| 摘要 |
The grid has receivers (5, 5', 5'') provided for transmitters (2, 2') such that transmission light beams (3, 3') of the transmitters are guided through a reflector (7) as received light beams (4, 4', 4'') at the receivers in a free monitoring area. The transmitters are individually activated one after the other such that a difference of the received light beams of the receivers is evaluated for each activated transmitter. An object (6) e.g. small object, in the monitoring area is identified when the difference of received light beams is different from a reference value. |
