Endoscope objective optical system

Patent metadata

Field	Value
Publication number	US-2016306162-A1
Application number	US-201615195778-A
Country	US
Kind code	A1
Filing date	Jun 28, 2016
Priority date	Aug 28, 2014
Publication date	Oct 20, 2016
Grant date	—

Abstract

An object of the present invention is to reduce the diameter, to make focus adjustment easy, and to achieve bright, wide-angle, high-resolution image quality.
Provided is an endoscope objective optical system including, in this order from the object side, a front group having negative refractive power, an aperture stop, and a positive rear group. The front group includes, in this order from the object side, a first lens, which is a single lens having negative refractive power, and a second lens, which is a single lens having positive refractive power. The rear group includes a third lens, which is a single lens having positive refractive power, a cemented lens formed of a fourth lens having positive refractive power and a fifth lens having negative refractive power, and a sixth lens having positive refractive power. The object-side surface of the first lens is a flat surface, the second lens has as meniscus shape, and the sixth lens is joined to the image-acquisition element, and the endoscope objective optical system satisfies the following conditional expression:
4< Fno×F 6/ F 1_5<500  (1)

where Fno is the effective F number of the endoscope objective optical system, F 6 is the focal length of the sixth lens, and F 1 _ 5 is the composite focal length of the first to fifth lenses.

First claim

1 . An endoscope objective optical system comprising, in this order from an object side:
a front group having negative refractive power as a whole; an aperture stop; and a rear group having positive refractive power as a whole, wherein the front group includes, in this order from the object side, a first lens, which is a single lens having negative refractive power, and a second lens, which is a single lens having positive refractive power, the rear group includes a third lens, which is a single lens having positive refractive power, a cemented lens formed of a fourth lens having positive refractive power and a fifth lens having negative refractive power, and a sixth lens having positive refractive power, an object-side surface of the first lens is a flat surface, the second lens has a meniscus shape, the sixth lens is joined to an image-acquisition element, and the endoscope objective optical system satisfies the following conditional expression:
4< Fno×F 6/ F 1_5<500  (1)

where Fno is the effective F number of the endoscope objective optical system, F 6 is the focal length of the sixth lens, and F 1 _ 5 is the composite focal length of the first to fifth lenses.

2 . The endoscope objective optical system according to claim 1 , satisfying the following conditional expression:
1.1< SH _ R 1 R 6<10  (2)

where SH_R 1 R 6 =|(R 1 R+R 6 L)/(R 1 R−R 6 L)|, R 1 R is the radius of curvature of an image-side surface of the first lens, and R 6 L is the radius of curvature of an object-side surface of the sixth lens.

3 . The endoscope objective optical system according to claim 1 , satisfying the following conditional expression:
−1.5< R 4 R/R 6 L<− 0.01  (3)

where R 4 R is the radius of curvature of an image-side surface of the fourth lens, and R 6 L is the radius of curvature of an object-side surface of the sixth lens.

4 . The endoscope objective optical system according to claim 1 , satisfying the following conditional expression:
2.2 <F 23/FL<4.0  (4)

where F 23 is the composite focal length of the second and third lenses, and FL is the composite focal length of the entire system.

5 . The endoscope objective optical system according to claim 1 , satisfying the following conditional expression:
−0.8< F 1/ F 6<−0.01  (5)

where F 1 is the focal length of the first lens, and F 6 is the focal length of the sixth lens.

6 . The endoscope objective optical system according to claim 1 , satisfying the following conditional expression:
0.0003< P 2 /( L×F 6)<0.015  (6)

where P is a distance between the fifth lens and the sixth lens, and L is the overall length of the endoscope objective optical system.

7 . The endoscope objective optical system according to claim 1 , satisfying the following conditional expression:
−2.0< F 12/ F 36<−0.6  (7)

where F 12 is the composite focal length of the front group (first and second lenses), and F 36 is the composite focal length of the rear group (from the third to sixth lenses).

8 . The endoscope objective optical system according to claim 1 , satisfying the following conditional expression:
0.05<FL/ L <0.12  (8)

9 . The endoscope objective optical system according to claim 1 , satisfying the following conditional expression:
0.06<IH/ L <0.12  (9)

where IH is the maximum image height.

10 . The endoscope objective optical system according to claim 1 , satisfying the following Conditional Expression (10):
ω>62°  (10)

where ω is the half angle of view.

Assignees

• Olympus Corp

Inventors

• Ushio Yasuaki

Classifications

• A61B1/04

  combined with photographic or television appliances · CPC title

• A61B1/00188

  with focusing or zooming features · CPC title

• G02B23/243 Primary

  Objectives for endoscopes · CPC title

• G02B27/0025

  for optical correction, e.g. distorsion, aberration · CPC title

• G02B27/0081

  with means for altering, e.g. enlarging, the entrance or exit pupil · CPC title