Imaging lens
An imaging lens includes a first lens; 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. The sixth lens is formed in a shape so that a surface thereof on the image plane side and a surface thereof on the object side have positive curvature radii near an optical axis thereof. The seventh lens is formed in a shape so that a surface thereof on the image plane side has a positive curvature radius near an optical axis thereof. The seventh lens is formed in the shape so that the surface thereof on the image plane side is aspheric. The fourth lens has a specific focal length.
1. An imaging lens comprising:
a first lens;
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,
wherein said sixth lens is formed in a shape so that a surface thereof on the image plane side and a surface thereof on the object side have positive curvature radii near an optical axis thereof,
said seventh lens is formed in a shape so that a surface thereof on the image plane side has a positive curvature radius near an optical axis thereof,
said seventh lens is formed in the shape so that the surface thereof on the image plane side is aspheric, and
said fourth lens has a focal length f4 so that the following conditional expression is satisfied:
2< f 4/ f< 15,
where f is a focal length of a whole lens system.
2. The imaging lens according to claim 1 , wherein said first lens, said second lens, said third lens, said fourth lens, said fifth lens, said sixth lens, and said seventh lens are arranged respectively with a space in between.
3. 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< 0.2.
4. The imaging lens according to claim 1 , wherein said first lens has a focal length f1 so that the following conditional expression is satisfied:
0.5< f 1/ f< 2.0.
5. 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:
−4< f 2/ f 1<−0.5.
6. 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:
0.5< f 3/ f 1<4.
7. The imaging lens according to claim 1 , wherein said fourth lens and said fifth lens have a composite focal length f45 and said sixth lens and said seventh lens have a composite focal length f67 so that the following conditional expression is satisfied:
0.5< f 45/ f 67<5.
8. 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:
−7< f 45/ f<− 1.5.
9. The imaging lens according to claim 1 , wherein said fourth lens has a focal length f4 and said fifth lens has a focal length f5 so that the following conditional expression is satisfied:
−8< f 4/ f 5<−1.5.
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:
−8< f 7/ f<− 1.
11. An imaging lens comprising:
a first lens;
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,
wherein said sixth lens is formed in a shape so that a surface thereof on the object side has a positive curvature radius near an optical axis thereof,
said seventh lens is formed in a shape so that a surface thereof on the image plane side and a surface thereof on the object side have positive curvature radii near an optical axis thereof,
said seventh lens is formed in the shape so that the surface thereof on the image plane side is aspheric; and
said fourth lens has a focal length f4 so that the following conditional expression is satisfied:
2< f 4/ f< 15,
where f is a focal length of a whole lens system.
12. The imaging lens according to claim 11 , wherein said first lens, said second lens, said third lens, said fourth lens, said fifth lens, said sixth lens, and said seventh lens are arranged respectively with a space in between.
13. 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< 0.2.
14. The imaging lens according to claim 11 , wherein said first lens has a focal length f1 so that the following conditional expression is satisfied:
0.5< f 1/ f< 2.0.
15. The imaging lens according to claim 11 , 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:
−4< f 2/ f 1<−0.5.
16. 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:
0.5< f 3/ f 1<4.
17. The imaging lens according to claim 11 , wherein said fourth lens and said fifth lens have a composite focal length f45 and said sixth lens and said seventh lens have a composite focal length f67 so that the following conditional expression is satisfied:
0.5< f 45/ f 67<5.
18. 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:
−7< f 45/ f<− 1.5.
19. The imaging lens according to claim 11 , wherein said fourth lens has a focal length f4 and said fifth lens has a focal length f5 so that the following conditional expression is satisfied:
−8< f 4/ f 5<−1.5.
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:
−8< f 7/ f<− 1.