Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
2007-09-07
2009-12-29
Collins, Darryl J (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S689000
Reexamination Certificate
active
07639431
ABSTRACT:
The invention relates to a zoom lens which, albeit being of simplified construction, makes sure brightness and holds back fluctuations of astigmatism, and facilitates making sure being fast and the angle of view and the zoom ratio at the wide-angle end. The zoom lens comprises a first group G1of positive power, a second group G2of negative power and a third group G3of positive power, with a stop S between the second group G2and the third group G3. Upon zooming from the wide-angle end to the telephoto end, the first group G1, the second group G2, and the third group G3moves; the second group G2moves toward the object side after moving toward the image side; the first group G1and the third group G3are positioned on the object side at the telephoto end with respect to the wide-angle end. The first group G1comprises one negative lens and one or two positive lenses, and the second group G2comprises a first negative meniscus lens convex on its object side, a second negative lens wherein the image side surface is larger in the absolute value of a curvature than the object side surface, and a third positive lens wherein the object side surface is larger in the absolute value of a curvature than the image side surface. Upon focusing from a far distance to a near distance, the second group G2moves.
REFERENCES:
patent: 6650475 (2003-11-01), Hamano
patent: 7199940 (2007-04-01), Obama et al.
patent: 7251081 (2007-07-01), Sato
patent: 2004/0136086 (2004-07-01), Ohtake
patent: 04-321007 (1992-11-01), None
Hosoya Takeshi
Ishii Atsujiro
Collins Darryl J
Kenyon & Kenyon LLP
Olympus Imaging Corp.
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