| 摘要 |
<p>The sensor (1) has two strips (8, 10) comprising transmitter elements (L1-Ln) and receiver elements (E1-En). The transmitter elements of one of the strips form transmitter/receiver pairs with receiver elements of the other strip for the formation of a protective field (14). A light beam (12) is between the transmitter elements and receiver elements counts when received light falls below a lower switching threshold (S1). An upper switching threshold (S2) is provided in an evaluation unit (22) whose value lies above the value of the lower switching threshold.</p> |
