US 2006/0215279 A1 · Zoom lens system

Abstract

Providing a zoom lens system that satisfies making the focusing lens light and reducing a moving amount for focusing, simultaneously. The zoom lens system includes a first lens group having positive power, a second lens group having negative power and a third lens group having positive power. When zooming from a wide-angle end state to a telephoto end state, at least the first and third lens groups are moved such that a distance between the first and second lens groups increases, and a distance between the second and third lens groups decreases. The first lens group is composed of a front lens group with positive power having at least one negative lens and at least one positive lens, and a rear lens group with positive power having one positive lens. Focusing from infinity to a close object is carried out by moving only the rear lens group to the object.

Claims23

Dependent claims

A zoom lens system comprising, in order from an object:

a first lens group having positive refractive power;
a second lens group having negative refractive power;
and
a third lens group having positive refractive power;
when a state of lens group positions varies from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group increasing, and a distance between the second lens group and the third lens group decreasing,
the first lens group being composed of, in order from the object, a front lens group having positive refractive power and a rear lens group having positive refractive power,
the front lens group being composed of, in order from the object, at least one negative lens and at least one positive lens,
the rear lens group being composed of a single positive lens, and
focusing from infinity to a close object being carried out by moving only the rear lens group to the object.

6 more elements

A method for forming an image of an object and varying a focal length of a zoom lens system that includes, in order from the object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power, comprising steps of:

providing the zoom lens system in which the first lens group is composed of, in order from the object, a front lens group having positive refractive power constructed by at least one negative lens and at least one positive lens, and a rear lens group having positive refractive power constructed by a single positive lens,
varying the focal length of the zoom lens system from a wide-angle end state to a telephoto end state by increasing a distance between the first lens group and the second lens group, and by decreasing a distance between the second lens group and the third lens group, and
varying focusing of the zoom lens system from infinity to a close object by moving only the rear lens group to the object.

Dependencies are inferred from the claim text.

Zoom lens system

Life of this patent

Zoom lens system

Life of this patent

Abstract

Claims23