| 摘要 |
PURPOSE:To prevent the destruction of recorded data by converting the reflected light quantity of the beam light obtained in a record mode into electric signals to apply the DC amplification to these signals, and detecting the lower end envelope curve of the output of said DC amplification to compare the detection result with a prescribed level. CONSTITUTION:When the beam light of an optical head 3 is shifted to a recorded track, the reflected light to be given to a recorded bit of an optical disk 1 is also supplied to a phototransistor TR10. While the amplified ones are also contained in those output signals of a DC amplifier 12. When the detection output level of a lower end envelope curve detecting circuit 13 is reduced less than a fixed level and then less than a slice level, a double recording detecting signal is delivered to an AND circuit 16 from a comparator 14 via an inverter 15. Then a gate of the circuit 16 is closed by the double recording detecting signal. Thus the output of a record data pulse is inhibited, and a laser driver 17 keeps the output of a laser oscillator 4 at a low level. Thus the double recording is avoided on the disk 1. This can prevent the destruction of the recorded data. |
