Imaging lens
There is provided an imaging lens with high-resolution which satisfies demand of the wide field of view, the low-profileness and the low F-number, and excellently corrects aberrations. An imaging lens comprises in order from an object side to an image side, a first lens having positive refractive power and a convex surface facing the object side near the optical axis, a second lens having negative refractive power near the optical axis, a third lens having the positive refractive power near the optical axis, a fourth lens, and a fifth lens having the negative refractive power and a concave surface facing the image side near the optical axis, wherein the image-side surface of said fifth lens is formed as an aspheric surface having at least one off-axial pole point, and predetermined conditional expressions are satisfied.
1. An imaging lens comprising in order from an object side to an image side,
a first lens having positive refractive power and a convex surface facing the object side near the optical axis,
a second lens having negative refractive power near the optical axis,
a third lens having the positive refractive power near the optical axis,
a fourth lens, and
a fifth lens having the negative refractive power and a concave surface facing the image side near the optical axis, wherein the image-side surface of said fifth lens is formed as an aspheric surface having at least one off-axial pole point, and below conditional expressions (1), (2), (3), and 7 are satisfied:
0.15<ν d 4/ν d 5<0.55 (1)
0.7< T 1/ T 2<3.0 (2)
1.1| r 7|/ r 8 (3)
2.35< T 2/ T 3<8.10 (7)
where
νd4: abbe number at d-ray of the fourth lens,
νd5: abbe number at d-ray of the fifth lens,
T1: distance along the optical axis from the image-side surface of the first lens to the object-side surface of the second lens,
T2: distance along the optical axis from the image-side surface of the second lens to the object-side surface of the third lens,
r7: paraxial curvature radius of the object-side surface of the fourth lens,
r8: paraxial curvature radius of the image-side surface of the fourth lens, and
T3: distance along the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens.
2. The imaging lens according to claim 1 , wherein an object-side surface of said third lens is a concave surface facing the object side near the optical axis.
3. The imaging lens according to claim 1 , wherein a below conditional expression (4) is satisfied:
6<( T 1/ f )×100<18 (4)
where
T1: distance along the optical axis from the image-side surface of the first lens to the object-side surface of the second lens,
f: focal length of the overall optical system of the imaging lens.
4. The imaging lens according to claim 1 , wherein a below conditional expression (6) is satisfied:
0.7<( T 3/ f )×100<2.7 (6)
where
T3: distance along the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens,
f: focal length of the overall optical system of the imaging lens.
5. The imaging lens according to claim 1 , wherein a below conditional expression (9) is satisfied:
−0.65< r 6/ f<− 0.10 (9)
where
r6: paraxial curvature radius of the image-side surface of the third lens,
f: focal length of the overall optical system of the imaging lens.
6. The imaging lens according to claim 1 , wherein a below conditional expression (10) is satisfied:
8.5<( D 3/ f 3)×100<50.0 (10)
where
D3: thickness along the optical axis of the third lens,
f3: focal length of the third lens.
7. The imaging lens according to claim 1 , wherein a below conditional expression (11) is satisfied:
0.35< f 3/ f< 1.60 (11)
where
f3: focal length of the third lens,
f: focal length of the overall optical system of the imaging lens.
8. The imaging lens according to claim 1 , wherein a below conditional expression (12) is satisfied:
−10.50< f 2/ f 3<−1.75 (12)
where
f2: focal length of the second lens,
f3: focal length of the third lens.
9. The imaging lens according to claim 1 , wherein a below conditional expression (13) is satisfied:
−1.10< f 3/ f 5<−0.15 (13)
where
f3: focal length of the third lens,
f5: focal length of the fifth lens.