Taking optical system

• US 20090102961A1
• Filed: 10/20/2008
• Published: 04/23/2009
• Est. Priority Date: 10/23/2007
• Status: Active Grant

• Current Assignee: Olympus Corporation
• Original Assignee: Olympus Medical Systems Corporation (Olympus Corporation)
• Inventors: Uzawa, Tsutomu
• Granted Patent: US 7,808,725 B2
• Time in Patent Office: Days
• US Class Current: 348/345
• CPC Class Codes: G02B 23/243 Objectives for endoscopes
• CPC Class Codes: G02B 9/10 one + and one - component
• CPC Class Codes: H04N 23/555 for picking-up images in sites, inaccessible due to their dimensions or hazardous conditions, e.g. endoscopes or borescopes

Abstract

The invention relates to an eyepiece-connected taking optical system well fit for TV camera heads using a small-format imaging device. The taking optical system comprises a field direction turning member 1P, 2P, a positive first group and a negative second group. The first group comprises a positive cemented lens convex on its object side, a positive single lens convex on its object side and a positive cemented lens convex on its object side, and the second group comprises a negative single lens. Focus adjustment is implemented by changing a spacing t2 between the first group and the second group. The taking optical system satisfies condition (1) for defining the position of the front focus with respect to the taking lens, condition (2) for defining the refracting power of each lens group, condition (3) for defining the imaging magnification of the second group, and condition (4) for defining the profile of refracting power in the first group.

Claims

1. A taking optical system comprising, in order from its object side, a positive first group and a negative second group, characterized in that focus adjustment is implemented by changing a spacing between the first group and the second group, with satisfaction of the following condition (1):

1.4<

L/f<

2  

 

(1)

where L is an absolute value of a distance of the first group from the lens surface nearest to the object side to a front focus, and

f is a focal length of the whole taking optical system.

2. The taking optical system according to claim 1, characterized by satisfaction of the following conditions (2), (3) and (4):

−

1.3 <

f₁/f₂<

−

0.7  

 

(2)

1.05<

β

₂<

1.4  

 

(3)

0.2<

f_1F/f_1R<

1.6  

 

(4)

where f₁ is a focal length of the first group,

f₂ is a focal length of the second group,

β

₂ is an imaging magnification of the second group,

f_1F is a focal length of the lens located in the first group and nearest to the object side, and

f_1R is a focal length of the lens located in the first group and nearest to an image side.

5. The taking optical system according to claim 1, characterized in that the negative single lens in said second group is joined to an imaging device, and during assembling, said first group and said second group are adjusted for decentration.

6. The taking optical system according to claim 2, characterized in that the negative single lens in said second group is joined to an imaging device, and during assembling, said first group and said second group are adjusted for decentration.

3. A taking optical system, which comprises, in order from its object side, a field direction turning member, a positive first group and a negative second group, characterized in that said first group comprises a positive cemented lens convex on its object side, a positive single lens convex on its object side and a positive cemented lens convex on its object side, said second group comprises a negative single lens, and focus adjustment is implemented by changing a spacing between said first group and said second group, with satisfaction of the following conditions (1), (2), (3) and (4):

1.4<

L/f<

2  

 

(1)

−

1.3<

f₁/f₂<

−

0.7  

 

(2)

1.05<

β

₂<

1.4  

 

(3)

0.2<

f_1F/f_1R<

1.6  

 

(4)

where L is an absolute value of a distance of the first group from the lens surface nearest to the object side to a front focus,

f is a focal length of the whole taking optical system,

f₁ is a focal length of the first group,

f₂ is a focal length of the second group,

β

₂ is an imaging magnification of the second group,

f_1F is a focal length of the lens located in the first group and nearest to the object side, and

f_1R is a focal length of the lens located in the first group and nearest to the image side.

7. The taking optical system according to claim 3, characterized in that the negative single lens in said second group is joined to an imaging device, and during assembling, said first group and said second group are adjusted for decentration.

4. A taking optical system, which comprises, in order from its object side, a field direction turning member, a positive first group and a negative second group, characterized in that said first group comprises a first positive cemented lens convex on its object side and a second positive cemented lens convex on its object side, said second group comprises a negative single lens, and focus adjustment is implemented by changing a spacing between said first group and said second group, with satisfaction of the following conditions (1), (2), (3) and (4):

1.4<

L/f<

2  

 

(1)

−

1.3<

f₁/f₂<

−

0.7  

 

(2)

1.05<

β

₂<

1.4  

 

(3)

0.2<

f_1F/f_1R<

1.6  

 

(4)

where L is an absolute value of a distance of the first group from the lens surface nearest to the object side to a front focus,

f is a focal length of the whole taking optical system,

f₁ is a focal length of the first group,

f₂ is a focal length of the second group,

β

₂ is an imaging magnification of the second group,

f_1F is a focal length of the lens located in the first group and nearest to the object side, and

f_1R is a focal length of the lens located in the first group and nearest to the image side.

8. The taking optical system according to claim 4, characterized in that the negative single lens in said second group is joined to an imaging device, and during assembling, said first group and said second group are adjusted for decentration.