1985-10-16
1986-12-30
Griffin, Donald A.
G03B 1320
Patent
active
046325310
ABSTRACT:
A focusing screen in a split image coincidence type range finder provided with an objective lens forming an imaging plane comprises a plurality of light diffusing portions each of which has a surface inclined with respect to the imaging plane. A number of minute depressions or projections are formed on the inclined surface. The depressions or projections are arranged in the form of a matrix along a first direction and a second direction intersecting each other and symmetrical with respect to a fixed direction parallel to the inclined surface and the imaging plane. Each of the depressions or projections is of a pyramidic shape having as the base a parallelogram having first and second sides parallel to the first direction and third and fourth sides parallel to the second direction and extended in the fixed direction. Each of the depressions or projections is arranged so that each side of the parallelogram is common to a side of another adjacent parallelogram.
REFERENCES:
patent: 3602085 (1971-08-01), Wagner
patent: 4003637 (1977-01-01), Masuoka
patent: 4071292 (1978-01-01), Ise et al.
patent: 4338012 (1982-07-01), Matsumura et al.
patent: 4352547 (1982-10-01), Sasaya
patent: 4519686 (1985-05-01), Seki et al.
Japanese Patent Publication No. 9531/1962, published Jul. 27, 1962, "Focusing Screen of Camera", Hideo Ohsawa.
Japanese Patent Publication No. 29123/1964, published Dec. 15, 1964, "Focusing Adjusting Screen", Yoshio Kuramoto.
Japanese Laid Open Patent Appln. No. 626/1979, published Jan. 6, 1979, "Focus Detecting Screen Used Diffraction Grating", Norio Shiotake.
Ichihara Yutaka
Iizuka Yutaka
Inaba Tomonari
Kunimatsu Shuji
Magome Nobutaka
Griffin Donald A.
Nippon Kogaku K. K.
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