Imaging lens and imaging apparatus

Patent metadata

Field	Value
Publication number	US-10168507-B2
Application number	US-201715717999-A
Country	US
Kind code	B2
Filing date	Sep 28, 2017
Priority date	Oct 4, 2016
Publication date	Jan 1, 2019
Grant date	Jan 1, 2019

Abstract

The imaging lens consists of, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. The first lens group has a positive lens, a positive lens, and a negative lens successively in order from a position closest to the object side. The second lens group consists of one negative lens. The third lens group includes two or less lenses. During focusing, only the second lens group moves. The following conditional expression, which relates to a focal length f of the whole system in a state where the object at infinity is in focus and a focal length f2 of the second lens group, is satisfied: 0.4<|f/f2|<1.3.

First claim

What is claimed is:

1. An imaging 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 negative refractive power; and
a third lens group that has a positive refractive power,
wherein the first lens group has a positive lens, a positive lens, and a negative lens, successively in order from a position closest to the object side,
wherein the second lens group consists of one negative lens,
wherein the number of lenses of the third lens group is equal to or less than two,
wherein during focusing, only the second lens group moves in the optical axis direction, and
wherein Conditional Expression (1) is satisfied,
0.4 <|f/f 2|<1.3   (1),

where f is a focal length of the whole system in a state where an object at infinity is in focus, and
f2 is a focal length of the second lens group.

2. The imaging lens according to claim 1 , wherein the first lens group consists of, in order from the object side, a front group having a positive or negative refractive power, an aperture stop, and a rear group having a positive refractive power.

3. The imaging lens according to claim 1 , wherein Conditional Expression (2) is satisfied,
0.4<|(1−β2 2 )×β3 2 |<1.8   (2),

where β2 is a paraxial lateral magnification of the second lens group in a state where the object at infinity is in focus, and
β3 is a paraxial lateral magnification of the third lens group in a state where the object at infinity is in focus.

4. The imaging lens according to claim 2 , wherein the rear group has at least one negative lens.

5. The imaging lens according to claim 2 , wherein the rear group has a cemented lens formed by one negative lens and one positive lens that are cemented together.

6. The imaging lens according to claim 5 , wherein the cemented lens closest to an image side in the rear group satisfies Conditional Expression (3),
5 <vG 1 bp−vG 1 bn< 70   (3),

where vG1bp is an Abbe number of a positive lens of the cemented lens closest to the image side in the rear group at a d line, and
vG1bn is an Abbe number of a negative lens of the cemented lens closest to the image side in the rear group at the d line.

7. The imaging lens according to claim 1 , wherein Conditional Expression (4) is satisfied,
50 <vG 2<75   (4),

where vG2 is an Abbe number of the negative lens of the second lens group at the d line.

8. The imaging lens according to claim 1 , wherein an image side surface of the second lens from the object side of the first lens group is a concave surface.

9. The imaging lens according to claim 2 , wherein a surface closest to the image side in the front group is a concave surface.

10. The imaging lens according to claim 5 , wherein a surface closest to the object side in the cemented lens closest to the image side within the rear group is a concave surface.

11. The imaging lens according to claim 2 , wherein Conditional Expression (5) is satisfied,
1 <f/f 1 b< 2   (5),

where f1b is a focal length of the rear group.

12. The imaging lens according to claim 1 , wherein an image side surface of the negative lens of the second lens group is a concave surface.

13. The imaging lens according to claim 1 , wherein Conditional Expression (6) is satisfied,
0.1 <f/f 3<2   (6),

where f3 is a focal length of the third lens group.

14. The imaging lens according to claim 1 , wherein the third lens group consists of a cemented lens formed by one negative lens and one positive lens that are cemented together in order from the object side.

15. The imaging lens according to claim 14 , wherein Conditional Expression (7) is satisfied,
−10 <vG 3 p−vG 3 n< 50   (7),

where vG3p is an Abbe number of the positive lens of the cemented lens of the third lens group at the d line, and
vG3n is an Abbe number of the negative lens of the cemented lens of the third lens group at the d line.

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

17. The imaging lens according to claim 1 , wherein Conditional Expression (1-1) is satisfied.
0.5 <f/f 2|<1.25   (1-1)

18. The imaging lens according to claim 3 , wherein Conditional Expression (2-1) is satisfied.
0.7<|(1−β2 2 )×β3 2 |<1.5   (2-1)

19. The imaging lens according to claim 11 , wherein Conditional Expression (5-1) is satisfied.
1.4 <f/f 1 b< 1.9   (5-1)

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

Assignees

• Fujifilm Corp

Inventors

• Nagami Ryosuke
• Ori Tetsuya

Classifications

• G03B13/32

  Means for focusing · CPC title

• G02B13/0035 Primary

  having three lenses · CPC title

• G02B13/00 Primary

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

• G02B13/0045

  having five or more lenses · CPC title

• G02B13/006

  at least one element being a compound optical element, e.g. cemented elements · CPC title