A projection tube includes a liquid crystal cell having liquid crystal material sandwiched between two plates. The cell is addressable by an electron beam and serves as a light valve for plane-parallel light with which the projection tube is illuminated from behind. On the side facing the liquid crystal...http://www.google.com.au/patents/US4838651?utm_source=gb-gplus-sharePatent US4838651 - Projection tube having an insulating layer of magnesium oxide and a high transmission metal grating
