Focusing screen for photographic cameras

Details Focusing screen for photographic cameras Focusing screen for photographic cameras

1978-08-01

1980-01-08

Griffin, Donald A.

350286, G02B 504, G03B 1328

Patent

active

041825640

ABSTRACT:
The invention relates to a focusing screen for photographic cameras with split-image range finder, of which the wedges lying side by side are inclined oppositely to one another and extend obliquely of the lateral edges of the focusing screen.
Known focusing screens of this kind each have a pair of coincidence wedges inclined oppositely at equal angles. In order that horizontal and vertical contours can be used for focusing, the single line of intersection between the coincidence wedge pair is arranged obliquely in relation to the lateral edges of the focusing screen. In comparison with a wedge pair with horizontal or vertical line of intersection, as a result of this oblique arrangement of the intersection line the accuracy of measurement reduces.
In accordance with the invention this is achieved in that on both sides of a central wedge there are provided lateral wedges inclined oppositely thereto which have the same angle of inclination as one another. Due to this arrangement one obtains at least two intersection lines extending parallel and with spacing from one another, so that the accuracy of measurement is increased for the same physiological perception threshold of the photographer.

REFERENCES:
patent: 3149547 (1964-09-01), Jurenz
patent: 3233533 (1966-02-01), Sauer
patent: 3500736 (1970-03-01), Ewald
patent: 3602085 (1971-08-01), Wagner
patent: 4003637 (1977-01-01), Masuoka

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