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 specified in the specification.
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 negative power;
a third lens having 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,
the imaging lens further satisfying conditional expression (1):
0.7 <f 1 /f< 1.1 (1)
wherein f 1 designates a focal length of the first lens.
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 n 1 designates a refractive index of the first lens at the d-line; and ν 1 designates an Abbe number of the first lens at the d-line.
3. The imaging lens according to claim 1 , further satisfying conditional expression (4):
0.8 <|f 2 /f|< 1.8 (4)
wherein f 2 designates a focal length of the second lens.
4. 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 satisfies conditional expressions (1) and (5):
0.7 <f 1 /f< 1.1 (1)
1.9 <f 3 /f< 20 (5)
wherein f 1 designates a focal length of the first lens; 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.
5. The imaging lens according to claim 4 , further satisfying conditional expressions (2) and (3):
1.45 <n 1<1.6 (2)
ν1>60 (3)
wherein n 1 designates a refractive index of the first lens at the d-line; and ν 1 designates an Abbe number of the first lens at the d-line.
6. The imaging lens according to claim 4 , further satisfying conditional expression (4):
0.8 <|f 2 /f 1|<1.8 (4)
wherein f 2 designates a focal length of the second lens.
7. The imaging lens according to claim 4 , wherein each of the second to fourth lenses includes at least one aspheric surface.
8. The imaging tens according to claim 4 , wherein the first lens is made of an optical glass.
9. 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 f 3 designates a focal length of the third lens,
the imaging lens further satisfying conditional expression (1):
0.7 <f 1 /f< 1.1 (1)
wherein f 1 designates a focal length of the first lens.
10. The imaging lens according to claim 9 , further satisfying conditional expressions (2) and (3):
1.45 <n 1<1.6 (2)
ν1>60 (3)
wherein n 1 designates a refractive index of the first lens at the d-line; and ν 1 designates an Abbe number of the first lens at the d-line.
11. The imaging lens according to claim 9 , further satisfying conditional expression (4):
0.8 <|f 2 /f|< 1.8 (4)
wherein f 2 designates a focal length of the second lens.
12. 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 satisfies conditional expressions (1) and (6):
0.7 <f 1 /f< 1.1 (1)
1.9< f 3 /f≦ 4.74 (6)
wherein f 1 designates a focal length of the first lens; f designates a total focal length; and f 3 designates a focal length of the third lens.
13. The imaging lens according to claim 12 , further satisfying conditional expressions (2) and (3):
1.45 <n 1<1.6 (2)
ν1>60 (3)
wherein n 1 designates a refractive index of the first tens at the d-line; and ν 1 designates an Abbe number of the first lens at the d-line.
14. The imaging lens according to claim 12 , further satisfying conditional expression (4):
0.8 <|f 2 /f|< 1.8 (4)
wherein f 2 designates a focal length of the second lens.
15. The imaging lens according to claim 12 , wherein each of the second to fourth lenses includes at least one aspheric surface
16. The imaging lens according to claim 12 , wherein each of the second to fourth lenses is made of a resin material.
17. The imaging lens according to claim 12 , wherein the first lens is made of an optical glass.