Digital exposure-duration control circuit with upper limit on exposure duration

US4273428A · kind A · utility

Assignee

• AGFA-Gervaert AG · DE

Inventors

• Kurt Borowski · Aschheim, DE
• Eduard Wagensonner · Aschheim, DE
• Istvan Cocron · Munich, DE

Key dates

• Filing date: Apr 24, 1979
• Grant date: Jun 16, 1981
• Expiry date: Apr 24, 1999

Classification

• Technology area (CPC G): Physics
• CPC primary: G03B7/17
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

A first pulse train whose pulse repetition frequency varies in dependence upon scene light, and a second pulse train whose pulse repetition frequency does not vary in dependence upon scene light, are counted by digital counting circuitry, and a terminate-exposure signal is produced when the digital counting circuitry reaches a predetermined count. The second pulse train serves to establish an upper permissible limit for the duration of the exposure to be performed.