| 摘要 |
<p>A touch-sensitive key has a radiation-propagating prism or plate (2) between a radiation source (1) and a radiation detector (6). Radiation is scattered from a top surface (3) of the prism or plate (2) so as to reach and activate the detector (6) through a side surface (5) when the top surface (3) is touched. External radiation (9) is free to enter the prism or plate and to leave through the side surface but this radiation is not capable of actuating the detector. In one embodiment (Fig. 1) the detector (6) is spaced from the side surface (5) so that it cannot be reached by external radiation. In an alternative embodiment (Fig. 2) external radiation (18) is subjected to multiple reflections within the prism or plate (2a) and at each reflection part of the radiation is transmitted through the pertaining surface (17) to be absorbed in a substrate layer (19). </p> |
