ID: 7254099

Claim:
A method for deriving a tracking error signal based on a first analog detection signal and a second analog detection signal, the method comprising: summing the first analog detection signal and the second analog detection signal to generate an analog sum signal; utilizing an analog delay device to delay the analog sum signal into a delay signal; digitalizing the delay signal into a digital delay signal; transforming the first analog detection signal and the second analog detection signal respectively into a first digital detection signal and a second digital detect signal; respectively comparing the digital delay signal with the first digital detection signal and comparing the digital delay signal with the second digital detection signal to generate the tracking error signal; providing a third analog detection signal and a fourth analog detection signal; summing the first analog detection signal, the second analog detection signal, the third analog detection signal, and the fourth analog detection signal to generate an analog summing signal; utilizing the analog delay device to delay the analog summing signal into a delay summing signal; digitalizing the delay summing signal into a digital delay summing signal; transforming the third analog detection signal and the fourth analog detection signal respectively into a third digital detection signal and a fourth digital detect signal; and applying a plurality of comparing processes to the digital delay summing signal respectively with the first digital detect signal, the second digital detect signal, the third digital detect signal, and the fourth digital detection signal to generate the tracking error signal.