Imaging lens
An imaging lens includes an aperture stop, a positive first lens with a biconvex shape, a negative second lens; a negative third lens, a positive fourth lens, and a negative fifth lens arranged in this order from an object side. When the whole lens system has a focal length f, focal lengths and Abbe's numbers of the first and the second lenses are f1, νd1, f2, and νd2, focal lengths of the fourth and fifth lenses are f4 and f5, a composite focal length of the first lens L 1 and the second lens L 2 is f12, and a distance from a surface of the first lens L 1 on the object side to a surface of the fifth lens L 5 on the image side is Σd, the imaging lens satisfies the following conditional expressions: 0.7<f12/f<1.4 0.2<|f1/f2|<0.6 15<νd1−νd2 0.4<f4/f<1.0 Σd/f<1.2 |f5/f|<1.0
1. An imaging lens, comprising:
a first lens having positive refractive power;
a second lens having negative refractive power;
a third lens having negative refractive power;
a fourth lens having positive refractive power; and
a fifth lens having negative refractive power in this order from an object side to an image side,
wherein said first lens is a biconvex lens,
said second lens has a concave surface facing the object side,
said third lens is a meniscus lens having a concave surface facing the object side, and
said fifth lens is a biconcave lens.
2. The imaging lens according to claim 1 , wherein said first lens and said second lens have a composite focal length f12 and a whole lens system has a focal length f so that the following conditional expression is satisfied:
0.7<f12/f<1.4.
3. The imaging lens according to claim 1 , wherein said first lens has a focal length f1 and said second lens has a focal length f2 so that the following conditional expression is satisfied:
0.2<f1/f21<0.6.
4. The imaging lens according to claim 1 , wherein said first lens has an Abbe's number νd1 and said second lens has an Abbe's number νd2 so that the following conditional expression is satisfied:
15<νd1−νd2.
5. The imaging lens according to claim 1 , wherein said fourth lens has a focal length f4 and a whole lens system has a focal length f so that the following conditional expression is satisfied:
0.4<f4/f<1.0.
6. The imaging lens according to claim 1 , wherein said first lens and said fifth lens are arranged so that a surface of the first lens on the object side is away from a surface of the fifth lens on the image side by a distance Σd on an optical axis and a whole lens system has a focal length f so that the following conditional expression is satisfied:
Σd/f<1.2.
7. The imaging lens according to claim 1 , wherein said fifth lens has a focal length f5 and a whole lens system has a focal length f so that the following conditional expression is satisfied:
|f5/f|<1.0.
8. An imaging lens, comprising:
a first lens having positive refractive power;
a second lens having negative refractive power;
a third lens having negative refractive power;
a fourth lens having positive refractive power; and
a fifth lens having negative refractive power in this order from an object side to an image side,
wherein said first lens is a biconvex lens,
said second lens has a concave surface facing the object side,
said third lens is a meniscus lens having a concave surface facing the object side, and
said fourth lens has a focal length f4 and a whole lens system has a focal length f so that the following conditional expression is satisfied:
0.4<f4/f<1.0.
9. The imaging lens according to claim 8 , wherein said first lens and said second lens have a composite focal length f12 and a whole lens system has a focal length f so that the following conditional expression is satisfied:
0.7<f12/f<1.4.
10. The imaging lens according to claim 8 , wherein said first lens has a focal length f1 and said second lens has a focal length f2 so that the following conditional expression is satisfied:
0.2<|f1/f2|<0.6.
11. The imaging lens according to claim 8 , wherein said first lens has an Abbe's number νd1 and said second lens has an Abbe's number νd2 so that the following conditional expression is satisfied:
15<νd1−νd2.
12. The imaging lens according to claim 8 , wherein said first lens and said fifth lens are arranged so that a surface of the first lens on the object side is away from a surface of the fifth lens on the image side by a distance Σd on an optical axis and a whole lens system has a focal length f so that the following conditional expression is satisfied:
Σd/f<1.2.
13. The imaging lens according to claim 8 , wherein said fifth lens has a focal length f5 and a whole lens system has a focal length f so that the following conditional expression is satisfied:
|f5/f1<1.0.
14. An imaging lens, comprising:
a first lens having positive refractive power;
a second lens having negative refractive power;
a third lens having negative refractive power;
a fourth lens having positive refractive power; and
a fifth lens having negative refractive power in this order from an object side to an image side,
wherein said first lens is a biconvex lens,
said second lens has a concave surface facing the object side,
said third lens is a meniscus lens having a concave surface facing the object side, and
said fifth lens has a focal length f5 and a whole lens system has a focal length f so that the following conditional expression is satisfied:
|f5/f1<1.0.
15. The imaging lens according to claim 14 , wherein said first lens and said second lens have a composite focal length f12 and a whole lens system has a focal length f so that the following conditional expression is satisfied:
0.7<f12/f<1.4.
16. The imaging lens according to claim 14 , wherein said first lens has a focal length f1 and said second lens has a focal length f2 so that the following conditional expression is satisfied:
0.2<|f1/f21<0.6.
17. The imaging lens according to claim 14 , wherein said first lens has an Abbe's number νd1 and said second lens has an Abbe's number νd2 so that the following conditional expression is satisfied:
15<νd1−νd2.
18. The imaging lens according to claim 14 , wherein said fourth lens has a focal length f4 and a whole lens system has a focal length f so that the following conditional expression is satisfied:
0.4<f4/f<1.0.
19. The imaging lens according to claim 14 , wherein said first lens and said fifth lens are arranged so that a surface of the first lens on the object side is away from a surface of the fifth lens on the image side by a distance Σd on an optical axis and a whole lens system has a focal length f so that the following conditional expression is satisfied:
Σd/f<1.2.
20. An imaging lens, comprising:
a first lens;
a second lens having negative refractive power;
a third lens;
a fourth lens; and
a fifth lens having negative refractive power, arranged in this order from an object side to an image side,
wherein said fourth lens has a convex surface facing the image side,
said fifth lens has a concave surface facing the image side, said concave surface being formed in an aspheric shape having an inflection point,
said first lens has a focal length f1 and said second lens has a focal length f2 so that the following conditional expression is satisfied:
0.2<|f1/f2|<0.6,
and
said first lens and said fifth lens are arranged so that a surface of the first lens on the object side is away from a surface of the fifth lens on the image side by a distance Σd on an optical axis and a whole lens system has a focal length f so that the following conditional expression is satisfied:
Σd/f<1.2.
21. The imaging lens according to claim 20, wherein said fourth lens has positive refractive power.
22. The imaging lens according to claim 20, wherein said first lens and said second lens have a composite focal length f12 so that the following conditional expression is satisfied:
0.7<f12/f<1.4.
23. The imaging lens according to claim 20, wherein said first lens has an Abbe's number νd1 and said second lens has an Abbe's number νd2 so that the following conditional expression is satisfied:
15<νd1−νd2.
24. The imaging lens according to claim 20, wherein said fourth lens has a focal length f4 so that the following conditional expression is satisfied:
0.4<f4/f<1.0.
25. The imaging lens according to claim 20, wherein said fifth lens has a focal length f5 so that the following conditional expression is satisfied:
|f5/f|<1.0.
26. An imaging lens, comprising:
a first lens having positive refractive power;
a second lens;
a third lens;
a fourth lens having positive refractive power; and
a fifth lens having negative refractive power, arranged in this order from an object side to an image side,
said fifth lens has a concave surface facing the image side, said concave surface being formed in an aspheric shape having an inflection point,
said first lens and said second lens have a composite focal length f12 and a whole lens system has a focal length f so that the following conditional expression is satisfied:
0.7<f12/f<1.4,
and
said first lens and said fifth lens are arranged so that a surface of the first lens on the object side is away from a surface of the fifth lens on the image side by a distance Σd on an optical axis so that the following conditional expression is satisfied:
Σd/f<1.2.
27. The imaging lens according to claim 26, wherein said second lens has a concave surface facing the object side, and
said second lens has negative refractive power.
28. The imaging lens according to claim 26, wherein said third lens is formed in a meniscus shape and has a concave surface facing the object side, and
said third lens has negative refractive power.
29. The imaging lens according to claim 26, wherein said first lens has a focal length f1 and said second lens has a focal length f2 so that the following conditional expression is satisfied:
0.2<|f1/f2|<0.6.
30. The imaging lens according to claim 26, wherein said first lens has an Abbe's number νd1 and said second lens has an Abbe's number νd2 so that the following conditional expression is satisfied:
15<νd1−νd2.
31. The imaging lens according to claim 26, wherein said fourth lens has a focal length f4 so that the following conditional expression is satisfied:
0.4<f4/f<1.0.
32. The imaging lens according to claim 26, wherein said fifth lens has a focal length f5 so that the following conditional expression is satisfied:
|f5/f|<1.0.
33. An imaging lens, comprising:
a first lens;
a second lens having negative refractive power;
a third lens;
a fourth lens; and
a fifth lens having negative refractive power, arranged in this order from an object side to an image side,
wherein said second lens is formed in a meniscus shape,
said fourth lens has a convex surface facing the image side,
said fifth lens has a concave surface facing the image side, and
said concave surface is formed in an aspheric shape having an inflection point.
34. The imaging lens according to claim 33, wherein said first lens and said second lens have a composite focal length f12 and a whole lens system has a focal length f so that the following conditional expression is satisfied:
0.7<f12/f<1.4.
35. The imaging lens according to claim 33, wherein said first lens has a focal length f1 and said second lens has a focal length f2 so that the following conditional expression is satisfied:
0.2<|f1/f2|<0.6.
36. The imaging lens according to claim 33, wherein said fourth lens has a focal length f4 and a whole lens system has a focal length f so that the following conditional expression is satisfied:
0.4<f4/f<1.0.
37. The imaging lens according to claim 33, wherein said fifth lens has a focal length f5 and a whole lens system has a focal length f so that the following conditional expression is satisfied:
|f5/f|<1.0.