# US 8,786,955 B2 · Endoscope objective optical system

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- Number: US 8,786,955 B2
- Document ID: US8786955B2
- Status: Granted
- Kind: B2
- Application number: 14/050,796
- Filed: 2013-10-10
- Published: 2014-04-10
- Granted: 2014-07-22
- Earliest claimed: 2012-05-17
- Assignees: Olympus Medical Systems Corp.
- Applicants: Olympus Medical Systems Corp.
- Inventors: Kazuo Morita
- Web page: https://patentgrep.com/patent/US8786955B2

## CPC

- A61B 1/00163: {Optical arrangements (A61B1/002, A61B1/06 take precedence)}
- A61B 1/00: Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes (examination of body cavities or body tracts using ultrasonic, sonic or infrasonic waves A61B8/12; endoscopic instruments for taking cell samples or for biopsy A61B10/04); Illuminating arrangements therefor (for the eyes A61B3/00)
- A61B 1/00188: {with focusing or zooming features}
- A61B 1/002: having rod-lens arrangements (A61B1/055 takes precedence)
- A61B 1/051: {Details of CCD assembly}
- G02B 9/12: having three components only
- G02B 23/243: {Objectives for endoscopes}
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

The diameter of an endoscope insertion portion is reduced, and a wide field angle of an endoscope insertion portion is obtained. An endoscope objective optical system includes, from an object side, a first lens formed of a plano-concave lens having a concave surface facing an image side, a second lens formed of a plano-concave lens having a concave surface facing the object side, an aperture stop, and a third lens formed of a plano-convex lens having a plane surface facing the object side, and satisfies 0.7≦|fab/f|0.9 1.7≦|fe/fab|≦2 2≦fb/fa≦4 where f: focal length of the entire system; fa: focal length of the first lens; fb: focal length of the second lens; fe: represents focal length of the third lens; fab: combined focal length from the first lens to the second lens.

## Claims

### Claim 1

An endoscope objective optical system comprising in order from an object side:
a first lens formed of a plano-concave lens having a concave surface facing an image side;
a second lens formed of a plano-concave lens having a concave surface facing the object side;
an aperture stop; and
a third lens formed of a plano-convex lens having a plane surface facing the object side,
the endoscope objective optical system satisfying the following conditional expressions (1) to (3):
0.7≦|fab/f|≦0.9 (1)
1.7≦|fe/fab|≦2 (2)
2≦fb/fa≦4 (3)
where f represents a focal length of the entire system,
fa represents a focal length of the first lens,
fb represents a focal length of the second lens,
fe represents a focal length of the third lens, and
fab represents a combined focal length from the first lens to the second lens.

### Claim 2 (depends on 1)

The endoscope objective optical system according to claim 1, satisfying the following conditional expression (4):
0.9≦Na/Nb≦1 (4)
where Na represents a refractive index at a d-line of a glass material forming the first lens, and
Nb represents a refractive index at a d-line of a glass material forming the second lens.