Zoom lens
AssigneeNikon Corporation
InventorsAtsushi Shibayama, Masatoshi Suzuki, Takanori Fujita
Life of this patent
Estimating the term…
Abstract
A zoom lens is composed of a first lens group of a negative refractive power, a second lens group of a positive refractive power and a third lens group of a positive refractive power, in which, in the zooming operation from the wide angle end to the telephoto end, the distance between the first and second lens groups decreases and the distance between the second and third lens groups varies.
Claims33
A zoom lens consisting, in the order from the object side, of a first lens group of a negative refractive power, a second lens group of a positive refractive power, and a third lens group of a positive refractive power, wherein, in the zooming operation from the wide angle end to the telephoto end, said first lens group remains fixed while said second and third lens groups move toward the object side, the distance between said second and third lens groups varies, and the imaging magnification of the second lens group does not become equal to -1 at any focal length state from the wide angle end to the telephoto end, wherein the focusing operation from a long object distance to a short object distance is executed by a movement of said second lens group toward the image plane.
A zoom lens consisting, in the order from the object side, of a first lens group of a negative refractive power, a second lens group of a positive refractive power, a third lens group of a positive refractive power, and a diaphragm between said second and third lens groups, wherein, in the zooming operation from the wide angle end to the telephoto end, said first lens group remains fixed while said second and third lens groups move toward the object side, the distance between said second and third lens groups varies, and the imaging magnification of the second lens group does not become equal to -1 at any focal length state from the wide angle end to the telephoto end.
A zoom lens comprising, in the order from the object side, a first lens group of a negative refractive power that is closer to the object side than any other lens group of the zoom lens, a second lens group of a positive refractive power, and a third lens group of a positive refractive power, wherein, in the zooming operation from the wide angle end to the telephoto end, the distance between the first and second lens groups decreases, the distance between said second and third lens groups varies, and the focusing operation from a long object distance to a short object distance is executed by a movement of said second lens group toward the image plane.
A zoom lens comprising, in the order from the object side, a first lens group of a negative refractive power, a second lens group of a positive refractive power, and a third lens group of a positive refractive power, wherein, in the zooming operation from the wide angle end to the telephoto end, the zooming effect is substantially achieved by decreasing the distance between said first and second lens groups and varying the distance between said second and third lens groups, and the following conditions are satisfied:
- 1<.vertline.f1.vertline./fw<1.5(f1<0)
- 0.5<f2/f3<2
- 0.8<x2/x3<1.2
- wherein
- fw:
- focal length of entire system at the wide angle end;
- f1:
- focal length of said first lens group;
- f2:
- focal length of said second lens group;
- f3:
- focal length of said third lens group;
- x2:
- amount of zooming movement of said second lens group from the wide angle end to the telephoto end, relative to the image plane;
- and
- x3:
- amount of zooming movement of said third lens group from the wide angle end to the telephoto end, relative to the image plane.
A zoom lens comprising, in the order from the object side, a first lens group composed of a negative meniscus lens convex to the object side, a negative lens and a positive lens and having a negative refractive power in total, a second lens group of a positive refractive power, and a third lens group of a positive refractive power, wherein, in the zooming operation from the wide angle end to the telephoto end, the distance between said first and second lens groups decreases, the distance between said second and third lens groups varies, and the following conditions are satisfied:
- 1<.vertline.f1.vertline./fw<1.5(f1<0)
- 0.5<f2/f3<2
- wherein
- fw:
- focal length of entire system at the wide angle end;
- f1:
- focal length of said first lens group;
- f2:
- focal length of said second lens group;
- and
- f3:
- focal length of said third lens group.
Dependencies are inferred from the claim text.