There is provided an imaging lens with excellent optical characteristics which satisfies demand of the wide field of view, the low-profileness and the low F-number. An imaging lens comprises, in order from an object side to an image side, a first lens with positive refractive power having a convex surface facing the object side near an optical axis, a second lens having negative refractive power near the optical axis, a third lens, a fourth lens, and a fifth lens with the negative refractive power having a concave surface facing the image side near the optical axis, wherein an image-side surface of the fifth lens is formed as an aspheric surface having at least one pole point in a position off the optical axis, and predetermined conditional expressions are satisfied.
1. An imaging lens comprising in order from an object side to an image side, a first lens with positive refractive power having a convex surface facing the object side near an optical axis,
a second lens having negative refractive power near the optical axis,
a third lens,
a fourth lens, and
a fifth lens with the negative refractive power having a concave surface facing the image side near the optical axis, wherein an image-side surface of said fifth lens is formed as an aspheric surface having at least one pole point in a position off the optical axis, and below conditional expressions (1), (2), (3) and (4) are satisfied:
10.00<ν d 3<39.00 (1)
0.25< T 2/ T 3<1.00 (2)
0.50< r 2/ f< 1.65 (3)
−5.00< r 9/ r 10<−2.20 (4)
where
νd3: an abbe number at d-ray of the third lens,
T2: a distance along the optical axis from an image-side surface of the second lens to an object-side surface of the third lens,
T3: a distance along the optical axis from an image-side surface of the third lens to an object-side surface of the fourth lens,
r2: paraxial curvature radius of an image-side surface of the first lens,
f: a focal length of the overall optical system of the imaging lens,
r9: paraxial curvature radius of an object-side surface of the fifth lens, and
r10: paraxial curvature radius of an image-side surface of the fifth lens.
2. The imaging lens according to claim 1 , wherein said fourth lens and said fifth lens has negative composite refractive power near the optical axis.
3. The imaging lens according to claim 1 , wherein an object-side surface of said second lens is a convex surface facing the object side near the optical axis.
4. The imaging lens according to claim 1 , wherein a below conditional expression (5) is satisfied:
1.90<( T 4/ f )×100<10.00 (5)
where
T4: a distance along the optical axis from an image-side surface of the fourth lens to an object-side surface of the fifth lens, and
f: a focal length of the overall optical system of the imaging lens.
5. The imaging lens according to claim 1 , wherein a below conditional expression (7) is satisfied:
1.10< T 3/ T 4<5.50 (7)
where
T3: a distance along the optical axis from an image-side surface of the third lens to an object-side surface of the fourth lens, and
T4: a distance along the optical axis from an image-side surface of the fourth lens to an object-side surface of the fifth lens.
6. The imaging lens according to claim 1 , wherein a below conditional expression (10) is satisfied:
0.35< r 4/ f< 1.25 (10)
where
r4: paraxial curvature radius of an image-side surface of the second lens, and
f: a focal length of the overall optical system of the imaging lens.
7. The imaging lens according to claim 1 , wherein a below conditional expression (12) is satisfied:
0.20< r 2/ r 3<1.30 (12)
where
r2: paraxial curvature radius of an image-side surface of the first lens, and
r3: paraxial curvature radius of an object-side surface of the second lens.
8. The imaging lens according to claim 1 , wherein a below conditional expression (13) is satisfied:
1.00< r 3/ r 4<9.50 (13)
where
r3: paraxial curvature radius of an object-side surface of the second lens, and
r4: paraxial curvature radius of an image-side surface of the second lens.
9. The imaging lens according to claim 1 , wherein said second lens and said third lens are made of a plastic material, and below conditional expressions (14) and (15) are satisfied:
1.65< Nd 2 (14)
1.60< Nd 3<1.70 (15)
where
Nd2: refractive index at d-ray of the second lens, and
Nd3: refractive index at d-ray of the third lens.
10. The imaging lens according to claim 1 , wherein a below conditional expression (16) is satisfied:
TTL/EPd≤2.50 (16)
where
TTL: a total track length, and
EPd: an entrance pupil diameter.
11. An imaging lens comprising in order from an object side to an image side, a first lens with positive refractive power having a convex surface facing the object side near an optical axis,
a second lens having negative refractive power near the optical axis,
a third lens,
a fourth lens, and
a fifth lens with the negative refractive power having a concave surface facing the image side near the optical axis, wherein an image-side surface of said fifth lens is formed as an aspheric surface having at least one pole point in a position off the optical axis, an image-side surface of said first lens is a concave surface facing the image side near the optical axis, an object-side surface of said second lens is a convex surface facing the object side near the optical axis, said fourth lens has the positive refractive power near the optical axis, composite refractive power of said fourth lens and said fifth lens is negative near the optical axis, and below conditional expressions (1) and (4) are satisfied:
10.00<ν d 3<39.00 (1)
−5.00< r 9/ r 10<−2.20 (4)
where
νd3: an abbe number at d-ray of the third lens,
r9: paraxial curvature radius of an object-side surface of the fifth lens, and
r10: paraxial curvature radius of an image-side surface of the fifth lens.
12. The imaging lens according to claim 11 , wherein a below conditional expression (6) is satisfied:
1.20< T 2/ T 1<7.00 (6)
where
T2: a distance along the optical axis from an image-side surface of the second lens to an object-side surface of the third lens, and
T1: a distance along the optical axis from an image-side surface of the first lens to an object-side surface of the second lens.
13. The imaging lens according to claim 11 , wherein a below conditional expression (8) is satisfied:
2.30< D 1/ D 2<3.80 (8)
where
D1: a thickness along the optical axis of the first lens, and D2: a thickness along the optical axis of the second lens.
14. The imaging lens according to claim 11 , wherein a below conditional expression (9) is satisfied:
0.50< r 3/ f< 9.00 (9)
where
r3: paraxial curvature radius of an object-side surface of the second lens, and
f: a focal length of the overall optical system of the imaging lens.
15. The imaging lens according to claim 11 , wherein a below conditional expression (11) is satisfied:
−2.30< r 9/ f<− 0.85 (11)
where
r9: paraxial curvature radius of an object-side surface of the fifth lens, and
f: a focal length of the overall optical system of the imaging lens.
16. The imaging lens according to claim 11 , wherein a below conditional expression (10) is satisfied:
0.35< r 4/ f< 1.25 (10)
where
r4: paraxial curvature radius of an image-side surface of the second lens, and
f: a focal length of the overall optical system of the imaging lens.
17. The imaging lens according to claim 11 , wherein a below conditional expression (12) is satisfied:
0.20< r 2/ r 3<1.30 (12)
where
r2: paraxial curvature radius of an image-side surface of the first lens, and
r3: paraxial curvature radius of an object-side surface of the second lens.
18. The imaging lens according to claim 11 , wherein a below conditional expression (13) is satisfied:
1.00< r 3/ r 4<9.50 (13)
where
r3: paraxial curvature radius of an object-side surface of the second lens, and
r4: paraxial curvature radius of an image-side surface of the second lens.
19. The imaging lens according to claim 11 , wherein said second lens and said third lens are made of a plastic material, and below conditional expressions (14) and (15) are satisfied:
1.65< Nd 2 (14)
1.60< Nd 3<1.70 (15)
where
Nd2: refractive index at d-ray of the second lens, and
Nd3: refractive index at d-ray of the third lens.
20. The imaging lens according to claim 11 , wherein a below conditional expression (16) is satisfied:
TTL/EPd≤2.50 (16)
where
TTL: a total track length, and
EPd: an entrance pupil diameter.