Zoom lens and imaging apparatus

Patent metadata

Field	Value
Publication number	US-10444479-B2
Application number	US-201715854280-A
Country	US
Kind code	B2
Filing date	Dec 26, 2017
Priority date	Jan 5, 2017
Publication date	Oct 15, 2019
Grant date	Oct 15, 2019

Abstract

The zoom lens consists of, in order from an object side: a first lens group that has a positive refractive power; a second lens group that has a positive refractive power; a third lens group that has a negative refractive power; a fourth lens group; and a fifth lens group that has a positive refractive power. The first lens group and the fifth lens group remain stationary with respect to an image plane during zooming. The second lens group, the third lens group, and the fourth lens group are moved by changing distances between the lens groups and adjacent groups in a direction of an optical axis during zooming, and are positioned to be closer to the image side at a telephoto end than at a wide-angle end. Conditional Expression (1) is satisfied.

0.8< pr 1/ f 1<2.6  (1).

First claim

What is claimed is:

1. A zoom lens consisting of, in order from an object side:
a first lens group that has a positive refractive power;
a second lens group that has a positive refractive power;
a third lens group that has a negative refractive power;
a fourth lens group; and
a fifth lens group that has a positive refractive power,
wherein the first lens group and the fifth lens group remain stationary with respect to an image plane during zooming,
wherein the second lens group, the third lens group, and the fourth lens group are moved by changing distances between the lens groups and adjacent groups in a direction of an optical axis during zooming, and are positioned to be closer to the image side at a telephoto end than at a wide-angle end, and
wherein Conditional Expression (1) is satisfied,
0.8< pr 1/ f 1<2.6  (1),

where pr1 is a distance on the optical axis from a surface toward the image side of a lens, which is closest to the image side in the first lens group, to a position of an image side principal point of the first lens group, and
f1 is a focal length of the first lens group.

2. The zoom lens according to claim 1 ,
wherein Conditional Expression (2) is satisfied,
2< f 1/( fw ·tan θ w )<5.8  (2),

where fw is a focal length of the whole system at the wide-angle end, and
θw is a half angle of view at the wide-angle end.

3. The zoom lens according to claim 2 ,
wherein Conditional Expression (2-1) is satisfied
2.5< f 1/( fw ·tan θ w )<4.6  (2-1).

4. The zoom lens according to claim 1 ,
wherein Conditional Expression (3) is satisfied,
0< f 1/ f 2<0.8  (3),

where f2 is a focal length of the second lens group.

5. The zoom lens according to claim 1 ,
wherein the first lens group consists of, in order from the object side, a first-a lens group that has a negative refractive power and remains stationary with respect to the image plane during focusing, a first-b lens group that has a positive refractive power and is moved by changing a distance in the direction of the optical axis between the first-b lens group and an adjacent lens group during focusing, and a first-c lens group that has a positive refractive power.

6. The zoom lens according to claim 5 ,
wherein Conditional Expression (4) is satisfied,
−3.4< f 1 c/f 1 a<− 0.5  (4),

where f1c is a focal length of the first-c lens group, and
f1a is a focal length of the first-a lens group.

7. The zoom lens according to claim 6 ,
wherein Conditional Expression (4-1) is satisfied
−2.9< f 1 c/f 1 a<− 1.3  (4-1).

8. The zoom lens according to claim 5 ,
wherein Conditional Expression (5) is satisfied,
3.1< f 1 b/f 1<8  (5),

where f1b is a focal length of the first-b lens group.

9. The zoom lens according to claim 8 ,
wherein Conditional Expression (5-1) is satisfied
3.7< f 1 b/f 1<6  (5-1).

10. The zoom lens according to claim 5 ,
wherein Conditional Expression (6) is satisfied,
2.4< f 1 b/f 1 c< 8  (6),

where f1b is a focal length of the first-b lens group, and
f1c is a focal length of the first-c lens group.

11. The zoom lens according to claim 10 ,
wherein Conditional Expression (6-1) is satisfied
3< f 1 b/f 1 c< 6  (6-1).

12. The zoom lens according to claim 5 ,
wherein Conditional Expression (7) is satisfied,
0.5< f 1 c/f 1<1.4  (7),

where f1c is a focal length of the first-c lens group.

13. The zoom lens according to claim 12 ,
wherein Conditional Expression (7-1) is satisfied
0.8< f 1 c/f 1<1.3  (7-1).

14. The zoom lens according to claim 5 ,
wherein the first-a lens group consists of, in order from the object side, a negative meniscus lens that is convex toward the object side, a negative lens that is concave toward the image side, and a positive meniscus lens that is convex toward the object side.

15. The zoom lens according to claim 5 ,
wherein the first-b lens group consists of a positive lens that is convex toward the image side, and
wherein the first-c lens group consists of, in order from the object side, a cemented lens that is formed by cementing a negative lens concave toward the image side and a biconvex lens in order from the object side, and a positive lens that is convex toward the object side.

16. The zoom lens according to claim 1 ,
wherein the fourth lens group has a negative refractive power.

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

18. The zoom lens according to claim 1 ,
wherein Conditional Expression (1-1) is satisfied
0.8< pr 1/ f 1<1.9  (1-1).

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

Assignees

• Fujifilm Corp

Inventors

• Tanaka Takuya
• Yonezawa Masaru

Classifications

• G02B15/24

  having a front fixed lens or lens group and two movable lenses or lens groups in front of a fixed lens or lens group · CPC title

• G02B15/167

  having an additional fixed front lens or group of lenses · CPC title

• G02B15/20 Primary

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

• G02B13/02

  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 title

• G02B13/06

  Panoramic objectives; So-called "sky lenses" {including panoramic objectives having reflecting surfaces} · CPC title