Camera apparatus and method for film double exposure prevention

Abstract

A camera and method of camera operation for automatically determining usage condition of film in a cartridge utilizing a cartridge radial bar coded data disc to discriminate among a plurality of possible initial angular settings of the film spool during a film loading operation. The possible initial angular settings can be representative of exposed, partially exposed, fully exposed or processed film. At the start of film loading, the spool is rotated in the reverse direction and bar code element transition counts sensed by a pair of angularly spaced opto-sensors are accumulated. A count comparison between the two sensors is initially made to determine if the film is unexposed and, if so, film loading proceeds in normal manner, otherwise an alternative action is taken. In a simple camera, the loading is terminated. In a more sophisticated MRI capable camera, when the count comparison indicates the film is not unexposed, the camera controller calculates an angular position of one of the sensors relative to a predetermined reference position on the data disc, based on sensed element transitions and known element widths, to discriminate among spool settings indicative of partially exposed film, fully exposed film and processed film with appropriate actions initiated depending on the discriminated spool position.