tantially horizontal surface such as a floor and walked over, or of being mounted on a non-horizontal...http://www.google.com/patents/US7145469?utm_source=gb-gplus-sharePatent US7145469 - Display system for use on horizontal or non-horizontal surfacesAdvanced Patent SearchPublication numberUS7145469 B2Publication typeGrantApplication numberUS 11/002,276Publication dateDec 5, 2006Filing dateDec 3,