# US 9,753,246 B2 · Eyepiece optical system, optical apparatus and method for manufacturing the eyepiece optical system

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- Number: US 9,753,246 B2
- Document ID: US9753246B2
- Status: Granted
- Kind: B2
- Application number: 14/675,790
- Filed: 2015-04-01
- Published: 2015-07-30
- Granted: 2017-09-05
- Earliest claimed: 2012-10-04
- Assignees: Nikon Corporation
- Applicants: Nikon Corporation
- Inventors: Taku Matsuo
- Web page: https://patentgrep.com/patent/US9753246B2

## CPC

- G02B 9/16: all the components being simple
- G02B 9/34: having four components only
- G02B 13/0035: {having three lenses}
- G02B 25/001: {Eyepieces}
- G03B 13/06: with lenses with or without reflectors
- H04N 23/62: Control of parameters via user interfaces
- G02B 13/18: with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration {(G02B13/002 takes precedence)}
- H04N 23/63: by using electronic viewfinders
- Y10T 29/49826: Assembling or joining
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G03B: APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR (optical parts of such apparatus G02B; photosensitive materials or processes for photographic purposes G03C; apparatus for processing exposed photographic materials G03D)
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

Provided is an eyepiece optical system including, in order from an observation object (Ob): a first lens (L11) having positive refractive power; a second lens (L12) which has negative refractive power and of which an observation object (Ob) side lens surface is concave; and a third lens (L13) which has positive refractive power and of which an eye point (EP) side lens surface is convex. The third lens (L13) is fixed on the optical axis with respect to the observation object (Ob) when adjusting the diopter, and the following conditional expressions are satisfied: 0.65<R31/fe<1.30 (1) −0.80<(R32+R31)/(R32−R31)<−0.10 (2) where fe denotes a focal length of the eyepiece optical system, R31 denotes a radius of curvature of the observation object (Ob) side lens surface of the third lens (L13), and R32 denotes a radius of curvature of the eye point (EP) side lens surface of the third lens (L13).

## Claims

### Claim 1

An eyepiece optical system comprising, in order from an observation object:
a first lens having positive refractive power;
a second lens which has negative refractive power and of which an observation object side lens surface is concave; and
a third lens which has positive refractive power and of which an eye point side lens surface is convex,
the third lens being fixed on an optical axis with respect to the observation object when adjusting a diopter, and
the following conditional expressions being satisfied:
0.65<R31/fe<1.30 (1)
−0.80<(R32+R31)/(R32−R31)<−0.10 (2)
1.00<fe/f3<1.60 (3A)
where fe denotes a focal length of the eyepiece optical system, R31 denotes a radius of curvature of an observation object side lens surface of the third lens, R32 denotes a radius of curvature of the eye point side lens surface of the third lens, and f3 denotes a focal length of the third lens.

### Claim 2 (depends on 1)

The eyepiece optical system according to claim 1, wherein the observation object is an image display element.

### Claim 3 (depends on 2)

The eyepiece optical system according to claim 2, wherein the image display element is a liquid crystal display element.

### Claim 4 (depends on 1)

The eyepiece optical system according to claim 1, wherein the following conditional expression is satisfied:
0.60<fe/f1<2.00
where fe denotes a focal length of the eyepiece optical system, and f1 denotes a focal length of the first lens.

### Claim 5 (depends on 1)

The eyepiece optical system according to claim 1, wherein the following conditional expression is satisfied:
0.40<f3/f1<2.50
where f1 denotes a focal length of the first lens, and f3 denotes a focal length of the third lens.

### Claim 6 (depends on 1)

The eyepiece optical system according to claim 1, wherein the following conditional expression is satisfied:
−2.00<(R12+R11)/(R12−R11)<−0.75
where R11 denotes a radius of curvature of an observation object side lens surface of the first lens, and R12 denotes a radius of curvature of an eye point side lens surface of the first lens.

### Claim 7 (depends on 1)

The eyepiece optical system according to claim 1, wherein the following conditional expression is satisfied:
1.35<(R22+R21)/(R22−R21)<2.40
where R21 denotes a radius of curvature of the observation object side lens surface of the second lens, and R22 denotes a radius of curvature of an eye point side lens surface of the second lens.

### Claim 8 (depends on 1)

The eyepiece optical system according to claim 1, wherein the following conditional expression is satisfied:
1.60<fe/(−f2)<2.20
where fe denotes a focal length of the eye piece optical system, and f2 denotes a focal length of the second lens.

### Claim 9 (depends on 1)

The eyepiece optical system according to claim 1, wherein the first lens, the second lens and the third lens are all made of plastic.

### Claim 10 (depends on 1)

The eyepiece optical system according to claim 1, wherein
the observation object side lens surface of the second lens is aspherical.

### Claim 11 (depends on 1)

The eyepiece optical system according to claim 1, wherein the eye point side lens surface of the third lens is aspherical.

### Claim 12 (depends on 1)

The eyepiece optical system according to claim 1, wherein the diopter is adjusted by moving the first lens and the second lens along the optical axis.

### Claim 13 (depends on 1)

An optical apparatus comprising:
an objective lens;
a picture element that captures an image formed by the objective lens;
an image display element that displays the image captured by the picture element; and
an eyepiece optical system for observing the image displayed on the image display element,
the eyepiece optical system being the eyepiece optical system according to claim 1.

### Claim 14

An eyepiece optical system comprising, in order from an observation object along an optical axis:
a first lens having positive refractive power;
a second lens which has negative refractive power, and of which an observation object side lens surface is concave; and
a third lens which has positive refractive power and of which an eye point side lens surface is convex,
at least one lens surface, out of lens surfaces constituting the first lens, the second lens and the third lens, being aspherical, and
the following conditional expressions being satisfied:
0.40<f3/f1<2.50 (5)
1.40<(R12+R11)/(R12−R11)<−0.75 (6A)
1.35<(R22+R21)/(R22−R21)<2.40 (7)
where f1 denotes a focal length of the first lens, f3 denotes a focal length of the third lens, R11 denotes a radius of curvature of an observation object side lens surface of the first lens, R12 denotes a radius of curvature of an eye point side lens surface of the first lens, R21 denotes a radius of curvature of the observation object side lens surface of the second lens, and R22 denotes a radius of curvature of an eye point side lens surface of the second lens.

### Claim 15 (depends on 14)

The eyepiece optical system according to claim 14, wherein the following conditional expression is satisfied:
1.60<fe/(−f2)<2.20
where fe denotes a focal length of the eyepiece optical system, and f2 denotes a focal length of the second lens.

### Claim 16 (depends on 14)

The eyepiece optical system according to claim 14, wherein the following conditional expression is satisfied:
0.60<fe/f1<2.00
where fe denotes a focal length of the eyepiece optical system.

### Claim 17 (depends on 14)

An optical apparatus comprising:
an objective lens;
a picture element that captures an image formed by the objective lens;
an image display element that displays the image captured by the picture element; and
an eyepiece optical system for observing the image displayed on the image display element,
the eyepiece optical system being the eyepiece optical system according to claim 14.

### Claim 18

A method for manufacturing an eyepiece optical system including, in order from an observation object side:
a first lens having positive refractive power;
a second lens which has negative refractive power and of which an observation object side lens surface is concave; and
a third lens which has positive refractive power and of which an eye point side lens surface is convex, the third lens being fixed on an optical axis with respect to the observation object when adjusting a diopter,
the method comprising:
disposing each lens in a lens barrel so as to satisfy the following conditional expressions:
0.65<R31/fe<1.30 (1)
−0.80<(R32+R31)/(R32−R31)<−0.10 (2)
1.00<fe/f3<1.60 (3A)
where fe denotes a focal length of the eyepiece optical system, R31 denotes a radius of curvature of an observation object side lens surface of the third lens, R32 denotes a radius of curvature of the eye point side lens surface of the third lens, and
f3 denotes a focal length of the third lens.

### Claim 19

A method for manufacturing an eyepiece optical system including in order from an observation object side along an optical axis:
a first lens having positive refractive power;
a second lens which has negative refractive power and of which an observation object side lens surface is concave; and
a third lens which has positive refractive power and of which an eye point side lens surface is convex,
at least one lens surface, out of lens surfaces constituting the first lens, the second lens and the third lens, being aspherical,
the method comprising:
disposing each lens in a lens barrel so as to satisfy the following conditional expression:
0.40<f3/f1<2.50 (5)
1.40<(R12+R11)/(R12−R11)<−0.75 (6A)
1.35<(R22+R21)/(R22−R21)<2.40 (7)
where f1 denotes a focal length of the first lens, f3 denotes a focal length of the third lens, R11 denotes a radius of curvature of an observation object side lens surface of the first lens, R12 denotes a radius of curvature of an eye point side lens surface of the first lens, R21 denotes a radius of curvature of the observation object side lens surface of the second lens, and R22 denotes a radius of curvature of an eye point side lens surface of the second lens.