Zoom lens system
AssigneeAsahi Kogaku Kabushiki Kaisha
InventorTakashi Enomoto
Life of this patent
Estimating the term…
Abstract
A zoom lens system including a positive first lens group and a negative second lens group in this order from the object, and in which zooming is performed by varying the distance between the positive first lens group and the negative second lens group; wherein a diaphragm is positioned between lens elements which constitute the first lens group, and wherein focusing is performed by moving the negative second lens group along the optical axis.
Claims11
A zoom lens system comprising a positive first lens group and a negative second lens group in this order from the object, and in which zooming is performed by varying the distance between said positive first lens group and said negative second lens group;
- wherein a diaphragm is positioned between lens elements which constitute said first lens group,
- wherein focusing is performed by moving said negative second lens group along the optical axis, and
- wherein said zoom lens has a half angle-of-view of more than 30° at a short focal length extremity, and
- wherein said zoom lens system satisfies the following condition:
- 0.7<Σds/Σd1G<1
- 0.6<H1/Hs<0.9
- wherein:
- Σd1G represents the distance from the most object-side surface to the most image-side surface of said first lens group;
- Σds represents the distance from the most object-side surface to the diaphragm of the first lens group;
- H1 represents the height of a paraxial ray which strikes the most object-side surface of said first lens group at the short focal length extremity;
- and
- Hs represents the height of the paraxial ray at the position of said diaphragm when said first lens group is at the short focal length extremity.
A zoom lens system comprising a positive first lens group and a negative second lens group in this order from the object, and in which zooming is performed by varying the distance between said positive first lens group and said negative second lens group;
- wherein a diaphragm is positioned between lens elements which constitute said first lens group,
- wherein focusing is performed by moving said negative second lens group along an optical axis, and
- wherein said zoom lens system satisfies the following condition:
- −1.23≦fw/fF<1.0
- wherein:
- fw designates a focal length of the entire zoom lens system at the short focal length extremity;
- and
- fF designates the focal length of said second lens group.
A zoom lens system consisting of:
- a positive first lens group and a negative second lens group in this order from an object, zooming being performed by varying a distance between said first lens group and said second lens group, a frontmost lens element of said positive first lens group comprising a negative meniscus lens element;
- a diaphragm positioned between lens elements of said first lens group;
- and
- focusing being performed by movement of said negative second lens group along an optical axis.
Dependencies are inferred from the claim text.