| 摘要 |
PURPOSE:To improve the rate of detection of a head frame by constituting a data mark of the head frame of each sector with plural bit strings, and identifying it as the head frame when one of the bit strings is detected at reproduction. CONSTITUTION:One sector of the recording format consists of n-set frames, different data marks DM1-DM3 are added just before data in the 1st frame, and only the DM4 is added to the 2nd and succeeding frames. Then a reproducing signal 6 from an optical detector 5 is formed into a binary-coded reproducing signal 10 via an equalizer 8 and a binary coding compartor 9 and it is subject to serial/parallel conversion at a shift register 13 according to a clock pulse 12 from a clock reproduction circuit 11. The pattern 14 after conversion is fed to a detection circuit 15, and when the same bit pattern as the DM1-DM3 is detected in the signal 10, a data mark detection signal 16 is outputted and the signal 10 is demodulated (17) in the timing. |
