High magnification zoom lens

Details High magnification zoom lens High magnification zoom lens

2007-08-23

2008-11-25

Spector, David N (Department: 2873)

Optical: systems and elements

Lens

With variable magnification

C359S686000

Reexamination Certificate

active

07457049

ABSTRACT:
A high magnification zoom lens system includes a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power, which are arranged in order from an object side. The third lens group includes three lens elements respectively having positive, positive, and negative refractive powers in order from the object side. The fourth lens group includes at least two positive lens elements and a doublet lens having positive refractive power as a whole, each lens group moves independently during magnification change. The high magnification zoom lens system satisfies the conditions that0.40<fwfbw<0.55⁢⁢and⁢⁢0.35<β3,4⁢⁢Wβ3,4⁢⁢T<0.43,where fwis the focal length of the overall lens system at a wide-angle end, fbwis the back focal length of the lens system at the wide-angle position, β3,4wis the combined magnification ratio of the third and fourth lens groups at the wide-angle position, and β3,4Tis the combined magnification ratio of the third and fourth lens groups at the telephoto position.

REFERENCES:
patent: 4657351 (1987-04-01), Mori
patent: 5032013 (1991-07-01), Shibayama
patent: 6353505 (2002-03-01), Yoneyama
patent: 7253965 (2007-08-01), Shibayama et al.
patent: 7256946 (2007-08-01), Yoneyama
patent: 7342730 (2008-03-01), Yoneyama
patent: 2003-241097 (2003-08-01), None

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