Control system for controlling the diaphragm in a photographic camera

US4079391A · kind A · utility

Assignee

• AGFA-Gervaert AG · DE

Inventors

• Eduard Wagensonner · Aschheim, DE
• Alois Rieder · Munich, DE
• Bernhard von Fischern · Ottobrunn, DE

Key dates

• Filing date: Nov 6, 1975
• Grant date: Mar 14, 1978
• Expiry date: Nov 6, 1995

Classification

• Technology area (CPC G): Physics
• CPC primary: G03B7/085
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

The output of a bridge circuit which is unbalanced when the quantity of light falling on a light-sensitive element is less than or more than a predetermined light quantity is applied to a differential amplifier circuit whose output varies from a minimum amplitude to a maximum amplitude. The output of the differential amplifier is connected to a first and second threshold circuit whose threshold values are symmetrical to the output value of the differential amplifier when the bridge is in balance. The gain of the differential amplifier is adjusted so that the differential output signal has an amplitude exceeding the first threshold value and less than the second threshold value for variations of light within an allowable range. Within this range the first threshold circuit furnishes an output signal and the second threshold circuit does not. When the first threshold circuit does not furnish an output signal or if the second threshold circuit does, a pulse generator is energized whose pulses are counted by a counter which is controlled to energize the windings of the stepmotor controlling the diaphragm aperture in pairs in a predetermined sequence for opening and the reverse sequence…