An optical panel includes a transparent serrated first side, and an opposite second side, and a black material provided on the serrated first side for intermittently blocking or absorbing light transmission. Image light may be transmitted through the panel at the serrations, with contrast provided by...http://www.google.de/patents/US6597417?utm_source=gb-gplus-sharePatent US6597417 - Optical panel having black material between apexes of serrations on the inlet face
