Imaging lens
An imaging lens includes a first lens having positive refractive power; a second lens; a third lens; a fourth lens; a fifth lens; a sixth lens; and a seventh lens having negative refractive power, arranged in this order from an object side to an image plane side. The seventh lens is formed in a meniscus shape near an optical axis thereof. The fourth lens has a specific focal length.
1. An imaging lens comprising:
a first lens having positive refractive power;
a second lens;
a third lens;
a fourth lens;
a fifth lens;
a sixth lens; and
a seventh lens having negative refractive power, arranged in this order from an object side to an image plane side,
wherein said seventh lens is formed in a meniscus shape near an optical axis thereof, and
said fourth lens has a focal length f4 so that the following conditional expression is satisfied:
2< f 4/ f< 15,
where f is a focal length of a whole lens system.
2. The imaging lens according to claim 1 , wherein said first lens, said second lens, said third lens, said fourth lens, said fifth lens, said sixth lens, and said seventh lens are arranged respectively with a space in between.
3. The imaging lens according to claim 1 , wherein said third lens is disposed away from the fourth lens by a distance D34 on an optical axis so that the following conditional expression is satisfied:
0.05< D 34/ f< 0.2.
4. The imaging lens according to claim 1 , wherein said first lens has a focal length f1 so that the following conditional expression is satisfied:
0.5< f 1/ f< 2.0.
5. 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:
−4< f 2/ f 1<−0.5.
6. 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:
0.5< f 3/ f 1<4.
7. 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 and said seventh lens have a composite focal length f67 so that the following conditional expression is satisfied:
0.5< f 45/ f 67<5.
8. The imaging lens according to claim 1 , wherein said fourth lens and said fifth lens have a composite focal length f45 so that the following conditional expression is satisfied:
−7< f 45/ f<− 1.5.
9. The imaging lens according to claim 1 , wherein said fourth lens has a focal length f4 and said fifth lens has a focal length f5 so that the following conditional expression is satisfied:
−8< f 4/ f 5<−1.5.
10. The imaging lens according to claim 1 , wherein said seventh lens has a focal length f7 so that the following conditional expression is satisfied:
−8< f 7/ f<− 1.
11. 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 having negative refractive power, arranged in this order from an object side to an image plane side,
wherein said seventh lens is formed in a meniscus shape near an optical axis thereof, and
said first lens has an Abbe's number νd1 and said fourth lens has a focal length f4 so that the following conditional expressions are satisfied:
40<ν d 1<75,
2 < f 4/ f< 15,
where f is a focal length of a whole lens system.
12. The imaging lens according to claim 11 , wherein said first lens, said second lens, said third lens, said fourth lens, said fifth lens, said sixth lens, and said seventh lens are arranged respectively with a space in between.
13. The imaging lens according to claim 11 , wherein said third lens is disposed away from the fourth lens by a distance D34 on an optical axis so that the following conditional expression is satisfied:
0.05< D 34/ f< 0.2.
14. The imaging lens according to claim 11 , wherein said first lens has a focal length f1 so that the following conditional expression is satisfied:
0.5< f 1/ f< 2.0.
15. The imaging lens according to claim 11 , 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:
−4< f 2/ f 1<−0.5.
16. 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:
0.5< f 3/ f 1<4.
17. The imaging lens according to claim 11 , wherein 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 expression is satisfied:
0.5< f 45/ f 67<5.
18. The imaging lens according to claim 11 , wherein said fourth lens and said fifth lens have a composite focal length f45 so that the following conditional expression is satisfied:
−7< f 45/ f<− 1.5.
19. The imaging lens according to claim 11 , wherein said fourth lens has a focal length f4 and said fifth lens has a focal length f5 so that the following conditional expression is satisfied:
−8< f 4/ f 5<−1.5.
20. The imaging lens according to claim 11 , wherein said seventh lens has a focal length f7 so that the following conditional expression is satisfied:
−8< f 7/ f<− 1.