Zoom lens system
AssigneePENTAX Corporation
InventorTakashi Enomoto
Life of this patent
Estimating the term…
Abstract
A zoom lens system includes a negative first lens group, a positive second lens group, and a negative third lens group. Zooming is performed by moving the first through third lens groups in the optical axis direction. The negative first lens group is constituted by a negative single lens element having a concave surface facing toward the object, and satisfies the following condition: −1<r1/fW<0 (1) wherein r1 designates the radius of curvature of the object-side concave surface of said negative single lens element; and fW designates the focal length of the entire zoom lens system at the short focal length extremity.
Claims29
A zoom lens system comprising a negative first lens group, a positive second lens group and a negative third lens group in this order from an object,
- wherein zooming is performed by moving said first through third lens groups in the optical axis direction,
- wherein said positive second lens group includes a doublet and a positive lens element, in this order from said object.
- wherein said negative first lens group consists of a negative single lens element having a concave surface facing toward said object, and
- wherein said zoom lens system satisfies the following condition:
- −1<r1/fW<−0.3
- wherein
- r1 designates the radius of curvature of the object-side concave surface of said negative single lens element:
- and
- fW designates the focal length of the entire zoom lens system at the short focal length extremity.
A zoom lens system that focuses on objects at variable distances up to infinity, said zoom lens system comprising a negative first lens group, a positive second lens group, and a negative third lens group, in this order from an object,
- wherein zooming is performed by moving said first through third lens groups in the optical axis direction,
- wherein said negative first lens group consists of a negative single lens element having a concave surface facing toward said object, and
- wherein said zoom lens system satisfies the following condition:
- −1<r1/fW<−0.3
- wherein
- r1 designates the radius of curvature of the object-side concave surface of said negative single lens element;
- and
- fW designates the focal length of the entire zoom lens system at the short focal length extremity.
A zoom lens system comprising a negative first lens group, a positive second lens group, and a negative third lens group, in this order from an object,
- wherein zooming is performed by moving said first through third lens groups in the optical axis direction,
- wherein said negative first lens group consists of a negative single lens element having a concave surface facing toward said object, and
- wherein said zoom lens system satisfies the following conditions:
- −1<r1/fW<−0.3
- and
- −5<fT/f1G<−3
- wherein
- r1 designates the radius of curvature of the object-side concave surface or said negative single lens element;
- fW designates the focal length of the entire zoom lens system at the short focal length extremity;
- fT designates the focal length of the entire loom lens system at the long focal length extremity;
- and
- f1G designates the focal length of said negative single lens element.
A zoom lens system comprising a negative first lens group, a positive second lens group, and a negative third lens group, in this order from an object,
- wherein zooming is performed by moving said first through third lens groups in the optical axis direction.
- wherein said negative first lens group consists of a negative single lens element having a concave surface facing toward said object, and
- wherein said zoom lens system satisfies the following conditions:
- −1<r1/fW<−0.3
- and
- 0.6<y/fW<0.9
- wherein
- r1 designates the radius of curvature of the object-side concave surface of said negative single lens element:
- fW designates the focal length of the entire zoom lens system at the short focal length extremity;
- and
- y designates the diagonal image height on a film surface.
A zoom lens system comprising a negative first lens group, a positive second lens group, and a negative third lens group, in this order from an object,
- wherein zooming is performed by moving said first through third lens groups in the optical axis direction.
- wherein said negative first lens group consists of a negative single lens element having a concave surface facing toward said object, and
- wherein said zoom lens system satisfies the following conditions:
- −1<r1/fW<−0.3
- and
- 3.5<fT/fW
- wherein
- r1 designates the radius of curvature of the object-side concave surface of said negative single lens element;
- fW designates the focal length of the entire zoom lens system at the short focal length extremity;
- and
- fT designates the focal length of the entire zoom lens system at the long focal length extremity.
Dependencies are inferred from the claim text.