Objective optical system

• US 20120057251A1
• Filed: 08/23/2011
• Published: 03/08/2012
• Est. Priority Date: 12/11/2009
• Status: Active Grant

• Current Assignee: Olympus Corporation
• Original Assignee: Olympus Medical Systems Corporation (Olympus Corporation)
• Inventors: Takato, Hideyasu
• Granted Patent: US 8,456,767 B2
• Time in Patent Office: Days
• US Class Current: 359/749
• CPC Class Codes: G02B 13/001 Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras G02B23/243 takes precedence
• CPC Class Codes: G02B 23/243 Objectives for endoscopes

Abstract

Provided is a high-performance objective optical system which is compatible with a high-pixel-count image acquisition device, in which focusing can be achieved according to a change in object point distance and which has sufficient depth of field at the individual object point distances. Provided is an objective optical system (1) including, in order from an object side, a first group (G1), a second group (G2), and a third group (G3), in which the first group (G1) includes, in order from the object side, a plano-concave lens (L1) and a meniscus lens (L2) whose convex surface is towards an image side and in which the second group (G2) includes a positive meniscus lens whose convex surface is towards the object side and moves in the direction of an optical axis to perform focusing.

Claims

1. An objective optical system comprising, in order from an object side, a first group, a second group, and a third group, wherein

the first group includes, in order from the object side, a plano-concave lens and a meniscus lens whose convex surface is towards an image side;

and

the second group includes a positive meniscus lens whose convex surface is towards the object side and moves in a direction of an optical axis to perform focusing.

2. A objective optical system according to claim 1, wherein

the first group has negative power;

and

the third group has positive power.

3. The objective optical system according to claim 1, wherein

the third group includes a first positive lens and a joined lens composed of a second positive lens and a negative lens.

4. A objective optical system according to claim 1, wherein the following Conditional Expressions (1) and (2) are satisfied:

|f/f2|<

0.12 

 

(1)

0.92<

f/IH<

1.08 

 

(2)

where

f;

a focal length of an entire system during far-point observation,

f2;

a focal length of a meniscus lens,

IH;

image height.

5. An objective optical system comprising, in order from an object side, a plano-concave lens, a meniscus lens whose convex surface is towards an image side, a positive meniscus lens whose convex surface is towards the object side, an aperture stop, a first positive lens having convex surfaces at both sides, and a joined lens composed of a second positive lens and a negative lens, and satisfying the following Conditional Expression (3):

0.08<

d/f<

0.32 

 

(3)

where

d;

the air gap between the meniscus lens and the first positive lens.