Imaging lens and imaging apparatus using imaging lens

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

a front group having a negative power;

a stop; and

a rear group having a positive power,

wherein the front group consists of, in order from the object side, a first lens having a negative power and having a concave surface on an image side thereof, a second lens having a negative power where an object-side lens surface thereof has a radius of curvature whose absolute value is larger than that of an image-side lens surface thereof, and a third lens having a positive power,

the rear group consists of, in order from the object side, a fourth lens having a positive power, a fifth lens having a negative power and having a meniscus shape with a concave surface on the object side, and a sixth lens having a positive power,

each of the first lens, the second lens, the fourth lens, and the sixth lens has an Abbe number of 40 or more at the d-line, and each of the third lens and the fifth lens has an Abbe number of 40 or less at the d-line, and

each lens in the front group and the rear group is a single lens.

2. An imaging lens consisting: in order from an object side thereof,

a front group having a negative power;

a stop; and

a rear group having a positive power,

wherein the front group consists of, in order from the object side, a first lens having a negative power and having a concave surface on an image side, a second lens having a negative power, and a third lens having a positive power,

the rear group consists of two lenses each having a positive power and one lens having a negative power,

each of the first lens and the second lens has an Abbe number of 45 or more at the d-line, and the third lens has an Abbe number of 25 or less at the d-line,

the lens having the negative power in the rear group has an Abbe number of 25 or less at the d-line, and each of the two lenses each having the positive power in the rear group has an Abbe number of 45 or more at the d-line,

each lens in the front group and the rear group is a single lens, and

a distance from an object-side lens surface of the first lens to the imaging surface of the imaging lens is equal to or smaller than 18 mm.

3. The imaging lens according to claim 1 , wherein the third lens has a biconvex shape where an object-side lens surface thereof has a radius of curvature whose absolute value is smaller than that of an image-side lens surface thereof.

4. The imaging lens according to claim 1 , wherein each of the two lenses each having the positive power in the rear group has a biconvex shape.

5. The imaging lens according to claim 1 , wherein the second lens is a lens having a plano-concave shape with a flat surface on the object side or a meniscus lens where an object-side lens surface thereof has a radius of curvature whose absolute value is larger than that of an image-side lens surface thereof.

6. The imaging lens according to claim 1 , wherein the following conditional expression (1) is satisfied:

0.5 <R 10 /R 9<1.0  (1)

wherein

R 9 represents a radius of curvature of an image-side lens surface of a lens nearest to the object side among the lenses in the rear group; and

R 10 represents a radius of curvature of an object-side lens surface of a lens adjacent to the image side of a lens nearest to the object side among the lenses in the rear group.

7. The imaging lens according to claim 1 , wherein the following conditional expression (2) is satisfied:

0.8 <|f 12 /f|< 1.8  (2)

wherein

f represents a focal length of the imaging lens, and

f 12 represents a composite focal length of the first lens and the second lens.

8. The imaging lens according to claim 1 , wherein the following conditional expression (3) is satisfied:

1.0 <|f 123 /f 456|<2.2  (3)

wherein

f 123 represents a composite focal length of the front group, and

f 456 represents a composite focal length of the rear group.

9. The imaging lens according to claim 1 , wherein the following conditional expression (4) is satisfied:

5 <L/f< 18  (4)

wherein

f represents a focal length of the imaging lens, and

L represents a distance from the object-side lens surface of the first lens to the imaging surface of the imaging lens.

10. The imaging lens according to claim 1 ,

wherein the following conditional expression (5) is satisfied:

0.5 <Bf/f< 3.0  (5)

wherein

f represents a focal length of the imaging lens, and

Bf represents a back focal length of the imaging lens.

11. The imaging lens according to claim 1 ,

wherein the following conditional expression (6) is satisfied:

2.0 <f 45 /f< 6.5  (6)

wherein

f represents a focal length of the imaging lens, and

f 45 represents a composite focal length of two adjacent lenses nearest to the object side from among the lenses constituting the rear group.

12. The imaging lens according to claim 1 , wherein each of the first lens to the sixth lens is a glass lens.

13. The imaging lens according to claim 2 , wherein the third lens has a biconvex shape where an object-side lens surface thereof has a radius of curvature whose absolute value is smaller than that of an image-side lens surface thereof.

14. The imaging lens according to claim 2 , wherein each of the two lenses each having the positive power in the rear group has a biconvex shape.

15. The imaging lens according to claim 2 , wherein the second lens is a lens having a plano-concave shape with a flat surface on the object side or a meniscus lens where an object-side lens surface thereof has a radius of curvature whose absolute value is larger than that of an image-side lens surface thereof.

16. The imaging lens according to claim 2 , wherein the following conditional expression (1) is satisfied:

0.5 <R 10 /R 9<1.0  (1)

wherein

R 9 represents a radius of curvature of an image-side lens surface of a lens nearest to the object side among the lenses in the rear group; and

R 10 represents a radius of curvature of an object-side lens surface of a lens adjacent to the image side of a lens nearest to the object side among the lenses in the rear group.

17. The imaging lens according to claim 2 , wherein the following conditional expression (2) is satisfied:

0.8 <|f 12 /f|< 1.5  (2)

wherein

f represents a focal length of the imaging lens, and

f 12 represents a composite focal length of the first lens and the second lens.

18. The imaging lens according to claim 2 , wherein the following conditional expression (3) is satisfied:

1.0 <|f 123 /f 456|<2.2  (3)

wherein

f 123 represents a composite focal length of the front group, and

f 456 represents a composite focal length of the rear group.

19. The imaging lens according to claim 2 , wherein the following conditional expression (4) is satisfied:

5 <L/f< 13  (4)

wherein

f represents a focal length of the imaging lens, and

L represents a distance from the object-side lens surface of the first lens to the imaging surface of the imaging lens.

20. The imaging lens according to claim 2 ,

wherein the following conditional expression (5) is satisfied:

0.5 <Bf/f< 3.0  (5)

wherein

f represents a focal length of the imaging lens, and

Bf represents a back focal length of the imaging lens.

21. The imaging lens according to claim 2 ,

wherein the following conditional expression (6) is satisfied:

2.0 <f 45 /f< 5.2  (6)

wherein

f represents a focal length of the imaging lens, and

f 45 represents a composite focal length of two adjacent lenses nearest to the object side from among the lenses constituting the rear group.

22. The imaging lens according to claim 2 , wherein each of the first lens to the sixth lens is a glass lens.

23. An imaging apparatus comprising:

an imaging lens according to claim 1 ; and

an imaging device converting an optical image formed by the imaging lens into an electrical signal.

24. An imaging apparatus comprising:

an imaging lens according to claim 2 ; and

an imaging device converting an optical image formed by the imaging lens into an electrical signal.