| 摘要 |
PURPOSE:To detect an ID part signal by delivering the prescrined number of pulses during the rotation of a turntable containing an optical disk and at the same time reading periodically the ID part and the data part out of the optical disk for calculation of the ID length and the data length. CONSTITUTION:An encoder 38 produces pulses equivalent to an integer multiple of the number of sectors while a turntable motor 37 has a rotation. The optical disk reproduction signal amplified by a read amplifier circuit 31 is converted into a pulse signal by a waveform shaping circuit 32 and supplied to a monostable multivibrating circuit 33. A data length calculating circuit 34 starts to count the encoder pulses by the ID part detection permitting signal designated by a control circuit 39 and with the fall of the output signal of the circuit 33. Then the circuit 34 counts the number of pulses designated by the circuit 39. While an ID length counting circuit 35 starts to count the encoder pulses by the output signal of the circuit 34 and then counts the number of pulses designated by the circuit 39. An ID part detecting signal generating circuit 36 can deliver the ID part detecting signals while the circuit 35 starts counting and then ends it. The second and subsequent counting actions of the circuit 34 are started with the output signal of the circuit 35.
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