Apparatus for scanning a marked web

Abstract

A web of photographic paper having at its rear side at least one longitudinally extending reference line and at least one row of equally spaced marks which is parallel to the reference line. The reference line and the marks are applied below a coat of liquid-repellent synthetic plastic material. The reference line is scanned by a first photoelectric detector and the row of marks is scanned by a second photoelectric detector which remains in register with the row of marks because the first detector is maintained in register with the reference line by a follow-up control system. The second detector furnishes signals which are used to arrest the advancing rolls for the web in a photoelectric copying machine or subsequent to development of images so that the web is severed during each interval of stoppage. The reference line and the marks are applied simultaneously but prior to the application of photosensitive emulsion to the front side of the web.

Dependencies are inferred from the claim text.