# US 8,570,662 B2 · Zoom lens and image pickup apparatus including the same

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- Number: US 8,570,662 B2
- Document ID: US8570662B2
- Status: Granted
- Kind: B2
- Application number: 13/298,544
- Filed: 2011-11-17
- Published: 2012-05-31
- Granted: 2013-10-29
- Earliest claimed: 2010-11-25
- Assignees: Canon Kabushiki Kaisha
- Applicants: Kaoru Eguchi; Norihito Hiasa
- Inventors: Kaoru Eguchi; Norihito Hiasa
- Web page: https://patentgrep.com/patent/US8570662B2

## CPC

- G02B 15/17: arranged +--
- G02B 15/144109: {arranged +--+}
- G02B 15/144113: {arranged +-++}
- G02B 15/145129: {arranged +-+++}
- G02B 15/1461: {the first group being positive}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A zoom lens includes, in order from an object side to an image side, a first lens unit having positive refractive power, a second lens unit having negative refractive power, a third lens unit having positive or negative refractive power, and a rear lens group including one or more lens units, an aperture stop is provided on the image side of the second lens unit. A sum of relative anomalous partial dispersion ΔθgF of materials of negative lenses included in the second lens unit, a sum of power of a negative lens formed of a material having relative anomalous partial dispersion that is equal to or more than an average value of relative anomalous partial dispersion of the materials of the negative lenses included in the second lens unit, and a refractive power of the second lens unit are appropriately set.

## Claims

### Claim 1

A zoom lens comprising:
a first lens unit having positive refractive power;
a second lens unit having negative refractive power;
a third lens unit having positive or negative refractive power; and
a rear lens group including one or more lens units,
wherein the first lens unit, the second lens unit, the third lens unit and the rear lens group are arranged in order from an object side to an image side along an optical axis of the zoom lens,
wherein, during zooming from a wide-angle end to a telephoto end, the second lens unit moves along the optical axis so that a distance between the first lens unit and the second lens unit increases,
wherein an aperture stop is provided on the image side of the second lens unit, and
wherein, when a sum of relative anomalous partial dispersion ΔθgF of materials of negative lenses included in the second lens unit is indicated by SUM(ΔθgF2N), a sum of optical power of negative lenses formed of a material having relative anomalous partial dispersion ΔθgF that is equal to or more than an average value of relative anomalous partial dispersion ΔθgF of the materials of the negative lenses included in the second lens unit is indicated by φ2SUM, and an optical power of the second lens unit is indicated by φ2, the following conditions are satisfied:
0.065<SUM(ΔθgF2N)<0.200
0.4<φ2SUM/φ2<2.0.

### Claim 2 (depends on 1)

The zoom lens according to claim 1, wherein the second lens unit includes a negative lens formed of a material satisfying a condition of 70<υ2N<100 when an Abbe number of the material of the negative lens is indicated by υ2N.

### Claim 3 (depends on 1)

The zoom lens according to claim 1, wherein, when a sum of relative anomalous partial dispersion ΔθgF of materials of positive lenses included in the first lens unit is indicated by SUM(ΔθgF1P), the following condition is satisfied:
0.030<SUM(ΔθgF1P)<0.300.

### Claim 4 (depends on 1)

The zoom lens according to claim 1, wherein, when a focal length of the first lens unit is indicated by f1, a focal length of the second lens unit is indicated by f2, a focal length of the third lens unit is indicated by f3, a focal length of the entire zoom lens at the wide-angle end is indicated by fw, and a focal length of the entire zoom lens at the telephoto end is indicated by ft, the following conditions are satisfied:
2.0<f1/√(fw×ft)<10.0
−1.5<f2/√(fw×ft)<−0.5
−10.0<f1/f2<−1.0
0.05<|f2/f3|<0.60.

### Claim 5 (depends on 1)

The zoom lens according to claim 1, wherein the rear lens group includes a fourth lens unit having positive refractive power at the most object side, and
wherein during zooming from the wide-angle end to the telephoto end, the second lens unit monotonously moves towards the image side, the third lens unit moves along a locus that is of convex shape towards the object side so that a distance between the third lens unit and the second lens unit changes, and the fourth lens unit moves so that a distance between the fourth lens unit and the third lens unit changes.

### Claim 6 (depends on 1)

The zoom lens according to claim 1, wherein the second lens unit includes, in order from the object side to the image side, a negative lens having a concave surface facing the image side, a negative lens having a concave surface facing the image side, and, on the image side thereof, two or more negative lenses and one or more positive lenses disposed in no particular order.

### Claim 7 (depends on 1)

The zoom lens according to claim 1, wherein, when a relative anomalous partial dispersion of a material of at least one positive lens of positive lenses included in the second lens unit is indicated by ΔθgF2P and a refractive index of the material of at least one positive lens of the positive lenses included in the second lens unit is indicated by N2P, the following conditions are satisfied:
−0.050<ΔθgF2P<0.017
1.40<N2P<1.70.

### Claim 8 (depends on 1)

The zoom lens according to claim 1, wherein the second lens unit includes, in order from the object side to the image side, a negative lens having a concave surface facing the image side, a negative lens having a concave surface facing the image side, a cemented lens obtained by cementing a positive lens and a negative lens, and a cemented lens obtained by cementing a positive lens and a negative lens.

### Claim 9 (depends on 1)

The zoom lens according to claim 1, wherein the second lens unit includes, in order from the object side to the image side, a negative lens having a concave surface facing the image side, a negative lens having a concave surface facing the image side, a negative lens, a negative lens, and a positive lens.

### Claim 10

An image pickup apparatus comprising:
a zoom lens; and
a solid-state image sensor configured to receive an image formed by the zoom lens,
wherein the zoom lens includes, in order from an object side to an image side:
a first lens unit having positive refractive power;
a second lens unit having negative refractive power;
a third lens unit having positive or negative refractive power; and
a rear lens group including one or more lens units,
wherein during zooming from a wide-angle end to a telephoto end, the second lens unit moves along an optical axis so that a distance between the first lens unit and the second lens unit increases,
wherein an aperture stop is provided on the image side of the second lens unit, and
wherein, when a sum of relative anomalous partial dispersion ΔθgF of materials of negative lenses included in the second lens unit is indicated by SUM(ΔθgF2N), a sum of power of negative lenses formed of a material having relative anomalous partial dispersion ΔθgF that is equal to or more than an average value of relative anomalous partial dispersion ΔθgF of the materials of the negative lenses included in the second lens unit is indicated by φ2SUM, and an optical power of the second lens unit is indicated by φ2, the following conditions are satisfied:
0.065<SUM(ΔθgF2N)<0.200
0.4<φ2SUM/φ2<2.0.