Patent ID: 7496010
Filing Date: 2009-02-24
Classification: G11B

Abstract:
1. A disk drive comprising: an optical head configured to emit a laser beam so as to illuminate a disk-shaped storage medium thereby writing or reading data on or from the disk-shaped storage medium, grooves serving as recording tracks being formed in a wobbling fashion on the disk-shaped storage medium, pre-pits being formed on lands between adjacent grooves, and the disk-shaped storage medium representing, using the pre-pits, address information indicating an address on the disk-shaped storage medium; a push-pull signal generator configured to generate a push-pull signal from reflected-light information detected by the optical head; an amplitude variation signal generator directly connected to the push-pull signal generator and configured to generate and output a fundamental amplitude variation signal indicating the fundamental amplitude variation of the push-pull signal, wherein the amplitude variation signal generator includes: a charging circuit for charging a capacitor in response to an increase in amplitude of the input push-pull signal, in a peak holding manner with a predetermined limited rising-up time constant, and a discharging circuit for discharging the capacitor such that the changed voltage of the capacitor falls down with a predetermined limited falling-down time constant whereby a signal corresponding to the charged level of the capacitor is output as the fundamental amplitude variation signal; an offset signal generator configured to generate an offset signal; a reference signal generator connected to the amplitude variation signal generator and to the offset signal generator and configured to generate a reference signal by adding the offset signal received from the offset signal generator to the fundamental amplitude variation signal received from the amplitude variation signal generator; a pre-pit detector directly connected to the push-pull signal generator and to the reference signal generator and configured to compare the push-pull signal with the reference signal and outputting a comparison result as a pre-pit detection signal; and an address decoder for acquiring address information represented by the pre-pits, from the output of the pre-pit detector.