A transparent screen is provided with a refraction/total reflection plate in a form of a Fresnel lens, the refraction/total reflection plate having a sawtooth light-incidence-side surface upon which light to be projected is incident, and a light-emitting-side surface via which the light to be projected...http://www.google.de/patents/US20050105177?utm_source=gb-gplus-sharePatent US20050105177 - Transparent screen and projection display apparatus
