# US 10,310,255 B2 · Zoom lens and image pickup apparatus including the same

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- Number: US 10,310,255 B2
- Document ID: US10310255B2
- Status: Granted
- Kind: B2
- Application number: 14/965,029
- Filed: 2015-12-10
- Published: 2016-07-07
- Granted: 2019-06-04
- Earliest claimed: 2015-01-07
- Assignees: Canon Kabushiki Kaisha
- Applicants: Canon Kabushiki Kaisha
- Inventors: Yoshihisa Tashiro
- Web page: https://patentgrep.com/patent/US10310255B2

## CPC

- G02B 27/0025: {for optical correction, e.g. distorsion, aberration}
- G02B 15/143105: {arranged +-+}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A zoom lens including: a positive first lens unit; a negative second lens unit; and a positive rear lens group, an interval of adjacent lens units is changed during zooming, the rear lens group includes from an object side: a positive lens system; an aperture stop; and a negative partial lens system, the first lens unit and the aperture stop are positioned closer to the object side at a telephoto end than at a wide angle end, and a combined focal length of a front lens system between the first lens unit and the aperture stop at the wide angle end, an absolute value of a distance on an optical axis from a first lens surface to the aperture stop at the wide angle end, a focal length of the first lens unit, and a focal length of the zoom lens at the wide angle end is appropriately set.

## Claims

### Claim 1

A zoom lens comprising, in order from an object side to an image side:
a first lens unit providing a positive refractive power;
a second lens unit providing a negative refractive power; and
a rear lens providing a positive refractive power over an entire zoom range,
wherein an interval between each pair of adjacent lens units changes during zooming,
wherein the rear lens group includes:
a partial lens system LRp1 providing a positive refractive power and disposed closest to the object side in the rear lens group, the partial lens system LRp1 including at least first and second positive lenses and at least one negative lens;
an aperture stop disposed on the image side of the partial lens system LRp1; and
at least one lens unit providing a negative refractive power and disposed between the aperture stop and an image plane,
wherein the first lens unit and the aperture stop are configured to be positioned closer to the object side at a telephoto end than at a wide angle end, and
wherein the following conditional expressions are satisfied:
0.00<fssFw/LssFw<0.75; and
3.0<f1/fw<20.0,
where fssFw represents a combined focal length of a front lens system consisting of all lenses disposed on the object side of the aperture stop at the wide angle end, LssFw represents an absolute value of a distance on an optical axis from a first lens surface closest to the object side in the zoom lens to the aperture stop at the wide angle end, f1 represents a focal length of the first lens unit, and fw represents a focal length of the zoom lens at the wide angle end.

### Claim 2 (depends on 1)

The zoom lens according to claim 1, wherein the following conditional expression is satisfied:
0.5<βssRw<1.5
where βssRw represents a combined lateral magnification of a rear lens system consisting of all lenses disposed on the image side of the aperture stop at the wide angle end.

### Claim 3 (depends on 1)

The zoom lens according to claim 1, wherein the following conditional expression is satisfied:
0.8<|f2|/fw<2.0,
where f2 represents a focal length of the second lens unit.

### Claim 4 (depends on 1)

The zoom lens according to claim 1, wherein the following conditional expression is satisfied:
0.8<fRp1/fw<2.5,
where fRp1 represents a focal length of the partial lens system LRp1.

### Claim 5 (depends on 1)

The zoom lens according to claim 1, wherein the following conditional expression is satisfied:
0.1<skw/fw<1.0,
where skw represents a backfocus of the zoom lens at the wide angle end.

### Claim 6 (depends on 1)

The zoom lens according to claim 1, wherein:
the second lens unit includes a negative lens G21n closest to the object side, and
the following conditional expression is satisfied:
−1.5<(R2nb+R2na)/(R2nb−R2na)<−0.5,
where R2na represents a curvature radius of a lens surface of the negative lens G21n on the object side, and R2nb represents a curvature radius of a lens surface of the negative lens G21n on the image side.

### Claim 7 (depends on 1)

The zoom lens according to claim 1, wherein:
the partial lens system LRp1 includes in order from the object side to the image side:
a partial lens system LRp1a consisting of the first positive lens; and
a partial lens system LRp1b including the second positive lens and the at least one negative lens, and
the following conditional expression is satisfied:
−1.0<fRp1a/fRp1b<−0.1,
where fRp1a represents a focal length of the partial lens system LRp1a, and fRp1b represents a focal length of the partial lens system LRp1b.

### Claim 8 (depends on 1)

The zoom lens according to claim 1, wherein the rear lens group includes a lens unit providing a negative refractive power and disposed closest to the image side.

### Claim 9 (depends on 1)

The zoom lens according to claim 1, wherein:
the rear lens group includes a lens unit disposed closest to the image side, and
the following conditional expression is satisfied:
1.0<|fRn2|/fw<5.0,
where fRn2 represents a focal length of the lens unit of the rear lens group disposed closest to the image side.

### Claim 10 (depends on 1)

The zoom lens according to claim 1, wherein the rear lens group includes a lens unit consisting of a single lens disposed closest to the image side and providing a negative refractive power.

### Claim 11 (depends on 1)

The zoom lens according to claim 1, wherein the rear lens group includes in order from the object side to the image side:
a third lens unit corresponding to the partial lens system LRp1;
the aperture stop;
a fourth lens unit corresponding to the at least one lens unit disposed between the aperture stop and an image plane;
a fifth lens unit providing a positive refractive power; and
a sixth lens unit providing a negative refractive power.

### Claim 12 (depends on 11)

The zoom lens according to claim 11, wherein the aperture stop is configured to move along the same locus as a locus of the third lens unit toward the object side during zooming from the wide angle end to the telephoto end.

### Claim 13

An image pickup apparatus comprising:
a zoom lens; and
a solid-state image pickup element configured to receive light of an image formed by the zoom lens,
wherein the zoom lens comprises in order from an object side to an image side:
a first lens unit providing a positive refractive power;
a second lens unit providing a negative refractive power; and
a rear lens group providing a positive refractive power over an entire zoom range,
wherein an interval between each pair of adjacent lens units is changed changes during zooming,
wherein the rear lens group includes:
a partial lens system LRp1 providing a positive refractive power and disposed closest to the object side in the rear lens group, the partial lens system LRp1 including at least two positive lenses and at least one negative lens;
an aperture stop disposed on the image side of the partial lens system LRp1; and
at least one lens unit providing a negative refractive power and disposed between the aperture stop and an image plane,
wherein the first lens unit and the aperture stop are configured to be positioned closer to the object side at a telephoto end than at a wide angle end, and
wherein the following conditional expressions are satisfied:
0.00<fssFw/LssFw<0.75; and
3.0<f1/fw<20.0,
where fssFw represents a combined focal length of a front lens system consisting of all lenses disposed on the object side of to the aperture stop at the wide angle end, LssFw represents an absolute value of a distance on an optical axis from a first lens surface closest to the object side in the zoom lens to the aperture stop at the wide angle end, f1 represents a focal length of the first lens unit, and fw represents a focal length of the zoom lens at the wide angle end.

### Claim 14

A zoom lens comprising, in order from an object side to an image side:
a first lens unit providing a positive refractive power;
a second lens unit providing a negative refractive power; and
a rear lens group providing a positive refractive power over an entire zoom range,
wherein an interval between each pair of adjacent lens units changes during zooming,
wherein the rear lens group includes, in order from the object side to the image side:
a third lens unit providing a positive refractive power;
an aperture stop;
a fourth lens unit providing a negative refractive power;
a fifth lens unit providing a positive refractive power; and
a sixth lens unit providing a negative refractive power,
wherein the first lens unit and the aperture stop are configured to be positioned closer to the object side at a telephoto end than at a wide angle end, and
wherein the following conditional expressions are satisfied:
0.00<fssFw/LssFw<0.75; and
3.0<f1/fw<20.0,
where fssFw represents a combined focal length of a front lens system consisting of all lenses disposed on the object side of the aperture stop at the wide angle end, LssFw represents an absolute value of a distance on an optical axis from a first lens surface closest to the object side in the zoom lens to the aperture stop at the wide angle end, f1 represents a focal length of the first lens unit, and fw represents a focal length of the zoom lens at the wide angle end.

### Claim 15 (depends on 14)

The zoom lens according to claim 14, wherein the aperture stop is configured to move along the same locus as a locus of the third lens unit toward the object side during zooming from the wide angle end to the telephoto end.

### Claim 16

An image pickup apparatus comprising:
a zoom lens; and
a solid-state image pickup element configured to receive light of an image formed by the zoom lens,
wherein the zoom lens comprises, in order from an object side to an image side:
a first lens unit providing a positive refractive power;
a second lens unit providing a negative refractive power; and
a rear lens group providing a positive refractive power over an entire zoom range,
wherein an interval between each pair of adjacent lens units changes during zooming,
wherein the rear lens group includes, in order from the object side to the image side:
a third lens unit providing a positive refractive power;
an aperture stop;
a fourth lens unit providing a negative refractive power;
a fifth lens unit providing a positive refractive power; and
a sixth lens unit providing a negative refractive power,
wherein the first lens unit and the aperture stop are configured to be positioned closer to the object side at a telephoto end than at a wide angle end, and
wherein the following conditional expressions are satisfied:
0.00<fssFw/LssFw<0.75; and
3.0<f1/fw<20.0,
where fssFw represents a combined focal length of a front lens system consisting of all lenses disposed on the object side of the aperture stop at the wide angle end, LssFw represents an absolute value of a distance on an optical axis from a first lens surface closest to the object side in the zoom lens to the aperture stop at the wide angle end, f1 represents a focal length of the first lens unit, and fw represents a focal length of the zoom lens at the wide angle end.