Imaging lens
An imaging lens includes 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. The imaging lens has a total of seven lenses. The fourth lens and the sixth lens have specific Abbe's numbers.
1. 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 fourth lens has an Abbe's number νd 4 and said sixth lens has an Abbe's number νd 6 so that the following conditional expressions are satisfied:
40<νd4<75,
20<νd6<35.
2. The imaging lens according to claim 1 , wherein said first lens has an Abbe's number νd 1 , said second lens has an Abbe's number νd 2 , and said third lens has an Abbe's number νd 3 so that the following conditional expressions are satisfied:
40<νd1<75,
20<νd2<35,
40<νd3<75.
3. The imaging lens according to claim 1 , wherein said seventh lens has an Abbe's number νd 7 so that the following conditional expression is satisfied:
40<νd7<75.
4. 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.
5. 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.
6. 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.
7. The imaging lens according to claim 1 , wherein said fourth lens and said fifth lens have a composite focal length f45 so that the following conditional expression is satisfied:
1.5< f 45/ f< 5.0,
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 D 34 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 D 56 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;
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 fourth lens is formed in a shape so that a surface thereof on the image plane side is convex near an optical axis thereof,
said seventh lens has negative refractive power, and
said fourth lens has an Abbe's number νd 4 and said sixth lens has an Abbe's number νd 6 so that the following conditional expressions are satisfied:
40<νd4<75,
20<νd6<35.
12. The imaging lens according to claim 11 , wherein said first lens has an Abbe's number νd 1 , said second lens has an Abbe's number νd 2 , and said third lens has an Abbe's number νd 3 so that the following conditional expressions are satisfied:
40<νd1<75,
20<νd2<35,
40<νd3<75.
13. The imaging lens according to claim 11 , wherein said seventh lens has an Abbe's number νd 7 so that the following conditional expression is satisfied:
40<νd7<75.
14. 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.
15. 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.
16. 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.
17. The imaging lens according to claim 11 , wherein said fourth lens and said fifth lens have a composite focal length f45 so that the following conditional expression is satisfied:
1.5< f 45/ f< 5.0,
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 D 34 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 D 56 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.