ZOOM LENS AND IMAGE PICKUP APPARATUS INCLUDING THE SAME

• US 20150130968A1
• Filed: 11/06/2014
• Published: 05/14/2015
• Est. Priority Date: 11/12/2013
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Shimomura, Kazuya, Nakamura, Tomoyuki, Inomoto, Yu, Wakazono, Tsuyoshi
• Granted Patent: US 9,268,120 B2
• Time in Patent Office: Days
• US Class Current: 348/240.3
• CPC Class Codes: G02B 13/009 having zoom function
• CPC Class Codes: G02B 15/144113 arranged +-++
• CPC Class Codes: G02B 15/145117 arranged +---+
• CPC Class Codes: G02B 15/173 arranged +-+
• CPC Class Codes: G02B 15/24 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 Class Codes: H04N 23/69 Control of means for changing angle of the field of view, e.g. optical zoom objectives or electronic zooming

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.

Claims

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<

β

nw<

−

1.45;

and

0<

β

n2<

0.75,

where β

nw represents a lateral magnification at a wide angle end of the N-th lens unit and β

n2 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<

fn1/fn2<

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:

|fn1/fn11|<

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<

θ

2<

0.70,

where θ

2 represents a partial dispersion ratio of a first convex lens, which has the smallest Abbe number with respect to 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 g-line, a refractive index for F-line, and a refractive index for C-line, and

an Abbe number ν

d 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<

ν

d2<

30; and

65<

ν

d2a<

85,

where ν

d2 represents an Abbe number with respect to d-line of a first convex lens, which has the smallest Abbe number with respect to d-line among convex lenses included in the second sub-lens unit, and ν

d2a 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 ν

d with respect to the d-line is expressed as follows;

ν

d=(Nd−

1)/(NF−

NC),

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

f1/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<

f11/f1<

−

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<

f13/f11<

−

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 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

n2<

0.75,

where β

nw represents a lateral magnification at a wide angle end of the N-th lens unit and β

n2 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.