| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain a crime-preventive sensor with a disturbance detecting function which can easily detect the presence of an obstacle when the obstacle such as a transparent seal is stuck on the external surface of a light-incidence side exclosure member of a crime-preventive sensor. SOLUTION: This sensor is equipped with a main body A which has an infrared detecting element 4, the light-incidence enclosure member 5, mounted in the main body A, like a lens which sets the detection area B of the infrared detecting element 4, a light projecting element 11 which projects a light beam L1 for disturbance detection on the light-incidence enclosure member 5 from the inside of the member 5, a photodetecting element 12 which photodetects reflected light L2 of the light beam for disturbance detection from the vicinity of the member 5, and a detecting circuit 15 which detects the obstacle 8 being stuck on the member 5 according to the photodetection quantity of the photodetecting element 12. Then a projection 7 is formed on the external surface of the member 5 to form a gap between the obstacle 8 stuck on its external surface and the external surface.</p> |
