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 fifth lens is disposed away from the sixth lens by a specific distance on an optical axis. The second lens has a specific Abbe's number.
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 fifth lens is disposed away from the sixth lens by a distance D56 on an optical axis and said second lens has an Abbe's number νd2 so that the following conditional expressions are satisfied:
0.08≤ D 56/ f< 0.25,
20<ν d 2<35,
where f is a focal length of a whole lens system.
2. The imaging lens according to claim 1 , further comprising an aperture stop disposed between the first lens and the second lens.
3. 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.
4. 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.
5. 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.
6. 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.
7. 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.
8. 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 is disposed away from the sixth lens by a distance D56 on an optical axis and said second lens has an Abbe's number νd2 so that the following conditional expressions are satisfied:
0.08≤ D 56/ f< 0.25,
20<ν d 2<35,
where f is a focal length of a whole lens system.
9. The imaging lens according to claim 8 , further comprising an aperture stop disposed between the first lens and the second lens.
10. The imaging lens according to claim 8 , 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.
11. The imaging lens according to claim 8 , 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.
12. The imaging lens according to claim 8 , wherein said fourth lens has a focal length f4 so that the following conditional expression is satisfied:
4.5< f 4/ f< 9.0.
13. The imaging lens according to claim 8 , 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.
14. The imaging lens according to claim 8 , wherein said seventh lens has a focal length f7 so that the following conditional expression is satisfied:
−4.0< f 7/ f<− 1.0.
15. An imaging lens comprising:
a first lens having at least one aspheric surface and positive refractive power;
an aperture stop;
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 meniscus shape 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 third lens is disposed away from the fourth lens by a distance D34 on an optical axis and said second lens has an Abbe's number νd2 so that the following conditional expressions are satisfied:
0.05< D 34/ f< 0.3,
20<ν d 2<35,
where f is a focal length of a whole lens system.
16. The imaging lens according to claim 15 , 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.
17. The imaging lens according to claim 15 , 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.
18. The imaging lens according to claim 15 , wherein said fourth lens has a focal length f4 so that the following conditional expression is satisfied:
4.5< f 4/ f< 9.0.
19. The imaging lens according to claim 15 , 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.
20. The imaging lens according to claim 15 , wherein said seventh lens has a focal length f7 so that the following conditional expression is satisfied:
−4.0< f 7/ f<− 1.0.