Patent Number: 6,166,863

Title: Zoom lens optical system

Abstract: A zoom lens having a high zoom ratio (>4.times.) and a large aperture ratio (FNO 2.8) and capable of providing close-range focus with only a small amount of aberration fluctuations. The zoom lens comprises either five or six lens groups. An exemplary zoom lens comprises, objectwise to imagewise, a first lens group having positive refractive power, a second lens group having negative refractive power and separated from the first lens group by a first air space, a third lens group having negative refractive power and separated from the second lens group by a second air space, a fourth lens group having positive refractive power and separated from the third lens group by a third air space, and a fifth lens group having a positive refractive power and separated from said fourth lens group by a fourth air space. The zoom lens is designed such that when zooming from the maximum wide-angle state to the maximum telephoto state, at least the second lens group moves imagewise and at least one of the first lens group and said fourth lens group moves so as to increase the first and second air spaces and decrease the third and fourth air spaces. The zoom lens also satisfies one or more of a number of preferred design conditions.

Inventors: Ohtake; Motoyuki (Kawasaki, JP)

Assignee: Nikon Corporation

International Classification: G02B 15/163 (20060101); G02B 15/17 (20060101); G02B 015/14 ()

Expiration Date: 12/26/2017