Patent ID: 8379497

Claim:
An optical disc apparatus comprising: a laser light source; a light-source driving portion configured to pulse-drive the laser light source; an optical system configured to irradiate an optical disc with a laser beam emitted from the laser light source; a means for converting information, which has been optically read from the optical disc by the laser beam irradiation, into an electrical pulsed read signal; a means for converting the electrical pulsed read signal into a sampled pulsed read signal; a means for decoding data recorded on the optical disc, based on the sampled pulsed read signal, said means including an asynchronous Viterbi decoder configured to operate with a clock asynchronous with a channel clock; a means for estimating a frequency and a phase of the channel clock based on the sampled pulsed read signal; a means for generating a target level with the use of the estimated value of the phase of the channel clock, the target level to be used by the asynchronous Viterbi decoder; a means for adjusting the sampling frequency of the sampled pulsed read signal, to be close to the frequency of the channel clock; and a controller configured to detect a read rate from the channel clock frequency, and then to set the means for adjusting the sampling frequency of the sampled pulsed read signal in accordance with the read rate.