Imaging lens
An imaging lens includes a first lens group having positive refractive power; a second lens group having positive 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 negative refractive power. The second lens group includes a fourth lens and a fifth lens. The third lens group includes a sixth lens and a seventh lens. The first to third lenses have specific Abbe's numbers.
1. An imaging lens comprising:
a first lens group having positive refractive power;
a second lens group having positive 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 negative refractive power,
said second lens group includes a fourth lens and a fifth lens,
said third lens group includes a sixth lens and a seventh lens, and
said sixth lens and said seventh lens have a composite focal length f 67 , 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:
−1.7< f 67/ f<− 0.5,
40<ν d 1<75,
20<ν d 2<35,
20<ν d 3<35,
where f is a focal length of a whole lens system.
2. The imaging lens according to claim 1 , wherein said first lens has a focal length f 1 , and said second lens and said third lens have a composite focal length f 23 so that the following conditional expression is satisfied:
−4.0< f 23/ f 1<−1.5.
3. The imaging lens according to claim 1 , wherein said second lens has a focal length f 2 , and said third lens has a focal length f 3 so that the following conditional expression is satisfied:
0.1< f 2/ f 3<0.6.
4. The imaging lens according to claim 1 , wherein said fourth lens has positive refractive power, and
said fourth lens has a focal length f 4 so that the following conditional expression is satisfied:
1.0< f 4/ f< 3.0.
5. The imaging lens according to claim 1 , wherein said seventh lens has negative refractive power, and
said seventh lens has a focal length f 7 so that the following conditional expression is satisfied:
−4.0< f 7/ f<− 0.8.
6. The imaging lens according to claim 1 , wherein said third lens is disposed away from said fourth lens by a distance D 34 on an optical axis thereof so that the following conditional expression is satisfied:
0.03< D 34/ f< 0.2
7. An imaging lens comprising:
a first lens group having positive refractive power;
a second lens group having positive 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 consists of a first lens having positive refractive power, a second lens having negative refractive power, and a third lens having negative refractive power,
said second lens group includes a fourth lens and a fifth lens,
said third lens group includes a sixth lens and a seventh lens, and
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,
20<ν d 2<35,
20<ν d 3<35.
8. The imaging lens according to claim 7 , wherein said first lens has a focal length f 1 , and said second lens and said third lens have a composite focal length f 23 so that the following conditional expression is satisfied:
−4.0< f 23/ f 1<−1.5.
9. The imaging lens according to claim 7 , wherein said second lens has a focal length f 2 , and said third lens has a focal length f 3 so that the following conditional expression is satisfied:
0.1< f 2/ f 3<0.6.
10. The imaging lens according to claim 7 , wherein said sixth lens and said seventh lens have a composite focal length f 67 so that the following conditional expression is satisfied:
−1.7< f 67/ f <−0.5,
where f is a focal length of a whole lens system.
11. The imaging lens according to claim 7 , wherein said fourth lens has positive refractive power, and
said fourth lens has a focal length f 4 so that the following conditional expression is satisfied:
1.0< f 4/ f< 3.0,
where f is a focal length of a whole lens system.
12. The imaging lens according to claim 7 , wherein said seventh lens has negative refractive power, and
said seventh lens has a focal length f 7 so that the following conditional expression is satisfied:
−4.0< f 7/ f<− 0.8,
where f is a focal length of a whole lens system.
13. The imaging lens according to claim 7 , wherein said third lens is disposed away from said fourth lens by a distance D 34 on an optical axis thereof so that the following conditional expression is satisfied:
0.03< D 34/ f< 0.2,
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 positive 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 negative refractive power,
said second lens group includes a fourth lens and a fifth lens,
said third lens group includes a sixth lens and a seventh lens having negative refractive power, and
said seventh lens has a focal length f 7 , 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:
−4.0< f 7/ f<− 0.8,
40<ν d 1<75,
20<ν d 2<35,
20<ν d 3<35,
where f is a focal length of a whole lens system.
15. The imaging lens according to claim 14 , wherein said first lens has a focal length f 1 , and said second lens and said third lens have a composite focal length f 23 so that the following conditional expression is satisfied:
−4.0< f 23/ f 1<−1.5.
16. The imaging lens according to claim 14 , wherein said second lens has a focal length f 2 , and said third lens has a focal length f 3 so that the following conditional expression is satisfied:
0.1< f 2/ f 3<0.6.
17. The imaging lens according to claim 14 , wherein said sixth lens and said seventh lens have a composite focal length f 67 so that the following conditional expression is satisfied:
−1.7< f 67/ f<− 0.5.
18. The imaging lens according to claim 14 , wherein said fourth lens has positive refractive power, and
said fourth lens has a focal length f 4 so that the following conditional expression is satisfied:
1.0< f 4/ f< 3.0.
19. The imaging lens according to claim 14 , wherein said seventh lens has a focal length f 7 so that the following conditional expression is satisfied:
−4.0< f 7/ f<− 0.8.
20. The imaging lens according to claim 14 , wherein said third lens is disposed away from said fourth lens by a distance D 34 on an optical axis thereof so that the following conditional expression is satisfied:
0.03< D 34/ f< 0.2.