| 摘要 |
An apparatus for detecting weak beams in an beam detecting system includes a plurality of emitters 60 for radiating beams of energy, a plurality of detectors 80 for providing detector signals in response to the beams of energy radiated by said plurality of emitters and means for detecting if the beams radiated by said plurality of emitters are weak. If weak beam is detected, the beam is determined inoperative by the obstruction detection system and is not considered in subsequent obstruction detection. <IMAGE> |
