Patent ID: 8542565

Claim:
An optical drive apparatus comprising: an optical system for irradiating a recording surface of an optical disk with an optical beam; an optical detector that is divided into a plurality of light receiving areas and outputs a signal indicating an amount of a reflected light of the optical beam reflected from the recording surface for each of the light receiving areas; a signal generating unit that generates a first signal that becomes high when an output signal of the optical detector corresponding to at least one of the light receiving areas is equal to or larger than a predetermined value and becomes low otherwise and a second signal that becomes high when an output signal of the optical detector corresponding to other at least one of the light receiving areas is equal to or larger than a predetermined value and becomes low otherwise; a first phase-difference detection-signal generating unit that generates a phase lead detection signal based on a first delay signal obtained by delaying a phase-lead output signal indicating a phase lead amount of the first signal with respect to the second signal by a predetermined time and a third logical signal that is changed to high at a timing at which a first logical signal that becomes low when both the first and second signals are high and becomes high when either one of the first and second signals is low is changed from high to low, and changed to low at a timing at which a second logical signal that becomes high when either one of the first and second signal is high and becomes low when both the first and second signals are low is changed from high to low, and generates a phase lag detection signal based on a second delay signal obtained by delaying a phase-lag output signal indicating a phase lag amount of the first signal with respect to the second signal by a predetermined time and the third logical signal; and a DPD signal generating unit that generates a phase difference signal indicating a phase difference between the first and second signals based on the phase lead detection signal and the phase lag detection signal, and generates a DPD signal based on the phase difference signal.