Photographic-camera focussing system with comparator receiving required-and actual-setting data

US4214824A · kind A · utility

Assignee

• AGFA-Gervaert AG · DE

Inventors

• Otto Stemme · Munich, DE
• Peter Lermann · Feldkirchen-Westerham, DE
• Eduard Wagensonner · Aschheim, DE
• Istvan Cocron · Munich, DE

Key dates

• Filing date: Jan 16, 1979
• Grant date: Jul 29, 1980
• Expiry date: Jan 16, 1999

Classification

• Technology area (CPC G): Physics
• CPC primary: G02B7/30
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

A photographic camera has an exposure objective and a focus adjuster device for changing the subject-distance setting of the exposure objective, as well as a transducer generating actual-setting signals dependent upon the setting of the focus adjuster device. An evaluating circuit, operative for ascertaining camera-to-subject distance on one basis or another, produces digital required-setting signals, expressed using a first encoding scheme, whereas the actual-setting signals generated by the aforementioned transducer are expressed using a different, second encoding scheme. The actual-setting signals are applied to the first input of a comparator stage, whose second input receives a transformed version of the required-setting signals, transformed from the first to the second encoding scheme, i.e., so that the comparator can compare, in a direct and simple way, the actual-setting signals and required-setting signals against each other with both signals expressed in accordance with one and the same encoding scheme. The output signals produced by the comparator control indicator which informs the user of the direction in which the manual focus adjuster of the camera should be moved to…