Optical disc medium, reproduction method thereof and reproduction apparatus

An optical disc medium comprising:

• a track structure in which pits are arranged spirally;
• a sector structure formed by recorded information and having sectors each holding a given amount of data, the sectors holding header information therein;
• and
• header regions in which header information is recorded and which are arranged at regular intervals in recorded pit arrays;
• wherein an integral multiple of a half of a period of the wobble is coincident with the interval at which the header regions are arranged;
• and
• wherein the header regions are present in positions where the amount of the wobble of the tracks is substantially zero.

A reproduction method for an optical disc medium having a track structure in which pits are arranged spirally, the tracks being wobbled radially, the wobble having a period of Twob in a circumferential direction, said reproduction method comprising the steps of:

• rotating the optical disc medium at a rotational speed of Frot;
• bringing the track present in a radial position R under tracking servo control using a control system possessing characteristics having a frequency bandwidth of Fc of a relationship given by Eq. (1);
• Twob<2π×R×Frot/Fc (1)
• generating a frequency reference signal having a frequency proportional to a channel frequency in the radial position from a tracking error signal;
• and
• providing a frequency acquisition of a PLL based on the frequency reference signal.

A reproduction method for an optical disc medium having a track structure in which pits are arranged spirally, the tracks being wobbled radially, the wobble having a period of Twob in a circumferential direction, said reproduction method comprising the steps of:

• rotating the optical disc medium at a rotational speed of Frot;
• bringing the track present in a radial position R under tracking servo control using a control system possessing characteristics having a frequency bandwidth of Fc of a relationship given by Eq. (5);
• Twob>2π×R×Frot/Fc (5)
• generating a frequency reference signal having a frequency proportional to a channel frequency in the radial position from an output signal from a compensator used for the tracking servo control or from a tracking drive signal;
• and
• providing a frequency acquisition of a PLL based on the frequency reference signal.

A reproduction apparatus for reproducing data by rotating an optical disc medium at a rotational speed of Frot, the medium having a track structure in which pits are arranged spirally, the tracks being wobbled radially, the wobble having a period of Twob in a circumferential direction, said reproduction apparatus comprising:

• a laser for directing laser light at the optical disc medium;
• an optical detector for detecting light returning from the optical disc medium;
• tracking error signal generating means for generating a tracking error signal based on an output from the optical detector;
• a compensator for appropriately compensating the tracking error signal in amplitude and phase;
• tracking drive signal generating means for generating a tracking drive signal based on an output from the compensator;
• a tracking servo system including a tracking actuator for adjusting a laser light position on a disc surface based on the tracking drive signal;
• reproducing signal generating means for generating a reproducing signal based on an output from the optical detector;
• a PLL for generating a clock signal phase-locked to the reproducing signal;
• and
• frequency reference signal generating means for generating a frequency reference signal synchronized with the wobble based on the tracking error signal;
• wherein, when the optical disc medium is read at a radial position of R, the tracking servo system having a frequency bandwidth of Fc is so designed as to satisfy Eq. (1)
• Twob<2π×R×Frot/Fc (1)
• and;
• wherein the PLL provides a frequency acquisition based on the frequency reference signal.

A reproduction apparatus for reproducing data by rotating an optical disc medium at a rotational speed of Frot, the medium having a track structure in which pits are arranged spirally, the tracks being wobbled radially, the wobble having a period of Twob in a circumferential direction, said reproduction apparatus comprising:

• a laser for directing laser light at the optical disc medium;
• an optical detector for detecting light returning from the optical disc medium;
• tracking error signal generating means for generating a tracking error signal based on an output from the optical detector;
• a compensator for appropriately compensating the tracking error signal in amplitude and phase;
• tracking drive signal generating means for generating a tracking drive signal based on an output from the compensator;
• a tracking servo system including a tracking actuator for adjusting a laser light position on a disc surface based on the tracking drive signal;
• reproducing signal generating means for generating a reproducing signal based on an output from the optical detector;
• a PLL for generating a clock signal phase-locked to the reproducing signal;
• and
• frequency reference signal generating means for generating a frequency reference signal synchronized with the wobble based on the tracking error signal;
• wherein, when the optical disc medium is read at a radial position of R, the tracking servo system having a frequency bandwidth of Fc is so designed as to satisfy Eq. (5)
• Twob>2π×R×Frot/Fc (5)
• and;
• wherein the PLL provides a frequency acquisition based on the frequency reference signal.