A head mountable apparatus is described for transmitting an image to the user's eye using switchable holographic optical elements. In one embodiment, an optical system is provided that is configured to receive an image provided by an image generator and which forms a light path along which light is transmitted...http://www.google.se/patents/US20040108971?utm_source=gb-gplus-sharePatent US20040108971 - Method of and apparatus for viewing an image
