Optical disk apparatus for recording/erasing information in the M-CAV format by using gain switching to increase the speed of the master clock

Claim 1

An optical disk apparatus for recording data onto an optical disk having a plurality of substantially concentric tracks which are divided into a plurality of zones arranged in a radial direction of the disk, each zone being divided into the same number of sector regions each used as a unit area and each sector region having a different assigned frequency at which its data are read, said apparatus comprising: data-generating means for generating data to be recorded; beam-generating means for generating a light beam; drive means for rotating an optical disk at a constant speed; beam-focusing means for focusing the light beam onto a track of the optical disk, detecting the light beam reflected from the track, and reproducing signals from the light beam reflected from the track; signal-detecting means for detecting a data clock signal from the signals reproduced; position-detecting means for detecting a start position of a sector region of the optical disk from the signals reproduced, generating a sector-start signal, and, in response to the sector-start signal, demodulating data obtained from the signals reproduced using the data clock signal; zone-switching detecting means for detecting, from the data reproduced, that the optical disk apparatus currently reading a first zone of the plurality of zones of the optical disk has been switched to begin reading a second zone of the plurality of zones of the optical disk, thereby generating a zone-switching signal, and generating a frequency-setting signal representing a frequency assigned to the second zone; a reference clock source for providing a reference clock signal; a phase-locked loop circuit for setting a frequency in accordance with the frequency-setting signal, generating a master clock signal having a frequency set by the reference clock signal input, and switching a gain of the phase-locked loop circuit to acquire a new response characteristic for the phase-locked loop circuit; gain-switching means for switching the gain of said phase-locked loop circuit in response to the zone-switching signal and the sector-start signal, thereby generating the master clock signal having the frequency set by said phase-locked loop circuit; and data-modulating means for modulating data into record signals by using the master clock signal generated by said phase-locked loop circuit, modulating the light beam generated by said beam-generating means by using the record signals, and applying the light beam onto the optical disk to write the data into the sector region of the optical disk.