Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
2011-05-10
2011-05-10
Sugarman, Scott J (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S684000
Reexamination Certificate
active
07940473
ABSTRACT:
A zoom lens includes, in order from object to image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power and movable during zooming, a third lens unit having a positive refractive power and including a positive lens element positioned nearest to an object-side end, and a fourth lens unit having a positive refractive power and movable during zooming. The second lens unit includes at least three negative lens elements arranged successively and independently along an optical axis and at least one positive lens element. The zoom lens satisfies specific numerical conditions defined for a focal length fw of the zoom lens at a wide-angle end, focal lengths f2and f3of the second and third lens units, and a focal length f31of a positive lens element of the third lens unit nearest to the object-side end.
REFERENCES:
patent: 5009492 (1991-04-01), Hamano
patent: 6084722 (2000-07-01), Horiuchi
patent: 6118593 (2000-09-01), Tochigi
patent: 6606194 (2003-08-01), Hamano et al.
patent: 7400453 (2008-07-01), Tomioka
patent: 2000-227548 (2000-08-01), None
patent: 2002-182109 (2002-06-01), None
patent: 2002-287027 (2002-10-01), None
Canon Kabushiki Kaisha
Canon U.S.A. Inc. IP Division
Sugarman Scott J
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