Focussing system with automatic control of emitted radiant power
First Claim
1. In the focussing system of a photographic camera having exposure optics of adjustable subject-distance setting, in combination, means emitting radiation from the camera towards a subject to be photographed, receiving the radiation reflected back from the subject to the camera, and developing from the reflected back radiation a signal dependent upon the true camera-to-subject distance;
- and means operative for automatically controlling the power of the emitted radiation in dependence upon said signal.
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Accused Products
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 or zero and is progressively increased to an automatically selected value without overshoot.
9 Citations
11 Claims
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1. In the focussing system of a photographic camera having exposure optics of adjustable subject-distance setting, in combination, means emitting radiation from the camera towards a subject to be photographed, receiving the radiation reflected back from the subject to the camera, and developing from the reflected back radiation a signal dependent upon the true camera-to-subject distance;
- and means operative for automatically controlling the power of the emitted radiation in dependence upon said signal.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
Specification