Imaging lens and imaging apparatus

• US 11,009,676 B2
• Filed: 09/10/2019
• Issued: 05/18/2021
• Est. Priority Date: 03/15/2017
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: Okada, Kazuyoshi
• Primary Examiner(s): Pichler, Marin
• Assistant Examiner(s): Duong, Henry A
• Application Number:
  US16/566,626
• Publication Number:
  US 20200003991A1
• Time in Patent Office: 616 Days
• Field of Search: 359682, 359691-692, 359748, 359753, 359793-795, 359702-704, 359826-830
• CPC Class Codes: G02B 13/02 Telephoto objectives, i.e. systems of the type + - in which the distance from the front vertex to the image plane is less than the equivalent focal length
• CPC Class Codes: G02B 13/18 with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration G02B13/002 takes precedence
• CPC Class Codes: G02B 13/24 for reproducing or copying at short object distances
• CPC Class Codes: G02B 9/10 one + and one - component
• CPC Class Codes: G02B 9/64 having more than six components

Abstract

The imaging lens consists of, in order from the object side, a positive first lens group that moves to the object side during focusing from a long distance to a short distance, and a second lens group that does not move during focusing. The first lens group has a first-B sub-lens group. The first-B sub-lens group consists of, in order from the object side, a positive b1 lens, a negative b2 lens concave toward the image side, an aperture stop, a negative b3 lens concave toward the object side, and a positive b4 lens. The second lens group consists of, in order from the object side, a negative lens, a positive lens, and a negative lens. Predetermined conditional expressions are satisfied.

Claims

1. An imaging lens consisting of, in order from an object side:

a first lens group that moves toward the object side during focusing from a distant object to a close-range object and has a positive refractive power; and

a second lens group that remains stationary with respect to an image plane during focusing,

wherein the first lens group has a first-B sub-lens group including an aperture stop in an inside thereof,

wherein the first-B sub-lens group consists of, in order from the object side, a b1 lens which is a positive lens, a b2 lens which is a negative lens concave toward an image side, an aperture stop, a b3 lens which is a negative lens concave toward the object side, and a b4 lens which is a positive lens,

wherein the second lens group consists of, in order from the object side, a negative lens, a positive lens, and a negative lens, and

wherein assuming that

a distance on an optical axis from an object side surface of the b1 lens to an image side surface of the b2 lens is Db12,

a distance on the optical axis from a surface closest to the object side in the first lens group to a surface closest to the image side in the first lens group is DG1,

a maximum image height is Ymax,

a total number of lens surfaces of the second lens group is k,

a refractive index of a medium, which forms an i-th lens surface from the object side in the second lens group, on the object side at a d line is Nif,

a refractive index of the medium, which forms the i-th lens surface from the object side in the second lens group, on the image side at the d line is Nir,

a radius of curvature of the i-th lens surface from the object side in the second lens group is sRi,

a radius of curvature of the image side surface of the b2 lens is Rb2r, and

a radius of curvature of an object side surface of the b3 lens is Rb3f,

Conditional Expressions (1), (2) and (3) are satisfied, which are represented by

2. The imaging lens according to claim 1, wherein assuming that

a focal length of the imaging lens during focusing on an object at infinity is f, and

a focal length of the second lens group is f2,

Conditional Expression (4) is satisfied, which is represented by

−

0.7<

f/f2<

0.3 

 

(4).

3. The imaging lens according to claim 2, wherein Conditional Expression (4-1) is satisfied, which is represented by

−

0.6<

f/f2<

0.2 

 

(4-1).

4. The imaging lens according to claim 1, wherein assuming that

a focal length of the imaging lens during focusing on an object at infinity is f,

a focal length of a j-th lens from the object side in the second lens group is f2j, and

an Abbe number of the j-th lens from the object side in the second lens group at the d line is v2j,

Conditional Expression (5) is satisfied, which is represented by

5. The imaging lens according to claim 4, wherein Conditional Expression (5-1) is satisfied, which is represented by

6. The imaging lens according to claim 1, wherein the first lens group consists of, in order from the object side, a first-A sub-lens group having a positive refractive power, the first-B sub-lens group, and a first-C sub-lens group having a positive refractive power.

7. The imaging lens according to claim 6, wherein the first-A sub-lens group consists of one or two lenses.

8. The imaging lens according to claim 6, wherein the first-C sub-lens group consists of one or two lenses.

9. The imaging lens according to claim 1, wherein the b1 lens and the b2 lens are cemented with each other.

10. The imaging lens according to claim 1, wherein the b3 lens and the b4 lens are cemented with each other.

11. The imaging lens according to claim 1, wherein the positive lens of the second lens group is a biconvex lens.

12. The imaging lens according to claim 1, wherein Conditional Expression (1-1) is satisfied, which is represented by

0.12<

Db12/DG1<

0.22 

 

(1-1).

13. The imaging lens according to claim 1, wherein Conditional Expression (2-1) is satisfied, which is represented by

14. The imaging lens according to claim 1, wherein Conditional Expression (3-1) is satisfied, which is represented by

−

0.2<

(Rb2r+Rb3f)/(Rb2r−

Rb3f)<

0.1 

 

(3-1).

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

16. An imaging lens consisting of, in order from an object side:

a first lens group that moves toward the object side during focusing from a distant object to a close-range object and has a positive refractive power; and

a second lens group that remains stationary with respect to an image plane during focusing,

wherein the first lens group has a first-B sub-lens group including an aperture stop in an inside thereof,

wherein the first-B sub-lens group consists of, in order from the object side, a b1 lens which is a positive lens, a b2 lens which is a negative lens concave toward an image side, an aperture stop, a b3 lens which is a negative lens concave toward the object side, and a b4 lens which is a positive lens,

wherein the second lens group consists of, in order from the object side, a negative lens, a positive lens, and a negative lens, and

wherein assuming that

a distance on an optical axis from an object side surface of the b1 lens to an image side surface of the b2 lens is Db12,

a distance on the optical axis from a surface closest to the object side in the first lens group to a surface closest to the image side in the first lens group is DG1,

a maximum image height is Ymax,

a total number of lens surfaces of the second lens group is k,

a refractive index of a medium, which forms an i-th lens surface from the object side in the second lens group, on the object side at a d line is Nif,

a refractive index of the medium, which forms the i-th lens surface from the object side in the second lens group, on the image side at the d line is Nir,

a radius of curvature of the i-th lens surface from the object side in the second lens group is sRi,

a radius of curvature of an object side surface of the b3 lens is Rb3f, and

a radius of curvature of an image side surface of the b3 lens is Rb3r,

Conditional Expressions (1), (2) and (6) are satisfied, which are represented by

17. The imaging lens according to claim 16, wherein Conditional Expression (6-1) is satisfied, which is represented by

−

0.75<

(Rb3f+Rb3r)/(Rb3f−

Rb3r)<

−

0.05 

 

(6-1).

18. An imaging apparatus comprising the imaging lens according to claim 16.

19. An imaging lens consisting of, in order from an object side:

a first lens group that moves toward the object side during focusing from a distant object to a close-range object and has a positive refractive power; and

a second lens group that remains stationary with respect to an image plane during focusing,

wherein the first lens group has a first-B sub-lens group including an aperture stop in an inside thereof,

wherein the first-B sub-lens group consists of, in order from the object side, a b1 lens which is a positive lens, a b2 lens which is a negative lens concave toward an image side, an aperture stop, a b3 lens which is a negative lens concave toward the object side, and a b4 lens which is a positive lens,

wherein the second lens group consists of, in order from the object side, a negative lens, a positive lens, and a negative lens, and

wherein assuming that

a distance on an optical axis from an object side surface of the b1 lens to an image side surface of the b2 lens is Db12,

a distance on the optical axis from a surface closest to the object side in the first lens group to a surface closest to the image side in the first lens group is DG1,

a maximum image height is Ymax,

a total number of lens surfaces of the second lens group is k,

a refractive index of a medium, which forms an i-th lens surface from the object side in the second lens group, on the object side at a d line is Nif,

a refractive index of the medium, which forms the i-th lens surface from the object side in the second lens group, on the image side at the d line is Nir,

a radius of curvature of the i-th lens surface from the object side in the second lens group is sRi,

a radius of curvature of an object side surface of the b2 lens is Rb2f, and

a radius of curvature of the image side surface of the b2 lens is Rb2r,

Conditional Expressions (1), (2) and (7) are satisfied, which are represented by

20. The imaging lens according to claim 19, wherein Conditional Expression (7-1) is satisfied, which is represented by

0.35<

(Rb2f+Rb2r)/(Rb2f−

Rb2r)<

1.2 

 

(7-1).