Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
2008-05-27
2009-10-27
Spector, David N (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S686000
Reexamination Certificate
active
07609457
ABSTRACT:
A zoom lens includes a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a fourth lens unit having a positive refractive power in that order from an object side to an image side. Zooming is performed by changing distances between the lens units. The first lens unit includes two or less lenses and the second lens unit consists of a negative lens and a positive lens in that order from the object side to the image side. The zoom lens satisfies the following condition:in-line-formulae description="In-line Formulae" end="lead"?−1.3<m1/√{square root over ((fw·fT))}<−0.8in-line-formulae description="In-line Formulae" end="tail"?where fw and fT are focal lengths of the entire lens unit at wide-angle and telephoto ends, respectively, and m1is an amount of movement of the first lens unit in an optical axis direction during zooming from the wide-angle end to the telephoto end.
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patent: 6577450 (2003-06-01), Hamano
patent: 6853496 (2005-02-01), Eguchi
patent: 7193790 (2007-03-01), Hamano
patent: 7236307 (2007-06-01), Noguchi et al.
patent: 7286298 (2007-10-01), Yamashita
patent: 7319562 (2008-01-01), Itoh
patent: 7561344 (2009-07-01), Itoh
Canon Kabushiki Kaisha
Canon USA Inc IP Div
Spector David N
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