Imaging lens
An imaging lens includes a first lens group having positive refractive power; a second lens group having negative refractive power; and a third lens group having negative refractive power, arranged in this order from an object side to an image plane side. The first lens group includes a first lens having positive refractive power, a second lens having negative refractive power, and a third lens having positive refractive power. The second lens group includes a fourth lens and a fifth lens. The third lens group includes a sixth lens having positive refractive power and a seventh lens having negative refractive power. The first to third lenses and the sixth to seventh lenses have specific Abbe's numbers.
1. An imaging lens comprising:
a first lens group having positive refractive power;
a second lens group having negative refractive power; and
a third lens group having negative refractive power, arranged in this order from an object side to an image plane side,
wherein said first lens group includes a first lens having positive refractive power, a second lens having negative refractive power, and a third lens having positive refractive power,
said second lens group includes a fourth lens and a fifth lens,
said third lens group includes a sixth lens having positive refractive power and a seventh lens having negative refractive power,
said fourth lens is formed in a meniscus shape so that a concave surface thereof faces the object side near an optical axis thereof,
said first lens has an Abbe's number νd1, said second lens has an Abbe's number νd2, said third lens has an Abbe's number νd3, said sixth lens has an Abbe's number νd6, and said seventh lens has an Abbe's number νd7 so that the following conditional expressions are satisfied:
40<ν d 1<75,
20<ν d 2<35,
40<ν d 3<75,
40<ν d 6<75,
20 <ν d 7<35, and
said fourth lens has a focal length f4 so that the following conditional expression is satisfied:
−15< f 4/ f<− 3
where f is a focal length of a whole lens system.
2. The imaging lens according to claim 1 , wherein said fourth lens has negative refractive power,
said fifth lens has negative refractive power, and
said fourth lens has an Abbe's number νd4 and said fifth lens has an Abbe's number νd5 so that the following conditional expressions are satisfied:
20<ν d 4<35
20<ν d 5<35.
3. The imaging lens according to claim 1 , wherein said fifth lens is disposed away from the sixth lens by a distance D56 on an optical axis so that the following conditional expression is satisfied:
0.02< D 56/ f< 0.15.
4. The imaging lens according to claim 1 , wherein said first lens, said second lens, and said third lens have a composite focal length f123 so that the following conditional expression is satisfied:
0.6< f 123/ f< 1.2.
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:
−15< f 67/ f<− 1.5.
6. 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 has a focal length f6 so that the following conditional expression is satisfied:
−2< f 45/ f 6<−0.1.
7. An imaging lens comprising:
a first lens group having positive refractive power;
a second lens group having negative refractive power; and
a third lens group having negative refractive power, arranged in this order from an object side to an image plane side,
wherein said first lens group includes a first lens having positive refractive power, a second lens having negative refractive power, and a third lens having positive refractive power,
said second lens group includes a fourth lens and a fifth lens,
said third lens group includes a sixth lens having positive refractive power and a seventh lens having negative refractive power,
said third lens is formed in a meniscus shape so that a convex surface thereof faces the object side near an optical axis thereof,
said fourth lens is formed in a meniscus shape so that a concave surface thereof faces the object side near an optical axis thereof, and
said first lens has an Abbe's number νd1, said second lens has an Abbe's number νd2, said third lens has an Abbe's number νd3, said sixth lens has an Abbe's number νd6, and said seventh lens has an Abbe's number νd7 so that the following conditional expressions are satisfied:
40<ν d 1<75,
20<ν d 2<35,
40<ν d 3<75,
40<ν d 6<75,
20<ν d 7<35.
8. The imaging lens according to claim 7 , wherein said fourth lens has negative refractive power,
said fifth lens has negative refractive power, and
said fourth lens has an Abbe's number νd4 and said fifth lens has an Abbe's number νd5 so that the following conditional expressions are satisfied:
20<ν d 4<35
20<ν d 5<35.
9. The imaging lens according to claim 7 , wherein said fifth lens is disposed away from the sixth lens by a distance D56 on an optical axis so that the following conditional expression is satisfied:
0.02< D 56/ f< 0.15
where f is a focal length of a whole lens system.
10. The imaging lens according to claim 7 , wherein said first lens, said second lens, and said third lens have a composite focal length f123 so that the following conditional expression is satisfied:
0.6< f 123/ f< 1.2
where f is a focal length of a whole lens system.
11. 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:
−15< f 67/ f<− 1.5
where f is a focal length of a whole lens system.
12. The imaging lens according to claim 7 , wherein said fourth lens and said fifth lens have a composite focal length f45, and said sixth lens has a focal length f6 so that the following conditional expression is satisfied:
−2< f 45/ f 6<−0.1.
13. The imaging lens according to claim 7 , wherein said fourth lens has a focal length f4 so that the following conditional expression is satisfied:
−15< f 4/ f<− 3
where f is a focal length of a whole lens system.
14. An imaging lens comprising:
a first lens group having positive refractive power;
a second lens group having negative refractive power; and
a third lens group having negative refractive power, arranged in this order from an object side to an image plane side,
wherein said first lens group includes a first lens having positive refractive power, a second lens having negative refractive power, and a third lens having positive refractive power,
said second lens group includes a fourth lens and a fifth lens,
said third lens group includes a sixth lens having positive refractive power and a seventh lens having negative refractive power,
said third lens is formed in a meniscus shape so that a convex surface thereof faces the object side near an optical axis thereof,
said first lens has an Abbe's number νd1, said second lens has an Abbe's number νd2, said third lens has an Abbe's number νd3, said sixth lens has an Abbe's number νd6, and said seventh lens has an Abbe's number νd7 so that the following conditional expressions are satisfied:
40<ν d 1<75,
20<ν d 2<35,
40<ν d 3<75,
40<ν d 6<75,
20<ν d 7<35, and
said fifth lens is disposed away from the sixth lens by a distance D56 on an optical axis so that the following conditional expression is satisfied:
0.02< D 56/ f< 0.15
where f is a focal length of a whole lens system.
15. The imaging lens according to claim 14 , wherein said fourth lens has negative refractive power,
said fifth lens has negative refractive power, and
said fourth lens has an Abbe's number νd4 and said fifth lens has an Abbe's number νd5 so that the following conditional expressions are satisfied:
20<ν d 4<35
20<ν d 5<35.
16. The imaging lens according to claim 14 , wherein said first lens, said second lens, and said third lens have a composite focal length f123 so that the following conditional expression is satisfied:
0.6< f 123/ f< 1.2.
17. 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:
−15< f 67/ f<− 1.5.
18. The imaging lens according to claim 14 , wherein said fourth lens and said fifth lens have a composite focal length f45, and said sixth lens has a focal length f6 so that the following conditional expression is satisfied:
−2< f 45/ f 6<−0.1.
19. The imaging lens according to claim 14 , wherein said fourth lens has a focal length f4 so that the following conditional expression is satisfied:
−15< f 4/ f<− 3.