Opto electronic device for detecting object in security zone

摘要

The device has a transmitter (2) and a pair of cooperating receivers (3,4) positioned at one edge of the security zone (1), with a reflector (6) at the opposite edge. The signal from one of the receivers (3) is evaluated via a threshold value. The other receiver (4) is provided with a resolution detector, for determining the length of the light path to the reflector or an object within the security zone. The outputs of both receivers are fed to an evaluation stage employing a combining logic.