Imaging lens and imaging apparatus

Patent metadata

Field	Value
Publication number	US-11442245-B2
Application number	US-201916689275-A
Country	US
Kind code	B2
Filing date	Nov 20, 2019
Priority date	Nov 27, 2018
Publication date	Sep 13, 2022
Grant date	Sep 13, 2022

Abstract

The imaging lens includes, as lens groups, only a positive first lens group, a positive second lens group, and a negative third lens group in order from the object side. An aperture stop is disposed between a lens surface closest to the image side in the first lens group and a lens surface closest to the object side in the third lens group. During focusing, the first lens group and the third lens group do not move, and the second lens group moves. The first lens group consists of a negative lens and a positive lens in order from the object side. The third lens group has a negative lens and a positive lens in order from the object side.

First claim

What is claimed is:

1. An imaging lens comprising, as lens groups,
only three lens groups that consist of, in order from an object side to an image side, a first lens group having a positive refractive power, a second lens group having a positive refractive power, and a third lens group having a negative refractive power,
wherein an aperture stop is disposed between a lens surface closest to the image side in the first lens group and a lens surface closest to the object side in the third lens group,
wherein during focusing from an object at infinity to a closest object, the first lens group and the third lens group remain stationary with respect to an image plane, and the second lens group moves along an optical axis,
wherein the first lens group consists of a negative lens and a positive lens in order from the object side to the image side,
wherein the third lens group includes a negative lens and a positive lens in order from the object side to the image side, and
wherein assuming that
a focal length of the second lens group is f2, and
a focal length of the first lens group is f1,
Conditional Expression (1) is satisfied, which is represented by
0.25< f 2/ f 1<1  (1).

2. An imaging lens comprising, as lens groups,
only three lens groups that consist of, in order from an object side to an image side, a first lens group having a positive refractive power, a second lens group having a positive refractive power, and a third lens group having a negative refractive power,
wherein an aperture stop is disposed between a lens surface closest to the image side in the first lens group and a lens surface closest to the object side in the third lens group,
wherein during focusing from an object at infinity to a closest object, the first lens group and the third lens group remain stationary with respect to an image plane, and the second lens group moves along an optical axis,
wherein the first lens group consists of a negative lens and a positive lens in order from the object side to the image side,
wherein the second lens group includes at least two cemented lenses in which at least one positive lens and at least one negative lens are cemented, and
wherein the third lens group includes a negative lens and a positive lens in order from the object side to the image side.

3. The imaging lens according to claim 1 , wherein assuming that a focal length of the imaging lens in a state where the object at infinity is in focus is f, and
the focal length of the first lens group is f1,
Conditional Expression (2) is satisfied, which is represented by
0.25< f/f 1<1  (2).

4. The imaging lens according to claim 1 , wherein assuming that
a focal length of the imaging lens in a state where the object at infinity is in focus is f, and
the focal length of the second lens group is f2,
Conditional Expression (3) is satisfied, which is represented by
0.8< f/f 2<1.6  (3).

5. The imaging lens according to claim 1 , wherein assuming that
a focal length of the imaging lens in a state where the object at infinity is in focus is f, and
a focal length of the third lens group is f3,
Conditional Expression (4) is satisfied, which is represented by
−0.8< f/f 3<0  (4).

6. The imaging lens according to claim 1 , wherein assuming that
a lateral magnification of the second lens group in the state where the object at infinity is in focus is β 2 , and
a lateral magnification of the third lens group in the state where the object at infinity is in focus is β 3 ,
Conditional Expression (5) is satisfied, which is represented by
1.15<(1−β 2 2 )×β 3 2 <2.5  (5).

7. The imaging lens according to claim 1 , wherein the negative lens and the positive lens of the first lens group are cemented with each other.

8. The imaging lens according to claim 1 , wherein the number of lenses included in the third lens group is two.

9. The imaging lens according to claim 1 , wherein a negative lens closest to the object side in the third lens group is a meniscus lens which is convex toward the image side.

10. The imaging lens according to claim 1 , wherein an image side surface of a positive lens closest to the image side in the third lens group is a convex surface.

11. The imaging lens according to claim 1 , wherein assuming that
an Abbe number of the positive lens of the first lens group based on a d line is ν1p, and
an Abbe number of the negative lens of the first lens group based on the d line is ν1n,
Conditional Expression (6) is satisfied, which is represented by
0<ν1 p−ν 1 n< 30  (6).

12. The imaging lens according to claim 1 , wherein assuming that a refractive index of a positive lens closest to the image side in the third lens group at a d line is N3p,
Conditional Expression (7) is satisfied, which is represented by
1.8< N 3 p< 2.2  (7).

13. The imaging lens according to claim 8 , wherein assuming that
an Abbe number of the positive lens of the third lens group based on a d line is ν3p, and
an Abbe number of the negative lens of the third lens group based on the d line is ν3n,
Conditional Expression (8) is satisfied, which is represented by
−5<ν3 p−ν 3 n< 15  (8).

14. The imaging lens according to claim 1 , wherein assuming that an average of Abbe numbers of all lenses included in the third lens group based on a d line is ν3ave,
Conditional Expression (9) is satisfied, which is represented by
20<ν3ave<30  (9).

15. The imaging lens according to claim 1 , wherein Conditional Expression (1-1) is satisfied, which is represented by
0.25< f 2/ f 1<0.9  (1-1).

16. The imaging lens according to claim 3 , wherein Conditional Expression (2-1) is satisfied, which is represented by
0.25< f/f 1<0.9  (2-1).

17. The imaging lens according to claim 4 , wherein Conditional Expression (3-1) is satisfied, which is represented by
0.9< f/f 2<1.45  (3-1).

18. The imaging lens according to claim 5 , wherein Conditional Expression (4-1) is satisfied, which is represented by
−0.75< f/f 3<0  (4-1).

19. The imaging lens according to claim 6 , wherein Conditional Expression (5-1) is satisfied, which is represented by
1.25<(1−β 2 2 )×β 3 2 <2.4  (5-1).

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

Assignees

• Fujifilm Corp

Inventors

• Nagami Ryosuke
• Ori Tetsuya

Classifications

• H04N23/55

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

• H04N23/45

  for generating image signals from two or more image sensors being of different type or operating in different modes, e.g. with a CMOS sensor for moving images in combination with a charge-coupled device [CCD] for still images · CPC title

• G02B13/18 Primary

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

• G02B13/00 Primary

  Optical objectives specially designed for the purposes specified below (with variable magnification {in general} G02B15/00) · CPC title

• G02B9/12 Primary

  having three components only · CPC title