Imaging lens
An imaging lens includes a first lens group and a second lens group, arranged in this order from an object side to an image plane side. The first lens group includes a first lens, a second lens, and a third lens having negative refractive power. The second lens group includes a fourth lens, a fifth lens having negative refractive power, and a sixth lens having negative refractive power. The fourth lens has a specific Abbe's number. The fifth lens has a specific Abbe's number.
1. An imaging lens comprising:
a first lens group; and
a second lens group, arranged in this order from an object side to an image plane side,
wherein said first lens group includes a first lens, a second lens, and a third lens having negative refractive power,
said second lens group includes a fourth lens, a fifth lens having negative refractive power, and a sixth lens having negative refractive power,
said imaging lens has a total of six single lenses, and
said fourth lens has an Abbe's number νd 4 and said fifth lens has an Abbe's number νd 5 so that the following conditional expressions are satisfied:
15<ν d 4<35,
40<ν d 5<75.
2. The imaging lens according to claim 1 , wherein said first lens group has positive refractive power and said second lens group has negative refractive power.
3. The imaging lens according to claim 1 , wherein said first lens has a focal length f 1 and said second lens has a focal length f 2 so that the following conditional expression is satisfied:
0.3< f 1/ f 2<0.9.
4. The imaging lens according to claim 1 , wherein said first lens has an Abbe's number νd 1 , said second lens has an Abbe's number νd 2 , and said third lens has an Abbe's number νd 3 so that the following conditional expressions are satisfied:
40<ν d 1<75,
40<ν d 2<75,
15<ν d 3<35.
5. The imaging lens according to claim 1 , wherein said first lens group has a focal length F 1 so that the following conditional expression is satisfied:
0.8< F 1/ f< 1.2,
where f is a focal length of a whole lens system.
6. The imaging lens according to claim 1 , wherein said second lens has a focal length f 2 so that the following conditional expression is satisfied:
1.0< f 2/ f< 2.0,
where f is a focal length of a whole lens system.
7. The imaging lens according to claim 1 , wherein said first lens has a focal length f 1 and said third lens has a focal length f 3 so that the following conditional expression is satisfied:
−1.2< f 1/ f 3<−0.4.
8. The imaging lens according to claim 1 , wherein said first lens group has a focal length F 1 and said second lens group has a focal length F 2 so that the following conditional expression is satisfied:
−12< F 2/ F 1<−1.5.
9. The imaging lens according to claim 1 , wherein said third lens is arranged away from the fourth lens by a distance D 34 on an optical axis thereof so that the following conditional expression is satisfied:
0.05< D 34/ f< 0.35,
where f is a focal length of a whole lens system.
10. The imaging lens according to claim 1 , wherein said sixth lens has an Abbe's number νd 6 so that the following conditional expression is satisfied:
40<ν d 6<75.
11. The imaging lens according to claim 1 , wherein said fourth lens has a focal length f 4 and said fifth lens has a focal length f 5 so that the following conditional expression is satisfied:
−15< f 5/ f 4<−5.
12. The imaging lens according to claim 1 , wherein said fifth lens and said sixth lens has a composite focal length f 56 so that the following conditional expression is satisfied:
−3< f 56/ f<− 0.8,
where f is a focal length of a whole lens system.
13. The imaging lens according to claim 1 , wherein said sixth lens has a focal length f 6 and said fifth lens and said sixth lens have a composite focal length f 56 so that the following conditional expression is satisfied:
0.7< f 6/ f 56<1.2.
14. The imaging lens according to claim 1 , wherein said sixth lens has a focal length f 6 so that the following conditional expression is satisfied:
−3.5< f 6/ f<− 0.5,
where f is a focal length of a whole lens system.