Film thickness detector

摘要

A film thickness detector system has first and second thickness detector positions. The first position includes a light source for projecting a light beam to a light detector. A guide roller positions a film strip such that the light beam is tangent to a portion of the film strip supported by the guide roller. The film strip lies between the light source and light detector and the light beam is intercepted by a portion of the film strip at an angle with respect to the longitudinal axis of the film strip. As the thickness of the film strip intercepting a portion of the light beam varies, the output from the light detector varies in a corresponding manner. The output is amplified and may be used for stopping motion of the film. The second thickness detector position also has a light source and at least one light detector positioned to receive a light beam from the light source. A sensing member is positioned to ride on a surface of the film strip and an opaque member connected to the sensing member is provided having an edge portion which intercepts a portion of the light beam such that variations in film thickness correspond to variations in the light detector output. Such variations are then amplified and may be employed to stop the film.