US 4,789,229 AGranted

Zoom lens system

AssigneeOlympus Optical Co., Ltd.

InventorTakanori Yamanashi

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Abstract

A zoom lens system comprising a first lens group G.sub.1 having positive refractive power, a second lens group G.sub.2 having negative refractive power, a third lens group G.sub.3 having positive refractive power, a fourth lens group G.sub.4 having positive refractive power, and a fifth lens group G.sub.5 having negative refractive power, in the order from the object side, and arranged to vary the focal length or the lens system as a whole by moving, out of the above-mentioned lens groups, at least the first lens group G.sub.1, third lens group G.sub.3 and fourth lens group G.sub.4 along the optical axis, the zoom lens system being arranged that the vari-focal range thereof includes a position in the range of wide field angle, the vair-focal ratio thereof is high, i.e., 6, favorable performance is maintained over the whole vari-focal range, and the lens system as a whole is made small in size.

Claims9

Dependent claims

A zoom lens system comprising a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power, and a fifth lens group having negative refractive power, in the order from the object side, and arranged to vary the focal length of the lens system as a whole by at least moving said first, third and fourth lens groups in the direction of the optical axis, said zoom lens system being arranged to fulfill the following conditions:

0.15<.vertline.f.sub.2 /f.sub.1 .vertline.<0.3 (1)
0.5<.vertline..beta..sub.3w .multidot..beta..sub.4w .vertline.<2.5 (2)
1.01<.beta..sub.5 <1.3 (3)
where, reference symbol f.sub.1 represents the focal length of the first lens group, reference symbol f.sub.2 represents the focal length of the second lens group, reference symbol .beta..sub.3w represents the lateral magnification of the third lens group in the wide position, reference symbol .beta..sub.4w represents the lateral magnification of the fourth lens group in the wide position, and reference symbol .beta..sub.5 represents the lateral magnification of the fifth lens group.

1 more element

Dependencies are inferred from the claim text.