There is provided an imaging lens with small telephoto ratio and excellent optical characteristics which satisfies demand of the downsizing, 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, a second lens, a third lens, a fourth lens being a double-sided aspheric lens, a fifth lens being a double-sided aspheric lens, and a sixth lens having a convex surface facing the image side, and a below conditional expression is satisfied: 0.60<TTL/ f <1.00 where TTL: a total track length, and f: a focal length of the overall optical system of the imaging lens.
1. An imaging lens comprising in order from an object side to an image side,
a first lens with positive refractive power,
a second lens,
a third lens,
a fourth lens being a double-sided aspheric lens,
a fifth lens being a double-sided aspheric lens, and
a sixth lens having a convex surface facing the image side, wherein said fifth lens has negative refractive power near the optical axis, and below conditional expressions (1), (2) and (3) are satisfied:
0.60<TTL/ f <1.00 (1)
1.00< r 2/ f< 1.90 (2)
0.72< D 2/ D 3<1.07 (3)
where
TTL: a total track length,
f: a focal length of the overall optical system of the imaging lens,
r2: a paraxial curvature radius of the image-side surface of the first lens,
D2: a thickness of the second lens along the optical axis, and
D3: a thickness of the third lens along the optical axis.
2. The imaging lens according to claim 1 , wherein an image-side surface of said fifth lens is concave near the optical axis, and has at least one off-axial pole point.
3. The imaging lens according to claim 1 , wherein a below conditional expression (4) is satisfied:
0.50< r 10/ f< 1.00 (4)
where
r10: a paraxial curvature radius of an image-side surface of the fifth lens, and
f: a focal length of the overall optical system of the imaging lens.
4. The imaging lens according to claim 1 , wherein a below conditional expression (5) is satisfied:
−13.00< r 12/ f<− 1.90 (5)
where
r12: a paraxial curvature radius of an image-side surface of the sixth 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 (6) is satisfied:
−0.20<( Nd 6−1)/ r 11≤0.0 (6)
where
Nd6: a refractive index at d-ray of the sixth lens, and
r11: a paraxial curvature radius of an object-side surface of the sixth lens.
6. The imaging lens according to claim 1 , wherein said second lens is formed in a meniscus shape having a concave surface facing the image side near the optical axis.
7. The imaging lens according to claim 1 , wherein said second lens has negative refractive power and a below conditional expression (7) is satisfied:
−1.30< f 2/ f<− 0.70 (7)
where
f2: a focal length of the second lens.
8. The imaging lens according to claim 1 , wherein said fifth lens satisfies a below conditional expression (8):
−1.80< f 5/ f<− 0.80 (8)
where
f5: a focal length of the fifth lens.
9. The imaging lens according to claim 1 , wherein a below conditional expression (9) is satisfied:
0.30< T 3/ T 4<0.90 (9)
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.
10. The imaging lens according to claim 1 , wherein a below conditional expression (10) is satisfied:
0.05< D 6/ f< 0.25 (10)
where
D6: a thickness of the sixth lens along the optical axis.
11. The imaging lens according to claim 1 , wherein a below conditional expression (11) is satisfied:
1.80<| r 9|/ f< 19.00 (11)
where
r9: a paraxial curvature radius of an object-side surface of the fifth lens.
12. The imaging lens according to claim 1 , wherein a below conditional expression (12) is satisfied:
3.5<| f 3|/ f (12)
where
f3: a focal length of the third lens.
13. The imaging lens according to claim 1 , wherein a below conditional expression (13) is satisfied:
−7.0<( D 5/ f 5)×100<−2.0 (13)
where
D5: a thickness of the fifth lens along the optical axis, and
f5: a focal length of the fifth lens.
14. The imaging lens according to claim 1 , wherein a below conditional expression (14) is satisfied:
9.0<( T 4/ f )×100<24.00 (14)
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.
15. The imaging lens according to claim 1 , wherein a below conditional expression (15) is satisfied:
0.60<TTL/(2× ih )<1.00 (15)
where
ih: a maximum image height.