Processor-controlled light screen wherein light beam carries coded

Abstract

A processor-controlled light screen system comprises spaced-apart Master and Slave units each having a plurality of light transmitters and light receivers. Each transmitter in the Master unit or Slave unit is adapted to provide a light beam carrying a respective binary coded signal to a corresponding receiver in the unit to enable the two otherwise independent units to interactively communicate with one another. The Master and Slave units respectively include a Master processor and a Slave processor, each programmed to sequentially actuate the transmitters and receivers in their respective units in pairs. Operation is initiated by the Master processor program which causes the transmitter of the first actuated transmitter-receiver pair of the Master unit to send its respective coded signal. The programs of both processors are responsive to the reception of an appropriately coded signal by an actuated receiver in their respective units for causing the next transmitter to be actuated therein to send its respective coded signal. In this manner the region of space between the Master and Slave units are scanned by the light beams passing between corresponding transmitters and receivers. The scanning occurs in repetitive cycles so long as all coded signals are correctly exchanged between the Master and Slave units. If a coded signal is not received, as a result of either the blockage of a beam by an object or a malfunction of the system, scanning is aborted and the two processors enter respective alarm states and issue alarm state signals.