RLOD#3 (07.05.2020) 1986 Pефлектор ИЛД3-С

The ИЛД3-С is a Soviet-made blue cathodoluminescent pixel lamp that was used giant displays and scoreboards. The tube features a very basic electron optics which floods the electroluminescent screen with a fast electrical current through vacuum. The spot size can be changed by varying the voltage applied to one of the secondary anodes though. In order to prevent the development of a negative space charge around the luminous end of the lamp, that side of the tube is coated with an electrically-conducting fluorine-doped tin oxide layer so as to provide a return path for electrons which can then be collected by the anode, thereby closing the circuit. Interestingly, the electroluminescent phosphor used in this lamp is a cerium-doped yttrium silicate material instead of the usual silver-doped zinc sulfide found in blue-emitting CRTs. In this particular design half of the emitted light is lost at the back of the lamp, an issue that could have been solved easily with a very thin aluminum coating applied behind the phosphor layer, a solution that was implemented in standard television and video projector CRTs.