| 摘要 |
<p>PURPOSE:To implement detection even at a short distance irrespective of stature, by a method wherein a lens plate formed of a Fresnel lens having a plurality of region, which is provided for setting a plurality of detection areas below the front of a hot-wire sensor in the longitudinal direction, is disposed in front of the detecting surface of the hot-wire sensor. CONSTITUTION:A pyroelectric element P as a hot-wire sensor and a printed circuit board 44 whereon a peripheral circuit element is mounted are fitted to a rotary frame 30. In front of a detecting surface of the element P mounted on this board 44, a lens plate 60 for setting detection areas is disposed. This lens plate 60 is a flat-plate-shaped Fresnel lens formed of a material transmitting infrared rays, such as high-density polyethylene, and it is formed to be rectangular. As for the detection areas, two regions are set therefor below the front of the detecting surface of the element P within a plane containing the axis of the rotary frame 30, and the respective center lines of the detection areas are set at 10 and 40 deg. downward from the element P. By this setting, human bodies, including little children and men whose average stature is about 100-170cm, can be detected even at a short distance, on condition that a general fitting height is set to be 120cm.</p> |
