Method of and apparatus for positioning photographic originals in a copying station

摘要

A filmstrip containing a series of images is conveyed along a path which passes by a copying station and a scanning station. The filmstrip is advanced in steps using transporting rolls and a narrow segment of the filmstrip is scanned at the scanning station after every step. A first set of measurements obtained upon scanning of the filmstrip is used to calculate the amounts of light and the exposure times required to properly reproduce the images. A second set of measurements is used to detect characteristic regions of the filmstrip having abrupt changes in density. The positions of the characteristic regions along the filmstrip are established by a counter which counts the steps undergone by the filmstrip and the measurement or measurements corresponding to each characteristic region are stored together with the respective position. The positions of the characteristic regions and the second set of measurements are used to calculate the positions of the images along the filmstrip. After the filmstrip has been completely scanned, the filmstrip is conveyed along the path once more. During the second trip along the path, the filmstrip is scanned again while the distance traveled by the filmstrip is measured by the counter. Upon detection of a characteristic region, the position of such region along the filmstrip as measured by the counter during the second trip is compared with the stored position obtained during the first trip. If the positions are different, the counter is changed to match the stored position. This compensates for slip between the filmstrip and the transporting rolls thereby allowing the images to be accurately positioned in the copying station for reproduction as the filmstrip travels along the path for the second time.