Endoscope objective optical system

Patent metadata

Field	Value
Publication number	US-9372336-B2
Application number	US-201314100257-A
Country	US
Kind code	B2
Filing date	Dec 9, 2013
Priority date	Jul 3, 2012
Publication date	Jun 21, 2016
Grant date	Jun 21, 2016

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.

First claim

The invention claimed is:

1. An endoscope objective optical system consisting of: 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.

2. 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.

3. 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.

4. 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.

5. 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.

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

7. 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.

8. An endoscope objective optical system consisting of: in order from an object side, a flat cover glass; 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.

9. The endoscope objective optical system according to claim 8 , 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.

10. The endoscope objective optical system according to claim 8 , 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.

11. The endoscope objective optical system according to claim 8 , 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.

12. The endoscope objective optical system according to claim 8 , 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.

13. The endoscope objective optical system according to claim 8 , not comprising a light-blocking member for mechanically blocking light, other than the aperture stop.

14. The endoscope objective optical system according to claim 8 , wherein a light-blocking area for blocking light is formed on at least one of lens surfaces of the rear group through evaporation.

Assignees

• Olympus Corp

Inventors

• Murata Keiji

Classifications

• G02B23/2407 Primary

  Optical details · CPC title

• G02B23/243 Primary

  Objectives for endoscopes · CPC title

• A61B1/055

  having rod-lens arrangements · CPC title

• A61B1/00197

  characterised by multiple eyepieces · CPC title

• A61B1/00096

  Optical elements · CPC title