Optical: systems and elements – Lens – With variable magnification
Patent
1996-04-01
1998-06-02
Sugarman, Scott J.
Optical: systems and elements
Lens
With variable magnification
359713, G02B 1514, G02B 1318
Patent
active
057609705
ABSTRACT:
A zoom lens of high magnification has first, second and third zoom groups which are sequentially arranged from an object side toward an image side and respectively have a positive focal length, a positive focal length and a negative focal length. The entire first to third zoom groups are moved onto the object side by zooming from a wide angle end for arranging the first and second zoom groups in proximity to each other to a telescopic end for arranging the second and third zoom groups in proximity to each other while a distance between the second and third zoom groups is reduced. The zoom lens is constructed by six lens groups composed of six lenses in which each of the zoom groups is constructed by one positive lens and one negative lens. A focal length f.sub.1 of the first zoom group, a combined focal length f.sub.T of the entire lens system at the telescopic end, a focal length f.sub.2 of the second zoom group and a combined focal length f.sub.W of the entire lens system at the wide angle end satisfy the following conditions, (1) 0.9<f.sub.1 /f.sub.T <1.5, (2) 0.6<f.sub.2 /f.sub.W <0.85 One lens face or more of the second zoom group and one lens face of more of the third zoom group are constructed by aspherical surfaces.
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patent: 5148321 (1992-09-01), Goto et al.
patent: 5216547 (1993-06-01), Ogata
patent: 5343329 (1994-08-01), Ito
patent: 5361167 (1994-11-01), Aoki
Ricoh & Company, Ltd.
Sugarman Scott J.
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