Determination of extreme density values of a transported strip of photographic originals

US4176964A · kind A · utility

Assignee

• AGFA-Gervaert AG · DE

Inventors

• Bernhard Knor · Munich, DE
• Bernd Payrhammer · Munich, DE
• Helmut Treiber · Munich, DE

Key dates

• Filing date: Sep 6, 1977
• Grant date: Dec 4, 1979
• Expiry date: Sep 6, 1997

Classification

• Technology area (CPC G): Physics
• CPC primary: G03B27/72
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

Light from a light source is transmitted through an original at a scanning station to a light detector. A rotating scanning disk located in the path of this light is provided with equiangularly spaced radial scanning slots. A light-blocking plate located between the light source and the scanning disk defines a scanning slot extending transverse to the transport direction of the original. Light passing through both the original and the transverse scanning slot is projected as a slot image onto the surface of the scanning disk. The radial slots and the transverse slot cooperate to define a scanning spot which sweeps across the original, and thereby performs one line-scan operation, as one radial slot sweeps across the slot image on the scanning disk. The angular span between adjoining radial slot is greater than that of the slot image so that, during intermediate intervals between successive line-scan operations, light transmitted through the original does not reach the light detector. During the intermediate time intervals, reference light from the light source is directed onto the light detector along a reference light path not passing through the original. An evaluating circuit re…