Imaging lens

1. An imaging lens configured to form an image of an object on a solid-state image sensor, in which the lenses are arranged in order from an object side to an image side of the imaging lens and are spaced from each other, the imaging lens comprising:

a first lens with a positive refractive power;

a second lens with a negative refractive power having a convex surface facing the object side near an optical axis and a concave surface facing the image side near the optical axis;

a third lens with a positive or a negative refractive power;

a fourth lens with a positive or a negative refractive power;

a fifth lens with a positive refractive power having a convex surface facing the image side near the optical axis;

a sixth lens with a positive or a negative refractive power;

a seventh lens with a negative refractive power, the seventh lens being a double-sided aspheric lens having a concave surface facing the object side near the optical axis and a concave surface facing the image side near the optical axis, wherein

the third lens, the fourth lens, the fifth lens, and the sixth lens each have at least one aspheric surface,

the seventh lens has a pole-change point spaced from an optical axis of the imaging lens on its aspheric image-side surface, and

an expression (21) is satisfied:

f /EPD<2.40, where  (21)

f: an overall focal length of the imaging lens, and

EPD: entrance pupil diameter.

2. The imaging lens according to claim 1 , wherein an expression (1) is satisfied:

−1.0< f 1/ f 2<−0.15, where  (1)

f1: a focal length of the first lens, and

f2: a focal length of the second lens.

3. The imaging lens according to claim 1 , wherein an expression (6) is satisfied:

20<ν d 1−ν d 2<40, where  (6)

νd1: abbe number of the first lens at d-ray, and

νd2: abbe number of the second lens at d-ray.

4. The imaging lens according to claim 1 , wherein an expression (7) is satisfied:

40<ν d 3<75, where  (7)

νd3: abbe number of the third lens at d-ray.

5. The imaging lens according to claim 1 , wherein an expression (8) is satisfied:

40<ν d 7<75, where  (8)

νd7: abbe number of the seventh lens at d-ray.

6. The imaging lens according to claim 1 , wherein an expression (9) is satisfied:

40<ν d 4<75, where  (9)

νd4: abbe number of the fourth lens at d-ray.

7. The imaging lens according to claim 1 , wherein an expression (10) is satisfied:

20<|ν d 5−ν d 6|<40, where  (10)

νd5: abbe number of the fifth lens at d-ray, and

νd6: abbe number of the sixth lens at d-ray.

8. The imaging lens according to claim 1 , wherein an expression (13) is satisfied:

1.0< TTL/f< 1.35, where  (13)

f: an overall focal length of the imaging lens, and

TTL: a distance along the optical axis from an image plane of the imaging lens to an object-side surface of an optical element located nearest an imaged object.

9. The imaging lens according to claim 1 , wherein an expression (19) is satisfied:

0.8<( r 9+ r 10)/( r 9− r 10)<2.5, where  (19)

r9: curvature radius of the object-side surface of the fifth lens, and

r10: curvature radius of the image-side surface of the fifth lens.

10. The imaging lens according to claim 1 , wherein an expression (14) is satisfied:

TTL/ 2 ih< 1.0, where  (14)

TTL: a distance along the optical axis from an image plane of the imaging lens to an object-side surface of an optical element located nearest an imaged object, and

ih: a maximum image height.

11. The imaging lens according to claim 1 , wherein an expression (2) is satisfied:

0.5< f 5/ f< 1.5, where  (2)

f: an overall focal length of the imaging lens, and

f5: a focal length of the fifth lens.