Light curtain alignment and light curtain structure spaced apart

摘要

Which is typically a plurality of support rods or support strips of light curtains formed by a plurality of light beams 21 transmitted between transmitters 13 and receivers 15 on each support rod 17,19. In order to properly align the devices 17 and 19, a separate alignment light source, typically a laser 29, is provided. A laser 29 emits a light beam 33 from a rod 17, which is one of the rods, to a receiver 35 of another rod 19. The beam 33 'in the opposite direction is ejected from one of the rods 19 to the other rod 17. The beam 33 'in the opposite direction away from the first direct beam 33 can be generated by the second laser 29' or provide a returning beam in the opposite direction to the first rod 17 Or by detecting the direct beam 33 received in the second rod 19 or on the second rod 19 at 180 [deg. This permits rapid alignment of each bar even for five directions of freedom of movement of each bar. Preferably, the laser is pulsed at a frequency between 1 and 5 Hz, and the time circuit is provided to short-circuit the laser or lasers after a suitable alignment time interval or after a safety interval such that the lifetime of the laser or lasers is Will correspond to the lifetime of the copy transmitter 13 and the receiver 15.