SERVO CALIBRATION MARK DETECTION CIRCUIT FOR HD-DVD OR DVD-RAM AND METHOD THEREOF

The invention provides a servo calibration mark detection circuit for use in an optical disk drive. In one embodiment, the servo calibration mark detection circuit comprises a summing processor, a slicing level generator, and a comparator. The summing processor sums an intensity of a light beam reflected from both an inner groove and an outer groove to obtain a first signal. The slicing level generator generates a slicing level. The comparator then compares the first signal with the slicing level to obtain a second signal, wherein the second signal indicates a first location of a first servo calibration mark recorded on the inner groove and a second location of a second servo calibration mark recorded on the outer groove.