Optical: systems and elements – Lens – With variable magnification
Patent
1992-10-20
1993-11-09
Sugarman, Scott J.
Optical: systems and elements
Lens
With variable magnification
359713, G02B 1514, G02B 1318
Patent
active
052608336
ABSTRACT:
A zoom lens system is disclosed in which a high zoom ratio of 2.5 or more, that is short in the overall lens length, that is composed of a smaller number of lens elements, that will experience less deterioration in performance due to manufacturing or assembly errors or less focus shift due to temperature or humidity changes, and which hence is suitable for use with a compact camera. The zoom lens system comprises at least three lens groups which are arranged, in order from the object side, as a first lens group having a positive focal length, a second lens group having a positive focal length and a third lens group having a negative focal length, wherein, when zooming is carried out from the wide-angle to the telephoto end, the first, second and third lens groups are moved towards the object so that the distance between the first and second lens groups is increased whereas the distance between the second and third lens groups is decreased; the third lens group comprises, in order from the object side, a lens element 3a having a small power and another lens element 3b having a large negative power the third lens group has at least one aspheric surface and satisfies the certain conditions.
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Ito Takayuki
Minefuji Nobutaka
Asahi Kogaku Kogyo K.K.
Sugarman Scott J.
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