Focusing screen of a camera

Details Focusing screen of a camera Focusing screen of a camera

1981-07-14

1982-10-05

Griffin, Donald A.

G03B 1320

Patent

active

043525474

ABSTRACT:
In a focusing screen capable of passing light therethrough and disposed between an objective lens and an eyepiece to enable the focused condition of the objective lens with respect to an object to be observed through the eyepiece and having a surface formed with a number of pyramidical faces, the angle of inclination .alpha. of each of said pyramids satisfies an inequality that ##EQU1## where F represents the F-number of the optical system from the objective lens to the focusing screen, f the focal length of the eyepiece, n the refractive index of the focusing screen and .DELTA. the required range finding accuracy, and the focusing screen satisfies ##EQU2## where A represents the visual angle whereat a length cos .alpha. times as great as the length of the slant face extending from the bottom surface to the vertex of the pyramid at the angle of inclination .alpha. is seen through said eyepiece.

REFERENCES:
patent: 3003387 (1961-10-01), Schiele
patent: 3498198 (1970-03-01), Fujii
patent: 4003637 (1977-01-01), Masuoka
patent: 4071292 (1978-01-01), Ise et al.

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