Optical barrier formed of a set of optical emitter and receiver elements

Abstract

An optical barrier is provided by an optical barrier unit that is made up of one or more emitter element modules and one or more receiver element modules. The emitter modules present are controlled by a control circuit to emit modulated beams encoded in a particular manner. In this regard, a particular beam of each emitter module is encoded with one of a pair of unique words that both indicate the identity of the module emitting that beam and further indicate a different binary word value depending on which of the pair is used as part of a further code that will identify the barrier unit. If more than one emitter module is part of the optical barrier, a corresponding number of particular beams, one for each emitter module present, are modulated with appropriate ones of other pairs of unique words to both identify those modules and to provide the proper binary word value as a further part of the optical barrier unit's identification number. The other beams of all of the one or more modules present are modulated with one of two other code words that indicate the high and low binary word values needed to complete the identification number of the optical barrier unit. This permits modules to exchange coded words that identify the barrier unit as well as identifying the modules being used, where the presence of the unique words that indicate the identity of the particular module emitting that particular modulated beam permits synchronization since the receiving element or elements in a particular receiving module intended to receive that particular modulated beam encoded with the identification number for the emitting module are known and what these elements or element actually receives as a modulated beam is easily determined.