Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
1999-04-19
2001-05-22
Epps, Georgia (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S684000, C359S685000, C359S686000, C359S692000, C359S691000, C359S713000, C359S714000, C359S715000, C359S716000, C359S717000, C359S718000, C359S742000
Reexamination Certificate
active
06236515
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a zoom lens system, and particularly to a compact zoom lens system suitable as a talking lens, for example, in a lens-shutter camera.
2. Description of the Prior Art
Conventionally, most zoom lens systems for lens-shutter cameras consist of lens units that are each composed of two or more lens elements. In order to reduce the size and the cost of such cameras, it is essential to compose their lens units of as few lens elements as possible.
To achieve the above purpose, U.S. Pat. No. 5,327,290 proposes a zoom lens system consisting of, from the object side, a first lens unit having a positive refractive power and a second lens unit having a negative refractive power. In this zoom lens system, each lens unit is composed of two lens elements. Moreover, Japanese Laid-open Patent Application No. H3-15881 proposes a zoom lens system consisting of two lens units, one having a positive refractive power and the other having a negative refractive power. In this zoom lens system, the number of lens elements composing each lens unit is reduced by the use of the aspherical surfaces; specifically, the first lens unit is composed of two lens elements, and the second lens unit is composed of as few as one lens element.
However, the zoom lens system proposed in these Japanese Laid-open Patent Applications have a defect in that it cannot satisfactorily correct the chromatic aberration over the whole system, because the chromatic aberration within each lens unit cannot be corrected sufficiently at high zooming ratios.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a zoom lens system that, despite being compactly constructed of as few lens elements as possible, is capable of correcting chromatic aberration properly.
To achieve the above object, according to the present invention, in a zoom lens system that includes a lens unit having a negative refractive power disposed at an image-side end and that performs zooming by varying distances between a plurality of lens units, said plurality of lens units include a surface having a power to diffract light.
Specifically, according to one aspect of the present invention, in a zoom lens system that comprises, from an object side, a first lens unit having a positive refractive power and a second lens unit having a negative refractive power and that performs zooming from a wide-angle end to a telephoto end by moving the first and second lens units in such a way that a distance between the first and second lens units decreases, said zoom lens system includes at least one surface having a power to diffract light.
Alternatively, according to another aspect of the present invention, in the above described zoom lens system, said first lens unit is composed of at least two lens elements, and said zoom lens system includes at least one surface having a power to diffract light.
Alternatively, according to still another aspect of the present invention, said second lens unit is composed of one lens element.
Alternatively, according to a further aspect of the present invention, said first lens unit is composed of one lens element, said second lens unit is composed of at least two lens elements, and said zoom lens system includes at least one surface having a power to diffract light.
REFERENCES:
patent: 4936661 (1990-06-01), Betensky et al.
patent: 4972075 (1990-11-01), Hamada et al.
patent: 5268790 (1993-12-01), Chen
patent: 5493441 (1996-02-01), Chipper
patent: 5619381 (1997-04-01), Anderson
patent: 5731914 (1998-03-01), Meyers
patent: 5982544 (1999-11-01), Ogata
patent: 6010537 (2000-01-01), Konno et al.
patent: 6067196 (1999-11-01), Yamamoto et al.
patent: 544174 (1993-06-01), None
Ori Yuichiro
Yamamoto Yasushi
Epps Georgia
Lester Evelyn A.
Minolta Co. , Ltd.
Price and Gess
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