A dispensed product detection system and method for use in a refrigerated vending machine utilizing an optical light beam crossing the path through which a dispensed product travels. An optical emitter transmits a light beam through at least one layer of substantially transparent anti-fog film to reduce...http://www.google.com.hk/patents/US6629625?utm_source=gb-gplus-share專利 US6629625 - Reflector and anti-fog film in an optical sensor system
