A sorting apparatus according to the present invention includes a conveyor belt having a solid translucent sheet segment for carrying a stream randomly-arranged articles, ones of which are translucent and others of which are opaque. Preferably, the translucent articles are pieces of post-consumer plastic...http://www.google.es/patents/US5335791?utm_source=gb-gplus-sharePatente US5335791 - Backlight sorting system and method
