| 摘要 |
PURPOSE:To extract and detect the component of a detected voltage corresponding to the light intensity of a succeeding low-level beam for confirmation and reproduction by passing the detected voltage proportional to a photovoltaic current detected by a photodetector through an upper-limit circuit. CONSTITUTION:A preceding beam A for recording and succeeding beam B for confirmation and reproduction are received by one photodetector 14. The photovoltaic current detected by the photodetector 14 becomes the sum of those of the two beams, but, since each beam contains erroneous fluctuating components, the component of each beam cannot be separated from each other in an uncomplicated way. When the voltage detected by the photodetector 14 is passed through an upper-limit circuit 18, the signal obtained from the circuit 18 becomes signals of a waveform containing no fluctuating component of the beam A for recording. When such signals are electrically processed, only the component corresponding to the light intensity of the succeeding beam for confirmation and reproduction having a low light intensity can be extracted and detected. Therefore, by controlling the light intensity of the succeeding beam B based on the detected result of the component, confirming and reproducing operations are performed under a fixed output. |
