| 摘要 |
<p>The method involves arranging several light barrier arrangements at or in openings, where the light barrier arrangements include several light emitting diodes (LED1) and a camera (K1) for receiving light emitting from the light emitting diodes. Time process of the light power received by the camera from the light emitting diodes is evaluated using a processor. An alarm is notified during failure of the light barrier arrangements. Radiation of the light emitting diodes and the reception of the camera are spectrally and/or temporally correlated with one another.</p> |
