Imaging lens and imaging apparatus equipped with the imaging lens

1. An imaging lens consisting of, in order from the object side to the image side:

a first lens having a positive refractive power and a meniscus shape with a convex surface toward the object side;

a second lens having a biconcave shape with the surface having the radius of curvature with the smaller absolute value toward the image side;

a third lens having a meniscus shape with a convex surface toward the object side;

a fourth lens having a negative refractive power and a meniscus shape with a convex surface toward the image side; and

a fifth lens having a negative refractive power and a meniscus shape with a concave surface toward the image side, the image-side surface having at least one inflection point,

wherein

the conditional formula below is satisfied:

−0.45< f/f 45<−0.23  (1-1),

where

f is the focal length of the entire system, and

f45 is the combined focal length of the fourth lens and the fifth lens.

2. The imaging lens as defined in claim 1 , wherein the conditional formula below is satisfied:

0.8< f/f 1<1.5  (6),

where

f1 is the focal length of the first lens.

3. The imaging lens as defined in claim 1 , wherein the conditional formula below is satisfied:

0.8< f/f 1≦1.268  (6-2),

where

f1 is the focal length of the first lens.

4. The imaging lens as defined in claim 1 , wherein the conditional formula below is satisfied:

1< f 3/ f 1<12  (3),

where

f3 is the focal length of the third lens, and

f1 is the focal length of the first lens.

5. The imaging lens as defined in claim 1 , wherein the conditional formula below is satisfied:

−1<( R 3 f−R 3 r )/( R 3 f+R 3 r )<0  (4),

where

R3f is the paraxial radius of curvature of the object-side surface of the third lens, and

R3r is the paraxial radius of curvature of the image-side surface of the third lens.

6. The imaging lens as defined in claim 1 , wherein the conditional formula below is satisfied:

0<( R 2 r−R 3 f )/( R 2 r+R 3 f )<1  (5),

where

R2r is the paraxial radius of curvature of the image-side surface of the second lens, and

R3f is the paraxial radius of curvature of the object-side surface of the third lens.

7. The imaging lens as defined in claim 1 , wherein the conditional formula below is satisfied:

0.1< f/f 3<0.6  (7),

where

f3 is the focal length of the third lens.

8. The imaging lens as defined in claim 1 , wherein the conditional formula below is satisfied:

−1< f/f 2<−0.2  (8),

where

f2 is the focal length of the second lens.

9. The imaging lens as defined in claim 1 , wherein the conditional formula below is satisfied:

0.05< D 7/ f< 0.2  (9),

where

D7 is the distance between the third lens and the fourth lens along the optical axis.

10. The imaging lens as defined in claim 1 , wherein the conditional formula below is satisfied:

2< f 3/ f 1<10  (3-1),

where

f3 is the focal length of the third lens, and f1 is the focal length of the first lens.

11. The imaging lens as defined in claim 1 , wherein the conditional formula below is satisfied:

−0.7<( R 3 f−R 3 r )/( R 3 f+R 3 r )<0  (4-1),

where

R3f is the paraxial radius of curvature of the object-side surface of the third lens, and

R3r is the paraxial radius of curvature of the image-side surface of the third lens.

12. The imaging lens as defined in claim 1 , wherein the conditional formula below is satisfied:

0<( R 2 r−R 3 f )/( R 2 r+R 3 f )<0.5  (5-1),

where

R2r is the paraxial radius of curvature of the image-side surface of the second lens, and

R3f is the paraxial radius of curvature of the object-side surface of the third lens.

13. The imaging lens as defined in claim 1 , wherein the conditional formula below is satisfied:

0.9< f/f 1≦1.268  (6-3),

where

f1 is the focal length of the first lens.

14. The imaging lens as defined in claim 1 , wherein the conditional formula below is satisfied:

0.1< f/f 3<0.5  (7-1),

where

f3 is the focal length of the third lens.

15. The imaging lens as defined in claim 1 , wherein the conditional formula below is satisfied:

0.5< f ·tan ω/ R 5 r< 10  (2),

where

ω is a half angle of view, and

R5r is the paraxial radius of curvature of the image-side surface of the fifth lens.

16. The imaging lens as defined in claim 15 , wherein the conditional formula below is satisfied:

1.5< f ·tan ω/ R 5 r< 4.5  (2-1).

17. An imaging apparatus equipped with the imaging lens as defined in claim 1 .

18. An imaging lens consisting of, in order from the object side to the image side:

a first lens having a positive refractive power and a meniscus shape with a convex surface toward the object side;

a second lens having a biconcave shape with the surface having the radius of curvature with the smaller absolute value toward the image side;

a third lens having a meniscus shape with a convex surface toward the object side;

a fourth lens having a negative refractive power and a meniscus shape with a convex surface toward the image side; and

a fifth lens having a negative refractive power and a meniscus shape with a concave surface toward the image side, the image-side surface having at least one inflection point,

wherein

the conditional formula below is satisfied:

0.8< f/f 1≦1.268  (6-2),

where

f is the focal length of the entire system, and

f1 is the focal length of the first lens.

19. The imaging lens as defined in claim 18 , wherein the conditional formula below is satisfied:

−0.7< f/f 45<−0.1  (1),

where

f45 is the combined focal length of the fourth lens and the fifth lens.

20. The imaging lens as defined in claim 19 , wherein the conditional formula below is satisfied:

−0.45< f/f 45<−0.23  (1-1).