Optical: systems and elements – Lens – With variable magnification
Patent
1999-02-19
2000-03-28
Epps, Georgia
Optical: systems and elements
Lens
With variable magnification
359676, 359684, 359791, G02B 1514
Patent
active
060439394
ABSTRACT:
A three-group zoom lens having positive, positive and negative refractive power, in order from the object side. A diaphragm is positioned between the first and second lens groups and nearest the second lens group. Zooming is performed by changing the spacings between the lens groups such that, when power is varied from the wide-angle end to the telephoto end, the distance between the first lens group G.sub.1 and the second lens group G.sub.2 increases, while the distance between the second lens group and the third lens group G.sub.3 decreases. The second lens group includes, in order from the object side, a meniscus lens element L.sub.4 having negative refractive power with its concave surface on the object side, a biconvex lens element L.sub.5, a negative lens element L.sub.6 and a biconvex lens element L.sub.7. In addition, the three-group zoom lens satisfies certain conditions in order to obtain favorable correction of aberrations over the entire range of zoom, thereby providing high resolution and contrast for all object distances.
REFERENCES:
patent: 4978204 (1990-12-01), Ito
patent: 5138493 (1992-08-01), Iwasaki
patent: 5379154 (1995-01-01), Shibayama et al.
patent: 5592334 (1997-01-01), Oshikiri et al.
patent: 5715096 (1998-02-01), Meyers
patent: 5726810 (1998-03-01), Meyers
Arnold Bruce Y.
Epps Georgia
Fuji Photo Optical Co., Ltd.
Spector David N.
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