Imaging lens
An imaging lens includes a first lens group having positive refractive power; a second lens group; 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, a second lens, and a third lens. The second lens group includes a fourth lens and a fifth lens. The third lens group includes a sixth lens and a seventh lens having negative refractive power. The first lens is formed in a meniscus shape at a paraxial region thereof. The fourth lens is formed in a meniscus shape at a paraxial region thereof. The seventh lens is formed in a meniscus shape at a paraxial region thereof. The seventh lens has a specific focal length. The second lens is disposed away from the third lens by a specific distance.
1. An imaging lens comprising:
a first lens group having positive refractive power;
a second lens group; 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, a second lens, and a third lens,
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,
said first lens is formed in a meniscus shape at a paraxial region thereof,
said fourth lens is formed in a meniscus shape at a paraxial region thereof,
said seventh lens is formed in a meniscus shape at a paraxial region thereof, and
said seventh lens has a focal length f7, and said second lens is disposed away from the third lens by a distance D23 on an optical axis thereof so that the following conditional expressions are satisfied:
2.38≤ f 7/ f< 0.8,
0.08≤ D 23/ f< 0.2,
where f is a focal length of a whole lens system.
2. 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:
0.1< f 2/ f 3<0.6.
3. The imaging lens according to claim 1 , wherein said fourth lens has a focal length f4 so that the following conditional expression is satisfied:
1.0 <f 4 /f< 3.0.
4. 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:
−1.7< f 67/ f<− 0.5.
5. 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 thereof so that the following conditional expression is satisfied:
0.03< D 34/ f< 0.2.
6. The imaging lens according to claim 1 , wherein said seventh lens has an Abbe's number νd7 so that the following conditional expression is satisfied:
40<ν d 7<75.
7. An imaging lens comprising:
a first lens group;
a second lens group; 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, a second lens, 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,
said first lens is formed in a meniscus shape at a paraxial region thereof,
said fourth lens is formed in a meniscus shape at a paraxial region thereof,
said seventh lens is formed in a meniscus shape at a paraxial region thereof, and
said second lens is disposed away from the third lens by a distance D23 on an optical axis thereof so that the following conditional expression is satisfied:
0.03< D 23/ f< 0.2,
where f is a focal length of a whole lens system.
8. The imaging lens according to claim 7 , 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:
0.1< f 2/ f 3<0.6.
9. The imaging lens according to claim 7 , wherein said fourth lens has a focal length f4 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.
10. The imaging lens according to claim 7 , wherein said seventh lens has a focal length f7 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.
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:
−1.7< f 67/ f<− 0.5,
where f is a focal length of a whole lens system.
12. The imaging lens according to claim 7 , wherein said third lens is disposed away from the fourth lens by a distance D34 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.
13. The imaging lens according to claim 7 , wherein said seventh lens has an Abbe's number νd7 so that the following conditional expression is satisfied:
40<ν d 7<75.
14. An imaging lens comprising:
a first lens group;
a second lens group; 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, a second lens, and a third lens,
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 at a paraxial region thereof,
said seventh lens is formed in a meniscus shape at a paraxial region thereof,
said seventh lens has a focal length f7, and
said third lens is disposed away from the fourth lens by a distance D34 on an optical axis thereof so that the following conditional expressions are satisfied:
−2.38≤ f 7/ f<− 0.8,
0.03< D 34/ f< 0.2,
where f is a focal length of a whole lens system.
15. The imaging lens according to claim 14 , 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:
0.1< f 2/ f 3<0.6.
16. The imaging lens according to claim 14 , wherein said fourth lens has a focal length f4 so that the following conditional expression is satisfied:
1.0< f 4/ f< 3.0.
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:
−1.7< f 67/ f<− 0.5.
18. The imaging lens according to claim 14 , wherein said second lens is disposed away from the third lens by a distance D23 on an optical axis thereof so that the following conditional expression is satisfied:
0.03< D 23/ f< 0.2.