Method and arrangement for evaluating a series of originals for copying

Abstract

An exposed and developed film strip having a series of frames is conveyed by a copying station via a pair of rolls driven by a motor. Two or more photoelectric sensors upstream of the copying station generate signals indicative of the transparency of the film strip. The sensors are located on a reference line which extends normal to the longitudinal direction of the film strip. The signals from the sensors are processed to yield processed signals which are representative of significant transparency changes. The processed signals are evaluated to determine the definition of each frame and thereby determine whether a frame is worth copying. In order to locate the frames, the processed signals derived from each sensor are delivered to a common AND gate. The gate emits a pulse when processed signals from all sensors arrive at the gate simultaneously. This is a strong indication that an edge of a frame is in register with the reference line on which the sensors are located. The presence of an edge may be verified by comparing the known length of a frame, or the known distance of separation between neighboring frames, with the distance travelled by the film strip during the time interval between detection of consecutive edges. The motor which advances the film strip is controlled in dependence upon the results of the evaluation of the processed signals and in dependence upon the pulses emitted by the AND gate.