Pentagonal prism for camera viewfinder

Details Pentagonal prism for camera viewfinder Pentagonal prism for camera viewfinder

1980-05-07

1982-01-05

Henry, Jon W.

Compositions: ceramic

Ceramic compositions

Glass compositions, compositions containing glass other than...

350276SL, 501 61, 501 65, 501 72, 501903, G02B 504, C03C 310, C03C 330

Patent

active

043090788

ABSTRACT:
A pentagonal prism for use in a viewfinder of a single lens reflex camera is made of a glass whose refractive index and Abbe number are not less than 1.6 and 45, respectively. Effective optical path regions on a pair of roof surfaces of the prism are left transparent so that viewfinder light can be totally reflected at both of the roof surfaces. A light absorbing paint is coated in an upper front surface, a pair of said surfaces of the prism as well as at regions other than effective optical path region of the roof surfaces, a bottom light incident surface and a rear light exit surface of the prism. The light absorbing paint prevents the occurrence of ghost images in the view field of the viewfinder. New type glasses suited for the prism are proposed.

REFERENCES:
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patent: 3030857 (1962-04-01), Shumway
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patent: 3958999 (1976-05-01), Izumitani et al.
patent: 3964918 (1976-06-01), Hares et al.
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patent: 4080216 (1978-03-01), Ishibashi et al.
patent: 4111707 (1978-09-01), Komorita et al.
patent: 4118238 (1978-10-01), Ishibashi et al.
patent: 4200467 (1980-04-01), Broemer et al.
Dalton, R. H., ". . . Glass to Metal Joints," Product Engineering, Apr. 26. 1965, pp. 62-71.

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