Pentagonal prism module for camera viewfinder

Details Pentagonal prism module for camera viewfinder Pentagonal prism module for camera viewfinder

1980-05-12

1981-07-14

Griffin, Donald A.

354225, G03B 1912, G03B 1308

Patent

active

042783399

ABSTRACT:
A pentagonal prism for use in a viewfinder of a single lens reflex camera makes use of total reflection of viewfinder light flux at effective optical path regions on its pair of roof surfaces. The prism constitutes a module together with a protection cover attachable thereto for protection of the roof surfaces. The cover is provided with a pair of roof walls accomodated to the roof surfaces of the prism and including recessed portions corresponding to the effective optical path regions on the roof surfaces and peripheral portions corresponding to portions on the roof walls out of the effective optical path regions. Upon attachment of the cover to the prism, the peripheral portions contact the portions on the roof surfaces out of the effective optical path regions and an air space which ensures the total reflection is left between the inner surfaces of the recessed portions and the effective optical path regions on the roof surfaces. A ghost may be prevented from occurring when the inner surfaces of the roof walls are black-frosted, black-ground or black-roughened for light absorption or when the roof walls are designed to intersect with one another at a ridge angle of less than 90.degree. .

REFERENCES:
patent: 937266 (1909-10-01), Robertson
patent: 2933991 (1960-04-01), Saver
patent: 3094579 (1963-06-01), Papke
patent: 3218946 (1965-11-01), Lange
patent: 3236166 (1966-02-01), Steisslinger et al.
patent: 3668993 (1972-06-01), Kurie
patent: 3732775 (1973-05-01), Warstat
patent: 3846805 (1974-11-01), Kiyohara et al.
patent: 3999194 (1976-12-01), Imura et al.

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