Objective lens for endoscope

• US 6,353,504 B1
• Filed: 09/13/2000
• Issued: 03/05/2002
• Est. Priority Date: 09/20/1999
• Status: Expired due to Term

• Current Assignee: Fujinon Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Optical Co. Ltd (Fujifilm Holdings Corporation)
• Inventors: Yamamoto, Chikara
• Primary Examiner(s): SCHWARTZ, JORDAN MARC
• Application Number:
  US09/661,409
• Time in Patent Office: 538 Days
• Field of Search: 359/686, 359/683-684, 359/676, 359/656-660
• US Class Current: 359/686
• CPC Class Codes: G02B 23/2438 Zoom objectives

Abstract

An objective lens for endoscope comprises, successively from an object side, a first lens group having a negative refracting power, a second lens group having a positive refracting power, a third lens group having a negative refracting power, and a fourth lens group having a positive refracting power; wherein the third lens group and one of the second and fourth lens groups are movable along an optical axis. The objective lens further satisfies the following conditional expressions:

2.0<β_1T/β_1W<10.0

1.2<f_T/f_w

where

β_1T is the magnification of the first lens group at the telephoto end;

β_1W is the magnification of the first lens group at the wide end;

f_T is the focal length of the whole lens at the telephoto end; and

f_W is the focal length of the whole lens at the wide end.

Claims

1. An endoscope objective lens comprising, successively from an object side, a first lens group having a negative refracting power, a second lens group having a positive refracting power, a third lens group having a negative refracting power, and a fourth lens group having a positive refracting power;

wherein two lens groups consisting of said third lens group and one of said second and fourth lens groups are moved along an optical axis so as to change magnification and carry out focusing;

said endoscope objective lens further satisfying the following conditional expressions (1) and (2);

2. An endoscope objective lens according to claim 1, wherein two lens groups consisting of said second and third lens groups are moved along the optical axis so as to change magnification and carry out focusing;

said endoscope objective lens further satisfying the following conditional expression (3);

3. An endoscope objective lens according to claim 2, wherein a stop is disposed between said second and third lens groups;

said endoscope objective lens further satisfying the following conditional expression (5);

4. An endoscope objective lens according to claim 3, further satisfying the following conditional expressions (6) and (7):

5. An endoscope objective lens according to claim 2, further satisfying the following conditional expressions (6) and (7):

6. An endoscope objective lens according to claim 1, wherein two lens groups consisting of said third and fourth lens groups are moved along the optical axis so as to change magnification and carry out focusing;

said endoscope objective lens further satisfying the following conditional expression (4);

7. An endoscope objective lens according to claim 6, wherein a stop is disposed between said second and third lens groups;

said endoscope objective lens further satisfying the following conditional expression (5);

8. An endoscope objective lens according to claim 6, further satisfying the following conditional expressions

9. An endoscope objective lens according to claim 7, further satisfying the following conditional expressions