Zoom lens and image pickup apparatus including the same

Patent metadata

Field	Value
Publication number	US-9268120-B2
Application number	US-201414534523-A
Country	US
Kind code	B2
Filing date	Nov 6, 2014
Priority date	Nov 12, 2013
Publication date	Feb 23, 2016
Grant date	Feb 23, 2016

Abstract

Provided is a zoom lens including, in order from an object side to an image side: a first lens unit having a positive refractive power which does not move for zooming; a second lens unit having a negative refractive power which moves during zooming; and an N-th lens unit having a positive refractive power which does not move for zooming and is arranged closest to the image side. In the zoom lens, the N-th lens unit includes in order from an object side: a first sub-lens unit; and a second sub-lens unit which is movable, and a lateral magnification at a wide angle end of the N-th lens unit and a lateral magnification at a wide angle end of the second sub-lens unit of the N-th lens unit when an axial ray enters from infinity in a state in which focus is at the infinity are appropriately set.

First claim

What is claimed is:

1. A zoom lens, comprising, in order from an object side to an image side:
a first lens unit having a positive refractive power which does not move for zooming;
a second lens unit having a negative refractive power which moves during zooming; and
an N-th lens unit having a positive refractive power which does not move for zooming and is arranged closest to the image side,
wherein the N-th lens unit comprises, in order from an object side to an image side:
a first sub-lens unit; and
a second sub-lens unit configured to be able to move in an optical axis direction, and

wherein the following conditional expressions are satisfied:
−2.70 <βnw<− 1.45; and

0<β n 2<0.75,

where βnw represents a lateral magnification at a wide angle end of the N-th lens unit and βn2 represents a lateral magnification at a wide angle end of the second sub-lens unit when an axial ray enters from infinity in a state in which focus is at the infinity.

2. A zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
0< fn 1/ fn 2<0.45,

where fn1 represents a focal length of the first sub-lens unit, and fn2 represents a focal length of the second sub lens unit.

3. A zoom lens according to claim 1 ,
wherein a lens closest to the image side of the first sub-lens unit comprises a convex lens or a cemented lens, and
wherein the following conditional expression is satisfied:
| fn 1/ fn 11|<0.3,

where fn11 represents a focal length of the lens closest to the image side of the first sub-lens unit.

4. A zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
0.58<θ2<0.70,

where θ2 represents a partial dispersion ratio of a first convex lens, which has the smallest Abbe number with respect to a d-line among convex lenses included in the second sub-lens unit,
provided, that the partial dispersion ratio θ is expressed as follows:
θ=( Ng−NF )/( NF−NC ),

where Ng, NF, and NC respectively represent a refractive index for a g-line, a refractive index for an F-line, and a refractive index for a C-line, and
an Abbe number νd with respect to the d-line is expressed as follows;
ν d =( Nd− 1)/( NF−NC ),

where Nd represents a refractive index for the d-line, NC represents the refractive index for the C-line, and NF represents the refractive index for the F-line.

5. A zoom lens according to claim 1 , wherein the following conditional expressions are satisfied:
15< νd 2<30; and
65< νd 2 a< 85,

where νd2 represents an Abbe number with respect to d-line of a first convex lens, which has the smallest Abbe number with respect to the d-line among convex lenses included in the second sub-lens unit, and νd2a represents an average Abbe number with respect to the d-line of the convex lenses other than the first convex lens,
provided that an Abbe number νd with respect to the d-line among convex lenses included in the second sub-lens unit is expressed as follows:
ν d =( Nd− 1)/( NF−NC ),

where NF represents a refractive index for an F-line, Nd represents a refractive index for the d-line, and NC represents a refractive index for a C-line.

6. A zoom lens according to claim 1 ,
wherein the first lens unit comprises:
a first sub-lens unit having negative refractive power which does not move for focusing;
second sub-lens unit having a positive refractive power which moves to the image side during focusing from an infinity side to a close range side; and
a third sub-lens unit having positive refractive power, and

wherein the following conditional expression is satisfied:
1.5< f 1/ fw< 3.5,

were f1 represents a focal length of the first lens unit, and fw represents a focal length at the wide angle end of the zoom lens.

7. A zoom lens according to claim 1 ,
wherein the first lens unit comprises:
first sub-lens unit having to negative refractive power which does not move for focusing;
a second sub lens unit having a positive refractive power which moves to the image side during focusing from an infinity side to a close range side; and
a third sub-lens unit having a positive refractive power, and

wherein the following conditional expressions are satisfied:
−1.5< f 11/ f 1<−0.9,

where f1 represents a focal length of the first lens unit, and f11 represents a focal length of the first sub-lens unit of the first lens unit.

8. A zoom lens according to claim 1 ,
wherein the first lens unit comprises:
a first sub-lens unit having a negative refractive power which does not move for focusing;
a second sub-lens unit having a positive refractive power which moves to the image side during focusing from an infinity side to a close range side; and
a third sub-lens unit having a positive refractive power, and

wherein the following conditional expressions are satisfied:
−1.5< f 13/ f 11<−0.9,

were f11 represents a focal length of the first sub-lens unit of the first lens unit, and f13 represents a focal length of the third sub-lens unit of the first lens unit.

9. A zoom lens according to claim 1 , wherein the second sub-lens unit is configured to be able to move in an optical axis direction for macro photography or flange back adjustment.

10. 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 which does not move for zooming;
a second lens unit having a negative refractive power which moves during zooming; and
an N-th lens unit having a positive refractive power which does not move for zooming and is arranged closest to the image side,
wherein the N-th lens unit comprises, in order from an object side to an image side:
a first sub-lens unit; and
a second sub-lens unit configured to be able to move in an optical axis direction, and

wherein the following conditional expressions are satisfied:
−2.70<β nw<− 1.45; and

0<β n 2<0.75,

where βnw represents a lateral magnification at a wide angle end of the N-th lens unit and βn2 represents a lateral magnification at a wide angle end of the second sub-lens unit when an axial ray enters from infinity in a state in which focus is at the infinity; and
a solid-state image pick-up element for receiving an image formed by the zoom lens.

Assignees

• Canon Kk

Inventors

• Shimomura Kazuya
• Nakamura Tomoyuki
• Inomoto Yu
• Wakazono Tsuyoshi

Classifications

• H04N23/69

  Control of means for changing angle of the field of view, e.g. optical zoom objectives or electronic zooming · CPC title

• G02B13/009

  having zoom function · CPC title

• G02B15/24 Primary

  having a front fixed lens or lens group and two movable lenses or lens groups in front of a fixed lens or lens group · CPC title

• G02B15/173 Primary

  arranged +-+ · CPC title

• G02B15/14

  by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective · CPC title