| 摘要 |
<p>The light-barrier arrangement for detecting flat or strip-type objects consists of a number of light source (1-10) and associated photosensors (1a-10a). The light sources and/or the receivers are activated in sequence and provide an output signal as long as there is no obstruction present (17). Instead of the individual light beams being focussed onto their normally opposite sensors (1-1a) to form a series of parallel, horizontal beams, the light path is deflected at an angle so that it falls onto the light sensor next in the series (1-2a). Since the falt strip object (17) has such a small cross-sectional area which meant poor detection with the former system, the angled beam arrangement provides a higher sensitivity. Alternatively, the emitters and sensors may be arranged on the same side with a retro-reflective plane on the other side of the target area.</p> |
