# US 2014/0155694 A1 · Endoscope Objective Optical System

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- Number: US 2014/0155694 A1
- Document ID: US20140155694A1
- Status: Published application
- Kind: A1
- Application number: 14/100,257
- Filed: 2013-12-09
- Published: 2014-06-05
- Earliest claimed: 2012-07-03
- Assignees: Olympus Corporation
- Applicants: Olympus Medical Systems Corp.
- Inventors: Keiji Murata
- Web page: https://patentgrep.com/patent/US20140155694A1

## CPC

- G02B 23/2407: {Optical details}
- A61B 1/00096: {Optical elements}
- A61B 1/00197: {characterised by multiple eyepieces}
- A61B 1/055: having rod-lens arrangements
- G02B 23/243: {Objectives for endoscopes}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)

## Abstract

Provided is an endoscope objective optical system including, in order from an object side, an aperture stop, a front group having positive refractive power, and a rear group having positive refractive power, in which the rear group is formed by joining a single lens having positive refractive power and a single lens having negative refractive power and is joined to an imaging device; a joining surface between the single lenses has positive refractive power; and the endoscope objective optical system satisfies following Conditional Expression (1): 0.15<fF/fR<0.5, (1) where fF indicates a focal length of the front group, and fR indicates a focal length of the rear group.

## Claims

### Claim 1

An endoscope objective optical system comprising: in order from an object side, an aperture stop; a front group having positive refractive power; and a rear group having positive refractive power,
wherein the rear group is formed by joining a single lens having positive refractive power and a single lens having negative refractive power and is joined to an imaging device;
a joining surface between the single lenses has positive refractive power; and
the endoscope objective optical system satisfies following Conditional Expression (1):
0.15<fF/fR<0.5, (1)
where fF indicates a focal length of the front group, and fR indicates a focal length of the rear group.

### Claim 2 (depends on 1)

The endoscope objective optical system according to claim 1, wherein the following Conditional Expression (2) is satisfied:
0.4<Φc·fR<1.8, (2)
where Φc indicates a refractive power of the joining surface.

### Claim 3 (depends on 1)

The endoscope objective optical system according to claim 1, wherein the following Conditional Expression (3) is satisfied:
2.0<L/f<3.4, (3)
where f indicates a focal length of an entire system, and L indicates an entire length from a front end to a rear end of the entire system.

### Claim 4 (depends on 1)

The endoscope objective optical system according to claim 1, wherein the following Conditional Expression (4) is satisfied:
0.707<Ih/f<0.956, (4)
where Ih indicates a maximum image height on the imaging device.

### Claim 5 (depends on 1)

The endoscope objective optical system according to claim 1, wherein the following Conditional Expression (5) is satisfied:
Hm<DR/2, (5)
where Hm indicates a height of an outermost off-axis chief ray at a refractive surface of the rear group that is closest to an object, and DR indicates a maximum outer diameter of the lenses in the rear group.

### Claim 6 (depends on 1)

The endoscope objective optical system according to claim 1, not comprising a light-blocking member for mechanically blocking light, other than the aperture stop.

### Claim 7 (depends on 1)

The endoscope objective optical system according to claim 1, wherein a light-blocking area for blocking light is formed on at least one of lens surfaces of the rear group through evaporation.