# US 9,775,494 B2 · Oblique-viewing objective optical system and endoscope for oblique viewing using the same

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- Number: US 9,775,494 B2
- Document ID: US9775494B2
- Status: Granted
- Kind: B2
- Application number: 15/342,352
- Filed: 2016-11-03
- Published: 2017-02-23
- Granted: 2017-10-03
- Earliest claimed: 2015-02-20
- Assignees: Olympus Corporation
- Applicants: Olympus Corporation
- Inventors: Yoshiharu Takasugi
- Web page: https://patentgrep.com/patent/US9775494B2

## CPC

- A61B 1/00179: {for off-axis viewing}
- A61B 1/00096: {Optical elements}
- A61B 1/00177: {for 90 degrees side-viewing}
- A61B 1/00186: {with imaging filters}
- G02B 13/04: Reversed telephoto objectives
- G02B 23/02: involving prisms or mirrors (G02B23/14 takes precedence)
- G02B 23/24: Instruments {or systems} for viewing the inside of hollow bodies, e.g. fibrescopes
- G02B 23/243: {Objectives for endoscopes}
- G02B 23/26: using light guides {(for illumination G02B23/2469)}
- A61B 1/05: characterised by the image sensor, e.g. camera, being in the distal end portion
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

An oblique-viewing objective optical system includes in order from an object side, a front-side lens group which includes a negative lens, an optical path converting element, an aperture stop, and a rear-side lens group having a positive refractive power, wherein the rear-side lens group includes a positive lens and a cemented lens having a positive refractive power, and the cemented lens includes in order from the object side a positive lens and a negative lens.

## Claims

### Claim 1

An oblique-viewing objective optical system, comprising in order from an object side:
a front-side lens group which includes a negative lens;
an optical path converting element;
an aperture stop; and
a rear-side lens group having a positive refractive power,
wherein:
the rear-side lens group includes a positive lens and a cemented lens having a positive refractive power,
the cemented lens includes in order from the object side, a positive lens and a negative lens, and
the following conditional expressions (1), (2), (3), (4), and (5) are satisfied:
−2.0<fF/f<−1.3 (1),
1.7<fR/f<2.7 (2),
0.63<|fF/fR|<0.88 (3),
2.4<D1/f<4.4 (4), and
1.1<D2/f<1.7 (5),
where:
fF denotes a focal length of the front-side lens group,
fR denotes a focal length of the rear-side lens group,
f denotes a focal length of the overall oblique-viewing objective optical system,
D1 denotes an air-conversion length from an image-side surface of the negative lens in the front-side lens group up to the aperture stop, and
D2 denotes an air-conversion length from an image-side surface of the negative lens of the cemented lens in the rear-side lens group up to an image plane.

### Claim 2 (depends on 1)

An endoscope for oblique viewing, comprising:
an oblique-viewing objective optical system according to claim 1.