# US 11,079,588 B2 · Relay optical system, and optical system for rigid endoscope and rigid endoscope using the same

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- Number: US 11,079,588 B2
- Document ID: US11079588B2
- Status: Granted
- Kind: B2
- Application number: 16/221,560
- Filed: 2018-12-16
- Published: 2019-04-25
- Granted: 2021-08-03
- Earliest claimed: 2016-06-17
- Assignees: Olympus Corporation
- Applicants: Olympus Corporation
- Inventors: Takahiro Amanai
- Web page: https://patentgrep.com/patent/US11079588B2

## CPC

- G02B 23/243: {Objectives for endoscopes}
- A61B 1/055: having rod-lens arrangements
- A61B 1/0661: {Endoscope light sources}
- A61B 1/07: using light-conductive means, e.g. optical fibres
- G02B 13/0095: {Relay lenses or rod lenses (in instruments for viewing the inside of hollow bodies G02B23/2446)}
- G02B 23/2446: {of the image relay (G02B23/26 takes precedence)}
- G02B 23/2461: {Illumination}
- G02B 23/26: using light guides {(for illumination G02B23/2469)}
- G02B 27/005: {for correction of secondary colour or higher-order chromatic aberrations}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)

## Abstract

A relay optical system includes a cemented lens in which a first lens, a second lens, and a third lens having are cemented. The first lens is a meniscus lens which is adjacent to the third lens, and a dispersion and a partial dispersion ratio differ for the first lens and the third lens. In a rectangular coordinate system in which a horizontal axis is set to be νdLA and a vertical axis is set to be θgFLA, when a straight line expressed by θgFLA=α×νdLA+βLA (where, α=−0.00163) is set, θgFLA and νdLA of medium of the first lens are included in an area determined by the following conditional expression (1) and conditional expression (2), and the following conditional expression (3) is satisfied: 0.67≤βLA (1) νdLA<50 (2) −1.4<mg<−0.6 (3).

## Claims

### Claim 1

A relay optical system, comprising:
a cemented lens in which a first lens having a positive refractive power, a second lens having a positive refractive power, and a third lens having a negative refractive power are cemented,
wherein:
the cemented lens is disposed in an optical path of the relay optical system, which is formed by an object-side optical path and an image-side optical path, and
the first lens is a meniscus lens which is adjacent to the third lens,
a dispersion and a partial dispersion ratio differ for the first lens and the third lens,
in a rectangular coordinate system in which a horizontal axis is set to be νdLA and a vertical axis is set to be θgFLA,
when a straight line expressed by θgFLA=α×νdLA+βLA is set, where α=−0.00163,
θgFLA and νdLA of a medium of the first lens are included in an area determined by the following conditional expression (1) and conditional expression (2), and
the following conditional expression (3) is satisfied:
0.67≤βLA (1)
νdLA<50 (2)
−1.4<mg<−0.6 (3)
where,
θgFLA denotes a partial dispersion ratio (ngLA−nFLA)/(nFLA−nCLA) of the medium of the first lens,
νdLA denotes Abbe number (ndLA−1)/(nFLA−nCLA) for the medium of the first lens,
ndLA, nCLA, nFLA, and ngLA are refractive indices of the medium of the first lens for a d-line, a C-line, an F-line, and a g-line respectively,
mg denotes a magnification of the relay optical system,
the object-side optical path is an optical path positioned on an object side of a center of the relay optical system, and
the image-side optical path is an optical path positioned on an image side of the center of the relay optical system.

### Claim 2 (depends on 1)

The relay optical system according to claim 1, wherein the first lens is positioned between the second lens and the third lens.

### Claim 3 (depends on 1)

The relay optical system according to claim 1, wherein the third lens is positioned between the second lens and the first lens.

### Claim 4 (depends on 1)

The relay optical system according to claim 1, wherein the first lens is a resin lens.

### Claim 5 (depends on 1)

The relay optical system according to claim 1, wherein the following conditional expression (4) is satisfied:
0<|(R1−R2)/(R1+R2)|<3 (4)
where,
R1 denotes a radius of curvature of an object side of the first lens, and
R2 denotes a radius of curvature of an image side of the first lens.

### Claim 6 (depends on 1)

The relay optical system according to claim 1, wherein the following conditional expressions (5) and (6) are satisfied:
1.4<ndLB<1.6 (5)
50<νdLB<100 (6)
where,
ndLB denotes a refractive index of a medium of the second lens for the d-line,
νdLB denotes Abbe number (ndLB−1)/(nFLB−nCLB) for the medium of the second lens, and
ndLB, nCLB, nFLB, and ngLB are refractive indices of the medium of the second lens for the d-line, the C-line, the F-line, and the g-line.

### Claim 7 (depends on 1)

The relay optical system according to claim 1, wherein the cemented lens is disposed in at least one of the object-side optical path and the image-side optical path.

### Claim 8 (depends on 1)

The relay optical system according to claim 1, wherein the cemented lens is disposed in each of the object-side optical path and the image-side optical path.

### Claim 9 (depends on 1)

The relay optical system according to claim 1, wherein the relay optical system includes at least one aspheric surface.

### Claim 10 (depends on 1)

The relay optical system according to claim 1, comprising:
an object-side lens which is disposed in the object-side optical path; and
an image-side lens which is disposed in the image-side optical path,
wherein:
the object-side lens has a positive refractive power, and is disposed such that a convex surface is directed toward the object side,
the image-side lens has a positive refractive power, and is disposed such that a convex surface is directed toward the image side, and
the cemented lens is disposed between the object-side lens and the image-side lens.

### Claim 11 (depends on 1)

The relay optical system according to claim 1, wherein:
a lens surface positioned nearest to image in the object-side optical path is a surface which is convex toward the image side, and
a lens surface positioned nearest to object in the image-side optical path is a surface which is convex toward the object side.

### Claim 12 (depends on 1)

The relay optical system according to claim 1, wherein the following conditional expression (7) is satisfied:
0.2<(OBH+IH)/Φce<1.8 (7)
where,
Φce denotes a light-ray effective diameter of the cemented lens,
OBH denotes a maximum object height, and
IH denotes a maximum image height.

### Claim 13 (depends on 1)

An image relay unit, comprising:
a plurality of relay optical systems,
wherein at least one relay optical system of the plurality of relay optical systems is the relay optical system according to claim 1.

### Claim 14 (depends on 13)

An optical system for rigid endoscope, comprising:
an objective optical system; and
an image relay unit which is disposed on an image side of the objective optical system,
wherein the image relay unit is the image relay unit according to claim 13.

### Claim 15 (depends on 14)

The optical system for rigid endoscope according to claim 14, comprising:
an eyepiece optical system which is disposed on an image side of the image relay unit.

### Claim 16 (depends on 14)

A rigid endoscope, comprising:
the optical system for rigid endoscope according to claim 14; and
an image pickup element which captures an image formed by the image relay unit.

### Claim 17 (depends on 15)

A rigid endoscope, comprising:
the optical system for rigid endoscope according to claim 15; and
an illuminating unit which illuminates an object to be observed.

### Claim 18 (depends on 16)

The rigid endoscope according to claim 16, comprising:
an illuminating unit for illuminating an object to be observed.