Optical: systems and elements – Lens – With variable magnification
Patent
1998-03-20
1999-10-19
Sugarman, Scott J.
Optical: systems and elements
Lens
With variable magnification
G02B 1514
Patent
active
059698802
ABSTRACT:
A zoom lens system comprising at least three lens groups including a positive first lens group, a positive second lens group having at least one negative lens element, and a third lens group having a negative focal length, wherein upon zooming from the shortest focal length toward the longest focal length, all the lens groups are moved toward the object side, and the distance between the first and second lens groups increases and the distance between the second and third lens groups decreases, and wherein the system satisfies the conditions (1) -0.3<f.sub.W /f.sub.1G +f.sub.W /f.sub.2G +f.sub.W /f.sub.3G <0, and (2) 1.845<N.sub.2Gn, wherein f.sub.W designates the focal length of the entire optical system at the short focal length extremity, f.sub.1G designates the focal length of the first lens group (f.sub.1G >0), f.sub.2G designates the focal length of the second lens group (f.sub.2G >0), f.sub.3G designates the focal length of the third lens group (f.sub.3G <0), N.sub.2Gn designates the average refractive index of all the negative lens elements of the second lens group.
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Enomoto Takashi
Hasushita Sachio
Ito Takayuki
Asahi Kogaku Kogyo Kabushiki Kaisha
Sugarman Scott J.
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