Imaging lens and imaging apparatus

Patent metadata

Field	Value
Publication number	US-10139600-B2
Application number	US-201715718290-A
Country	US
Kind code	B2
Filing date	Sep 28, 2017
Priority date	Oct 6, 2016
Publication date	Nov 27, 2018
Grant date	Nov 27, 2018

Abstract

The imaging lens includes, 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. During focusing, only the second lens group moves in the direction of the optical axis. A lens closest to the object side in the first lens group and a lens adjacent to the lens on the image side have positive refractive powers, and the second lens group includes two or three lenses. Further, predetermined Conditional Expressions (1), (2), (3a), and (3b) are satisfied.

First claim

What is claimed is:

1. An imaging lens comprising, 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 during focusing from an object at infinity to a closest object, only the second lens group moves in a direction of an optical axis,
wherein a lens closest to the object side in the first lens group and a lens adjacent to the lens closest to the object side on an image side have positive refractive powers,
wherein the second lens group includes two or three lenses,
wherein the following conditional expressions are satisfied,
0< AT /(CT11+CT12)<0.1  (1),

15<ν11<40  (2),

65<ν12<90  (3a), and

0.0<θ gF 12−(−0.001682·ν12+0.6438)  (3b),

where CT11 is a center thickness of the lens closest to the object side in the first lens group on the optical axis,
CT12 is a center thickness of the lens adjacent to the lens closest to the object side on the image side in the first lens group on the optical axis,
AT is an air gap on the optical axis between the lens closest to the object side in the first lens group and the lens adjacent to the lens closest to the object side on the image side,
ν11 is an Abbe number of the lens closest to the object side in the first lens group,
ν12 is an Abbe number of the lens adjacent to the lens closest to the object side on the image side in the first lens group, and
θgF12 is a partial dispersion ratio of the lens adjacent to the lens closest to the object side on the image side in the first lens group between a g line and an F line.

2. The imaging lens according to claim 1 , wherein the first lens group has two groups of cemented lenses, where in each group, at least one lens having a positive refractive power and at least one lens having a negative refractive power are combined.

3. The imaging lens according to claim 1 , wherein the third lens group has two groups of cemented lenses, where in each group, at least one lens having a positive refractive power and at least one lens having a negative refractive power are combined.

4. The imaging lens according to claim 3 ,
wherein one group of the cemented lenses closest to the object side in the two groups of cemented lenses of the third lens group includes a lens having a positive refractive power and a lens having a negative refractive power in order from the object side, and
wherein the following conditional expressions are satisfied,
60<ν31<90  (4a),

0.0<θ gF 31−(−0.001682·ν31+0.6438)  (4b), and

15<ν32<45  (5),

where ν31 is an Abbe number of the lens which has a positive refractive power and constitutes one group of the cemented lenses closest to the object side in the two groups of cemented lenses of the third lens group,
θgF31 is a partial dispersion ratio of the lens, which has a positive refractive power and constitutes one group of the cemented lenses closest to the object side in the two groups of cemented lenses of the third lens group, between the g line and the F line, and
ν32 is an Abbe number of the lens which has a negative refractive power and constitutes one group of the cemented lenses closest to the object side in the two groups of cemented lenses of the third lens group.

5. The imaging lens according to claim 3 ,
wherein one group of the cemented lenses closest to the image side in the two groups of cemented lenses of the third lens group includes a lens having a positive refractive power and a lens having a negative refractive power in order from the object side, and
wherein the following conditional expressions are satisfied,
60<ν33<80  (6a),

0.0<θ gF 33−(−0.001682·ν33+0.6438)  (6b), and

15<ν34<35  (7),

where ν33 is an Abbe number of the lens which has a positive refractive power and constitutes one group of the cemented lenses closest to the image side in the two groups of cemented lenses of the third lens group,
θgF33 is a partial dispersion ratio of the lens, which has a positive refractive power and constitutes one group of the cemented lenses closest to the image side in the two groups of cemented lenses of the third lens group, between the g line and the F line, and
ν34 is an Abbe number of the lens which has a negative refractive power and constitutes one group of the cemented lenses closest to the image side in the two groups of cemented lenses of the third lens group.

6. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied,
−2.5< f/f 2<−1.0  (8),

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

7. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied,
0.9< f/f 1<1.5  (9),

where f is a focal length of the whole system in a state where the object at infinity is in focus, and
f1 is a focal length of the first lens group.

8. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied,
1.0< f/f 3<2.0  (10),

where f is a focal length of the whole system in a state where the object at infinity is in focus, and
f3 is a focal length of the third lens group.

9. The imaging lens according to claim 1 , wherein the second lens group includes two lenses, a lens close to the object side in the two lenses has a positive refractive power, a lens close to the image side in the two lenses has a negative refractive power, and the two lenses are cemented.

10. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied,
1.70< N 2<2.2  (11),

where N2 is a refractive index of the lens closest to the object side in the second lens group.

11. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied,
15<ν21<30  (12),

where ν21 is an Abbe number of the lens closest to the object side in the second lens group.

12. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied,
1.65< N 1<2.2  (13),

where N1 is a refractive index of the lens closest to the object side in the first lens group.

13. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied,
30<Δν1 r< 50  (14),

where Δν1r is a difference in Abbe number between a lens closest to the image side in the first lens group and a lens adjacent to the lens closest to the image side on the object side.

14. The imaging lens according to claim 1 , wherein an aperture stop is disposed between the first lens group and the second lens group, and the aperture stop remains stationary during focusing from the object at infinity to the closest object.

15. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied,
0.10< BF/f< 0.50  (15),

where BF is an air conversion length from an image side surface of the lens, which is closest to the image side, to the image plane, and
f is a focal length of the whole system in a state where the object at infinity is in focus.

16. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied.
0.005< AT /(CT11+CT12)<0.05  (1-1)

17. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied.
20<ν11<36  (2-1)

18. The imaging lens according to claim 1 , wherein the following conditional expression is satisf

Assignees

• Fujifilm Corp

Inventors

• Kondo Masato

Classifications

• G02B7/04

  with mechanism for focusing or varying magnification · CPC title

• G02B9/14 Primary

  arranged + - + · CPC title

• G02B13/006 Primary

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

• G02B15/173 Primary

  arranged +-+ · CPC title