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 negative refractive power and a seventh lens.
1. An imaging lens comprising:
a first lens group having positive composite refractive power;
a second lens group having negative composite refractive power; and
a third lens group having negative composite 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, and
said third lens group includes a sixth lens having negative refractive power and a seventh lens.
2. 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
where f is a focal length of a whole lens system.
3. 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
where f is a focal length of a whole lens system.
4. 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.
5. 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.
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 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.
7. 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.
8. 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, 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,
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 second lens is formed in a shape so that a surface on the object side thereof has a positive curvature radius,
said third lens is formed in a shape so that a surface on the object side thereof has a positive curvature radius,
said fifth lens is formed in a shape so that a surface on the image plane side thereof has a positive curvature radius, and
said seventh lens is formed in a shape so that a surface on the image plane side thereof has a positive curvature radius.
9. The imaging lens according to claim 8 , 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
where f is a focal length of a whole lens system.
10. The imaging lens according to claim 8 , wherein said first lens has a focal length f1 so that the following conditional expression is satisfied:
0.5< f 1/ f< 2.0
where f is a focal length of a whole lens system.
11. The imaging lens according to claim 8 , 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.
12. The imaging lens according to claim 8 , 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.
13. The imaging lens according to claim 8 , 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.
14. The imaging lens according to claim 8 , 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.
15. An imaging lens comprising:
a first lens group having positive refractive power;
a second lens group; and
a third lens group, 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,
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 fourth lens has a focal length f4 and said seventh lens has a focal length f7 so that the following conditional expressions are satisfied:
2< f 4/ f< 15
−8< f 7/ f<− 1
where f is a focal length of a whole lens system.
16. The imaging lens according to claim 15 , 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.
17. The imaging lens according to claim 15 , wherein said first lens has a focal length f1 so that the following conditional expression is satisfied:
0.5< f 1/ f< 2.0.
18. The imaging lens according to claim 15 , 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.
19. The imaging lens according to claim 15 , 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.
20. The imaging lens according to claim 15 , 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.
21. The imaging lens according to claim 15 , wherein said fifth lens has a focal length f5 so that the following conditional expression is satisfied:
−8< f 4/ f 5<−1.5.