Optical: systems and elements – Lens – Reverse telephoto
Patent
1997-09-04
1999-02-09
Nelms, David C.
Optical: systems and elements
Lens
Reverse telephoto
359753, 359761, 359763, 359770, 359713, 359714, G02B 1304, G02B 960, G02B 302
Patent
active
058702342
ABSTRACT:
This invention relates to a compact wide-angle lens which consists of five members. The first member and the last member are each divergent lenses of low deviation, which consist of low refractivity crown glass. The second member and the third member are convergent lenses made of high refractivity crown glass. The fourth member, which is the final member of the lens according to the invention, consists of a convergent lens and a divergent lens which are cemented to each other. Type of glass are used for this cemented member which have a very low difference in refractive index but a very high difference in dispersion. The convergent lens has a low dispersion and the divergent lens has a high dispersion. One of the two glass/air surfaces of the cemented member is aspherical. A lens such as this according to the invention has a maximum aperture ratio of at least 1:5.6 and an image angle of 105.degree.. The chromatic correction is well defined and is very substantially independent of the distance of the object. Amongst other effects, this results in scarcely any losses of image quality occurring, even at short range. The distortion of the object is very low.
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Dubno Herbert
Jos. Schneider Optische Werke Kreuznach GmbH & Co. KG
Lester Evelyn A.
Nelms David C.
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