Focussing system

US4240727A · kind A · utility

Assignee

• AGFA-Gervaert AG · DE

Inventors

• Peter Lermann · Feldkirchen-Westerham, DE
• Istvan Cocron · Munich, DE
• Gunter Fauth · Unterhaching, DE

Key dates

• Filing date: Jan 12, 1979
• Grant date: Dec 23, 1980
• Expiry date: Jan 12, 1999

Classification

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

Abstract

A first photodetector arrangement comprises three adjoining photodetectors, and a second comprises six. First and second optics, and the two photodetector arrangements, are located immovable on the camera, and the optics project onto the first arrangement an image of a subject which is to form the basis of a subject-distance measurement, without shift between image and photodetectors of the first arrangement so long as the subject-distance is within one of the ranges the system is to furnish; whereas the image projected onto the second photodetector arrangement shifts relative thereto in dependence upon the distance to the subject. The six photodetectors of the second arrangement are subdivided, for signal-processing purposes, into four successive groups, respectively comprised of the first, second and third photodetector, the second, third and fourth, the third, fourth and fifth, etc. A plurality of comparisons are performed by signal-evaluating circuitry, on the basis of absolute-value versions of the differences between the output signals of individual photodetectors in the first arrangement and in successive photodetector-groups within the second arrangement, to automatically a…