Imaging lens
An imaging lens includes a first lens having at least one aspheric surface; a second lens having at least one aspheric surface; a third lens having at least one aspheric surface; a fourth lens having at least one aspheric surface; a fifth lens having at least one aspheric surface; a sixth lens having two aspheric surfaces; and a seventh lens having two aspheric surfaces, arranged in this order from an object side to an image plane side respectively with a space in between. The imaging lens has a total of seven lenses. The first lens is formed in a shape so that a surface on the object side is convex near an optical axis. The seventh lens is formed in a shape so that a surface on the image plane side is concave near the optical axis. The fifth lens and the sixth lens have specific Abbe's numbers.
1. An imaging lens comprising:
a first lens having at least one aspheric surface;
a second lens having at least one aspheric surface;
a third lens having at least one aspheric surface;
a fourth lens having at least one aspheric surface;
a fifth lens having at least one aspheric surface;
a sixth lens having two aspheric surfaces; and
a seventh lens having two aspheric surfaces, arranged in this order from an object side to an image plane side respectively with a space in between,
wherein said imaging lens has a total of seven lenses,
said first lens is formed in a shape so that a surface thereof on the object side is convex near an optical axis thereof,
said seventh lens is formed in a shape so that a surface thereof on the image plane side is concave near an optical axis thereof, and
said fifth lens has an Abbe's number νd5 and said sixth lens has an Abbe's number νd6 so that the following conditional expressions are satisfied:
20<ν d 5<35,
20<ν d 6<35.
2. The imaging lens according to claim 1 , wherein said first lens has an Abbe's number νd1, said second lens has an Abbe's number νd2, and said third lens has an Abbe's number νd3 so that the following conditional expressions are satisfied:
40<ν d 1<75,
20<ν d 2<35,
40<ν d 3<75.
3. The imaging lens according to claim 1 , wherein said fourth lens has an Abbe's number νd4 so that the following conditional expression is satisfied:
40<ν d 4<75.
4. The imaging lens according to claim 1 , wherein said seventh lens has an Abbe's number νd7 so that the following conditional expression is satisfied:
40<ν d 7<75.
5. The imaging lens according to claim 1 , wherein said first lens has a focal length f1 and said third lens has a focal length f3 so that the following conditional expression is satisfied:
0.3< f 3/ f 1<3.0.
6. The imaging lens according to claim 1 , wherein said second lens has a focal length f2 and said third lens has a focal length f3 so that the following conditional expression is satisfied:
−3.0< f 2/ f 3<−0.3.
7. The imaging lens according to claim 1 , wherein said fourth lens has a focal length f4 so that the following conditional expression is satisfied:
4.5< f 4/ f< 9.0,
where f is a focal length of a whole lens system.
8. The imaging lens according to claim 1 , wherein said third lens is disposed away from the fourth lens by a distance D34 on an optical axis so that the following conditional expression is satisfied:
0.05< D 34/ f< 0.3,
where f is a focal length of a whole lens system.
9. The imaging lens according to claim 1 , wherein said fifth lens is disposed away from the sixth lens by a distance D56 on an optical axis so that the following conditional expression is satisfied:
0.05< D 56 /f< 0.25,
where f is a focal length of a whole lens system.
10. The imaging lens according to claim 1 , wherein said seventh lens has a focal length f7 so that the following conditional expression is satisfied:
−4.0< f 7/ f<− 1.0,
where f is a focal length of a whole lens system.
11. An imaging lens comprising:
a first lens having at least one aspheric surface and positive refractive power;
a second lens having at least one aspheric surface;
a third lens having at least one aspheric surface;
a fourth lens having at least one aspheric surface;
a fifth lens having at least one aspheric surface;
a sixth lens having two aspheric surfaces; and
a seventh lens having two aspheric surfaces and negative refractive power, arranged in this order from an object side to an image plane side respectively with a space in between,
wherein said imaging lens has a total of seven lenses, and
said fifth lens has an Abbe's number νd5 and said sixth lens has an Abbe's number νd6 so that the following conditional expressions are satisfied:
20<ν d 5<35,
20<ν d 6<35.
12. The imaging lens according to claim 11 , wherein said first lens has an Abbe's number νd1, said second lens has an Abbe's number νd2, and said third lens has an Abbe's number νd3 so that the following conditional expressions are satisfied:
40<ν d 1<75,
20<ν d 2<35,
40<ν d 3<75.
13. The imaging lens according to claim 11 , wherein said fourth lens has an Abbe's number νd4 so that the following conditional expression is satisfied:
40<ν d 4<75.
14. The imaging lens according to claim 11 , wherein said seventh lens has an Abbe's number νd7 so that the following conditional expression is satisfied:
40<ν d 7<75.
15. The imaging lens according to claim 11 , wherein said first lens has a focal length f1 and said third lens has a focal length f3 so that the following conditional expression is satisfied:
0.3< f 3/ f 1<3.0.
16. The imaging lens according to claim 11 , wherein said second lens has a focal length f2 and said third lens has a focal length f3 so that the following conditional expression is satisfied:
−3.0< f 2/ f 3<−0.3.
17. The imaging lens according to claim 11 , wherein said fourth lens has a focal length f4 so that the following conditional expression is satisfied:
4.5< f 4/ f< 9.0,
where f is a focal length of a whole lens system.
18. The imaging lens according to claim 11 , wherein said third lens is disposed away from the fourth lens by a distance D34 on an optical axis so that the following conditional expression is satisfied:
0.05< D 34/ f< 0.3,
where f is a focal length of a whole lens system.
19. The imaging lens according to claim 11 , wherein said fifth lens is disposed away from the sixth lens by a distance D56 on an optical axis so that the following conditional expression is satisfied:
0.05< D 56/ f< 0.25,
where f is a focal length of a whole lens system.
20. The imaging lens according to claim 11 , wherein said seventh lens has a focal length f7 so that the following conditional expression is satisfied:
−4.0< f 7/ f<− 1.0,
where f is a focal length of a whole lens system.