Patent
1976-09-17
1978-04-04
Clark, Conrad J.
350212, G02B 708
Patent
active
040824349
ABSTRACT:
A wide-angle optical system for a door viewer comprises a concave objective lens of a larger diameter of about 13 to 25 mm which is provided with a convex surface of a large radius of curvature of about 20 to 30 mm at the front surface thereof and with a concave surface of a small radius of curvature of about 4 to 6 mm at the central portion of the rear surface thereof, an intermediate concave lens of a smaller diameter of about 9 to 12 mm which has a concave surface of a small radius of curvature of about 4 to 7 mm provided at the front surface thereof and a convex eyepiece lens of a diameter somewhat smaller than that of the intermediate lens, said eyepiece lens having convex surfaces of a large radius of curvature of about 20 to 30 mm. The intermediate concave lens is positioned so that it contacts at the front surface thereof with the rear surface of the objective lens and so as to align the optical axis thereof with that of the objective lens. The convex eyepiece lens is positioned a a predetermined distance from the rear surface of the objective lens in such a manner that the optical axis thereof is aligned with that of the objective lens.
REFERENCES:
patent: 2538077 (1951-01-01), Blosse
patent: 3514188 (1970-05-01), Blosse et al.
Hayashi Tadaaki
Nakahara Teruto
Clark Conrad J.
Kabushiki Kaisha Ka-Pu
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