Focussing system with automatic control of emitted radiant power

US4313655A · kind A · utility

Assignee

• Agfa-Gevaert NV · BE

Inventors

• August Hell · Straubing, DE
• Kurt Borowski · Aschheim, DE
• Istvan Cocron · Munich, DE
• Theodor Huber · Munich, DE

Key dates

• Filing date: Apr 9, 1979
• Grant date: Feb 2, 1982
• Expiry date: Apr 9, 1999

Classification

• Technology area (CPC G): Physics
• CPC primary: G02B7/32
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A focussing system of the type which emits radiation from the camera towards the subject, with the radiation reflected from the subject being incident upon a receiving transducer generating an electrical signal from which focus-control information is derived. The emitted radiant-power level is automatically controlled in dependence upon camera-to-subject distance, preferably in dependence upon the power level of the reflected-back radiation incident upon the receiving transducer, even when the focus-control information required for primary system operation is independent of such power level. This makes possible various important improvements, including: automatic lowering of the emitted-power level in close-up contexts, especially where a danger of eye damage might exist; more generally, automatic matching of emitted-power level to the needs of the signal-processing circuitry, permitting signal-processing stages of narrower operative range to be employed on account of the narrower variations in power level of the signal produced by the receiving transducer; and lowered power consumption. Preferably, when a focussing operation is initiated, the emitted power level is initially low o…