| 摘要 |
PURPOSE:To attain to enhance safety by detecting an invader, by arranging plural sets of infrared beam emitters and receivers at desired intervals in parallel, and transmitting and receiving pulse beams respectively modulated by carrier waves having different frequencies. CONSTITUTION:Beam emitters 5, 6 and beam receivers 7, 8 of infrared beams 3, 4 are respectively attached to stakes 1, 2 provided to both sides of a part to be detected at desired intervals in an up-and-down direction. Next, carrier waves mutually different in frequency are applied to a light emitting diode while modulated by rectangular pulse waves and infrared beams are emitted from the beam emitters 5, 6 while received by phototransistors in the beam receivers 7, 8 and applied to a narrow band pass filter to pass only the signal of the corresponding transmitter and, thereafter, said signal is detected and amplified to issue an alarm. By this method, if infrared beam is blocked even if it is one, an alarm is certainly issued and safety can be secured. |
