| 摘要 |
PURPOSE:To detect a fault without interrupting a laser beam over the whole scanning period by forming a detector for detecting a scanning range in which no laser beam is sent after the detection of the other detector. CONSTITUTION:A laser beam scanned by a rotary polyhedral mirror 7 is detected by a detector through a reflector 14 prior to the scanning of a prescribed scanning range AB of a photosensitive body 6 and a recording control part 1 sends recording information while regarding a detecting signal generated from the detector 8 as a reference signal and generates a control signal for interrupting or sending the laser beam. When the sending of the laser beam is not interrupted even if the detector 8 detects the laser beam at the generation of a fault in the control part 1, an analog converter 2, an ultrasonic modulator 3, etc., the laser beam is detected by a detector 9 and an alarm circuit 10 generates an alarm. Thus, the fault in the control part 1, the converter 2, the modulator 3, etc. can be detected.
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