# US 5,703,725 A · Compact high-performance zoom lens

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- Number: US 5,703,725 A
- Document ID: US5703725A
- Status: Granted
- Kind: A
- Application number: 08/552,195
- Filed: 1995-11-02
- Granted: 1997-12-30
- Earliest claimed: 1994-11-14
- Assignees: Nikon Corporation
- Inventors: Masayuki Aoki
- Web page: https://patentgrep.com/patent/US5703725A

## CPC

- G02B 15/144109: {arranged +--+}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A compact, high-performance zoom lens is disclosed. The zoom lens comprises four lens groups having positive, negative, negative, and positive refractive power, respectively. The lens groups are disposed so as to enable the zoom lens to produce an image of an object on an image plane over a range of magnifications from a wide-angle end to a telephoto end. The second and third lens groups move along the optical axis during zooming. The first lens group preferably includes, objectwise to imagewise, a negative lens element and first, second, and third positive lens elements. The zoom lens satisfies at least the following conditions: 0.6<F.sub.T.sup.1/2 (f.sub.1 /f.sub.T)<1.0 0.7<1.beta..sub.2W .multidot.V.sup.1/21 <1.1 wherein f.sub.1 is the focal length of the first lens group, F.sub.T is the F-number of the zoom lens at the telephoto end, .beta..sub.2W is the lateral magnification of the second lens group at the wide-angle end, f.sub.T is the focal length of the zoom lens at the telephoto end, and V is the zoom ratio of the zoom lens.

## Claims

### Claim 1

A zoom lens comprising, objectwise to imagewise:
first, second, third, and fourth lens groups having positive, negative, negative, and positive refractive power, respectively, disposed on an optical axis;
the first lens group having a focal length f.sub.1 and including, sequentially objectwise to imagewise, a negative lens element and first, second, and third positive lens elements;
each of the first, second, and third positive lens elements in the first lens group having an Abbe number, wherein V.sub.d1 is the minimum Abbe number of all said positive lens elements, V.sub.d12 is the Abbe number of the first positive lens element, and V.sub.d13 is the Abbe number of the second positive lens element, the zoom lens satisfying the conditions:
V.sub.d1 .gtoreq.65.0
V.sub.d12 .gtoreq.94.0
V.sub.d13 >81.0;
the second lens group comprising at least four lens elements;
the zoom lens being operable to zoom over a zoom ratio V from a wide-angle end to a telephoto end, at which wide-angle end the second lens group has a lateral magnification .beta..sub.2W and at which telephoto end the zoom lens has a focal length f.sub.T and an F-number F.sub.T, wherein, during zooming from the wide-angle end to the telephoto end, the second lens group moves linearly objectwise to imagewise on the optical axis, the third lens group moves on the optical axis, and the first and fourth lens groups remain stationary on the optical axis; and
the zoom lens satisfying the conditions:
0.6<F.sub.T.sup.1/2 (f.sub.1 /f.sub.T)<1.0
0.7<.vertline..beta..sub.2W .multidot.V.sup.1/2 <1.1.

### Claim 2 (depends on 1)

The zoom lens of claim 1, wherein, in the first lens group, the negative lens element has an objectwise surface having a radius of curvature R.sub.1 and an imagewise surface having a radius of curvature R.sub.2, the zoom lens satisfying the condition:.
-1.4<(R.sub.2 +R.sub.1)/(R.sub.2 -R.sub.1)<-0.9.
3.

### Claim 3 (depends on 1)

The zoom lens of claim 1, further comprising an aperture stop disposed coaxially objectwise of the fourth lens group.

### Claim 4 (depends on 1)

The zoom lens of claim 1, wherein the fourth lens group comprises an objectwise lens subgroup and an imagewise lens subgroup.

### Claim 5 (depends on 1)

An optical system, comprising:
(a) the zoom lens of claim 1 operable to form an image at an image plane of an object;
(b) a light sensor operable to sense the image; and
(c) a recorder for recording the sensed image.

### Claim 6 (depends on 1)

An optical system, comprising:
(a) the zoom lens of claim 1, operable to form an image at an image plane; and
(b) a color-separating prism disposed between the zoom lens and the image plane.

### Claim 7 (depends on 6)

The optical system of claim 6 further comprising an optical bandpass filter disposed between the color-separating prism and the image plane.

### Claim 8 (depends on 1)

An optical system comprising:
(a) the zoom lens of claim 1 operable to form an image at an image plane; and
(b) a light-sensitive recording medium operable to record the image.

### Claim 9 (depends on 1)

The zoom lens of claim 1, wherein, in the first lens group, the negative lens element has an objectwise surface having a radius of curvature R.sub.1 and an imagewise surface having a radius of curvature R.sub.2, the zoom lens satisfying the condition:
-1.4<(R.sub.2 +R.sub.1)/(R.sub.2 -R.sub.1)<-0.9

### Claim 10 (depends on 4)

The zoom lens of claim 4, wherein each of the objectwise and imagewise lens subgroups has a positive refractive power.

### Claim 11 (depends on 10)

The zoom lens of claim 10 wherein the objectwise lens subgroup comprises, objectwise to imagewise, three positive lens elements and a negative lens element.

### Claim 12

A zoom lens comprising, objectwise to imagewise:
first, second, third, and fourth lens groups having positive, negative, negative, and positive refractive power, respectively, disposed on an optical axis;
the first lens group having a focal length f.sub.1 and including, sequentially objectwise to imagewise, a negative lens eIement and first, second, and third positive lens elements;
the zoom lens being operable to zoom over a zoom ratio V from a wide-angle end to a telephoto end, at which wide-angle end the second lens group has a lateral magnification .beta..sub.2W and at which telephoto end the zoom lens has a focal length f.sub.T and an F-number F.sub.T, wherein, during zooming from the wide-angle end to the telephoto end, the second lens group moves linearly objectwise to imagewise on the optical axis, the third lens group moves on the optical axis, and the first and fourth lens groups remain stationary on the optical axis;
the zoom lens satisfying the conditions:
0.6<F.sub.T.sup.1/2 (f.sub.1 /f.sub.T)<1.0
0.7<.vertline..beta..sub.2W .multidot.V.sup.1/2 <1.1;
and
the third lens group being operable to move, during zooming from the wide-angle end to the telephoto end, first imagewise then objectwise.

### Claim 13

A zoom lens having characteristics as set forth in Tables 1, 2, 3, and Table A.

### Claim 14

A zoom lens having characteristics as set forth in Tables 4, 5, 6, and Table A.

### Claim 15

A zoom lens having characteristics as set forth in Tables 7, 8, 9, and Table A.

### Claim 16

A zoom lens comprising, objectwise to imagewise:
first, second, third, and fourth lens groups having positive, negative, negative, and positive refractive power, respectively, disposed on an optical axis;
the first lens group having a focal length f.sub.1 and including, sequentially objectwise to imagewise, a negative lens element and first, second, and third positive lens elements;
the fourth lens group comprising an objectwise lens subgroup and an imagewise lens subgroup,
each of the objectwise and imagewise lens subgroups having a positive refractive power;
the objectwise lens subgroup comprising, objectwise to imagewise, three positive lens elements and a negative lens element;
the zoom lens being operable to zoom over a zoom ratio V from a wide-angle end to a telephoto end, at which wide-angle end the second lens group has a lateral magnification .beta..sub.2W and at which telephoto end the zoom lens has a focal length f.sub.T and an F-number F.sub.T, wherein, during zooming from the wide-angle end to the telephoto end, the second lens group moves linearly objectwise to imagewise on the optical axis, the third lens group moves on the optical axis, and the first and fourth lens groups remain stationary on the optical axis;
the zoom lens satisfying the conditions:
0. 6<F.sub.T.sup.1/2 (f.sub.1 /f.sub.T)<1.0
0.7<.vertline..beta..sub.2W .multidot.V.sup.1/2 .vertline.<1.1;
and
wherein the imagewise lens subgroup comprises, objectwise to imagewise, a positive lens element, first, second, and third compound lenses, and a negative lens element.

### Claim 17

A zoom lens comprising, objectwise to imagewise:
first, second, third, and fourth lens groups having positive, negative, negative, and positive refractive power, respectively, disposed on an optical axis;
the first lens group having a focal length f.sub.1 and including, sequentially objectwise to imagewise, a negative lens element and first, second, and third positive lens elements;
the zoom lens being operable to zoom over a zoom ratio V from a wide-angle end to a telephoto end, at which wide-angle end the second lens group has a lateral magnification .beta..sub.2W and at which telephoto end the zoom lens has a focal length f.sub.T and an F-number F.sub.T, wherein, during zooming from the wide-angle end to the telephoto end, the second lens group moves linearly objectwise to imagewise on the optical axis, the third lens group moves on the optical axis, and the first and fourth lens groups remain stationary on the optical axis;
the zoom lens satisfying the conditions:
0.6<F.sub.T.sup.1/2)f.sub.1 /f.sub.T)<1/0
0.7<.vertline..beta..sub.2W .multidot.V.sup.1/2 .vertline.<1.1;
wherein the third lens group moves, during zooming from the wide-angle end to the telephoto end, first imagewise then objectwise; and
wherein the third lens group comprises a compound lens including, objectwise to imagewise, a biconcave lens element and a biconvex lens element.

### Claim 18

A zoom lens comprising, objectwise to imagewise:
first, second, third, and fourth lens groups having positive, negative, negative, and positive refractive power, respectively, disposed on an optical axis;
the second lens group comprising at least four lens components;
the first lens group having a focal length f.sub.1 and comprising, sequentially objectwise to imagewise, a negative lens element and first, second, and third positive lens elements, the negative lens element having an objectwise surface having a radius of curvature R.sub.1 and an imagewise surface having a radius of curvature R.sub.2 ;
the zoom lens being operable to zoom over a zoom ratio V from a wide-angle end to a telephoto end, at which wide-angle end the second lens group has a lateral magnification .beta..sub.2W and at which telephoto end the zoom lens has a focal length f.sub.T and an F-number F.sub.T, wherein, during zooming from the wide-angle end to the telephoto end, the second lens group moves linearly objectwise to imagewise on the optical axis, the third lens group moves on the optical axis, and the first and fourth lens groups remain stationary on the optical axis; and
the zoom lens satisfying the conditions:
0.6<F.sub.T.sup.1/2 (f.sub.1 /f.sub.T)<1.0
0.7<.vertline..beta..sub.2W .multidot.V.sup.1/2 .vertline.<1.1
-1.4<(R.sub.2 +R.sub.1)/(R.sub.2 -R.sub.1)<-1.2.