| 摘要 |
PURPOSE:To prevent clouding in a short response time and prevent disturbance on function, by disposing glass plates with heater in a way to cover the front faces of emitter and detector, and heating when the quantity of light received becomes less than the specified limit due to deposit of moisture. CONSTITUTION:Emitters 2 and detectors 8 are opposedly provided, and an object is designed to pass between them. In thus constituted photoelectric detector, glass plates with heater 6, 12 are disposed in a way to cover the front faces of the emitters 2 and detectors 8. Only when the quantity of light received by the detector 8, while not detecting any object, becomes less than the specified limit due to deposit of moisture, a controlling relay 20 is actuated by a guantity of light received detecting circuit 14 for controlling the glass plates with heater 6, 12 provided on a specified detector 8 to put the glass plates with heater 6, 12 into heating operation. Thus, clouding may be prevented in a short response time, and disturbance on function may be also prevented. |
