Frequency demodulating circuit, optical disk apparatus thereof and preformating device

Abstract

A frequency demodulating circuit, optical disk and preformatting device having a decoder for decoding a bit “0” and a bit “1” for reproducing address information recorded as a wobble groove. The decoder determines whether an output is a digital “1” or a digital “0” so that even if the waveform of the reproduced signal is erratic or unstable due to a defect, a digital “1” or a digital “0” can be correctly identified by utilizing window pulses. Changes in the slop of a zero cross point of the groove wobble are prevented from occurring by making the groove wobble amplitude fluctuate according to the signal frequency modulation which also greatly reduces jitter and allowing satisfactory acquisition of the address information. Oversampling clock signals of biphase bits are generated by frequency division of data clock signals. Since demodulation is accomplished with a single phase lock loop circuit in the data system using clock signals for both the data and the addresses, the configuration can be made extremely simple. By means of polarity of the playback signal mark having phase information, it is determined whether the beam that scans the optical disk is above the land or above the groove. The marks containing phase information are formed on the base disk surface solely by the on and off control of the paired cutting beams with respect to the direction of the time axis, for easy preformatting of a mark to permit acquiring (phase) position information with high precision.

Dependencies are inferred from the claim text.