Imaging lens
An imaging lens having from an object to image side, a first lens having positive refractive power and a convex surface facing the object side, a second lens having a meniscus shape with negative refractive power and a concave surface facing the image side, a third lens having positive refractive power and a convex surface facing the object side, a fourth lens having a meniscus shape with positive refractive power and a convex surface facing the image side, and a fifth lens having negative refractive power and a concave surface facing the image side as a double-sided aspheric lens. A pole point at an off-axial point is provided on the image-side surface, and a below conditional expression (1) is satisfied: (1) 40<|r6/f|<90 where f: the focal length of the overall optical system of the imaging lens, and r6: curvature radius of the image-side surface of the third lens.
1. An imaging lens forming an image of an object on a solid-state image sensor, comprising in order from an object side to an image side,
a first lens having a meniscus shape with positive refractive power and a convex surface facing the object side,
a second lens having a meniscus shape with negative refractive power and a concave surface facing the image side,
a third lens having positive refractive power and a convex surface facing the object side,
a fourth lens having a meniscus shape with positive refractive power and a convex surface facing the image side, and
a fifth lens having negative refractive power and concave surfaces facing the object side and the image side near an optical axis, as a double-sided aspheric lens,
wherein a pole point at an off-axial point is provided on the image-side surface of said fifth lens, and below conditional expressions (1) and (9) are satisfied:
40< |r 6/ f|< 90 (1)
6< r 6/ r 7 (9)
where
f: the focal length of the overall optical system of the imaging lens,
r6: curvature radius of the image-side surface of the third lens, and
r7: curvature radius of the object-side surface of the fourth lens.
2. The imaging lens according to claim 1 , wherein a conditional expression (2) below is satisfied:
0.5<( T 1/ f )*100<3.1 (2)
where
f: the focal length of the overall optical system of the imaging lens, and
T1: distance along the optical axis from the image-side surface of the first lens to the object-side surface of the second lens.
3. The imaging lens according to claim 1 , wherein a conditional expression (3) below is satisfied:
0.3< f 1/| f 2|<0.6 (3)
where
f1: focal length of the first lens, and
f2: focal length of the second lens.
4. The imaging lens according to claim 1 , wherein a conditional expression (4) below is satisfied:
−27< f 45/ f<− 3 (4)
where
f: the focal length of the overall optical system of the imaging lens, and
f45: the composite focal length of the fourth lens and the fifth lens.
5. The imaging lens according to claim 1 , wherein a conditional expression (5) below is satisfied:
0.6< D 4/ D 5<1.6 (5)
where
D4: thickness on the optical axis of the fourth lens, and
D5: thickness on the optical axis of the fifth lens.
6. The imaging lens according to claim 1 , wherein a conditional expression (6) below is satisfied:
−6.9< r 9/ r 10<−1.2 (6)
where
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.
7. The imaging lens according to claim 1 , wherein a conditional expression (7) below is satisfied:
TLA/2 ih< 0.9 (7)
where
TLA: total track length in air, and
ih: maximum image height.
8. The imaging lens according to claim 1 , wherein a conditional expression (8) below is satisfied:
0.7 <ih/f <1.0 (8)
where
f: the focal length of the overall optical system of the imaging lens, and
ih: maximum image height.
9. The imaging lens according to claim 1 , wherein said third lens has a convex surface facing an image side.