Imaging lens
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 with negative refractive power,
a third lens with negative refractive power,
a fourth lens with positive refractive power being a double-sided aspheric lens,
a fifth lens with negative refractive power being a double-sided aspheric lens, and
a sixth lens with positive refractive power having a convex surface facing the image side,
wherein said fourth lens has a convex surface facing the object-side at a paraxial region, and below conditional expressions (4), (9), and (17) are satisfied:
0.50< r 10/ f< 1.00 (4)
0.30< T 3/ T 4<0.90 (9)
2.0<| f 6|/ f< 25.0 (17)
where
f: a focal length of the overall optical system of the imaging lens,
f6: a focal length of the sixth lens,
r10: a paraxial curvature radius of an image-side surface of the fifth 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, 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.
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 (5) is satisfied:
−13.00< r 12/ f<− 1.90
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.
4 . The imaging lens according to claim 1 , wherein a below conditional expression (6) is satisfied:
−0.20<( Nd 6−1)/ r 11≤0.0
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.
5 . 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.
6 . 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
where
f2: a focal length of the second lens.
7 . The imaging lens according to claim 1 , wherein said fifth lens satisfies a below conditional expression (8):
−1.80< f 5/ f<− 0.80
where
f5: a focal length of the fifth lens.
8 . The imaging lens according to claim 1 , wherein a below conditional expression (9) is satisfied:
0.30< T 3/ T 4<0.90
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.
9 . The imaging lens according to claim 1 , wherein a below conditional expression (10) is satisfied:
0.05< D 6/ f< 0.25
where
D6: a thickness of the sixth lens along the optical axis.
10 . The imaging lens according to claim 1 , wherein a below conditional expression (11) is satisfied:
1.80<| r 9|/ f< 19.00
where
r9: a paraxial curvature radius of an object-side surface of the fifth lens.
11 . The imaging lens according to claim 1 , wherein a below conditional expression (12) is satisfied:
3.5<| f 3|/ f
where
f3: a focal length of the third lens.
12 . The imaging lens according to claim 1 , wherein a below conditional expression (13) is satisfied:
−7.0<( D 5/ f 5)×100<−2.0
where
D5: a thickness of the firth lens along the optical axis, and
f5: a focal length of the fifth lens.
13 . The imaging lens according to claim 1 , wherein a below conditional expression (14) is satisfied:
8.0<( T 4/ f )×100<24.00
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.
14 . The imaging lens according to claim 1 , wherein a below conditional expression (15) is satisfied:
0.60<TTL/(2 xih )<1.00
where
ih: a maximum image height.