Optical two‐dimensional alarm system using electron trapping optical material

Abstract

An alarm system was constructed and tested to demonstrate for the first time an all-optical system that uses electron trapping material with unsupervised learning. The alarm system provides an output when there is a deviation from a time weighted average of a 2-D input image. Classic Hebbian unsupervised learning is used to update the 2-D time weighted average weight array recursively with an all-optical loop. The fabrication of micrometer resolution nanosecond response electron trapping material is described and equations derived to show for the first time that electron trapping materials correctly multiply in parallel elements in a 2-D input image with corresponding elements in a second 2-D weight array. The alarm system equations and associated optic implementation are modified for a binary system instead of a bipolar one because of positivity of intensity. The system uses two electron trapping spatial light rebroadcasters (SLRs), one stores the 2-D weight array and the other the scalar output for synchronization and delay of the all-optical loop. The experiment uses a folded configuration to save cost by using only one image intensifier and liquid crystal light valve for both SLRs. Optical experimental results show the correct functioning of the system.