Imaging lens including five lenses of +−++−refractive powers
There is provided an imaging lens with excellent optical characteristics which satisfies demand of a low profile and a low F-number. An imaging lens comprises in order from an object side to an image side: a first lens with positive refractive power formed in a biconvex shape having an object-side surface being convex in a paraxial region; a second lens with negative refractive power having an object-side surface being convex in a paraxial region; a third lens with positive refractive power having an image-side surface being concave in a paraxial region; a fourth lens with positive refractive power in a paraxial region; and a fifth lens with negative refractive power having an object-side surface being concave in a paraxial region; and predetermined conditional expressions are satisfied.
1. An imaging lens comprising in order from an object side to an image side:
a first lens with positive refractive power formed in a biconvex shape having an object-side surface being convex in a paraxial region;
a second lens with negative refractive power having an object-side surface being convex in a paraxial region;
a third lens with positive refractive power having an image-side surface being concave in a paraxial region;
a fourth lens with positive refractive power in a paraxial region; and
a fifth lens with negative refractive power having an object-side surface being concave in a paraxial region,
wherein the imaging lens has a total of five single lenses, and
the following conditional expression (1) is satisfied:
9.00<ν d 5<36.00 (1)
where
νd5: an abbe number at d-ray of the fifth lens.
2. The imaging lens according to claim 1 , wherein the following conditional expression (2) is satisfied:
9.00<ν d 4<36.00 (2)
where
νd4: an abbe number at d-ray of the fourth lens.
3. The imaging lens according to claim 1 , wherein the following conditional expression (3) is satisfied:
−3.00< r 2/ f<− 0.50 (3)
where
r2: a paraxial curvature radius of an image-side surface of the first lens, and
f: a focal length of the overall optical system of the imaging lens.
4. The imaging lens according to claim 1 , wherein the following conditional expression (4) is satisfied:
r 10/ r 3<−6.50 (4)
where
r10: a paraxial curvature radius of an image-side surface of the fifth lens, and
r3: a paraxial curvature radius of an object-side surface of the second lens.
5. The imaging lens according to claim 1 , wherein the following conditional expression (5) is satisfied:
0.10< r 5/ f< 0.35 (5)
where
r5: a paraxial curvature radius of an object-side surface of the third lens, and
f: a focal length of the overall optical system of the imaging lens.
6. The imaging lens according to claim 1 , wherein the following conditional expression (6) is satisfied:
r 10/ f<− 2.50 (6)
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.
7. The imaging lens according to claim 1 , wherein the following conditional expression (9) is satisfied:
0.05< r 4/ f< 0.30 (9)
where
r4: a paraxial curvature radius of an image-side surface of the second lens, and
f: a focal length of the overall optical system of the imaging lens.