Wide-angle photographic lens system

Details Wide-angle photographic lens system Wide-angle photographic lens system

1997-03-27

1998-08-04

Epps, Georgia Y.

Optical: systems and elements

Lens

Reverse telephoto

359755, G02B 1304

Patent

active

057903247

ABSTRACT:
A compact wide-angle photographic lens system of a retrofocus type includes, from the object side, a first, a sixth, and a seventh meniscus lens group of positive refractive powers, a second and a third meniscus lens group of negative refractive powers, a fourth lens group of a positive refractive power being convex toward an object side, and a fifth cemented lens group of a negative refractive power. The lens system satisfies the conditions, 1.0 f<.vertline.f.sub.(1,2,3,4) .vertline.<2.0 f, f.sub.(1,2,3,4) <0, 0.4 f<d(6)+d(7)<0.6 f, 0.1<f/r(5)<0.2, length of overall lens system, f.sub.(1,2,3,4) represents a combined focal length of the first, second, third and fourth lens group, d(6) represents a distance between the third lens group and the fourth lens group, d(7) represents a thickness of the fourth lens group, r(5) represents a radius of curvature of the third lens group toward an object side, r(11) represents a radius of curvature of the fifth lens group, n(7) represents a refractive index of the sixth lens group, and n(8) represents a refractive index of the seventh lens group.

REFERENCES:
patent: 4286847 (1981-09-01), Nakamura et al.
patent: 4487485 (1984-12-01), Hisada

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