ZOOM LENS AND IMAGING APPARATUS

• US 20180299656A1
• Filed: 06/20/2018
• Published: 10/18/2018
• Est. Priority Date: 01/27/2016
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: YONEZAWA, Masaru, IKEDA, Shinkichi
• Granted Patent: US 10,642,008 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 13/0015 characterised by the lens design
• CPC Class Codes: G02B 13/0045 having five or more lenses
• CPC Class Codes: G02B 13/009 having zoom function
• CPC Class Codes: G02B 13/02 Telephoto objectives, i.e. systems of the type + - in which the distance from the front vertex to the image plane is less than the equivalent focal length
• CPC Class Codes: G02B 13/18 with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration G02B13/002 takes precedence
• CPC Class Codes: G02B 15/14 by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective
• CPC Class Codes: G02B 15/144109 arranged +--+
• CPC Class Codes: G02B 15/145119 arranged ++--+
• CPC Class Codes: G02B 15/145121 arranged +-+-+
• CPC Class Codes: G02B 15/167 having an additional fixed front lens or group of lenses
• CPC Class Codes: G02B 3/04 with continuous faces that are rotationally symmetrical but deviate from a true sphere , e.g. so called "aspheric" lenses
• CPC Class Codes: G02B 5/005 Diaphragms for cameras G03B9/02
• CPC Class Codes: G02B 9/34 having four components only
• CPC Class Codes: G02B 9/60 having five components only
• CPC Class Codes: G02B 9/62 having six components only
• CPC Class Codes: G02B 9/64 having more than six components

Abstract

The zoom lens consists of, in order from the object side, a first lens group that has a positive refractive power and remains stationary during zooming, a plurality of movable lens groups that move during zooming, and a final lens group that has a positive refractive power and remains stationary during zooming. The first lens group consists of, in order from the object side, a first lens group front group that has a negative refractive power, a first lens group intermediate group that has a positive refractive power and moves during focusing, and a first lens group rear group that has a positive refractive power. The first lens group front group has, successively in order from a position closest to the object side, a negative meniscus lens concave toward an image side, and a negative lens concave toward the object side. The components of the zoom lens satisfy predetermined conditional expressions.

Claims

1. A zoom lens comprising, in order from an object side:

a first lens group that has a positive refractive power and remains stationary with respect to an image plane during zooming;

a plurality of movable lens groups that move by changing distances between groups adjacent to each other in a direction of an optical axis during zooming; and

a final lens group that has a positive refractive power and remains stationary with respect to the image plane during zooming,

wherein in the plurality of movable lens groups, at least one movable lens group has a negative refractive power,

wherein the first lens group includes, in order from the object side, a first lens group front group that has a negative refractive power and remains stationary with respect to the image plane during focusing, a first lens group intermediate group that has a positive refractive power and moves in the direction of the optical axis during focusing, and a first lens group rear group that is set such that a distance in the direction of the optical axis between the first lens group rear group and the first lens group intermediate group changes during focusing and has a positive refractive power,

wherein the first lens group front group has, successively in order from a position closest to the object side, a first negative lens which is a negative meniscus lens concave toward an image side, and a second negative lens which is a negative lens concave toward the object side, and

wherein all Conditional Expressions (1) to (4) are satisfied,

−

0.5<

DD12/f1a<

−

0.2 

 

(1),

50<

ν

n2<

68 

 

(2),

0.634<

θ

gFn2+0.001625×

ν

n2<

0.675 

 

(3), and

1<

DDG1/f1<

1.5 

 

(4),

where DD12 is a distance on the optical axis between the first negative lens and the second negative lens,

f1a is a focal length of the first lens group front group,

ν

n2 is an Abbe number of the second negative lens at the d line,

θ

gFn2 is a partial dispersion ratio of the second negative lens between the g line and the F line,

DDG1 is a distance on the optical axis from a lens surface closest to the object side in the first lens group to a lens surface closest to the image side in the first lens group in a state where an object at infinity is in focus, and

f1 is a focal length of the first lens group in a state where the object at infinity is in focus.

2. The zoom lens according to claim 1, wherein Conditional Expression (5) is satisfied,

0.3<

DDrp/f1<

0.63 

 

(5),

where DDrp is a distance on the optical axis from a lens surface closest to the image side in the first lens group to an image side principal point of the first lens group in a state where an object at infinity is in focus, and

f1 is a focal length of the first lens group in a state where the object at infinity is in focus.

3. The zoom lens according to claim 1, wherein the following Conditional Expression (6) is satisfied,

DDG1/ft<

1 

 

(6),

where DDG1 is a distance on the optical axis from a lens surface closest to the object side in the first lens group to a lens surface closest to the image side in the first lens group in a state where an object at infinity is in focus, and

ft is a focal length of the whole system at a telephoto end in a state where the object at infinity is in focus.

4. The zoom lens according to claim 1, wherein the following Conditional Expression (7) is satisfied,

1<

(R1+R2)/(R1−

R2)<

3 

 

(7),

where R1 is a radius of curvature of an object side surface of the first negative lens, and

R2 is a radius of curvature of an image side surface of the first negative lens.

5. The zoom lens according to claim 1, wherein a lens closest to the image side in the first lens group front group is a positive meniscus lens concave toward the image side.

6. The zoom lens according to claim 1, wherein the first lens group front group has one or more positive lenses, and Conditional Expression (8) is satisfied,

15<

ν

p<

30 

 

(8),

where ν

p is an Abbe number of the positive lens closest to the image side in the first lens group front group at the d line.

7. The zoom lens according to claim 1, wherein the first lens group front group includes three lenses composed of the first negative lens, the second negative lens, and a positive meniscus lens, and all the three lenses are single lenses.

8. The zoom lens according to claim 1, wherein in the plurality of movable lens groups, a movable lens group closest to the image side has a negative refractive power.

9. The zoom lens according to claim 1, wherein Conditional Expression (1-1) is satisfied.

−

0.4<

DD12/f1a<

−

0.25 

 

(1-1)

10. The zoom lens according to claim 1, wherein Conditional Expression (2-1) is satisfied.

56<

ν

n2<

65 

 

(2-1)

11. The zoom lens according to claim 1, wherein Conditional Expression (3-1) is satisfied.

0.635<

θ

gFn2+0.001625×

ν

n2<

0.665 

 

(3-1)

12. The zoom lens according to claim 1, wherein Conditional Expression (4-1) is satisfied.

1.2<

DDG1/f1<

1.5 

 

(4-1)

13. The zoom lens according to claim 1, wherein Conditional Expression (5-1) is satisfied,

0.4<

DDrp/f1<

0.58 

 

(5-1)

where DDrp is a distance on the optical axis from a lens surface closest to the image side in the first lens group to an image side principal point of the first lens group in a state where an object at infinity is in focus, and

f1 is a focal length of the first lens group in a state where the object at infinity is in focus.

14. The zoom lens according to claim 1, wherein Conditional Expression (6-1) is satisfied,

0.5<

DDG1/ft<

0.9 

 

(6-1)

where DDG1 is a distance on the optical axis from a lens surface closest to the object side in the first lens group to a lens surface closest to the image side in the first lens group in a state where an object at infinity is in focus, and

ft is a focal length of the whole system at a telephoto end in a state where the object at infinity is in focus.

15. The zoom lens according to claim 1, wherein Conditional Expression (7-1) is satisfied,

1.1<

(R1+R2)/(R1−

R2)<

2.5 

 

(7-1)

where R1 is a radius of curvature of an object side surface of the first negative lens, and

R2 is a radius of curvature of an image side surface of the first negative lens.

16. The zoom lens according to claim 1, wherein the plurality of movable lens groups includes a lens group having a negative refractive power and a lens group having a negative refractive power.

17. The zoom lens according to claim 1, wherein the plurality of movable lens groups includes, in order from the object side, a lens group having a positive refractive power, a lens group having a negative refractive power, and a lens group having a negative refractive power.

18. The zoom lens according to claim 1, wherein the plurality of movable lens groups includes, in order from the object side, a lens group having a negative refractive power, a lens group having a positive refractive power, and a lens group having a negative refractive power.

19. The zoom lens according to claim 1, wherein Conditional Expression (4-1′

) is satisfied.

1<

DDG1/f1≤

1.35 

 

(4-1′

)

20. An imaging apparatus comprising the zoom lens according to claim 1.