1981-02-18
1983-05-24
Evans, F. L.
354200, G03B 1328
Patent
active
043847625
ABSTRACT:
A focusing screen device for use in a photographic camera or other suitable optical instrument includes a light refracting structure having a number of sets of light refracting surfaces. Each set of surfaces provides a different light refracting direction than that of the other sets. A light control assembly including an electro-optical element controls the passage of light through each surface of each set. The focusing condition of the optical system of the camera then is perceived by observing whether or not an object image changes its position, as a whole or in part, after light from the object passes through the device. For example, the position of the image may change continuously or periodically as a split line scans the image. Accordingly, the observer is able to recognize the focusing condition of the optical system with extreme clarity.
REFERENCES:
patent: 4208115 (1980-06-01), Proske
patent: 4338012 (1982-07-01), Matsumura et al.
Fujibayashi Kazuo
Suzuki Ryoichi
Uchiyama Takashi
Canon Kabushiki Kaisha
Evans F. L.
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