| 摘要 |
PURPOSE: To secure the safety of an operator by surely stopping the light emitting of a semiconductor laser when he opens the door. CONSTITUTION: When the door of the device is opened, a door switch 6, which is normally closed, is opened to shut off a power supply circuit Vccd of an LD (a semiconductor laser) 5a from a power supply Vcc (DC 5V) of an engine driver 40. Then, the output of a comparator (a voltage detector), which always monitors and compares the voltage and a threshold voltage (4.5V), becomes low, a gate (a gate means) 1 is closed and video signals are shut off. Thus, the video signals detour into the circuit Vccd through a surge protecting diode D2, charges up a condenser C1 whose voltage does not become zero. Thus, the light emitting of the laser LD5a stops and the trouble is surely eliminated. |
