# US 8,570,663 B2 · Zoom lens and image pickup apparatus equipped with the zoom lens

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- Number: US 8,570,663 B2
- Document ID: US8570663B2
- Status: Granted
- Kind: B2
- Application number: 13/588,907
- Filed: 2012-08-17
- Published: 2013-02-28
- Granted: 2013-10-29
- Earliest claimed: 2011-08-30
- Assignees: Canon Kabushiki Kaisha
- Applicants: Shinichiro Saito
- Inventors: Shinichiro Saito
- Web page: https://patentgrep.com/patent/US8570663B2

## CPC

- G02B 15/144113: {arranged +-++}
- G02B 13/18: with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration {(G02B13/002 takes precedence)}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A zoom lens includes a first lens unit of a positive refractive power, a second lens unit of a negative refractive power, a third lens unit of a positive refractive power, and a fourth lens unit of a positive refractive power, wherein the first lens unit does not move for zooming, at least the second and fourth lens units are moved during zooming, the first lens unit includes at least one positive lens, and an Abbe number and a relative partial dispersion of a material of the positive lens, an average refractive index of materials of negative lenses included in the second lens unit, a movement amount of the second lens unit for zooming from a wide-angle end to a telephoto end, a focal length of the second lens unit, and a focal length of the entire zoom lens at the telephoto end are appropriately set.

## Claims

### Claim 1

A zoom lens comprising, in order from an object side to an image side, a first lens unit of a positive refractive power, a second lens unit of a negative refractive power, a third lens unit of a positive refractive power, and a fourth lens unit of a positive refractive power,
wherein the first lens unit does not move for zooming, at least the second and fourth lens units are moved during zooming, the first lens unit includes at least one positive lens 1i, and the following conditions are satisfied:
0.5826<θgF1i+0.001618×(νd1i×36.23)<0.8000,
0.040<√(|f2|×m2)/ft<0.095, and
1.90<n2na<2.50,
where νd1i and θgF1i denote an Abbe number and a relative partial dispersion, respectively, of a material of the positive lens 1i, n2na denotes an average refractive index of materials of negative lenses included in the second lens unit, m2 denotes a movement amount of the second lens unit for zooming from a wide-angle end to a telephoto end, f2 denotes a focal length of the second lens unit, and ft denotes a focal length of the entire zoom lens at the telephoto end.

### Claim 2 (depends on 1)

The zoom lens according to claim 1, wherein a negative lens is arranged in a position closest to the object side of the second lens unit, and the following condition is satisfied:
0.4<|f2n1|/fw<1.8,
where f2n1 denotes a focal length of the negative lens, and fw denote a focal length of the entire zoom lens at the wide-angle end.

### Claim 3 (depends on 1)

The zoom lens according to claim 1, wherein the following condition is satisfied:
−1.8<SF1p<−0.8,
where SF1p denotes a shape factor of a positive lens closest to the object side of the first lens unit.

### Claim 4 (depends on 1)

The zoom lens according to claim 1, wherein the following condition is satisfied:
0.8<|f1n1|/f1p1<1.4,
where f1n1 denotes a focal length of a negative lens closest to the object side of the first lens unit, and f1p1 denotes a focal length of a positive lens closest to the object side of the first lens unit.

### Claim 5 (depends on 1)

The zoom lens according to claim 1, wherein the following condition is satisfied:
1.2<f1/√(fw×ft)<1.8,
where f1 denotes a focal length of the first lens unit, and fw denotes a focal length of the entire zoom lens at the wide-angle end.

### Claim 6 (depends on 1)

The zoom lens according to claim 1, further comprising an aperture stop on the object side of the third lens unit, wherein the following condition is satisfied:
0.40<DSP/TDw<0.55,
where TDw denotes an entire lens length of the zoom lens at the wide-angle end, and DSP denotes an air-equivalent distance from the aperture stop to an image plane at the wide-angle end.

### Claim 7 (depends on 1)

The zoom lens according to claim 1, wherein the following condition is satisfied:
0.8<|m2|/√(fw×ft)<1.4
where fw denotes a focal length of the entire zoom lens at the wide-angle end.

### Claim 8 (depends on 1)

The zoom lens according to claim 1, further comprising an aperture stop on the object side of the third lens unit, wherein the following condition is satisfied:
0.50<D1SP/TDw<0.62
where TDw denotes an entire lens length of the zoom lens at the wide-angle end, and D1SP denotes a distance from a lens surface on the object side of the first lens unit to the aperture stop.

### Claim 9 (depends on 1)

The zoom lens according to claim 1, wherein the following condition is satisfied:
4.80<f3/fw<6.00,
where f3 denotes a focal length of the third lens unit, and fw denotes a focal length of the entire zoom lens at the wide-angle end.

### Claim 10

An image pickup apparatus comprising:
zoom lens comprising, in order from an object side to an image side, a first lens unit of a positive refractive power, a second lens unit of a negative refractive power, a third lens unit of a positive refractive power, and a fourth lens unit of a positive refractive power,
wherein the first lens unit does not move for zooming, at least the second and fourth lens units are moved during zooming, the first lens unit includes at least one positive lens 1i, and the following conditions are satisfied:
0.5826<θgF1i+0.001618×(νd1i×36.23)<0.8000,
0.040<√(|f2|×m2)/ft<0.095, and
1.90<n2na<2.50,
where vd1i and θgF1i denote an Abbe number and a relative partial dispersion, respectively, of a material of the positive lens 1i, n2na denotes an average refractive index of materials of negative lenses included in the second lens unit, m2 denotes a movement amount of the second lens unit for zooming from a wide-angle end to a telephoto end, f2 denotes a focal length of the second lens unit, and ft denotes a focal length of the entire zoom lens at the telephoto end; and
an image sensor configured to receive an image formed by the zoom lens.