US 5,329,402 A · Wide-angle zoom lens

Abstract

A small-sized and bright wide-angle zoom lens having a variable power ratio on the order of 2 at a field angle of approximately 84.degree. and constructed of a small number of constructional lens. The wide-angle zoom lens, sequentially from an object, comprises a first lens group having negative refracting power on the whole and a second lens group having positive refracting power on the whole, wherein a magnification is varied by altering an air space between the two lens groups. In this wide-angle zoom lens, the first lens group is constructed of, sequentially from the object, two pieces of negative meniscus lenses with their convex surfaces toward the object and a positive lens with its convex surface toward the object. At least one of the negative meniscus lenses is formed with an aspherical surface. The second lens group is constructed, sequentially from the object, two pieces of positive lenses, a negative lens and a positive lens. The zoom lens is further constructed to satisfy the various conditions.

Claims29

Dependent claims

A wide-angle zoom lens, sequentially from an object, comprising:

a first lens group having negative refracting power on the whole and constructed of two pieces of negative meniscus lenses with their convex surfaces toward the object, at least any one of said lenses being formed with an aspherical surface, and a positive lens with a convex surface toward the object;
and
a second lens group having positive refracting power on the whole and constructed of a plurality of lenses,
wherein said first and second lens groups move along the optical axis to alter a space therebetween for variable power and are constructed to further satisfy the following conditions:
0.65<.vertline.f.sub.1 .vertline./(f.sub.W .multidot.f.sub.T)1/2<1.1
0.9<f.sub.2 /.vertline.f.sub.1 .vertline.<1.1
where
f.sub.1 :
the focal length of said first lens group,
f.sub.2 :
the focal length of said second lens group,
f.sub.W :
the focal length of the whole system at the wide-angle, and
f.sub.T :
the focal length of the whole system at the telephoto end.

12 more elements

A wide-angle zoom lens, sequentially from an object, comprising:

a first lens group having negative refracting power on the whole and constructed of two pieces of negative meniscus lenses with their convex surfaces toward the object, at least any one of said lenses being formed with an aspherical surface, and a positive lens with a convex surface toward the object;
and
a second lens group having positive refracting power on the whole and constructed of two pieces of positive lenses, one negative lens and further at least one positive lens
wherein said first and second lens groups move to alter a space therebetween for variable power and are constructed to further satisfy the following conditions:
0.65<.vertline.f.sub.1 .vertline./(f.sub.W .multidot.f.sub.T)1/2<1.1
0.9<f.sub.2 /.vertline.f.sub.1 .vertline.<1.1
where
f.sub.1 :
the focal length of said first lens group,
f.sub.2 :
the focal length of said second lens group,
f.sub.W :
the focal length of the whole system at the wide-angle, and
f.sub.T :
the focal length of the whole system at the telephoto end.

12 more elements

Dependencies are inferred from the claim text.

Wide-angle zoom lens

Life of this patent

Wide-angle zoom lens

Life of this patent

Abstract

Claims29