Zoom lens and imaging apparatus having four lens groups

Patent metadata

Field	Value
Publication number	US-11360289-B2
Application number	US-202016915763-A
Country	US
Kind code	B2
Filing date	Jun 29, 2020
Priority date	Aug 24, 2017
Publication date	Jun 14, 2022
Grant date	Jun 14, 2022

Abstract

The zoom lens consists of, in order from the object side, a first lens group that has a negative refractive power; a second lens group that has a positive refractive power; a third lens group that has a negative refractive power; and a fourth lens group that has a positive refractive power. During zooming, in each lens group, distances between the adjacent groups in the direction of the optical axis are changed. The first lens group consists of, in order from the object side, a first lens having a negative refractive power, a second lens having a negative refractive power, and a third lens having a positive refractive power. The third lens group consists of a negative lens. During focusing, only the third lens group moves along the optical axis. The zoom lens satisfies predetermined conditional expressions.

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 negative refractive power;
a second lens group that has a positive refractive power;
a third lens group that has a negative refractive power; and
a fourth lens group that has a positive refractive power,
wherein during zooming, distances between adjacent groups of the first lens group, the second lens group, the third lens group, and the fourth lens group in a direction of an optical axis are changed,
wherein the third lens group consists of a negative lens,
wherein during focusing, only the third lens group moves along the optical axis,
wherein assuming that
a back focal length at the wide-angle end is Bf, and
a focal length of the fourth lens group is f4,
Conditional Expression (5-2) is satisfied
0.21≤Bf/f4<0.3  (5-2),

wherein the second lens group has a stop, and has lenses adjacent to the object side and the image side of the stop,
wherein the fourth lens group remains stationary during zooming, and
wherein, assuming that a maximum image height is IH, Conditional Expression (4) is satisfied
0.6<Bf/IH<1.2 ...   (4).

2. The zoom lens according to claim 1 ,
wherein Conditional Expression (5-3) is satisfied
0.23≤Bf/f4<0.3  (5-3).

3. The zoom lens according to claim 1 ,
wherein the second lens group has, successively in order from the object side, a positive lens and the stop.

4. The zoom lens according to claim 1 ,
wherein the second lens group has a cemented lens comprising at least one positive lens and at least one negative lens on the image side of the stop.

5. The zoom lens according to claim 4 ,
wherein the cemented lens consists of one positive lens and one negative lens, and
wherein assuming that a difference between Abbe numbers of the positive lens and the negative lens composing the cemented lens is Δνcd, Conditional Expression (8) is satisfied
15<Δνcd<60  (8).

6. The zoom lens according to claim 5 ,
wherein Conditional Expression (8-1) is satisfied
20<Δνcd<50  (8-1).

7. The zoom lens according to claim 1 ,
wherein the fourth lens group consists of a positive lens.

8. The zoom lens according to claim 1 ,
wherein the second lens group has a vibration reduction lens group that performs vibration reduction by moving in a direction orthogonal to the optical axis, and
wherein assuming that
a focal length of the whole system during focusing on an object at infinity at the telephoto end is ft, and
a focal length of the vibration reduction lens group is fois,
Conditional Expression (6) is satisfied
0.5<ft/fois<2  (6).

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

10. The zoom lens according to claim 1 ,
wherein Conditional Expression (4-2) is satisfied
0.6<Bf/IH≤0.81  (4-2).

11. A zoom lens consisting of, in order from an object side:
a first lens group that has a negative refractive power;
a second lens group that has a positive refractive power;
a third lens group that has a negative refractive power; and
a fourth lens group that has a positive refractive power,
wherein during zooming, distances between adjacent groups of the first lens group, the second lens group, the third lens group, and the fourth lens group in a direction of an optical axis are changed,
wherein the third lens group consists of a negative lens,
wherein during focusing, only the third lens group moves along the optical axis,
wherein the second lens group has a stop, and has lenses adjacent to the object side and the image side of the stop,
wherein the second lens group has a cemented lens comprising at least one positive lens and at least one negative lens on the image side of the stop,
wherein the second lens group has a vibration reduction lens group that performs vibration reduction by moving in a direction orthogonal to the optical axis,
wherein the vibration reduction lens group is arranged on the image side of the stop,
wherein the fourth lens group remains stationary during zooming, and
wherein assuming that
a back focal length at the wide-angle end is Bf, and
a maximum image height is IH,
Conditional Expression (4) is satisfied
0.6<Bf/IH<1.2  (4).

12. The zoom lens according to claim 11 ,
wherein assuming that
a focal length of the whole system during focusing on an object at infinity at the telephoto end is ft, and
a focal length of the vibration reduction lens group is fois,
Conditional Expression (6) is satisfied
0.5<ft/fois<2  (6).

13. The zoom lens according to claim 11 ,
wherein the fourth lens group consists of a positive lens.

14. The zoom lens according to claim 13 ,
wherein the cemented lens consists of one positive lens and one negative lens, and
wherein assuming that a difference between Abbe numbers of the positive lens and the negative lens composing the cemented lens is Δνcd, Conditional Expression (8) is satisfied
15<Δνcd<60  (8).

15. The zoom lens according to claim 14 ,
wherein Conditional Expression (8-1) is satisfied
20<Δνcd<50  (8-1).

16. The zoom lens according to claim 11 ,
wherein the cemented lens consists of one positive lens and one negative lens, and
wherein assuming that a difference between Abbe numbers of the positive lens and the negative lens composing the cemented lens is Δνcd, Conditional Expression (8) is satisfied
15<Δνcd<60  (8).

17. The zoom lens according to claim 16 ,
wherein Conditional Expression (8-1) is satisfied
20<Δνcd<50  (8-1).

18. The zoom lens according to claim 16 ,
wherein Conditional Expression (8-2) is satisfied
31.23≤Δνcd<60  (8-2).

19. An imaging apparatus comprising the zoom lens according to claim 11 .

20. The zoom lens according to claim 11 ,
wherein Conditional Expression (4-3) is satisfied
0.6<Bf/IH≤0.76  (4-3).

Assignees

• Fujifilm Corp

Inventors

• Nagami Ryosuke

Classifications

• H04N23/55

  Optical parts specially adapted for electronic image sensors; Mounting thereof · CPC title

• G02B27/646

  compensating for small deviations, e.g. due to vibration or shake (movement of one or more optical elements for control of motion blur in cameras, projectors or printers G03B2205/0007; image stabilisation in cameras peculiar to the presence or use of an electronic image sensor H04N23/68) · CPC title

• G02B27/0025

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

• G02B15/177

  having a negative front lens or group of lenses · CPC title

• G02B15/144511 Primary

  arranged -+-+ · CPC title