| 摘要 |
A retroreflective detector (<B>3</B>) comprises a detection unit (<B>31</B>), housing at least two transmitting elements (<B>51, 52</B>) and at least two receiving elements (<B>61, 62</B>). A transmitting element and a receiving element form a pair, two or more such pairs being disposed in a matrix on the transmitting/receiving surface of the housing (<B>32</B>) so that every row and column of the matrix includes one or more transmitting elements. The detector is less prone to false signalling triggered by the passing of small objects as both transmitters are not in vertical or horizontal alignment.
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