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 is concave at a paraxial region thereof. The seventh lens is formed in a shape so that a surface thereof on the image plane side is aspheric. The first lens and the second lens have a specific composite focal length. The third lens have a specific focal length. The fourth lens and the fifth lens have a specific composite focal length. The sixth lens and the seventh lens have a specific composite 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 is concave at a paraxial region thereof,
said seventh lens is formed in a shape so that a surface thereof on the image plane side is aspheric, and
said first lens and said second lens have a composite focal length f12, said third lens has a focal length f3, 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 expressions are satisfied:
−1.0< f 12/ f 3<−0.1,
−3< f 45/ f 67<−0.8.
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 first lens and said second lens have a composite focal length f12 so that the following conditional expression is satisfied:
0.5< f 12/ f< 1.1,
where f is a focal length of a whole lens system.
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:
−1.0< f 2/ f 3<−0.2.
5. The imaging lens according to claim 1 , wherein said sixth lens and said seventh lens have a composite focal length f67 so that the following conditional expression is satisfied:
−1.5< f 67/ f<− 0.5,
where f is a focal length of a whole lens system.
6. The imaging lens according to claim 1 , 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.
7. 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,
where f is a focal length of a whole lens system.
8. 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 first lens is formed in a shape so that a surface thereof on the image plane side is concave at a paraxial region thereof,
said sixth lens is formed in a shape so that a surface thereof on the object side is convex at a paraxial region thereof, and
said first lens has a focal length f1, said second lens has a focal length f2, said first lens and said second lens have a composite focal length f12, said third lens has a focal length f3, 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 expressions are satisfied:
2.5< f 1/ f 2<30,
−1.0< f 12/ f 3<−0.1,
−3< f 45/ f 67<−0.8.
9. The imaging lens according to claim 8 , wherein said first lens and said second lens have a composite focal length f12 so that the following conditional expression is satisfied:
0.5< f 12/ f< 1.1,
where f is a focal length of a whole lens system.
10. 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:
−1.0<f2/f3<−0.2.
11. The imaging lens according to claim 8 , wherein said sixth lens and said seventh lens have a composite focal length f67 so that the following conditional expression is satisfied:
−1.5< f 67/ f<− 0.5,
where f is a focal length of a whole lens system.
12. The imaging lens according to claim 8 , 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 8 , 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,
where f is a focal length of a whole lens system.
14. 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 second lens is formed in a shape so that a surface thereof on the object side is convex at a paraxial region thereof,
said sixth lens is formed in a shape so that a surface thereof on the object side is convex at a paraxial region thereof, and
said sixth lens has a focal length f6, said seventh lens has a focal length f7, said first lens and said second lens have a composite focal length f12, said third lens has a focal length f3, 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 expressions are satisfied:
0.02< f 7/ f 6<0.3,
−1.0< f 12/ f 3<−0.1,
−3< f 45/ f 67<−0.8.
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 first lens and said second lens have a composite focal length f12 so that the following conditional expression is satisfied:
0.5< f 12/ f< 1.1,
where f is a focal length of a whole lens system.
17. 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.
18. The imaging lens according to claim 14 , wherein said sixth lens and said seventh lens have a composite focal length f67 so that the following conditional expression is satisfied:
−1.5< f 67/ f<− 0.5,
where f is a focal length of a whole lens system.