An imaging lens is provided and includes: in order from an object side of the imaging lens, a first lens having a convex surface directed to the object side on an optical axis and having a positive power; an aperture diaphragm placed between a top position of an object-side surface of the first lens and a position of an image-side surface of the first lens on the optical axis; a second lens having a meniscus shape with a concave surface directed to the object side on the optical axis; and a third lens having a meniscus shape with a convex surface directed to the object side on the optical axis. Further, the imaging lens satisfies specific conditional expressions.
1. An imaging lens comprising: in order from an object side of the imaging lens,
a first lens having a convex surface directed to the object side on an optical axis and having a positive power;
an aperture diaphragm placed between a top position of an object-side surface of the first lens and a position of an image-side surface of the first lens on the optical axis;
a second lens having a meniscus shape with a concave surface directed to the object side on the optical axis; and
a third lens having a meniscus shape with a convex surface directed to the object side on the optical axis,
wherein
the imaging lens satisfies all conditional expressions (1) to (3) and 7′:
0.5 <f 1/ f< 2.0 (1)
0.5<(| R 2 |−R 1)/( R 1+ |R 2|)≦1.0 (2)
0.5 <|f 2/ f|< 3.0 (3)
v1−v2≧28.2 (7′)
wherein
f represents a focal length of the imaging lens;
f 1 represents a focal length of the first lens;
f 2 represents a focal length of the second lens;
R 1 represents a radius of curvature of the object-side surface of the first lens;
R 2 represents a radius of curvature of the image-side surface of the first lens; and
v1 represents an Abbe number of the first lens; and v2 represents an Abbe number of the second lens.
2. The imaging lens according to claim 1 , further satisfying conditional expression (4):
0.9 <f 3/ f< 3.0 (4)
wherein f 3 represents a focal length of the third lens.
3. The imaging lens according to claim 2 , wherein the second lens has a negative power, and the imaging lens satisfies conditional expression (7):
v 1 −v 2>20 (7)
wherein v 1 represents an Abbe number of the first lens; and v 2 represents an Abbe number of the second lens.
4. The imaging lens according to claim 3 , further satisfying conditional expression (5):
bf/TL> 0.2 (5)
wherein bf represents a distance from the image-side surface of the third lens to an image formation surface in terms of air; and TL represents a distance from the object-side surface of the first lens to the image formation surface in terms of air.
5. The imaging lens according to claim 4 , further satisfying conditional expression (6):
TL /(2× Ih )<1.2 (6)
wherein Ih represents a maximum image height on an image formation surface.
6. The imaging lens according to claim 5 , wherein the aperture diaphragm is placed between the top position of the object-side surface of the first lens and an edge position of the object-side surface of the first lens on the optical axis.
7. The imaging lens according to claim 3 , wherein the aperture diaphragm is placed between the top position of the object-side surface of the first lens and an edge position of the object-side surface of the first lens on the optical axis.
8. The imaging lens according to claim 2 , further satisfying conditional expression (5):
bf/TL> 0.2 (5)
wherein bf represents a distance from the image-side surface of the third lens to an image formation surface in terms of air; and TL represents a distance from the object-side surface of the first lens to the image formation surface in terms of air.
9. The imaging lens according to claim 8 , further satisfying conditional expression (6):
TL /(2× Ih )<1.2 (6)
wherein Ih represents a maximum image height on an image formation surface.
10. The imaging lens according to claim 9 , wherein the aperture diaphragm is placed between the top position of the object-side surface of the first lens and an edge position of the object-side surface of the first lens on the optical axis.
11. The imaging lens according to claim 2 , wherein the aperture diaphragm is placed between the top position of the object-side surface of the first lens and an edge position of the object-side surface of the first lens on the optical axis.
12. The imaging lens according to claim 1 , wherein the second lens has a negative power, and the imaging lens satisfies conditional expression (7):
v 1 −v 2>20 (7)
wherein v 1 represents an Abbe number of the first lens; and v 2 represents an Abbe number of the second lens.
13. The imaging lens according to claim 12 , further satisfying conditional expression (5):
bf/TL> 0.2 (5)
wherein bf represents a distance from the image-side surface of the third lens to an image formation surface in terms of air; and TL represents a distance from the object-side surface of the first lens to the image formation surface in terms of air.
14. The imaging lens according to claim 13 , further satisfying conditional expression (6):
TL /(2× Ih )<1.2 (6)
wherein Ih represents a maximum image height on an image formation surface.
15. The imaging lens according to claim 14 , wherein the aperture diaphragm is placed between the top position of the object-side surface of the first lens and an edge position of the object-side surface of the first lens on the optical axis.
16. The imaging lens according to claim 12 , wherein the aperture diaphragm is placed between the top position of the object-side surface of the first lens and an edge position of the object-side surface of the first lens on the optical axis.
17. The imaging lens according to claim 1 , further satisfying conditional expression (5):
bf/TL> 0.2 (5)
wherein bf represents a distance from the image-side surface of the third lens to an image formation surface in terms of air; and TL represents a distance from the object-side surface of the first lens to the image formation surface in terms of air.
18. The imaging lens according to claim 17 , further satisfying conditional expression (6):
TL /(2× Ih )<1.2 (6)
wherein Ih represents a maximum image height on an image formation surface.
19. The imaging lens according to claim 18 , wherein the aperture diaphragm is placed between the top position of the object-side surface of the first lens and an edge position of the object-side surface of the first lens on the optical axis.
20. The imaging lens according to claim 1 , wherein the aperture diaphragm is placed between the top position of the object-side surface of the first lens and an edge position of the object-side surface of the first lens on the optical axis.
21. The imaging lens according to claim 1 , further satisfying conditional expression (4′):
1.7<f3/f<3.0 (4′)
wherein f3 represents a focal length of the third lens.
22. The imaging lens according to claim 1 , wherein the aperture diaphragm is disposed toward the image side with respect to the top position of the object-side surface of the first lens.