Zoom optical system

• US 7,167,318 B2
• Filed: 02/13/2006
• Issued: 01/23/2007
• Est. Priority Date: 03/11/2005
• Status: Active Grant

• Current Assignee: Fujinon Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujinon Corporation (Fujifilm Holdings Corporation)
• Inventors: Tomioka, Ukyo
• Primary Examiner(s): Lester; Evelyn A.
• Application Number:
  US11/352,236
• Publication Number:
  US 20060203355A1
• Time in Patent Office: 344 Days
• Field of Search: 359/676, 359/680, 359/682, 359683-685, 359/691, 359/717, 359/740, 359/793
• US Class Current: 359/682
• CPC Class Codes: G02B 15/177 having a negative front lens or group of lenses

Abstract

A simple two-group zoom optical system that favorably corrects aberrations includes, in order from the object side, a first lens group of negative refractive power, a stop, and a second lens group of positive refractive power. The first lens group includes, in order from the object side, a lens element having negative refractive power and a meniscus shape with its concave surface on the image side, a biconcave lens element, and a lens element having positive refractive power. The second lens group includes, in order from the object side, a lens element having positive refractive power and at least one aspheric surface, a lens element having negative refractive power, and a biconvex lens element. Certain conditions are satisfied that relate to the focal lengths of the zoom optical system, the focal lengths of the two lens groups, and to the Abbe numbers of lens elements.

Claims

1. A zoom optical system comprising, arranged along an optical axis in order from the object side as follows:

a first lens group having negative refractive power and consisting of three lens elements;

a stop; and

a second lens group having positive refractive power and consisting of three lens elements;

wherein

both the first lens group and the second lens group move along the optical axis during zooming;

the object-side lens element of said second lens group has positive refractive power and has at least one aspheric surface;

said second lens group includes, arranged along the optical axis in order from the object side, as follows

said object-side lens element;

a fifth lens element having negative refractive power and a meniscus shape with its concave surface on the image side; and

a biconvex sixth lens element;

said three lens elements of said first lens group are arranged along the optical axis in order from the object side as follows;

a first lens element having negative refractive power and a meniscus shape with its concave surface on the image side;

a biconcave second lens element; and

a third lens element having positive refractive power.

4. The zoom optical system of claim 1, wherein the following conditions are satisfied:

2.0<

|f₁/f_w|<

3.0

1.0<

|f₂/f₁|<

1.8

ν

_d13<

27

ν

_d22<

27

where

f₁ is the focal length of said first lens group,

f_w is the focal length of the entire zoom optical system at the wide-angle end,

f₂ is the focal length of said second lens group,

ν

_d13 is the Abbe number at the d-line of said third lens element, and

ν

_d22 is the Abbe number at the d-line of said fifth lens element.

2. A zoom optical system comprising, arranged along an optical axis in order from the object side as follows:

a first lens group having negative refractive power and consisting of three lens elements;

a stop; and

a second lens group having positive refractive power and consisting of three lens elements;

wherein,

both the first lens group and the second lens group move along the optical axis during zooming;

the object-side lens element of said second lens group has positive refractive power and has at least one aspheric surface;

said second lens group includes, arranged along the optical axis in order from the object side, as follows

said object-side lens element;

a fifth lens element having negative refractive power and a meniscus shape with its concave surface on the image side;

a biconvex sixth lens element; and

during zooming from the wide-angle end to the telephoto end, said first lens group moves along the optical axis first toward the image side and then toward the object side and said second lens group moves toward the object side.

3. A zoom optical system comprising, arranged along an optical axis in order from the object side as follows:

a first lens group having negative refractive power and consisting of three lens elements;

a stop; and

a second lens group having positive refractive power and consisting of three lens elements;

wherein

both the first lens group and the second lens group move along the optical axis during zooming;

the object-side lens element of said second lens group has positive refractive power and has at least one aspheric surface;

said three lens elements of said first lens group are arranged along the optical axis in order from the object side as follows

a first lens element having negative refractive power and a meniscus shape with its concave surface on the image side;

a biconcave second lens element; and

a third lens element having positive refractive power; and

the following conditions are satisfied

2.0<

|f₁/f_w|<

3.0

1.0<

|f₂/f₁|<

1.8

ν

_d13<

27

where

f₁ is the focal length of said first lens group,

f_w is the focal length of the entire zoom optical system at the wide-angle end,

f₂ is the focal length of said second lens group, and

ν

_d13 is the Abbe number at the d-line of said third lens element.

5. A zoom optical system comprising, arranged along an optical axis in order from the object side as follows:

a first lens group having negative refractive power and consisting of three lens elements;

a stop; and

a second lens group having positive refractive power and consisting of three lens elements;

wherein

both the first lens group and the second lens group move along the optical axis during zooming;

the object-side lens element of said second lens group has positive refractive power and has at least one aspheric surface; and

the following conditions are satisfied

2.0<

|f₁/f_w|<

3.0

1.0<

|f₂/f₁|<

1.8

where

f₁ is the focal length of said first lens group,

f_w is the focal length of the entire zoom optical system at the wide-angle end, and

f₂ is the focal length of said second lens group.

6. A zoom optical system comprising, arranged along an optical axis in order from the object side as follows:

a first lens group having negative refractive power and consisting of three lens elements;

a stop; and

a second lens group having positive refractive power and consisting of three lens elements;

wherein

both the first lens group and the second lens group move along the optical axis during zooming;

the object-side lens element of said second lens group has positive refractive power and has at least one aspheric surface;

said second lens group includes, arranged along the optical axis in order from the object side, as follows

said object-side lens element;

a fifth lens element having negative refractive power and a meniscus shape with its concave surface on the image side; and

a biconvex sixth lens element; and

the following conditions are satisfied;

2.0<

|f₁/f_w|<

3.0

1.0<

|f₂/f₁|<

1.8

where

f₁ is the focal length of said first lens group,

f_w is the focal length of the entire zoom optical system at the wide-angle end, and

f₂ is the focal length of said second lens group.