# US 7,612,949 B2 · Zoom lens and imaging apparatus

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- Number: US 7,612,949 B2
- Document ID: US7612949B2
- Status: Granted
- Kind: B2
- Application number: 11/979,673
- Filed: 2007-11-07
- Published: 2008-07-03
- Granted: 2009-11-03
- Earliest claimed: 2006-12-27
- Assignees: Sony Corporation
- Inventors: Motoyuki Ohtake; Atsushi Suzuki
- Web page: https://patentgrep.com/patent/US7612949B2

## CPC

- G02B 15/177: having a negative front lens or group of lenses
- G02B 15/143507: {arranged -++}
- G02B 27/646: {compensating for small deviations, e.g. due to vibration or shake (movement of one or more optical elements for control of motion blur in cameras, projectors or printers G03B2205/0007; image stabilisation in cameras peculiar to the presence or use of an electronic image sensor H04N23/68)}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A zoom lens includes, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power. When a lens positional state changes from a maximum wide angle state to a maximum telephoto state, the second lens group moves on an optical axis toward an object, and the first and the third lens groups also move in an optical axis direction such that a gap between the first lens group and the second lens group decreases, while gap between the second lens group and the third lens group is increased. When a change in subject position occurs, close-range focusing is performed by movement of the third lens group, and image shift is provided by shifting the second lens group in directions approximately perpendicular to the optical axis.

## Claims

### Claim 1

A zoom lens comprising, in order from an object side;
a first lens group having a negative refractive power;
a second lens group having a positive refractive power; and
a third lens group having a positive refractive power;
wherein when a lens position state changes from a maximum wide-angle state to a maximum telephoto state, the second lens group moves in an optical axis toward the object side, and the first and the third lens groups move in an optical axis direction such that a gap between the first lens group and the second lens group decreases, while a gap between the second lens group and the third lens group is increased;
when a change in subject position occurs, close-range focusing is performed by movement of the third lens group;
image shift is provided by shifting the second lens group in directions substantially perpendicular to the optical axis; and
conditional equations (1) and (2) shown below are satisfied
0.8<TLw/TLt<0.95 (1)
0.6<|fl|/ft<0.8 (2)
where TLw is a total lens length in the maximum wide-angle state, TLt is a total lens length in the maximum telephoto state, fl is a focal length of the first lens group, and ft is a focal length of an overall lens system in the maximum telephoto end state.

### Claim 2 (depends on 1)

The zoom lens according to claim 1, wherein:
an aperture stop is placed adjacent to the object side of the second lens group, and
the second lens group includes a positive lens and a cemented negative lens, the cemented negative lens being arranged on the image side of the positive lens and formed of a convexo-convex positive lens and a concavo-concave negative lens, and
a conditional equation (3) shown below is satisfied
0.5<RN2/Ds<0.85 (3)
where RN2 is a radius of curvature of an image-side lens surface of the cemented negative lens, and Ds is a distance from the aperture stop to the image-side lens surface of the cemented negative lens.

### Claim 3 (depends on 2)

The zoom lens according to claim 2, wherein:
at least one of the object-side lens surface and the image-side lens surface of the positive lens of the second lens group is of aspherical shape, and
a conditional equation (4) shown below is satisfied
1<fw/faw<1.5 (4)
where faw is a composite focal length of the first lens group and the positive lens in the maximum wide-angle state, and fw is a focal length of an overall lens system in the maximum telephoto state.

### Claim 4 (depends on 3)

The zoom lens according to claim 3, wherein:
a conditional equation (6) is satisfied
1.8<f3/fw<3 (6)
where f3 is a focal length of the third lens group.

### Claim 5 (depends on 3)

The zoom lens according to claim 3, wherein:
the first lens group includes a negative lens and a meniscus positive lens, the negative lens having an aspheric concave surface facing toward the image side, the meniscus positive lens being arranged on the image side of the negative lens with an air gap in between, having a positive refractive power, and having a convex surface facing toward the object side, and
a conditional equation (7) shown below is satisfied
0.18<D12/fw<0.3 (7)
where D12 is an optical axial length of an air gap formed between the negative lens and the positive lens arranged in the first lens group.

### Claim 6 (depends on 1)

The zoom lens according to claim 1, wherein:
a conditional equation (5) shown below is satisfied
Ymax./Da<0.26 (5)
where Ymax. is a maximum image height, and Da is a distance between an aperture stop and an image plane in the maximum wide-angle state.

### Claim 7 (depends on 1)

The image capture apparatus according to claim 1, wherein:
the first lens group includes a negative lens and a meniscus positive lens, the negative lens having an aspheric concave surface facing toward the image side, the meniscus positive lens being arranged on the image side of the negative lens with an air gap in between, having a positive refractive power, and having a convex surface facing toward the object side.

### Claim 8

An image capture apparatus comprising:
a zoom lens; and
an imaging device for converting an optical image formed by the zoom lens into an electric signal;
wherein the zoom lens includes, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power;
when a lens positional state changes from a maximum wide angle state to a maximum telephoto state, the second lens group moves on an optical axis toward the object side, and at the same time, the first and the third lens groups also move in an optical axis direction such that a gap between ten first lens group and the second lens group decreases, while gap between the second lens group and the third lens group is increases;
when a change in subject position occurs, close-range focusing is performed by movement of the third lens group, and image shift is provided by shifting the second lens group in directions approximately perpendicular to the optical axis; and
conditional equations (1) and (2) shown below are satisfied
0.8<TLw/TLt<0.95 (1)
0.6<|fl|/ft<0.8 (2)
where TLw is a total lens length in a maximum wide angle state, TLt is a total lens length in a maximum telephoto state, fl is a focal length of the first lens group, and ft is a focal length of an overall lens system in the maximum telephoto state.

### Claim 9 (depends on 8)

The image capture apparatus according to claim 8, wherein:
the first lens group includes a negative lens and a meniscus positive lens, the negative lens having an aspheric concave surface facing toward the image side, the meniscus positive lens being arranged on the image side of the negative lens with an air gap in between, having a positive refractive power, and having a convex surface facing toward the object side.