An apparatus for and method of detecting and signifying the presence or absence of a product identity mark or the like on a transparent sheet includes detecting facilities having a first part including light transmitting facilities and a second part including light detecting facilities, the first and...http://www.google.fr/patents/US4665392?utm_source=gb-gplus-shareBrevet US4665392 - Method of and apparatus for detecting presence of a mark on a transparent substrate
Method of and apparatus for detecting presence of a mark on a transparent ...
