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 first lens is formed in a meniscus shape at a paraxial region thereof. The third lens is formed in a shape so that a surface thereof directing to the image plane side is concave at a paraxial region thereof. The fourth lens is formed in a meniscus shape at a paraxial region thereof. The seventh 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 first lens is formed in a meniscus shape at a paraxial region thereof,
said third lens is formed in a shape so that a surface thereof directing to the image plane side is concave at a paraxial region thereof,
said fourth lens is formed in a meniscus shape at a paraxial region thereof, and
said seventh lens has a focal length f7 and an Abbe's number νd7 so that the following conditional expressions are satisfied:
−4.0< f 7/ f<− 0.8, and
40<ν d 7<75,
where f is a focal length of a whole lens system.
2. 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:
0.1< f 2/ f 3<0.6.
3. The imaging lens according to claim 1 , wherein said fourth lens has a focal length f4 so that the following conditional expression is satisfied:
1.0< f 4/ f 3<3.0.
4. 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:
−1.7< f 67/ f<− 0.5.
5. The imaging lens according to claim 1 , wherein said second lens is disposed away from the third lens by a distance D23 on an optical axis thereof so that the following conditional expression is satisfied:
0.03< D 23/ f< 0.2.
6. The imaging lens according to claim 1 , wherein said third lens is disposed away from the fourth lens by a distance D34 on the optical axis thereof so that the following conditional expression is satisfied:
0.03< D 34/ f< 0.2.
7. An imaging lens comprising:
a stop;
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 fifth lens is formed in a shape so that a surface thereof directing to the object side is convex at a paraxial region thereof,
said seventh lens has a focal length f7, and said fourth lens has a focal length f4 so that the following conditional expressions are satisfied:
−4.0< f 7/ f<− 0.8, and
1.0< f 4/ f< 3.0,
where f is a focal length of a whole lens system.
8. 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:
0.1< f 2/ f 3<0.6.
9. The imaging lens according to claim 7 , wherein said sixth lens and said seventh lens have a composite focal length f67 so that the following conditional expression is satisfied:
−1.7< f 67/ f<− 0.5.
10. The imaging lens according to claim 7 , wherein said second lens is disposed away from the third lens by a distance D23 on an optical axis thereof so that the following conditional expression is satisfied:
0.03< D 23/ f< 0.2.
11. The imaging lens according to claim 7 , wherein said third lens is disposed 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.
12. The imaging lens according to claim 7 , wherein said seventh lens has an Abbe's number νd7 so that the following conditional expression is satisfied:
40<ν d 7<75.
13. An imaging lens comprising:
a stop;
a first lens;
a second lens;
a third lens;
a fourth lens;
a fifth lens having negative refractive power;
a sixth lens; and
a seventh lens, arranged in this order from an object side to an image plane side,
wherein said third lens is formed in a shape so that a surface thereof directing to the image plane side is concave at a paraxial region thereof,
said seventh lens has a focal length f7, and said third lens is disposed away from the fourth lens by a distance D34 on the optical axis thereof so that the following conditional expressions are satisfied:
−4.0< f 7/ f<− 0.8, and
0.03< D 34/ f< 0.2,
where f is a focal length of a whole lens system.
14. The imaging lens according to claim 13 , 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:
0.1< f 2/ f 3<0.6.
15. The imaging lens according to claim 13 , wherein said fourth lens has a focal length f4 so that the following conditional expression is satisfied:
1.0< f 4/ f 3<3.0.
16. The imaging lens according to claim 13 , wherein said sixth lens and said seventh lens have a composite focal length f67 so that the following conditional expression is satisfied:
−1.7< f 67/ f<− 0.5.
17. The imaging lens according to claim 13 , wherein said second lens is disposed away from the third lens by a distance D23 on an optical axis thereof so that the following conditional expression is satisfied:
0.03< D 23/ f< 0.2.