ZOOM LENS AND IMAGING APPARATUS

• US 20180188511A1
• Filed: 12/15/2017
• Published: 07/05/2018
• Est. Priority Date: 01/05/2017
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Granted Patent: US 10,146,032 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 15/144109 arranged +--+
• CPC Class Codes: G02B 15/145119 arranged ++--+
• CPC Class Codes: G02B 15/145127 arranged ++-++
• CPC Class Codes: G02B 15/20 having an additional movable lens or lens group for varying the objective focal length
• CPC Class Codes: G02B 27/0025 for optical correction, e.g. distorsion, aberration
• CPC Class Codes: G02B 7/021 for more than one lens
• CPC Class Codes: G02B 7/04 with mechanism for focusing or varying magnification

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 final lens group has two or more positive ED lenses formed of a material satisfying predetermined conditional expressions. The predetermined conditional expressions, which relate to extraordinary low dispersion and temperature coefficients of the refractive indices of the positive lenses in the movable lens group closest to the image side and the final lens group, are satisfied.

Claims

1. A zoom lens consisting of, 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 in a direction of an optical axis between groups adjacent to each other during zooming; and

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

wherein the final lens group has at least two positive ED lenses formed of a lens material satisfying Conditional Expressions (1) and (2),

wherein at least one of the movable lens group closest to an image side and the final lens group has at least one positive lens other than the positive ED lenses, and

wherein all Conditional Expressions (3) to (5) are satisfied,

62<

ν

d 

 

(1)

0.64<

θ

gF+0.001625×

ν

d<

0.70 

 

(2)

4.0×

10<sup>−

6</sup><

(dN/dT)aveB<

8.2×

10<sup>−

6</sup> 

 

(3)

0.7×

10<sup>−

6</sup><

(dN/dT)aveA<

4.0×

10<sup>−

6</sup> 

 

(4)

0.655<

(θ

gF+0.001625×

ν

d)aveA<

0.670 

 

(5)

where ν

d is an Abbe number of the lens material at a d line,

θ

gF is a partial dispersion ratio of the lens material between a g line and an F line,

(dN/dT)aveB is an average value of dN/dT of positive lenses other than the positive ED lenses in the movable lens group closest to the image side and the final lens group,

(dN/dT)aveA is an average value of dN/dT of positive lenses in the movable lens group closest to the image side and the final lens group,

(θ

gF+0.001625×

ν

d)aveA is an average value of θ

gF+0.001625×

ν

d of the positive lenses in the movable lens group closest to the image side and the final lens group, and

dN/dT is defined as a temperature coefficient of a refractive index in air at the d line, and is an average value in a temperature range of 0°

C. to 40°

C.

2. The zoom lens according to claim 1, herein Conditional Expression (6) is satisfied,

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

0.15<

ft×

(tan ω

t)/fGe<

0.5 

 

(7),

where ft is a focal length of the zoom lens at the telephoto end in a state where an object at infinity is in focus,

ω

t is a maximum half angle of view of the zoom lens at the telephoto end in a state where the object at infinity is in focus, and

fGe is a focal length of the final lens group.

4. The zoom lens according to claim 1,

wherein a lens closest to the image side in the final lens group is a positive lens, and

wherein Conditional Expression (8) is satisfied,

0.65<

DD2/DD1<

0.85 

 

(8),

where DD2 is a distance on the optical axis between a lens surface closest to the object side in the final lens group and an image side lens surface of a second lens from the image side, and

DD1 is a distance on the optical axis between the lens surface closest to the object side in the final lens group and a lens surface closest to the image side.

5. The zoom lens according to claim 1,

wherein a lens closest to the object side in the final lens group is a positive lens, and

wherein Conditional Expressions (9) and (10) are satisfied,

1.8<

Ndp 

 

(9), and

0.65<

θ

gFp+0.001625×

ν

dp<

0.67 

 

(10),

where Ndp is a refractive index of the positive lens closest to the object side in the final lens group at the d line,

θ

gFp is a partial dispersion ratio of the positive lens closest to the object side in the final lens group between the g line and the F line, and

ν

dp is an Abbe number of the positive lens closest to the object side in the final lens group at the d line.

6. The zoom lens according to claim 1, wherein the final lens group has, successively in order from a position closest to the object side, a positive lens, and a cemented lens that is formed by cementing two lenses having refractive powers of which the signs are different from each other.

7. The zoom lens according to claim 1, wherein focusing is performed by moving at least one lens in the first lens group in a direction of the optical axis.

8. The zoom lens according to claim 1, wherein the first lens group consists of, 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.

9. The zoom lens according to claim 1, wherein the final lens group consists of ten or less lenses.

10. The zoom lens according to claim 1, wherein the movable lens group closest to the image side has a negative refractive power.

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

−

2.0<

β

Gew<

−

0.8 

 

(11),

where β

Gew is a lateral magnification of the final lens group at a wide-angle end in a state where the object at infinity is in focus.

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

4.1×

10<sup>−

6</sup><

(dN/dT)aveB<

8.1×

10<sup>−

6</sup> 

 

(3-1)

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

0.8×

10<sup>−

6</sup><

(dN/dT)aveA<

3.5×

10<sup>−

6</sup> 

 

(4-1)

14. The zoom lens according to claim 1, wherein the at least two positive ED lenses of the final lens group is formed of a lens material satisfying at least one of Conditional Expression (1-1) or (2-1).

70<

ν

d<

100 

 

(1-1)

0.65<

θ

gF+0.001625×

ν

d<

0.69 

 

(2-1)

15. The zoom lens according to claim 2, wherein Conditional Expression (6-1) is satisfied,

16. The zoom lens according to claim 3, wherein Conditional Expression (7-1) is satisfied.

0.25<

ft×

(tan ω

t)/fGe<

0.45 

 

(7-1)

17. The zoom lens according to claim 4, wherein Conditional Expression (8-1) is satisfied.

0.67<

DD2/DD1<

0.81 

 

(8-1)

18. The zoom lens according to claim 5, wherein at least one of Conditional Expression (9-1) or (10-1) is satisfied.

1.8<

Ndp<

1.95 

 

(9-1)

0.65<

θ

gFp+0.001625×

ν

dp<

0.66 

 

(10-1)

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

−

1.2<

β

Gew<

−

0.82 

 

(11-1)

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