Zoom lens and projection display device which uses same

Details Zoom lens and projection display device which uses same Zoom lens and projection display device which uses same

2006-01-24

2006-01-24

Epps, Georgia (Department: 2873)

Optical: systems and elements

Lens

With variable magnification

C359S649000

Reexamination Certificate

active

06989940

ABSTRACT:
A zoom lens includes, in order from the enlarging side: a first lens group that has negative refractive power, is movable for focusing, and is stationary during zooming; second, third, and fourth lens groups that are movable for zooming; and a fifth lens group that is stationary during zooming. The second and fifth lens groups have positive refractive power and the third and fourth lens groups have negative refractive power. The second and third lens groups move nearer the enlarging side when the zoom lens zooms toward the telephoto end and the fourth lens group is positioned nearer the reducing side when at the telephoto end than when at the wide-angle end. The ratios of the focal lengths of the first, second, fourth, and fifth lens groups to the focal length of the zoom lens satisfy four conditions. A projection display device uses the zoom lens.

REFERENCES:
patent: 4116536 (1978-09-01), Moscovich
patent: 5416639 (1995-05-01), Yamanashi
patent: 6636361 (2003-10-01), Wada
patent: 2000-292701 (2000-10-01), None
patent: 2001-4919 (2001-01-01), None

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