| 摘要 |
PURPOSE:To detect a peak value of information by constituting a photodetector receiving reflected or transmitted light from a recording medium by >=2 photodetecting sections at least and forming a difference of signals from each photodetecting section. CONSTITUTION:Outputs of the photodetectors 16a, 16d are added and a signal 30 proportional to the intensity of one side of a distributed pattern is obtained. Another signal 31 is obtained similarly by the photodetectos 16d, 16c. Further, a signal 33 representing the change in the entire reflected light amount is obtained by the photodetectors. A waveform risen at the zero point is formed by passing the signal 32 through a comparator 40 for detecting the zero point, inputted to a monostable multivibrator 41 from which a pulse is outputted in response to the leading. The signal 33 outputs a pulse keeping ''1'' while the spot passes through a pit through a comparator 42. A gate 43 passes through the output of the 41 by taking an output of the 42 as a gate signal. Then, a pulse is outputted when the spot is made incident to the center of the pit. This pulse represents accurately the center of the pit. |
