Zoom lens and imaging apparatus

Patent metadata

Field	Value
Publication number	US-11125986-B2
Application number	US-202016828622-A
Country	US
Kind code	B2
Filing date	Mar 24, 2020
Priority date	Mar 26, 2019
Publication date	Sep 21, 2021
Grant date	Sep 21, 2021

Abstract

The zoom lens consists of, in order from an object side, a positive first lens group, a negative second lens group, a third lens group, a positive fourth lens group, and a positive fifth lens group. During zooming, the second lens group, the third lens group, and the fourth lens group move. The fourth lens group includes a plurality of positive lenses and a negative lens disposed on a most-image-side. Assuming that an average value of Abbe numbers in positive lenses within the fourth lens group is vdp and an Abbe number of a negative lens disposed on a most-image-side of the fourth lens group is vdn, the zoom lens satisfies a conditional expression: 0<vdp−vdn<15.

First claim

What is claimed is:

1. A zoom lens consisting of, in order from an object side to an image side:
a first lens group that has a positive refractive power;
a second lens group that has a negative refractive power;
a third lens group that has a refractive power;
a fourth lens group that has a positive refractive power; and
a fifth lens group that has a positive refractive power,
wherein during zooming from a wide-angle end to a telephoto end, the first lens group and the fifth lens group remain stationary with respect to an image plane, the second lens group, the third lens group and the fourth lens group move along an optical axis while changing a distance with each of adjacent lens groups,
wherein the fourth lens group includes at least two positive lenses and a negative lens disposed on a most-image-side, and
wherein assuming that an average value of Abbe numbers of the positive lenses included in the fourth lens group based on a d line is vdp and an Abbe number of the negative lens disposed on a most-image-side of the fourth lens group based on a d line is vdn, the following Conditional Expression (1) is satisfied,
0 <vdp−vdn <15  (1).

2. The zoom lens according to claim 1 ,
wherein assuming that a minimum value of Abbe numbers of the positive lenses included in the fourth lens group based on a d line is vdpm, the following Conditional Expression (2) is satisfied,
0 <vdn−vdpm   (2).

3. The zoom lens according to claim 2 ,
wherein the following Conditional Expression (2-1) is satisfied,
2< vdn−vdpm< 10  (2-1).

4. The zoom lens according to claim 1 ,
wherein assuming that a partial dispersion ratio between a g line and an F line of the negative lens disposed on a most-image-side of the fourth lens group is θn and a partial dispersion ratio between a g line and an F line of a positive lens having a smallest Abbe number based on a d line among the positive lenses included in the fourth lens group is θpm, the following Conditional Expression (3) is satisfied,
θ n<θpm   (3).

5. The zoom lens according to claim 1 ,
wherein assuming that a partial dispersion ratio between a g line and an F line of the negative lens disposed on a most-image-side of the fourth lens group is θn, the following Conditional Expression (4) is satisfied,
0.54<θ n< 0.58  (4).

6. The zoom lens according to claim 5 ,
wherein the following Conditional Expression (4-1) is satisfied,
0.56<θ n< 0.57  (4-1).

7. The zoom lens according to claim 1 , wherein the third lens group has a positive refractive power.

8. The zoom lens according to claim 7 ,
wherein assuming that a total number of the positive lenses included in the fourth lens group is k, a number sequentially assigned to the positive lenses included in the fourth lens group in order from an object side is i, and a focal length of an i-th positive lens of the fourth lens group from an object side is fpi, a focal length of the negative lens disposed on a most-image-side of the fourth lens group is fn, and a focal length of the fourth lens group is f4, the following Conditional Expression (5A) is satisfied,

0.6
<

f
⁢

⁢
4
×

{

(

∑

i
=
1

k

⁢

1
fpi

)

-



1
fn



}

<

0.8
.

(

5
⁢
A

)

9. The zoom lens according to claim 8 ,
wherein the following Conditional Expression (5A-1) is satisfied,

0.68
<

f
⁢

⁢
4
×

{

(

∑

i
=
1

k

⁢

1
fpi

)

-



1
fn



}

<

0.78
.

(

5
⁢
A
⁢

-

⁢
1

)

10. The zoom lens according to claim 7 ,
wherein assuming that a focal length of the fourth lens group is f4 and a focal length of the zoom lens at a wide-angle end in a state of being focused on an object at infinity is fw, the following Conditional Expression (6A) is satisfied,
0.1 <fw/f 4<0.6  (6A).

11. The zoom lens according to claim 10 ,
wherein the following Conditional Expression (6A-1) is satisfied,

Assignees

• Fujifilm Corp

Inventors

• Tanaka Takuya
• Tanaka Takuya

Classifications

• G02B15/145129

  arranged +-+++ · CPC title

• G02B15/1451 Primary

  the first group being positive · CPC title

• G02B15/145125 Primary

  arranged +--++ · CPC title

• G02B15/173 Primary

  arranged +-+ · CPC title

• G02B15/16 Primary

  with interdependent non-linearly related movements between one lens or lens group, and another lens or lens group (G02B15/22 takes precedence) · CPC title