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US 9,678,318 B2Granted
Zoom lens and image pickup apparatus including the same
AssigneeCanon Kabushiki Kaisha
InventorsTomoyuki Nakamura, Kazuya Shimomura
Life of this patent
Estimating the term…
Abstract
Provided is a zoom lens, including, in order from an object side to an image side: a positive first lens unit that does not move for zooming; a negative second lens unit that moves during zooming; and a positive N-th lens unit that does not move for zooming and is arranged closest to the image side. Among lenses constructing the second lens unit, two lenses closest to the image side are a positive lens and a negative lens, and partial dispersion ratios for g-line and F-line and Abbe numbers for a d-line of the positive and negative lenses, and an average value of refractive indices of all the lenses of the second lens unit are appropriately set.
Claims18
A zoom lens, comprising, in order from an object side to an image side:
- a first lens unit having a positive refractive power that does not move for zooming;
- a second lens unit having a negative refractive power that moves during zooming;
- and
- an N-th lens unit having a positive refractive power that does not move for zooming, the N-th lens unit being arranged closest to the image side,
- wherein the first lens unit comprises in order from the object side to the image side:
- a first sub-lens unit having a negative refractive power that does not move for focusing;
- a second sub-lens unit having a positive refractive power that moves along an optical axis during focusing;
- and
- a third sub-lens unit having a positive refractive power that does not move for focusing,
- wherein two lenses, among lenses of the second lens unit, disposed closest to the image side of the second lens unit, comprise a positive lens and a negative lens, and
- wherein the following conditional expressions are satisfied:
- −9.0<f11/f1<−0.9;
- −1.5<f13/f11<−0.5;
- −3.0×10−3<(θp−θn)/(νp−νn)<0;
- and
- 1.7<nave<2.0,
- where f1 represents a focal length of the first lens unit, f11 represents a focal length of the first sub-lens unit, f13 represents a focal length of the third sub-lens unit, θp and νp represent a partial dispersion ratio and an Abbe number of the positive lens, respectively, θn and νn represent a partial dispersion ratio and an Abbe number of the negative lens, respectively, and nave represents an average value of refractive indices of all the lenses of the second lens unit,
- provided that the Abbe number ν and the partial dispersion ratio θ are respectively expressed as follows:
- ν=(nd−1)/(nF−nC);
- and
- θ=(ng−nF)/(nF−nC),
- where ng represents a refractive index for a g-line, nF represents a refractive index for an F-line, nd represents a refractive index for a d-line, and nC represents a refractive index for a C-line.
19 more elements
A zoom lens comprising in order from an object side to an image side:
- a first lens unit having a positive refractive power that does not move for zooming;
- a second lens unit having a negative refractive power that moves during zooming;
- a third lens unit that moves during focusing;
- and
- an N-th lens unit having a positive refractive power that does not move for zooming, the N-th lens unit being arranged closest to the image side,
- wherein the first lens unit comprises in order from the object side to the image side:
- a first sub-lens unit having a negative refractive power that does not move for focusing;
- a second sub-lens unit having a positive refractive power that moves along an optical axis during focusing;
- and
- a third sub-lens unit having a positive refractive power that does not move for focusing,
- wherein two lenses, among lenses of the second lens unit and the third lens unit, disposed closest to the image side comprise a positive lens and a negative lens, and
- wherein the following conditional expressions are satisfied:
- −9.0<f11/f1<−0.9;
- −1.5<f13/f11<−0.5;
- −3.0×10−3<(θp−θn)/(νp−νn)<0;
- and
- 1.7<nave<2.0,
- where f1 represents a focal length of the first lens unit, f11 represents a focal length of the first sub-lens unit, f13 represents a focal length of the third sub-lens unit, θp and νp represent a partial dispersion ratio and an Abbe number of the positive lens, respectively, θn and νn represent a partial dispersion ratio and an Abbe number of the negative lens, respectively, and nave represents an average value of refractive indices of all the lenses of the second lens unit and the third lens unit,
- provided that the Abbe number v and the partial dispersion ratio θ are respectively expressed as follows:
- ν=(nd−1)/(nF−nC);
- and
- θ=(ng−nF)/(nF−nC),
- where ng represents a refractive index for a g-line, nF represents a refractive index for an F-line, nd represents a refractive index for a d-line, and nC represents a refractive index for a C-line.
20 more elements
An image pickup apparatus, comprising:
- a zoom lens, comprising, in order from an object side to an image side:
- a first lens unit having a positive refractive power that does not move for zooming;
- a second lens unit having a negative refractive power that moves during zooming;
- and
- an N-th lens unit having a positive refractive power that does not move for zooming, the N-th lens unit being arranged closest to the image side,
- wherein the first lens unit comprises in order from the object side to the image side:
- a first sub-lens unit having a negative refractive power that does not move for focusing;
- a second sub-lens unit having a positive refractive power that moves along an optical axis during focusing;
- and
- a third sub-lens unit having a positive refractive power that does not move for focusing,
- wherein two lenses, among lenses of the second lens unit, disposed closest to the image side of the second lens unit, comprise a positive lens and a negative lens, and
- wherein the following conditional expressions are satisfied:
- −9.0<f11/f1<−0.9;
- −1.5<f13/f11<−0.5;
- −3.0×10−3<(θp−θn)/(νp−νn)<0;
- and
- 1.7<nave<2.0,
- where f1 represents a focal length of the first lens unit, f11 represents a focal length of the first sub-lens unit, f13 represents a focal length of the third sub-lens unit, θp and νp represent a partial dispersion ratio and an Abbe number of the positive lens, respectively, θn and νn represent a partial dispersion ratio and an Abbe number of the negative lens, respectively, and nave represents an average value of refractive indices of all the lenses of the second lens unit,
- provided that the Abbe number v and the partial dispersion ratio θ are respectively expressed as follows:
- ν=(nd−1)/(nF−nC);
- and
- θ=(ng−nF)/(nF−nC),
- where ng represents a refractive index for a g-line, nF represents a refractive index for an F-line, nd represents a refractive index for a d-line, and nC represents a refractive index for a C-line.
20 more elements
An image pickup apparatus comprising a zoom lens,
- the zoom lens comprising in order from an object side to an image side:
- a first lens unit having a positive refractive power that does not move for zooming;
- a second lens unit having a negative refractive power that moves during zooming;
- a third lens unit that moves during focusing;
- and
- an N-th lens unit having a positive refractive power that does not move for zooming, the N-th lens unit being arranged closest to the image side,
- wherein the first lens unit comprises in order from the object side to the image side:
- a first sub-lens unit having a negative refractive power that does not move for focusing;
- a second sub-lens unit having a positive refractive power that moves along an optical axis during focusing;
- and
- a third sub-lens unit having a positive refractive power that does not move for focusing,
- wherein two lenses, among lenses of the second lens unit and the third lens unit, disposed closest to the image side comprise a positive lens and a negative lens, and
- wherein the following conditional expressions are satisfied:
- −9.0<f11/f1<−0.9;
- −1.5<f13/f11<−0.5;
- −3.0×10−3<(θp−θn)/(νp−νn)<0;
- and
- 1.7<nave<2.0,
- where f1 represents a focal length of the first lens unit, f11 represents a focal length of the first sub-lens unit, f13 represents a focal length of the third sub-lens unit, θp and νp represent a partial dispersion ratio and an Abbe number of the positive lens, respectively, θn and νn represent a partial dispersion ratio and an Abbe number of the negative lens, respectively, and nave represents an average value of refractive indices of all the lenses of the second lens unit and the third lens unit,
- provided that the Abbe number v and the partial dispersion ratio θ are respectively expressed as follows:
- ν=(nd−1)/(nF−nC);
- and
- θ=(ng−nF)/(nF−nC),
- where ng represents a refractive index for a g-line, nF represents a refractive index for an F-line, nd represents a refractive index for a d-line, and nC represents a refractive index for a C-line.
21 more elements
Dependencies are inferred from the claim text.