Objective optical system

• US 20110211267A1
• Filed: 10/13/2010
• Published: 09/01/2011
• Est. Priority Date: 04/16/2009
• Status: Active Grant

• Current Assignee: Olympus Corporation
• Original Assignee: Olympus Medical Systems Corporation (Olympus Corporation)
• Inventors: Takato, Hideyasu
• Granted Patent: US 8,203,798 B2
• Time in Patent Office: Days
• US Class Current: 359/784
• CPC Class Codes: A61B 1/00188 with focusing or zooming features
• CPC Class Codes: G02B 13/04 Reversed telephoto objectives
• CPC Class Codes: G02B 23/243 Objectives for endoscopes
• CPC Class Codes: G02B 7/105 with movable lens means specially adapted for focusing at close distances

Abstract

The invention provides a high-performance objective lens that is capable of implementing focusing relative to an object point distance change with no or little angle-of-view change, and is well compatible with a high-pixel type imaging device. The objective optical system comprises, in order from an object side thereof, a first group of negative power, a second group of positive power, an aperture stop, and a third group of positive power. Only the second group moves thereby implementing focusing relative to an object point distance change, with satisfaction of the following conditions (1)-1, (1)-2 and (8):

ωf>60  (1)-1

ωn>60  (1)-2

−1.2<f1/ff<−0.6  (8)

where

• • ωf is a maximum half angle of view (°) upon viewing at a far distance object point,
  • ωn is a maximum half angle of view (°) upon close-up viewing,
  • f1 is a focal length of the first lens group, and
  • ff is a focal length of the whole system upon viewing at a far distance. See FIG. 1.

Claims

1. An objective optical system, characterized by comprising, in order from an object side thereof, a first group of negative power, a second group of positive power, an aperture stop, and a third group of positive power, wherein:

only said second group moves thereby implementing focusing relative to an object point distance change, with satisfaction of the following conditions (1)-1, (1)-2 and (8);

ω

f>

60 

 

(1)-1

ω

n>

60 

 

(1)-2

−

1.2<

f1/ff<

−

0.6 

 

(8)

where

ω

f is a maximum half angle of view (°

) upon viewing at a far distance object point,

ω

n is a maximum half angle of view (°

) upon close-up viewing,

f1 is a focal length of said first lens group, and

ff is a focal length of the whole system upon viewing at a far distance.

2. An objective optical system, characterized by comprising, in order from an object side thereof, a first group of negative power, a second group of positive power, an aperture stop, and a third group of positive power, wherein:

only said second group moves thereby implementing focusing relative to an object point distance change, with satisfaction of the following conditions (2) and (8);

0.8<

ω

n/ω

f<

1.2 

 

(2)

−

1.2<

f1<

ff<

−

0.6 

 

(8)

where

ω

f is a maximum half angle of view (°

) upon viewing at a far distance object point,

ω

n is a maximum half angle of view (°

) upon close-up viewing,

f1 is a focal length of said first lens group, and

ff is a focal length of the whole system upon viewing at a far distance.