Optical objective focus indicator and display

US4117325A · kind A · utility

Assignee

• Ernst Leitz Wetzlar, GmbH · DE

Inventors

• Werner Holle · Wetzlar, DE
• Walter Bletz · Solms, DE

Key dates

• Filing date: Oct 26, 1977
• Grant date: Sep 26, 1978
• Expiry date: Oct 26, 1997

Classification

• Technology area (CPC G): Physics
• CPC primary: G03B17/20
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

Apparatus for indicating and displaying the focus of an optical objective and particularly a photographic camera. An image of the object is projected by means of the objective onto a scanning disk or plate where the light rays are divided into two separate light beams originating from two different areas of the exit pupil of the objective. Two photoelectric detectors are provided behind said scanning disk with one of said light beams impinging on one detector. Each detector delivers an electrical signal, the phase difference between these signals being a measure of the degree of focus of the objective. For indicating said degree of focus two LED's (Light Emitting Diodes) are provided which are so coupled that for focus (phase difference = null) they are equally luminous and that for lack of focus they indicate the direction of the image offset from the focusing plane and approximately also the magnitude of this offset on account of their special coupling and their change in luminosity which is independent of object brightness.