| 摘要 |
An address is reliably demodulated when a phase shift in a wobble signal has been induced by a crosstalk signal from an adjacent track. Address information is modulated by a binary phase modulation scheme and embedded into an optical disk as a wobble signal. A 0-degree phase wobble signal and a 180-degree phase wobble signal are brought out of phase with each other by crosstalk from an adjacent track. An address decoder performs exclusive-OR operation of the wobble signal and a reference clock signal, to thus compute a ratio at which an exclusive-OR result assumes a value of 1 (H) every half period of the reference clock signal. The thus-computed ratio is compared with a threshold ratio. The threshold ratio is usually set to 50%. However, when a phase shift has been caused by crosstalk, a system controller changes the threshold ratio to a ratio of 50% or less.
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