Importance

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Abstract

A method and apparatus for determining whether a predetermined cut position lies within an unexposed portion of a roll of film is provided. A first density sensor 20 senses film density of a roll of film (10) and produces film density data. The film density data is stored in a first data storage device (50). A second data storage device (52) reads and stores a film density data value indicative of the lowest value of the film density stored in the first data storage device (50) and outputs this as base density data. A second density sensor (22) senses the film density at a predetermined cut position and produces cut position density data. A counter (66) counts pulses produced by a film drive and, when a predetermined number of pulses has been counted, indicating the arrival of the film at the predetermined cut position, the counter (66) produces a control signal that causes a comparator (26) to compare the base density data to the cut position density data. The comparator (26) produces a cutter control signal that causes a film cutter to cut the film (10) at the predetermined cut position only when the value of the cut position density data indicates that the film density at the cut position is within a predetermined range of the base density. In a typical installation, the film is comprised of several rolls of film spliced together. The invention includes a first splice detector (54) that detects a splice at a first time and a second splice detector (56) that detects the splice at a second subsequent time to identify each roll of film. The base density information is then keyed to a particular roll of film.

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First Claim