An imaging lens is provided and includes: in order from an object side of the imaging lens, a first lens having a convex surface on the object side and having a positive power; a second lens having a concave surface on the object side and having a negative power; a third lens having a positive power; and a fourth lens having a convex surface on the object side near a paraxial axis and having a meniscus shape. The imaging lens satisfies conditional expressions as specified.
1. An imaging lens comprising: in order from an object side of the imaging lens, a first lens having a convex surface on the object side and having a positive power;
a second lens having a concave surface on the object side and having a negative power;
a third lens having a positive power; and
a fourth lens having a convex surface on the object side near a paraxial axis and having a meniscus shape,
wherein the imaging lens has an air distance between the first lens and the second lens, and the imaging lens satisfies conditional expression (5):
1.9< f 3 /f< 20 (5)
wherein f designates a total focal length; and f 3 designates a focal length of the third lens, and
wherein each of the second to fourth lenses is made of a resin material.
2. The imaging lens according to claim 1 , further satisfying conditional expressions (2) and (3):
1.45<n1<1.6 (2)
ν1>60 (3)
wherein n1 designates a refractive index of the first lens at the d-line; and ν1 designates an Abbe number of the first lens at the d-line.
3. The imaging lens according to claim 2 , further satisfying conditional expression (4):
0.8<| f 2 /f|< 1.8 (4)
wherein f2 designates a focal length of the second lens.
4. The imaging lens according to claim 1 , further satisfying conditional expression (4):
0.8<| f 2 /f|< 1.8 (4)
wherein f2 designates a focal length of the second lens.
5. The imaging lens according to claim 1 , wherein each of the second to fourth lenses includes at least one aspheric surface.
6. The imaging lens according to claim 1 , wherein the first lens is made of an optical glass.
7. An imaging lens comprising: in order from an object side of the imaging lens, a first lens having a convex surface on the object side and having a positive power;
a second lens having a concave surface on the object side and having a negative power;
a third lens having a positive power; and
a fourth lens having a convex surface on the object side near a paraxial axis and having a meniscus shape,
wherein the imaging lens has an air distance between the first lens and the second lens, and the imaging lens satisfies conditional expression (6):
1.9< f 3/ f≦ 4.74 (6)
wherein f designates a total focal length; and B designates a focal length of the third lens, and
wherein each of the second to fourth lenses is made of a resin material.
8. The imaging lens according to claim 7 , further satisfying conditional expressions (2) and (3):
1.45<n1<1.6 (2)
ν1 >60 (3)
wherein n1 designates a refractive index of the first lens at the d-line; and ν1 designates an Abbe number of the first lens at the d-line.
9. The imaging lens according to claim 8 , further satisfying conditional expression (4):
0.8<| f 2/ f|< 1.8 (4)
wherein f2 designates a focal length of the second lens.
10. The imaging lens according to claim 7 , further satisfying conditional expression (4):
0.8<| f 2 /f|< 1.8 (4)
wherein f2 designates a focal length of the second lens.
11. The imaging lens according to claim 7 , wherein each of the second to fourth lenses includes at least one aspheric surface.
12. The imaging lens according to claim 7 , wherein the first lens is made of an optical glass.