Zoom lens and optical apparatus
AssigneeCanon Kabushiki Kaisha
InventorYoshinori Ito
Life of this patent
Estimating the term…
Abstract
A zoom lens including, in the order from the object end thereof, a first lens unit having positive refractive power, a second lens unit having negative refractive power and being movable during zooming, and including four single lenses, separated one from another, three of these lenses each having negative refractive power, and one lens element having positive refractive power, a third lens unit, having positive refractive power, including at least one lens having positive refractive power and having aspherical surfaces on the two sides thereof, and a fourth lens unit having positive refractive power and being movable during zooming.
Claims10
A zoom lens comprising, in order from the object end thereof:
- a first lens unit having positive refractive power;
- a second lens unit having negative refractive power and being movable during zooming, and consisting of four single lenses, separated one from another, three of said four single lenses each having negative refractive power, and one lens having positive refractive power;
- a third lens unit, having positive refractive power, comprising at least one lens having positive refractive power and having aspherical surfaces on the two sides thereof;
- and
- a fourth lens unit having positive refractive power and being movable during zooming,
- wherein the first lens unit comprises a first lens having negative refractive power, a second lens having positive refractive power, and a third lens having positive refractive power, and wherein the condition of 1.72<(n12+n13)/2<1.77 holds, where n12 represents the index of refraction of the second lens and n13 represents the index of refraction of the third lens.
An optical apparatus comprising a zoom lens, the zoom lens comprising in order from the object end thereof:
- a first lens unit having positive refractive power;
- a second lens unit having refractive power and being movable during zooming, and consisting of four single lenses, separated one from another, three of said single lenses each having negative refractive power, and one lens having positive refractive power;
- a third lens unit having positive refractive power comprising at least one lens having positive refractive power and having aspherical surfaces on the two sides thereof;
- a fourth lens unit having positive refractive power and being movable during zooming;
- and
- image pick up element for receiving the image which the zoom lens forms,
- wherein the first lens unit comprises a first lens having negative refractive power, a second lens having positive refractive power, and a third lens having positive refractive power, and wherein the condition of 1.72<(n12+n13)/2<1.77 holds, where n12 represents the index of refraction of the second lens and n13 represents the index of refraction of the third lens.
Dependencies are inferred from the claim text.