Zoom lens and imaging apparatus

Patent metadata

Field	Value
Publication number	US-10634874-B2
Application number	US-201815999029-A
Country	US
Kind code	B2
Filing date	Aug 20, 2018
Priority date	Aug 22, 2017
Publication date	Apr 28, 2020
Grant date	Apr 28, 2020

Abstract

The zoom lens consists of, in order from an object side, a first lens group having a positive power, a second lens group having a negative power, a third lens group having a negative power, a stop, a fourth lens group having a positive power, and a fifth lens group having a positive power. During zooming, the first lens group and the fifth lens group remain stationary, and the other lens groups and the stop move. The most image side positive lens is disposed to be closest to the image side in the first lens group. The following conditional expression relating to a partial dispersion ratio θgF1p of the most image side positive lens between the g line and the F line and an Abbe number ν1p is satisfied: 0.6376<θgF1p+0.0017×ν1p<0.7.

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 negative refractive power;
a stop;
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, the stop, and the fourth lens group move in a direction of an optical axis, and all distances between adjacent lens groups in the direction of the optical axis changes,
wherein a most image side positive lens having a positive refractive power is disposed to be closest to the image side in the first lens group, and
wherein assuming that a partial dispersion ratio of the most image side positive lens between a g line and an F line is θgF1p and an Abbe number of the most image side positive lens at a d line is ν1p, Conditional Expression (1) is satisfied,
0.6376< θgF 1 p+ 0.0017×ν1 p< 0.7  (1).

2. The zoom lens according to claim 1 , wherein assuming that an average of Abbe numbers of all positive lenses included in the first lens group at the d line is νave1p, Conditional Expression (2) is satisfied,
76<ν ave 1 p< 93  (2).

3. The zoom lens according to claim 1 , wherein assuming that a refractive index of the most image side positive lens at the d line is N1p, Conditional Expression (3) is satisfied,
1.68< N 1 p< 1.78  (3).

4. The zoom lens according to claim 1 , wherein a most object side negative lens having a negative refractive power is disposed to be closest to the object side in the first lens group.

5. The zoom lens according to claim 4 , wherein assuming that a focal length of the first lens group in a state where an object at infinity is in focus is fG1 and a focal length of the most object side negative lens is f1n, Conditional Expression (4) is satisfied,
−0.72< fG 1 /f 1 n<− 0.52  (4).

6. The zoom lens according to claim 1 , wherein assuming that a focal length of the most image side positive lens is f1p and a focal length of the first lens group in a state where an object at infinity is in focus is fG1, Conditional Expression (5) is satisfied,
2.2< f 1 p/fG 1<3.7  (5).

7. The zoom lens according to claim 1 , wherein assuming that a focal length of the zoom lens at the telephoto end in a state where an object at infinity is in focus is ft and a focal length of the first lens group in a state where an object at infinity is in focus is fG1, Conditional Expression (6) is satisfied,
2.2< ft/fG 1<3  (6).

8. The zoom lens according to claim 1 , wherein focusing is performed by moving a part of lenses in the first lens group.

9. The zoom lens according to claim 1 , wherein the first lens group consists of, in order from the object side to the image side, a first-a sub-lens group that remains stationary with respect to the image plane during focusing, a first-b sub-lens group that has a positive refractive power and moves toward the object side during focusing from an object at infinity to a close-range object, and a first-c sub-lens group that has a positive refractive power and moves toward the object side along a locus different from the first-b sub-lens group during focusing from the object at infinity to the close-range object.

10. The zoom lens according to claim 9 , wherein an average of refractive indexes of all positive lenses included in the first-c sub-lens group at the d line is greater than an average of refractive indexes of all positive lenses included in the first-b sub-lens group at the d line.

11. The zoom lens according to claim 1 , wherein the first lens group has three or more positive lenses.

12. The zoom lens according to claim 1 , wherein the third lens group consists of, in order from the object side to the image side, a negative lens and a positive lens.

13. The zoom lens according to claim 12 , wherein assuming that an Abbe number of the negative lens of the third lens group at the d line is ν3n and an Abbe number of the positive lens of the third lens group at the d line is ν3p, Conditional Expression (7) is satisfied,
14<ν3 n−ν 3 p< 30  (7).

14. The zoom lens according to claim 1 , wherein the stop and the fourth lens group integrally move during zooming from the wide-angle end to the telephoto end.

15. The zoom lens according to claim 1 , wherein Conditional Expression (1-1) is satisfied,
0.6377< θgF 1 p+ 0.0017×ν1 p< 0.644  (1-1).

16. The zoom lens according to claim 2 , wherein Conditional Expression (2-1) is satisfied,
79<ν ave 1 p< 90  (2-1).

17. The zoom lens according to claim 3 , wherein Conditional Expression (3-1) is satisfied,
1.69< N 1 p< 1.77  (3-1).

18. The zoom lens according to claim 5 , wherein Conditional Expression (4-1) is satisfied,
−0.69< fG 1 /f 1 n<− 0.55  (4-1).

19. The zoom lens according to claim 6 , wherein Conditional Expression (5-1) is satisfied,
2.5< f 1 p/fG 1<3.4  (5-1).

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

Assignees

• Fujifilm Corp

Inventors

• Shimada Yasutaka

Classifications

• G02B15/14

  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 title

• G02B15/20

  having an additional movable lens or lens group for varying the objective focal length · CPC title

• G02B15/17

  arranged +-- · CPC title

• G02B13/18

  with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration {(G02B13/002 takes precedence)} · CPC title

• G02B5/005

  Diaphragms (for cameras G03B9/02) · CPC title