Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
2001-01-23
2002-05-21
Lester, Evelyn A (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S689000, C359S740000
Reexamination Certificate
active
06392815
ABSTRACT:
BACKGROUND OF THE INVENTION
To date, many different types of small-sized, large-aperture, wide-angle zoom lenses that are used in video cameras and electronic still cameras, such as digital cameras, have been proposed. Among them, for instance, one described in Japanese Patent Publication No. 2556048 is known that has a relatively light-weight front lens element and yields a bright image. The F
NO
is in the range 1.0-1.7 and the zoom lens is formed of, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power. This zoom lens has some problems, however, in that the F
NO
changes during zooming and the image angle at the wide-angle end is rather small.
BRIEF SUMMARY OF THE INVENTION
The objects of the present invention are to provide a small-sized, large-aperture, wide-angle zoom lens in which the F
NO
remains constant during zooming, and which ensures a wider image angle at the wide-angle end. Further, it is desired that the zoom lens satisfactorily correct aberrations over the entire range of zoom so as to provide bright images of high quality throughout the range of zoom. More specifically, the present invention aims to provide a small-sized, large-aperture wide-angle zoom lens having an F
NO
of approximately 1.4 with the F
NO
remaining constant during zooming, an image angle that is approximately 110 degrees, and a zoom ratio of about 2.6.
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Arnold Bruce Y.
Fuji Photo Optical Co., Ltd.
International Arnold
Lester Evelyn A
LandOfFree
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