One sensor constituted of a light emission element and a light-receiving element is provided in a path through which a wafer is transferred. The sensor is positioned so that the wafer passes through an area between the light emission element and the light-receiving element. Coordinates of the center...http://www.google.ca/patents/US8025475?utm_source=gb-gplus-sharePatent US8025475 - Wafer transfer apparatus, wafer transfer method and storage medium
