Abstract: A light barrier having at least one transmitter (6) and at least one receiver (8) for a light beam and having a light path (1), which runs between a first side (2) and a second side (4) of a region to be monitored, can be produced flexibly and with little complexity by virtue of the transmitter (6) and of the receiver (8) being situated on the first side (2) and by virtue of the second side (4) containing an optical system (10) which picks up the primary light beam (7) emitted by the transmitter and which deflects the primary light beam (7) and returns it to the receiver (8) via the light path (1) to the first side (2) as a secondary light beam (9), which is separate from the primary light beam (7), at a distance from the primary light beam (7).

Abstract: Pulsed operation of a light barrier that can be operated in a normal mode and in a compensation mode includes repeating a cycle of transmitting electromagnetic radiation over a transmission period recording measured radiation values at various measurement times and establishing whether extraneous light is incident on the detector by examining a measured value curve of the recorded measured radiation values. The respectively next cycle in the normal mode being run through when no extraneous light is incident, and in the compensation mode when extraneous light is incident, at least one compensation measure being carried out in the compensation mode in order to compensate the influence of extraneous light.

Abstract: The invention relates to a photoelectric barrier with a transmission device (2) for the transmission of a beam of electromagnetic radiation along a first path (6), a diverter for diverting the transmitted beam of electromagnetic radiation from the first path (6) onto a second path (12), and a reception device (16) for receiving the beam of electromagnetic radiation, characterized by the fact that the diverter is designed for a diversion that retains the beam's constellation relative to a plane containing the first path (6) and the second path (12).