Zoom lens

Optical: systems and elements – Lens – With variable magnification

Reexamination Certificate

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Details

C359S680000, C359S683000

Reexamination Certificate

active

06967782

ABSTRACT:
The invention relates to a high-performance, large-aperture yet wide-angle zoom lens system that can be used with an electronic image pickup device in particular, a method for focusing the same. In particular, the invention is concerned with a high-performance, large-aperture yet wide-angle zoom lens system which has a zoom ratio of the order of 3 at a diagonal field angle of 75° at its wide-angle end, so that it can be used with a single-lens reflex camera using an electronic image pickup device with the number of pixels being of the order of 6,000,000. The zoom lens system comprises a first lens group G1having negative refracting power, a second lens group G2having positive refracting power, a third lens group G3having negative refracting power, a fourth lens group G4having positive refracting power and a fifth lens group G5having positive refracting power. Upon movement of an object point, focusing is carried out with the fifth lens group G5.

REFERENCES:
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patent: 5739960 (1998-04-01), Tanaka
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patent: 6118592 (2000-09-01), Kohno et al.
patent: 6285509 (2001-09-01), Nakayama et al.
patent: 6320698 (2001-11-01), Suzuki
patent: 2080966 (1982-02-01), None
patent: 59229517 (1984-12-01), None
patent: 5-107476 (1993-04-01), None
patent: 5-323196 (1993-12-01), None
patent: 06-102455 (1994-04-01), None

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