Imaging lens
An imaging lens includes 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. The first lens is formed in a shape so that a surface thereof on the object side is convex near an optical axis thereof. The seventh lens is formed in a shape so that a surface thereof on the image plane side is concave near the optical axis thereof. The first lens and the sixth lens have specific Abbe's numbers.
1. 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 and negative refractive power, 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 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 the optical axis thereof, and
said first lens has an Abbe's number νd1, said fourth lens has an Abbe's number νd4, and said sixth lens has an Abbe's number νd6 so that the following conditional expressions are satisfied:
40 <νd 1<75,
40 <νd 4<75,
20 <νd 6<35.
2. 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.
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:
−3.0< f 2/ f 3<−0.3.
4. 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
where f is a focal length of a whole lens system.
5. 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
where f is a focal length of a whole lens system.
6. 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,
wherein 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 sixth lens is formed in a shape so that a surface thereof on the image plane side is concave near the optical axis thereof,
said seventh lens is formed in a shape so that a surface thereof on the image plane side is concave near the optical axis thereof, and
said first lens has an Abbe's number νd1, said second lens has an Abbe's number νd2, and said fifth lens has an Abbe's number νd5 so that the following conditional expressions are satisfied:
40<ν d 1<75,
20<ν d 2<35,
20<ν d 5<35.
7. The imaging lens according to claim 6 , 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.
8. The imaging lens according to claim 6 , 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.
9. The imaging lens according to claim 6 , wherein said fourth lens has a focal length f4 so that the following conditional expression is satisfied:
4.5< f 4/ f< 9.0
where f is a focal length of a whole lens system.
10. The imaging lens according to claim 6 , wherein said seventh lens has a focal length f7 so that the following conditional expression is satisfied:
−4.0< f 7/ f<− 1.0
where f is a focal length of a whole lens system.
11. An imaging lens comprising:
a first lens having positive refractive power and 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,
wherein said first lens is formed in a shape so that a surface thereof on the object side and a surface thereof on the image plane side are convex near an optical axis thereof,
said second lens is formed in a shape so that a surface thereof on the object side is convex near the optical axis thereof,
said fourth lens is formed in a meniscus shape so that a surface thereof on the object side is concave near the optical axis thereof, and
said seventh lens is formed in a shape so that a surface thereof on the image plane side is concave near the optical axis thereof.
12. 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:
0.3< f 3/ f 1<3.0.
13. The imaging lens according to claim 11 , 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.
14. The imaging lens according to claim 11 , wherein said fourth lens has a focal length f4 so that the following conditional expression is satisfied:
4.5< f 4/ f< 9.0
where f is a focal length of a whole lens system.
15. The imaging lens according to claim 11 , wherein said seventh lens has a focal length f7 so that the following conditional expression is satisfied:
−4.0< f 7/ f<− 1.0
where f is a focal length of a whole lens system.
16. An imaging lens comprising:
a first lens having positive refractive power and at least one aspheric surface;
a second lens having negative refractive power and 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,
wherein said first lens is formed in a meniscus shape so that a surface thereof on the object side is convex near an optical axis thereof,
said second lens is formed in a shape so that a surface thereof on the image plane side is concave near the optical axis thereof,
said third lens is formed in a shape so that a surface thereof on the object side is convex near the optical axis thereof,
said fourth lens is formed in a meniscus shape so that a surface thereof on the object side is concave near the optical axis thereof,
said seventh lens is formed in a shape so that a surface thereof on the image plane side is concave near the optical axis thereof, and
said fourth lens has an Abbe's number νd4 so that the following conditional expression is satisfied:
40<ν d 4<75.
17. The imaging lens according to claim 16 , 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.
18. The imaging lens according to claim 16 , 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.
19. The imaging lens according to claim 16 , wherein said fourth lens has a focal length f4 so that the following conditional expression is satisfied:
4.5< f 4/ f< 9.0
where f is a focal length of a whole lens system.
20. The imaging lens according to claim 16 , wherein said seventh lens has a focal length f7 so that the following conditional expression is satisfied:
−4.0< f 7/ f<− 1.0
where f is a focal length of a whole lens system.