# US 7,746,566 B2 · Observation optical system

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- Number: US 7,746,566 B2
- Document ID: US7746566B2
- Status: Granted
- Kind: B2
- Application number: 12/099,539
- Filed: 2008-04-08
- Published: 2008-10-09
- Granted: 2010-06-29
- Earliest claimed: 2007-04-09
- Assignees: Olympus Corporation
- Inventors: Masayuki Mizusawa
- Web page: https://patentgrep.com/patent/US7746566B2

## CPC

- G02B 13/22: Telecentric objectives or lens systems
- G02B 13/06: Panoramic objectives; So-called "sky lenses" {including panoramic objectives having reflecting surfaces}
- G02B 17/0896: {with variable magnification or multiple imaging planes, including multispectral systems (systems with only refractive elements G02B15/14)}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

An observation optical system has a negative lens unit including a cemented lens, arranged at the most object-side position; an annular reflecting mirror placed on the image side of the negative lens unit, with a reflecting surface facing the image side; and an imaging lens unit arranged on the image side of the negative lens unit and the annular reflecting mirror.

## Claims

### Claim 1

An observation optical system comprising:
a negative lens unit including a cemented lens, arranged at a most object-side position;
an annular reflecting mirror placed on an image side of the negative lens unit, with a reflecting surface facing the image side; and
an imaging lens unit arranged on the image side of the negative lens unit and the annular reflecting mirror,
wherein the negative lens unit and the imaging lens unit constitute a forward observation optical system and the annular reflecting mirror and the imaging lens unit constitute a backward observation optical system so that an image produced by the backward observation optical system and an image produced by the forward observation optical system are formed at different positions on an imaging plane.

### Claim 2 (depends on 1)

An observation optical system according to claim 1, wherein the negative lens unit and the annular reflecting mirror are cemented.

### Claim 3

An observation optical system comprising:
a negative lens unit including a cemented lens, arranged at a most object-side position;
an annular reflecting mirror placed on an image side of the negative lens unit, with a reflecting surface facing the image side; and
an imaging lens unit arranged on the image side of the negative lens unit and the annular reflecting mirror, wherein an area in which a dead angle is formed with respect to both the negative lens unit and the annular reflecting mirror is provided on a side of the negative lens unit and the annular reflecting mirror, and an illumination means is placed in the area in which the dead angle is formed.

### Claim 4 (depends on 1)

An observation optical system according to claim 1, wherein the forward observation optical system and the backward observation optical system have an aperture stop common to each other.

### Claim 5

An observation optical system comprising:
a negative lens unit including a cemented lens, arranged at a most object-side position;
an annular reflecting mirror placed on an image side of the negative lens unit, with a reflecting surface facing the image side; and
an imaging lens unit arranged on the image side of the negative lens unit and the annular reflecting mirror, wherein the negative lens unit and the imaging lens unit constitute a forward observation optical system and the annular reflecting mirror and the imaging lens unit constitute a backward observation optical system; the negative lens unit and the annular reflecting mirror are cemented; an image produced by the backward observation optical system and an image produced by the forward observation optical system are formed at different positions on an imaging plane; and the forward observation optical system and the backward observation optical system have an aperture stop common to each other.

### Claim 6

An observation optical system comprising:
a negative lens unit including a cemented lens, arranged at a most object-side position;
an annular reflecting mirror placed on an image side of the negative lens unit, with a reflecting surface facing the image side; and
an imaging lens unit arranged on the image side of the negative lens unit and the annular reflecting mirror, wherein the negative lens unit and the imaging lens unit constitute a forward observation optical system and the annular reflecting mirror and the imaging lens unit constitute a backward observation optical system; an area in which a dead angle is formed with respect to both the negative lens unit and the annular reflecting mirror is provided on a side of the negative lens unit and the annular reflecting mirror and an illumination means is placed in the area in which the dead angle is formed; an image produced by the backward observation optical system and an image produced by the forward observation optical system are formed at different positions on an imaging plane; and the forward observation optical system and the backward observation optical system have an aperture stop common to each other.

### Claim 7 (depends on 1)

An observation optical system according to claim 1, used in an endoscope.

### Claim 8 (depends on 2)

An observation optical system according to claim 2, used in an endoscope.

### Claim 9 (depends on 3)

An observation optical system according to claim 3, used in an endoscope.

### Claim 10 (depends on 4)

An observation optical system according to claim 4, used in an endoscope.

### Claim 11 (depends on 5)

An observation optical system according to claim 5, used in an endoscope.

### Claim 12 (depends on 6)

An observation optical system according to claim 6, used in an endoscope.