High-speed light output signals from electroluminescent storage systems

The possibility that a matrix of electroluminescent cells could be used for storage of information in digital form has long been realized. The problems involved in reading information from a simple type of permanent store are discussed. It has been shown that the read-out time is limited by the afterglow of the phosphor, and, for a particular (ZnS, Cu, Cl) phosphor, it is 25¿30 microsec per digit. A theoretical calculation of the discrimination ratio, i.e. the ratio of the output signal from a `1¿ to the interference signal obtained when a `0¿ is selected, shows that it should be possible to operate matrices with as many as 642 cells. This conclusion is not borne out by measurements made on experimental panels; these suggest that 322 is about the maximum. Results obtained in the paper are regarded as preliminary since arbitrary choices have had to be made concerning some aspects of the operation of the matrices. There is little doubt that considerable improvement in performance is possible.