Large zoom ratio zoom lens

Details Large zoom ratio zoom lens Large zoom ratio zoom lens

2006-07-18

2006-07-18

Thompson, Timothy (Department: 2873)

Optical: systems and elements

Lens

With variable magnification

C359S683000

Reexamination Certificate

active

07079327

ABSTRACT:
A zoom lens with a large zoom ratio suitable for surveillance cameras includes, and may only include, four lens groups, in order from the object side, a first lens group of positive refractive power, a second lens group of negative refractive power, a third lens group of positive refractive power, and a fourth lens group of negative refractive power. The second and third lens groups move during zooming. Each of the first, second, and third lens groups is formed of three lens elements that comprise two lens components of particular constructions. Certain conditions are satisfied by the ratio of the focal lengths of the first lens group and the zoom lens, the ratio of focal lengths of the second and third lens groups, and the arithmetic mean of the Abbe numbers and indexes of refraction of lens elements having positive refractive power in the first lens group.

REFERENCES:
patent: 6519095 (2003-02-01), Takato
patent: 2003-107345 (2003-04-01), None
patent: 3486560 (2003-10-01), None

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