Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
2007-12-12
2009-02-10
Sugarman, Scott J (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S682000, C359S686000
Reexamination Certificate
active
07489449
ABSTRACT:
A zoom lens for projection is provided and includes a first group having a negative refractive power, a second group having a positive refractive power, a third group having a positive refractive power, and a fourth group having a positive or negative refractive power, in order from the magnification side. At variable power from a wide-angle end to a telephoto end, the second, third and fourth groups are moved to the magnification side, and the first group is slightly moved to the reduction side. Also, the following conditional expression (1) is satisfied.in-line-formulae description="In-line Formulae" end="lead"?0.95<frw/frt<1.05 (1)in-line-formulae description="In-line Formulae" end="tail"?Where frw is a composite focal length of the second, third and the fourth groups at the wide-angle end, and frt is a composite focal length of the second, third group and fourth groups at the telephoto end.
REFERENCES:
patent: 5157550 (1992-10-01), Tsuchida et al.
patent: 5867326 (1999-02-01), Yamamoto
patent: 6204976 (2001-03-01), Nagahara
patent: 2000-271668 (2000-10-01), None
patent: 2006-78705 (2006-03-01), None
patent: 2007-271695 (2007-10-01), None
Birch & Stewart Kolasch & Birch, LLP
Fujinon Corporation
Sugarman Scott J
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