| 摘要 |
PURPOSE:To confirm visually easily whether or not a scanning beam is made incident on a photodetector for detecting horizontal synchronization by providing a horizontal synchronizing display means for displaying that the photodetector detects the scanning beam. CONSTITUTION:When a light beam is detected periodically by a PIN photodiode 20 at each scanning, a pulse A (horizontal synchronizing signal) is outputted from a voltage comparator 21 at each detection. The pulse A is transmitted from an output terminal to a write (recording) control circuit of a laser recorder and inputted to an IC timer 22, where the pulse width is widened and fed to a light emitting diode 23. A pulse B obtained by widening the pulse width of the puls Ais outputted from the IC timer 22, then a light emitting diode 23 is lighted and it is observed by human eyes as if the diode is lighted always. Thus, whether or not the scanning beam is made incident on the photodetector, that is, whether or not the horizontal synchronizing signal is obtained normally is confirmed by confirming the lighting of the light emitting diode 23.
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