Metal detection apparatus for detecting metal objects in a web of photographic material

摘要

A photofinishing apparatus for reading and/or writing magnetic information on a web of photographic film. The web comprises a plurality of individual strips of film secured together end to end. The apparatus includes a film track for receiving the web, a pair of drive rollers for moving the film web through the film track, a magnetic reader and/or writer for reading and/or writing magnetic data on the web, and a detection device for detecting metal objects in the web. The detection device is located at a point in the film track prior to the magnetic reader and/or writer. A monitoring device monitors the change in voltage across two space points on the film track for determining when a metal object is in the web and for producing a signal which is used to stop the film web.