# US 10,120,169 B2 · Variable-power optical system

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- Number: US 10,120,169 B2
- Document ID: US10120169B2
- Status: Granted
- Kind: B2
- Application number: 15/241,370
- Filed: 2016-08-19
- Published: 2016-12-08
- Granted: 2018-11-06
- Earliest claimed: 2014-02-19
- Assignees: Nikon Vision Co., Ltd.
- Applicants: Nikon Vision Co., Ltd
- Inventors: Yosuke Miyazaki
- Web page: https://patentgrep.com/patent/US10120169B2

## CPC

- G02B 15/16: with interdependent non-linearly related movements between one lens or lens group, and another lens or lens group (G02B15/22 takes precedence)
- G02B 15/14: by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective
- G02B 15/143107: {arranged +++}
- G02B 23/16: Housings; Caps; Mountings; Supports, e.g. with counterweight
- G02B 27/0025: {for optical correction, e.g. distorsion, aberration}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A variable-power optical system includes, in order from an object, an objective optical system (O), a relay optical system (R), and an eyepiece optical system (E), wherein the relay optical system is provided with, in order from the object, a first lens group (G1) having positive refractive power, a second lens group (G2) having positive refractive power, and a third lens group (G3) having positive refractive power, and is an optical system in which an image formed by the objective optical system with variable optical power, and the variable-power optical system is configured so as to satisfy expressions: 0.7<|β|min<1.4, and 12 (mm)<fmin<15 (mm), where |β|min denotes a minimum of absolute value of imaging magnification of the relay optical system, and fmin denotes a shortest focal length.

## Claims

### Claim 1

A variable-power optical system comprising, in order from an object, an objective optical system, a relay optical system, and an eyepiece optical system,
wherein the relay optical system is provided with, in order from the object consecutively, a first lens group having positive refractive power, a second lens group having positive refractive power, and a third lens group having positive refractive power, and is an optical system by which an image formed by the objective optical system is reimaged with variable optical power, and
the following conditional expression (1) is satisfied:
0.7<|β|min<1.4 (1)
where |β|min denotes a minimum of absolute value of imaging magnification of the relay optical system.

### Claim 2 (depends on 1)

The variable-power optical system according to claim 1, wherein the following conditional expressions (3) and (4) are satisfied:
0.8<|β|min<1.3 (3)
12.5 (mm)<fmin<14.5 (mm) (4)
where fmin denotes a shortest focal length of the relay optical system.

### Claim 3 (depends on 1)

The variable-power optical system according to claim 1, wherein the following conditional expressions (5) and (6) are satisfied:
0.2<fmin/f1<0.4 (5)
0.7<f2/f3<1.0 (6)
where fmin denotes a shortest focal length of the relay optical system, f1 denotes a focal length of the first lens group, f2 denotes a focal length of the second lens group, and f3 denotes a focal length of the third lens group.

### Claim 4 (depends on 1)

The variable-power optical system according to claim 1, wherein the third lens group comprises, in order from the object, a convex single lens, and a cemented lens which is configured by a convex lens and a concave lens and has negative refractive power.

### Claim 5 (depends on 4)

The variable-power optical system according to claim 4, wherein the following conditional expressions (7) and (8) are satisfied:
1.6<n31<1.8 (7)
50<ν31 (8)
where n31 denotes a refractive index of the convex single lens, and ν31 denotes the Abbe number of the convex single lens.

### Claim 6 (depends on 1)

The variable-power optical system according to claim 1, wherein imaging magnification of the relay optical system is varied by moving the second lens group and the third lens group in the relay optical system.

### Claim 7 (depends on 1)

The variable-power optical system according to claim 1, wherein the relay optical system has a support part for supporting the first lens group in a predetermined position relative to the objective optical system.

### Claim 8 (depends on 1)

The variable-power optical system according to claim 1, further comprising a tilt mechanism for tilting the relay optical system.

### Claim 9 (depends on 1)

The variable-power optical system according to claim 1, wherein the following conditional expression (2) is satisfied:
12 (mm)<fmin<15 (mm) (2 )
where fmin denotes a shortest focal length of the relay optical system.

### Claim 10 (depends on 1)

An optical apparatus comprising the variable-power optical system according to claim 1.

### Claim 11

A variable-power optical system comprising, in order from an object, an objective optical system, a relay optical system, and an eyepiece optical system,
wherein the relay optical system consists of, in order from the object, a first lens group having positive refractive power, a second lens group having positive refractive power, and a third lens group having positive refractive power, and is an optical system by which an image formed by the objective optical system is reimaged with variable optical power, and
the following conditional expression (1) is satisfied:
0.7<|β|min<1.4 (1)
where |β|min denotes a minimum of absolute value of imaging magnification of the relay optical system.

### Claim 12 (depends on 11)

The variable-power optical system according to claim 11, wherein the following conditional expressions (3) and (4) are satisfied:
0.8<|β|min<1.3 (3)
12.5 (mm)<fmin<14.5 (mm) (4)
where fmin denotes a shortest focal length of the relay optical system.

### Claim 13 (depends on 11)

The variable-power optical system according to claim 11, wherein the following conditional expressions (5) and (6) are satisfied:
0.2<fmin/f1<0.4 (5)
0.7<f2/f3<1.0 (6)
where fmin denotes a shortest focal length of the relay optical system, f1 denotes a focal length of the first lens group, f2 denotes a focal length of the second lens group, and f3 denotes a focal length of the third lens group.

### Claim 14 (depends on 11)

The variable-power optical system according to claim 11, wherein the following conditional expression (2) is satisfied:
12 (mm)<fmin<15 (mm) (2)
where fmin denotes a shortest focal length of the relay optical system.