In a first aspect, an apparatus is provided for detecting substrates. The apparatus includes (1) a transmitter/receiver unit adapted to transmit a light beam through a substrate located within a transfer chamber; (2) a reflector adapted to receive the light beam transmitted from the transmitter/receiver...http://www.google.com/patents/US6992316?utm_source=gb-gplus-sharePatent US6992316 - Angled sensors for detecting substrates
