| 摘要 |
<p>A coin mechanism having a coin storage tube (102) and an optical sensor for sensing the level of coins in the tube, the sensor comprising a light source (108) arranged to direct a light beam across the tube, means for returning the beam across the tube and a light detector (112) for detecting the returned beam, characterised in that the means for returning the beam is a concave mirror (114) having a curvature such as to give the beam an area, where it approaches the detector, substantially greater than the effective area of the detector. This enables, in a compact sensor, the light intensity at the detector to be enhanced and at the same time the sensivity to misalignment of components to be reduced.</p> |
