Optical: systems and elements – Image stabilization – By movable refractive structure
Reexamination Certificate
1994-05-17
2001-06-12
Nguyen, Thong (Department: 2872)
Optical: systems and elements
Image stabilization
By movable refractive structure
C359S554000, C359S676000
Reexamination Certificate
active
06246519
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a zoom lens system with the function of preventing image shake, and particularly is suitable for a photographic zoom lens system.
2. Related Background Art
There are known a zoom lens system as disclosed in U.S. Pat. No. 5,270,857 wherein any lens unit in a zoom lens system comprised of two or more lens units is displaced in a direction perpendicular to the optical axis thereof to correct image shake, and a zoom lens system as disclosed in U.S. Pat. No. 5,040,881 wherein some lenses in a first lens unit fixed during zooming are displaced in a direction perpendicular to the optical axis thereof to correct image shake.
However, in the prior art as described above, it has been impossible to secure a back focal length sufficient for a single-lens reflex camera (SLR) and thus, it has been impossible to realize a desired great zoom ratio. Therefore, the zoom lens systems as described above are unsuitable as lenses for a compact and high-performance 35 mm photographic SLR.
SUMMARY OF THE INVENTION
So, it is an object of the present invention to realize a sufficient back focal length and a great zoom ratio and to provide a compact and high-performance zoom lens system with image vibration reduction function.
To achieve the above object a zoom lens system with vibration reduction function according to an embodiment of the present invention is designed to include, in succession from the object side:
a first lens unit having positive refractive power;
a second lens unit movable along a direction across the optical axis thereof and having negative refractive power;
a third lens unit;
a fourth lens unit having positive refractive power;
a fifth lens unit having negative refractive power;
during the focal-length change from the wide angle end to the telephoto end, the spacing between said first lens unit and said second lens unit being increased, the spacing between said second lens unit and said third lens unit being varied, and the spacing between said fourth lens unit and said fifth lens unit being decreased; and
a vibration reduction device for moving said second lens unit along a direction across said optical axis;
the stabilization of an image on an image plane being accomplished by the movement of said second lens unit caused by said vibration reduction device.
Also, to achieve the above object, a zoom lens system with vibration reduction function according to another embodiment of the present invention is designed to include, in succession from the object side:
a first lens unit having positive refractive power;
a second lens unit movable along a direction across the optical axis thereof and having negative refractive power;
a lens unit disposed subsequently to said second lens unit; and
a vibration reduction device for moving said second lens unit so as to cross said optical axis;
during the focal-length change from the wide angle end to the telephoto end, the spacing between said first lens unit and said second lens unit being increased.
Also, to achieve the above object, a zoom lens system with vibration reduction function according to still another embodiment of the present invention is designed to include, in succession from the object side:
a first lens unit having positive refractive power;
a second lens unit movable along a direction across the optical axis thereof to stabilize an image on an image plane and having negative refractive power;
a third lens unit;
a fourth lens unit having positive refractive power; and
a fifth lens unit having negative refractive power;
during the focal-length change from the wide angle end to the telephoto end, the spacing between said first lens unit and said second lens unit being increased, the spacing between said second lens unit and said third lens unit being varied and the spacing between said fourth lens unit and said fifth lens unit being decreased.
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patent: 4974950 (1990-12-01), Yamazaki et al.
patent: 5040881 (1991-08-01), Tsuji
patent: 5042927 (1991-08-01), Ogawa et al.
patent: 5105311 (1992-04-01), Tokumaru et al.
patent: 5121978 (1992-06-01), Maruyama
patent: 5270857 (1993-12-01), Oizumi et al.
patent: 4-301811 (1992-10-01), None
patent: 5-113538 (1993-05-01), None
Miles & Stockbridge P.C.
Nguyen Thong
Nikon Corporation
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