| 摘要 |
<p>PURPOSE:To detect a small body with high accuracy in a detection space wherein a difference in air density is large by making respective spot light sources using an optical fiber bundle illuminate successively and detecting whether or not light is received at every light emission timing. CONSTITUTION:A light projector 21 and a light-receiver 22 are arranged opposed to each other in the detection space 23 in a heat furnace or on a cooling floor, etc., where the air has a large difference in density owing to the temperature difference, and the respective spot light sources composed of the optical fiber bundle 26 are arranged at the focus of a condenser lens 24. Then a control part 33 allows the spot light sources to be turned on successively and a decision part 33 decides whether or not light is received at every light emission timing point. When the body S is not present in the space 23, the light receiving output passes through a gate 36 which is opened at the light emission timing, an output circuit 44 outputs the absence of article and a display part 41 displays the corresponding spot light source. Further, when the body is present in the space 23, the respective display parts 41 are turned off and the presence of the article is outputted.</p> |
