Automatic image focusing system for cameras

Details Automatic image focusing system for cameras Automatic image focusing system for cameras

1976-12-27

1978-05-16

Hix, L. T.

Optics: motion pictures

Removable film strip magazine type

352 14D, G03B 310

Patent

active

040902099

ABSTRACT:
A light refracting optical element such as a prism is inserted in the optical path of the objective of a camera substantially on the focal plane of the objective. The light refracting optical element is mounted on a transparent plate and periodically moved in a plane perpendicular to the optical path. A photodetector is provided on which an image of the real image formed by the objective is focused by way of a focusing lens. The photodetector is connected to an electric circuit which amplifies an alternating current component of the output of the photodetector. When the real image of the objective is formed on the light refracting optical element, the output of the photodetector does not contain an alternating component. When the real image of the objective is formed on a plane displaced from the light refracting optical element, the output of the photodetector contains an alternating current component having the same frequency as that of the periodical movement of the light refracting optical element.

REFERENCES:
patent: 2258903 (1941-10-01), Mitchell
patent: 3367254 (1968-02-01), Townsley
patent: 3631785 (1972-01-01), Perlman et al.
patent: 3691922 (1972-09-01), Konig et al.
patent: 3896457 (1975-07-01), Yamamishi et al.
Automatic Focusing by Peter MacKeith, Brit. J. of Photo., Jul. 4, 1975, pp. 594-596.

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