Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
2006-06-06
2006-06-06
Sugarman, Scott J. (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S688000, C359S674000, C359S675000
Reexamination Certificate
active
07057827
ABSTRACT:
A zoom lens includes first to fourth lens units arranged in order from an object, respectively. The first lens unit is fixed during power-varying and has positive optical power. The second lens unit is movable during power-varying. The third lens unit is movable so as to compensate image-plane fluctuation in accordance with the power-varying. The fourth lens unit is fixed during the power-varying and has positive optical power. The first lens unit includes a first lens subunit having positive optical power, and a second lens subunit having negative optical power, arranged in order from the object, respectively. One of the first and second lens subunits moves upon focus adjustment. Further, the following conditions are satisfied:in-line-formulae description="In-line Formulae" end="lead"?−2.5<f1b/f1a<−0.6 and 0.2<f1/fT<0.8.in-line-formulae description="In-line Formulae" end="tail"?Wherein f1, f1a, f1b, and fT respectively represent the focal lengths of the first lens unit, the first lens subunit, the second lens subunit, and the overall system of the zoom lens at its telephoto end.
REFERENCES:
patent: 5442486 (1995-08-01), Sato
patent: 5771123 (1998-06-01), Hamano et al.
patent: 1092999 (2003-09-01), None
patent: 10-90599 (1998-04-01), None
Canon Kabushiki Kaisha
Canon U.S.A. Inc IP Division
Sugarman Scott J.
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