Imaging lens including a lens with convex surfaces facing each of an object and an image side
A compact low-cost imaging lens which provides high brightness with an F-value of 2.5 or less and a wide field of view and corrects aberrations properly, meeting the demand for low-profile design. The imaging lens elements are arranged in the following order from an object side to an image side: an aperture stop; a first lens with positive refractive power having a convex surface on each of the object and image sides; a second lens with negative refractive power; a third lens with positive refractive power having a convex surface on each of the object and image sides; a fourth lens with negative refractive power; and a fifth lens with negative refractive power as a double-sided aspheric lens. The imaging lens satisfies a conditional expression (1) below: 1.5< f 3/ f <5.0 (1) where f: focal length of the overall optical system of the imaging lens f3: focal length of the third lens.
1. An imaging lens which forms an image of an object on a solid-state image sensor comprising, in order from an object side to an image side of the imaging lens:
an aperture stop;
a first lens having positive refractive power and convex surfaces facing each of the object side and the image side;
a second lens having negative refractive power;
a third lens having positive refractive power and convex surfaces facing each of the object side and the image side;
a fourth lens having negative refractive power; and
a fifth lens having negative refractive power that is a double-sided aspheric lens,
wherein conditional expressions (1) and (2) below are satisfied:
1.5< f 3/ f< 5.0 (1)
−42.0< f 4/ f<− 8.0 (2)
where
f: focal length of an overall optical system of the imaging lens
f3: focal length of the third lens
f4: focal length of the fourth lens.
2. The imaging lens according to claim 1 , wherein a conditional expression (3) below is satisfied:
−8.5< f 5/ f<− 2.0 (3)
where
f5: focal length of the fifth lens.
3. The imaging lens according to claim 1 , wherein a conditional expression (4) below is satisfied:
0.8<TLA/ f< 1.2 (4)
where
TLA: distance on an optical axis from an object-side surface of the first lens to an image plane without filters.
4. The imaging lens according to claim 1 , wherein conditional expressions (5) and (6) below are satisfied:
0< r 4/ r 5<0.3 (5)
0< r 7/ r 6<0.5 (6)
where
r4: curvature radius of an image-side surface of the second lens
r5: curvature radius of an object-side surface of the third lens
r6: curvature radius of an image-side surface of the third lens
r7: curvature radius of an object-side surface of the fourth lens.
5. An imaging lens which forms an image of an object on a solid-state image sensor, comprising, in order from an object side to an image side of the imaging lens:
an aperture stop;
a first lens having positive refractive power and convex surfaces facing each of the object side and the image side;
a second lens having negative refractive power, a convex surface facing the object side, 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 negative refractive power; and
a fifth lens having negative refractive power that is a double-sided aspheric lens,
wherein conditional expressions (2a) and (5) below are satisfied:
−34.46≦ f 4/ f<− 8.0 (2a)
0< r 4/ r 5<0.3 (5)
where
f: focal length of an overall optical system of the imaging lens
f4: focal length of the fourth lens
r4: curvature radius of an image-side surface of the second lens
r5: curvature radius of an object-side surface of the third lens.
6. The imaging lens according to claim 5 , wherein a conditional expression (1) below is satisfied:
1.5< f 3/ f< 5.0 (1)
where
f3: focal length of the third lens.
7. The imaging lens according to claim 5 , wherein a conditional expression (3) below is satisfied:
−8.5< f 5/ f<− 2.0 (3)
where
f5: focal length of the fifth lens.
8. The imaging lens according to claim 5 , wherein a conditional expression (4) below is satisfied:
0.8<TLA/ f< 1.2 (4)
where
TLA: distance on an optical axis from an object-side surface of the first lens to an image plane without filters.
9. The imaging lens according to claim 5 , wherein a conditional expression (6) below is satisfied:
0< r 7/ r 6<0.5 (6)
where
r6: curvature radius of an image-side surface of the third lens
r7: curvature radius of an object-side surface of the fourth lens.