Close-distance correcting lens system

1. A close-distance correcting lens system comprising a positive first lens group and a negative second lens group,

wherein traveling distances of said first lens group and said second lens group toward the object side differ from each other when performing a focusing operation on an object at infinity to an object at a close distance, each lens group being defined such that a distance between adjacent lens elements of the first and second lens groups changes as a focusing operation is performed;

wherein said first lens group includes a positive first sub lens group, a negative second sub lens group, a diaphragm, and a positive third sub lens group, in that order from the object side;

wherein said second sub lens group includes an image-stabilizing lens group which is configured to move in a direction orthogonal to the optical axis to change an imaging position of the object image to thereby correct image shake of said object image, and

wherein the following conditions are satisfied:

2.5<β 1b <3.2

and

0.35<β R <0.50

wherein β 1b designates the lateral magnification of said second sub lens group when focused on an object at infinity, and β R designates the lateral magnification of the lens groups which are located closer to the image side than said second sub lens group, when focused on an object at infinity.

2. The close-distance correcting lens system according to claim 1 , wherein said second sub lens group comprises a cemented lens including a negative lens element having a concave surface on the image side and a positive lens element having a concave surface on the image side, in that order from the object side.

3. The close-distance correcting lens system according to claim 2 , wherein the following condition is satisfied:

νd 1bn >30. . . wherein

νd 1bn designates the Abbe number, with respect to the d-line, of said negative lens element provided in said second sub lens group.

4. The close-distance correcting lens system according to claim 2 , wherein the following condition is satisfied:

0 <νd 1bn −νd 1bp <20 . . .

wherein νd 1bn designates the Abbe number, with respect to the d-line, of said negative lens element provided in said second sub lens group, and νd 1bp designates the Abbe number, with respect to the d-line, of said positive lens element provided in said second sub lens group.

5. The close-distance correcting lens system according to claim 2 , wherein the following conditions and are satisfied:

nd 1bn <1.7. . . and

nd 1bp >1.8. . . wherein

nd 1bn designates the refractive index at the d-line of said negative lens element provided in said second sub lens group, and

nd 1bp designates the refractive index at the d-line of said positive lens element provided in said second sub lens group.

6. The close-distance correcting lens system according to claim 1 , wherein said second sub lens group comprises a single negative lens element having a concave surface on the image side.

7. The close-distance correcting lens system according to claim 6 , where the following condition is satisfied:

ν d 1b >45 . . .

wherein νd 1b designates the Abbe number, with respect to the d-line, of said single negative lens element provided in said second sub lens group.

8. The close-distance correcting lens system according to claim 1 , wherein the following condition is satisfied:

1.9 <|f 2 /f 1|<3.9( f 2<0) . . . wherein

f 1 designates the focal length of said first lens group, and f 2 designates the focal length of said second lens group.

9. The close-distance correcting lens system according to claim 1 , wherein the following condition is satisfied:

0.74 <Δd 2 /Δd 1<0.88 . . .

wherein Δd 1 designates the traveling distance of said first lens group between a focusing operation performed on an object at infinity to and a focusing operation performed on an object at a close distance, and Δd 2 designates the traveling distance of said second lens group between a focusing operation performed on an object at infinity and a focusing operation performed on an object at a close distance.

10. A close-distance correcting lens system comprising a positive first lens group and a negative second lens group,

wherein traveling distances of said first lens group and said second lens group toward the object side differ from each other when performing a focusing operation on an object at infinity to an object at a close distance, each lens group being defined such that a distance between adjacent lens elements of the first and second lens groups changes as a focusing operation is performed;

wherein said first lens group includes a positive first sub lens group, a negative second sub lens group, a diaphragm, and a positive third sub lens group, in that order from the object side; and

wherein said second sub lens group includes a cemented lens including a negative lens element having a concave surface on the image side and a positive lens element having a concave surface on the image side, in that order from the object side, and

wherein the following conditions are satisfied:

0<νd 1bn −νd 1bp <20

1.9 <|f 2 /f 1|<3.9( f 2<0)

wherein νd 1bn designates the Abbe number, with respect to the d-line, of said negative lens element provided in said second sub lens group, and

νd 1bp designates the Abbe number, with respect to the d-line, of said positive lens element provided in said second sub lens group, and f 1 designates the focal length of said first lens group, and f 2 designates the focal length of said second lens group.

11. The close-distance correcting lens system according to claim 10 , wherein the following condition is satisfied:

νd 1bn >30 . . . wherein

νd 1bn designates the Abbe number, with respect to the d-line, of said negative lens element provided in said second sub lens group.

12. The close-distance correcting lens system according to claim 10 , wherein the following conditions are satisfied:

nd 1bn <1.7. . . and

nd 1bp >1.8 wherein

nd 1bn designates the refractive index at the d-line of said negative lens element provided in said second sub lens group, and

nd 1bp designates the refractive index at the d-line of said positive lens element provided in said second sub lens group.

13. A close-distance correcting lens system comprising a positive first lens group and a negative second lens group,

wherein traveling distances of said first lens group and the second lens group toward the object side differ from each other when performing a focusing operation on an object at infinity to an object at a close distance, each lens group being defined such that a distance between adjacent lens elements of the first and second lens groups changes as a focusing operation is performed;

wherein said first lens group includes a positive first sub lens group, a negative second sub lens group, a diaphragm and a positive third sub lens group, in that order from the object side;

wherein said second sub lens group includes a single negative lens element having a concave surface facing toward the image, and

wherein the following is conditions are satisfied:

νd 1b > 45 . . . and

1.9 <|f 2 /f 1|<3.9( f 2<0) wherein

f 1 designates the focal length of said first lens group, and f 2 designates the focal length of said second lens group, and

νd 1b designates the Abbe number, with respect to the d-line, of said single negative lens element provided in said second sub lens group.

14. A close-distance correcting lens system comprising a positive first lens group and a negative second lens group,

wherein at least said first lens group moves toward the object side when performing a focusing operation on an object at infinity to an object at a close distance, each lens group being defined such that a distance between adjacent lens elements of the first and second lens groups changes as a focusing operation is performed;

wherein said second lens group includes a negative lens element having a concave surface on the image side, a positive lens element, and a negative lens element having a concave surface on the object side, in that order from the object side; and

wherein the following condition is satisfied:

−1.6<(R 21i +R 21o )/(R 21i −R 21o )<−0.6

wherein R 21i designates the radius of curvature of the surface on the image side of said negative lens element having the concave surface on the image side, and

R 21o designates the radius of curvature of the surface on the object side of said negative lens element having the concave surface on the image side.

15. The close-distance correcting lens system according to claim 14 , wherein the following condition is satisfied:

0.1 <R 23o /f 2 <2.0 . . . , wherein

R 23o designates the radius of curvature of the surface on the object side of said negative lens element having the concave surface on the object side, and

f 2 designates the focal length of said second lens group.

16. The close-distance correcting lens system according to claim 14 , wherein the following condition is satisfied:

0.2 <f 21 /f 2 <0.7 . . . ,

wherein f 21 designates the focal length of said negative lens element having a concave surface on the image side, and

f 2 designates the focal length of said second lens group.

17. The close-distance correcting lens system according to claim 14 , wherein the following condition is satisfied:

0.2 <f 23 /f 2 <0.9 . . . ,

wherein f 23 designates the focal length of said negative lens element having a concave surface on the object side, and

f 2 designates the focal length of said second lens group.

18. The close-distance correcting lens system according to claim 15 , wherein the following condition is satisfied:

νd 23 <60 . . . wherein

νd 23 designates the Abbe number, with respect to the d-line, of said negative lens element having a concave surface on the object side.

19. The close-distance correcting lens system according to claim 14 , wherein said first lens group comprises a negative lens element which has a concave surface on the image side and is provided closest to the object side.

20. The close-distance correcting lens system according to claim 19 , wherein the following conditions are satisfied:

nd 11 >1.65 . . . , and

ν d 11 >40 . . . , wherein

nd 11 designates the refractive index at the d-line of said negative lens element, of said first lens group, having a concave surface on the image side and provided closest to the object side, and

νd 11 designates the Abbe number, with respect to the d-line, of said negative lens element, of said first lens group, having a concave surface on the image side and provided closest to the object side.

21. The close-distance correcting lens system according to claim 15 , wherein said first lens group comprises at least one positive lens element, and wherein the following conditions are satisfied:

nd P1 >1.7 . . . and

ν d P1 <60 . . .

wherein nd P1 designates the refractive index at the d-line of said at least one positive lens element provided within said first lens group, and

νd P1 designates the Abbe number, with respect to the d-line, of said at least one positive lens element provided within said first lens group.

22. The close-distance correcting lens system according to claim 14 , wherein, when performing a focusing operation on an object at infinity and performing a focusing operation on an object at a close distance, said second lens group moves toward the object side at a moving rate different from a moving rate of said first lens group, and wherein the following condition is satisfied:

0.1 <Δd 2 /Δd 1<0.9 . . . wherein

Δd 1 designates the traveling distance of said first lens group between performing a focusing operation on an object at infinity to and performing a focusing operation on an object at a close distance, and

Δd 2 designates the traveling distance of said second lens group between performing a focusing operation on an object at infinity to and performing a focusing operation on an object at a close distance.

23. The close-distance correcting lens system according to claim 14 , wherein, between performing a focusing operation on an object at infinity and performing a focusing operation an object at a close distance, said second lens group does not move in the optical axis direction relative to the imaging plane.

24. The close-distance correcting lens system according to claim 14 , wherein said first lens group comprises a positive first sub lens group, a negative second sub lens group, a diaphragm, and a positive third sub lens group, in that order from the object side,

wherein said second sub lens group comprises a cemented lens including a negative lens element having a concave surface on the image side, and a positive lens element having a concave surface on the image side, in that order from the object side.

25. The close-distance correcting lens system according to claim 24 , wherein the following condition is satisfied:

ν d 1bn >30 . . . wherein

νd 1bn designates the Abbe number, with respect to the d-line, of said negative lens element provided in said second sub lens group.

26. The close-distance correcting lens system according to claim 24 , wherein the following condition is satisfied:

0 <νd 1bn −νd 1bp <20 . . .

wherein νd 1bn designates the Abbe number, with respect to the d-line, of said negative lens element provided in said second sub lens group, and

νd 1bp designates the Abbe number, with respect to the d-line, of said positive lens element provided in said second sub lens group.

27. The close-distance correcting lens system according to claim 24 , wherein the following conditions are satisfied:

nd 1bn <1.7 . . .

nd 1bp >1.8 . . . wherein

nd 1bn designates the refractive index at the d-line of said negative lens element provided in said second sub lens group, and

nd 1bp designates the refractive index at the d-line of said positive lens element provided in said second sub lens group.