Circuit for a control device for focussing a lens system

US4583123A · kind A · utility

Assignee

• International Business Machines Corporation · US

Inventors

• Heinz Baier · Sindelfingen, DE
• Michael Kallmeyer · Eppelheim, DE
• Peter Koepp · Holzgerlingen, DE
• Erwin Pfeffer · Eppelheim, DE
• Martin Schneiderhan · Stuttgart, DE

Key dates

• Filing date: Feb 22, 1985
• Grant date: Apr 15, 1986
• Expiry date: Feb 22, 2005

Classification

• Technology area (CPC G): Physics
• CPC primary: G02B7/36
• WIPO field: Audio-visual technology
• WIPO sector: Electrical engineering

Abstract

In this circuit, video signals with a continuously increasing or decreasing amplitude are applied to the signal input of a threshold difference comparator at whose reference inputs selectively determined high and low threshold signals are applied. The output of the threshold difference comparator is applied at the first input of a threshold AND gate having a second input connected to a clock. The output of the threshold AND gate supplies a clock pulse sequence which has a duration corresponding with the time during which the input video signal has an amplitude which continuously increases or decreases from one of the threshold reference amplitudes to the other. The clock pulse sequences contained in successive measuring intervals have their respective pulses counted by a counter, and are stored in a buffer. A measurement series is performed corresponding to different focus settings, optimum focus adjustment being achieved when a minimum count of clock pulses in a clock pulse sequence is obtained.