Imaging lens
An imaging lens includes a first lens having positive refractive power; a second lens; a third lens; a fourth lens; a fifth lens having positive refractive power; a sixth lens having negative refractive power; and a seventh lens, arranged in this order from an object side to an image plane side with a space between each of the lenses. The second lens is formed in a shape so that a surface thereof on the object side has a positive curvature radius. The third lens is formed in a shape so that a surface thereof on the image plane side has a positive curvature radius. The seventh lens has a specific Abbe's number. The sixth lens and the seventh lens have a specific composite focal length.
1. An imaging lens comprising:
a first lens having positive refractive power;
a second lens;
a third lens;
a fourth lens;
a fifth lens;
a sixth lens; and
a seventh lens, arranged in this order from an object side to an image plane side with a space between each of the lenses,
wherein
said third lens is formed in a shape so that a surface thereof on the image plane side has a positive curvature radius, and
said sixth lens has a focal length f6 and said seventh lens has a focal length f7, and said sixth lens and said seventh lens have a composite focal length f67 so that the following conditional expressions are satisfied:
0.02< f 7/ f 6<0.3,
−1.5< f 67/ f<− 0.5,
where f is a focal length of a whole lens system.
2. 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:
2.5< f 1/ f 2<30.
3. 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:
−1.0< f 2/ f 3<−0.2.
4. The imaging lens according to claim 1 , wherein said first lens and said second lens have a composite focal length f12 and said third lens has a focal length f3 so that the following conditional expression is satisfied:
−1.0< f 12/ f 3<−0.1.
5. 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:
−3< f 45/ f 67<−0.8.
6. The imaging lens according to claim 1 , said third lens is arranged to be away from the fourth lens by a distance D34 on an optical axis thereof so that the following conditional expression is satisfied:
0.03< D 34/ f< 0.2.
7. An imaging lens comprising:
a first lens having positive refractive power;
a second lens;
a third lens;
a fourth lens;
a fifth lens having positive refractive power;
a sixth lens having negative refractive power; and
a seventh lens, arranged in this order from an object side to an image plane side with a space between each of the lenses,
wherein said second lens is formed in a shape so that a surface thereof on the object side has a positive curvature radius,
said third lens is formed in a shape so that a surface thereof on the object side and a surface thereof on the image plane side have positive curvature radii, and
said seventh lens has an Abbe's number νd7, and said sixth lens and said seventh lens have a composite focal length f67 so that the following conditional expressions are satisfied:
40<ν d 7<75,
−1.5< f 67/ f<− 0.5,
where f is a focal length of a whole lens system.
8. The imaging lens according to claim 7 , 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:
2.5< f 1/ f 2<30.
9. The imaging lens according to claim 7 , 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:
−1.0< f 2/ f 3<−0.2.
10. The imaging lens according to claim 7 , wherein said first lens and said second lens have a composite focal length f12 and said third lens has a focal length f3 so that the following conditional expression is satisfied:
−1.0< f 12/ f 3<−0.1.
11. The imaging lens according to claim 7 , wherein said fourth lens and said fifth lens have a composite focal length f45 so that the following conditional expression is satisfied:
−3< f 45/ f 67<−0.8.
12. The imaging lens according to claim 7 , wherein said sixth lens has a focal length f6 and said seventh lens has a focal length f7 so that the following conditional expression is satisfied:
0.02< f 7/ f 6<0.3.
13. The imaging lens according to claim 7 , said third lens is arranged to be away from the fourth lens by a distance D34 on an optical axis thereof so that the following conditional expression is satisfied:
0.03< D 34/ f< 0.2.
14. An imaging lens comprising:
a first lens having positive refractive power;
a second lens;
a third lens;
a fourth lens;
a fifth lens having positive refractive power;
a sixth lens having negative refractive power; and
a seventh lens, arranged in this order from an object side to an image plane side with a space between each of the lenses,
wherein said second lens is formed in a shape so that a surface thereof on the object side has a positive curvature radius,
said third lens is formed in a shape so that a surface thereof on the image plane side has a positive curvature radius,
said sixth lens is formed in a shape so that a surface thereof on the image plane side has a positive curvature radius, and
said seventh lens has an Abbe's number νd7, and said sixth lens and said seventh lens have a composite focal length f67 so that the following conditional expressions are satisfied:
40<ν d 7<75,
−1.5< f 67/ f<− 0.5,
where f is a focal length of a whole lens system.
15. 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:
2.5< f 1/ f 2<30.
16. The imaging lens according to claim 14 , 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:
−1.0< f 2/ f 3<−0.2.
17. The imaging lens according to claim 14 , wherein said first lens and said second lens have a composite focal length f12 and said third lens has a focal length f3 so that the following conditional expression is satisfied:
−1.0< f 12/ f 3<−0.1.
18. The imaging lens according to claim 14 , wherein said fourth lens and said fifth lens have a composite focal length f45 so that the following conditional expression is satisfied:
−3< f 45/ f 67<−0.8.
19. The imaging lens according to claim 14 , wherein said sixth lens has a focal length f6 and said seventh lens has a focal length f7 so that the following conditional expression is satisfied:
0.02< f 7/ f 6<0.3.
20. The imaging lens according to claim 14 , said third lens is arranged to be away from the fourth lens by a distance D34 on an optical axis thereof so that the following conditional expression is satisfied:
0.03< D 34/ f< 0.2.