Imaging lens
An imaging lens elements are arranged in order from an object side, an aperture stop, positive first lens having convex object-side and image-side surfaces, negative meniscus second lens having a concave image-side surface, positive third lens having at least one aspheric surface, positive double-sided aspheric fourth lens, and negative double-sided aspheric fifth lens having concave object-side and image-side surfaces with its image-side surface having a pole-change point off the axis. It satisfies conditional expressions below: 0.5< f 1/ f <1.0 (1) 10.0< f 3/ f (2) 0.8<( r 3+ r 4)/( r 3− r 4)<2.0 (3) where f: focal length of the imaging lens overall optical system f1: first lens focal length f3: third lens focal length r3: curvature radius of the second lens object-side surface r4: curvature radius of the second lens image-side surface.
1. An imaging lens which forms an image of an object on a solid-state image sensor, in which elements are arranged in order from an object side to an image side, comprising:
an aperture stop;
a first lens having positive refractive power and a convex surface near an optical axis on each of the object side and the image side;
a second lens as a meniscus lens having negative refractive power and a concave surface on the image side;
a third lens having positive refractive power and at least one aspheric surface;
a fourth lens as a double-sided aspheric lens having positive refractive power; and
a fifth lens as a double-sided aspheric lens having negative refractive power and a concave surface near an optical axis on each of the object side and the image side, the image-side surface of the fifth lens having a pole-change point in a position off the optical axis,
wherein conditional expressions (1) to (3), (7) and (8) below are satisfied:
0.5< f 1/ f< 1.0 (1)
10.0< f 3/ f <330.01 (2)
0.8<( r 3+ r 4)/( r 3− r 4)<2.0 (3)
50<ν d 3, ν d 4, ν d 5<80 (7)
ih/f≧ 0.78 (8)
where
f: focal length of an overall optical system of the imaging lens
f1: focal length of the first lens
f3: focal length of the third lens
r3: curvature radius of the object-side surface of the second lens
r4: curvature radius of the image-side surface of the second lens
νd3: Abbe number of the third lens at d-ray
νd4: Abbe number of the fourth lens at d-ray
νd5: Abbe number of the fifth lens at d-ray
ih: maximum image height.
2. The imaging lens according to claim 1 ,
wherein the third lens has a biconvex shape in which the object-side surface and the image-side surface are convex near the optical axis; and
wherein the fourth lens has a meniscus shape in which the image-side surface is convex near the optical axis.
3. The imaging lens according to claim 1 ,
wherein a conditional expression (4) below is satisfied:
0.4< f 4/ f< 1.2 (4)
where
f: focal length of an overall optical system of the imaging lens
f4: focal length of the fourth lens.
4. The imaging lens according to claim 1 ,
wherein a conditional expression (5) below is satisfied:
−1.0< f 5/ f<− 0.4 (5)
where
f: focal length of an overall optical system of the imaging lens
f5: focal length of the fifth lens.
5. The imaging lens according to claim 1 ,
wherein conditional expressions (6) below is satisfied:
20<ν d 1−ν d 2 (6)
where
νd1: Abbe number of the first lens at d-ray
νd2: Abbe number of the second lens at d-ray.