Zoom lens
AssigneeFujinon Corporation
InventorYoshikazu Shinohara
Life of this patent
Estimating the term…
Abstract
A zoom lens includes, in order from an object side, a first lens group fixed upon zooming and wholly having a negative refractive power, a second lens group formed by an optical-path bending prism fixed upon zooming and, a third lens group allowed to move upon zooming and wholly having a positive refractive power, a fourth lens group allowed to move upon zooming and wholly having a negative refractive power, and a fifth lens group fixed upon zooming and wholly having a positive refractive power. By arranging a zooming group having the positive third and negative fourth lens groups without arranging a positive fixed lens group in back of the prism, the overall length can be easily reduced as compared to the structure arranging a fixed lens group between a prism and a zooming group.
Claims14
A zoom lens comprising, in order from an object side:
- a first lens group that is fixed upon zooming and wholly has a negative refractive power;
- a second lens group that comprises an optical path bending prism, the second lens group which is fixed upon zooming;
- a third lens group that is allowed to move upon zooming and wholly has a positive refractive power;
- a fourth lens group that is allowed to move upon zooming and wholly has a negative refractive power;
- and
- a fifth lens group that is fixed upon zooming and wholly has a positive refractive power,
- wherein the following Conditional Expressions (1) to (2) are satisfied:
- −1.5<f3/f4<−0.5 (1)
- 2.0<DA/fw<3.0 (2)
- where
- f3 denotes focal length of the third lens group,
- f4 denotes focal length of the fourth lens group,
- fw denotes focal length of a system overall at a wide end, and
- DA denotes optical path length from an image-side surface of the first lens group to an object-side surface of the third lens group, at a telephoto end.
A zoom lens comprising, in order from an object side:
- a first lens group that is fixed upon zooming and wholly has a negative refractive power;
- a second lens group that comprises an optical path bending prism, the second lens group which is fixed upon zooming;
- a third lens group that is allowed to move upon zooming and wholly has a positive refractive power;
- a fourth lens group that is allowed to move upon zooming and wholly has a negative refractive power, wherein the fourth lens group includes at least two lenses;
- and
- a fifth lens group that is fixed upon zooming and wholly has a positive refractive power.
A zoom lens comprising, in order from an object side:
- a first lens group that is fixed upon zooming and wholly has a negative refractive power;
- a second lens group that comprises an optical path bending prism, the second lens group which is fixed upon zooming;
- a third lens group that is allowed to move upon zooming and wholly has a positive refractive power;
- a fourth lens group that is allowed to move upon zooming and wholly has a negative refractive power;
- and
- a fifth lens group that is fixed upon zooming and wholly has a positive refractive power,
- wherein the following Conditional Expression (3) is satisfied:
- 50<νG3 (3)
- where
- νG3:
- mean value of Abbe numbers at d-line over lenses in the third lens group.
Dependencies are inferred from the claim text.