Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
2005-11-29
2005-11-29
Lester, Evelyn A. (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S682000, C359S684000, C359S740000, C359S771000, C359S686000, C359S715000, C359S783000
Reexamination Certificate
active
06970298
ABSTRACT:
A zoom lens system has four lens units, i.e., in order from an object side to an image side, a first lens unit of negative optical power, a second lens unit of positive optical power, a third lens unit of positive optical power, and a fourth lens unit of positive optical power. During zooming from a wide-angle end to a telephoto end, a space between the first lens unit and the second lens unit decreases, a space between the second lens unit and the third lens unit varies, and a space between the third lens unit and the fourth lens unit increases. Two negative lens elements constituting the first lens unit are made from high refractive index materials. Accordingly, a small-sized zoom lens system capable of obtaining a desired wide angle of field at the wide-angle end, a desired zoom ratio and high optical performance with a minimum number of lens elements can be provided.
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Canon USA, Inc
Lester Evelyn A.
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