| 摘要 |
PURPOSE:To prevent optical parts from deteriorating and poor working from occurring in a beam conduct by providing a smoke detecting means in the beam duct shielding laser beams and actuating an output control means by signals from this smoke detecting means. CONSTITUTION:When smoke powder 20, etc., flows into the beam duct light emitted from a light emitting diode 13 is scattered by the smoke powder 20 and part of the light arrives at a light sensor 14. This light is detected by the sensor 14, becomes electrically conductive, is amplified by a light receiving amplifier circuit 15 and outputted as pulse signals. Since an analog switch 17 repeats ONs, OFFs synchronizing with signals of the synchronous pulse generating circuit 16, only signals by the induced light sensor 14 are inputted into a voltage hold circuit 18. The circuit 18 clamps a signal from the light receiving amplifier circuit 15, converts it into a DC signal, and outputs it. When a comparison circuit 19 compares it with a threshold value signal VTH and the signal of the voltage hold circuit 18 is larger than the threshold value signal VTH, the relay is excited and the laser beam stops oscillation as soon as buzzer operates. |
