Zoom lens and imaging apparatus

Patent metadata

Field	Value
Publication number	US-11125985-B2
Application number	US-202016826822-A
Country	US
Kind code	B2
Filing date	Mar 23, 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 second lens group has a negative lens and a cemented lens successively in order from a most object side to an image side. The cemented lens of the second lens group has a first negative lens and a first positive lens successively in order from an object side to an image side. A predetermined conditional expression for the first positive lens is satisfied.

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 moves to an image side, and 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 second lens group has, successively in order from a most object side to an image side, a negative lens and a cemented lens,
wherein the cemented lens has, successively in order from an object side to an image side, a first negative lens and a first positive lens, and
wherein assuming that a refractive index of the first positive lens with respect to a d line is Np and an Abbe number of the first positive lens based on a d line is vp, the following Conditional Expression (1) is satisfied,
0.05<0.00816× vp− 2.040724+ Np< 0.5  (1).

2. The zoom lens according to claim 1 ,
wherein assuming that an Abbe number of the first negative lens based on a d line is vn, the following Conditional Expression (2) is satisfied,
60< vn< 105  (2).

3. The zoom lens according to claim 2 ,
wherein the following Conditional Expression (2-1) is satisfied,
65< vn< 100  (2-1).

4. The zoom lens according to claim 1 ,
wherein the following Conditional Expression (3) is satisfied,
1.9< Np< 2.2  (3).

5. The zoom lens according to claim 4 ,
wherein the following Conditional Expression (3-1) is satisfied,
1.95< Np< 2.2  (3-1).

6. The zoom lens according to claim 1 ,
wherein the following Conditional Expression (4) is satisfied,
25< vp< 60  (4).

7. The zoom lens according to claim 6 ,
wherein the following Conditional Expression (4-1) is satisfied,
26.5< vp< 60  (4-1).

8. The zoom lens according to claim 1 ,
wherein a stop is disposed in the fourth lens group, and
wherein a distance between the fourth lens group and the fifth lens group at a wide-angle end is longer than a distance between the fourth lens group and the fifth lens group at a telephoto end.

9. The zoom lens according to claim 8 ,
wherein assuming that a lateral magnification of the fourth lens group in a state of being focused on an object at infinity is β4, the following Conditional Expression (5) is satisfied,
−0.3<1/β4<0  (5).

10. The zoom lens according to claim 9 ,
wherein the following Conditional Expression (5-1) is satisfied,
−0.2<1/β4<0  (5-1).

11. The zoom lens according to claim 1 ,
wherein in a state of being focused on an object at infinity, assuming that a focal length of the second lens group is f2 and a focal length of the zoom lens at a wide-angle end is fw, the following Conditional Expression (6) is satisfied,
−3 <f 2/ fw< 0  (6).

12. The zoom lens according to claim 11 ,
wherein the following Conditional Expression (6-1) is satisfied,
−2.5< f 2/ fw<− 0.5  (6-1).

13. The zoom lens according to claim 1 ,
wherein in a state of being focused on an object at infinity, assuming that a focal length of the first lens group is f1 and a focal length of the second lens group is f2, the following Conditional Expression (7) is satisfied,
−5< f 1/ f 2<0  (7).

14. The zoom lens according to claim 13 ,
wherein the following Conditional Expression (7-1) is satisfied,
−4< f 1/ f 2<−0.5  (7-1).

15. The zoom lens according to claim 1 ,
wherein the first lens group consists of, in order from an object side to an image side, a first a lens group that remains stationary with respect to an image plane during focusing and has a negative refractive power, a first b lens group that moves along an optical axis during focusing and has a positive refractive power, and a first c lens group that remains stationary with respect to an image plane during focusing and has a positive refractive power.

16. The zoom lens according to claim 15 ,
wherein assuming that a focal length of the first c lens group is f1c and a focal length of the second lens group is f2, the following Conditional Expression (8) is satisfied,
−5< f 1 c/f 2<0  (8).

17. The zoom lens according to claim 16 ,
wherein the following Conditional Expression (8-1) is satisfied,
−4< f 1 c/f 2<−0.5  (8-1).

18. The zoom lens according to claim 1 ,
wherein the following Conditional Expression (1-1) is satisfied,
0.1<0.00816× vp− 2.040724+ Np< 0.4  (1-1).

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

Assignees

• Fujifilm Corp

Inventors

• Tanaka Takuya
• Tanaka Takuya

Classifications

• G02B15/1451 Primary

  the first group being positive · CPC title

• G02B27/0025

  for optical correction, e.g. distorsion, aberration · CPC title

• G02B15/20

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

• G02B15/167 Primary

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

• G02B27/005

  for correction of secondary colour or higher-order chromatic aberrations · CPC title