Imaging lens
An imaging lens includes a first lens group having positive refractive power and a second 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. The second lens group includes a front side lens group having negative refractive power and a rear side lens group having positive refractive power. The front side lens group includes a fourth lens and a fifth lens. The rear side lens group includes a sixth lens and a seventh lens. The first lens group is arranged to be away from the second lens group by a specific distance on an optical axis thereof. The first to third lenses have specific Abbe's numbers.
1. An imaging lens comprising:
a first lens group having positive refractive power; and
a second 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,
said second lens group includes a front side lens group having negative refractive power and a rear side lens group having positive refractive power,
said front side lens group includes a fourth lens and a fifth lens,
said rear side lens group includes a sixth lens and a seventh lens, and said first lens group is arranged to be away from the second lens group by a distance Da on an optical axis thereof, said first lens has an Abbe's number vd 1 , said second lens has an Abbe's number vd 2 , and said third lens has an Abbe's number vd 3 so that the following conditional expressions are satisfied:
05 <Da/f <0.3,
35<vd1<75,
15<vd2<35,
35<vd3<75,
where f is a focal length of a whole lens system.
2. The imaging lens according to claim 1 , wherein said third lens has positive refractive power, and
said fourth lens has negative refractive power.
3. The imaging lens according to claim 1 , wherein said sixth lens has positive refractive power, and
said seventh lens has negative refractive power.
4. 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:
0.6 <F 1/ f <1.3.
5. The imaging lens according to claim 1 , wherein said front side lens group has a focal length Ff and said rear side lens group has a focal length Fr so that the following conditional expression is satisfied:
−1.5 <Ff/Fr <−0.1.
6. The imaging lens according to claim 1 , wherein said front side lens group is arranged to be away from the rear side lens group by a distance Db on an optical axis thereof so that the following conditional expression is satisfied:
02 <Db/f <0.1.
7. The imaging lens according to claim 1 , wherein said rear side lens group has a focal length Fr so that the following conditional expression is satisfied:
1 <Fr/f <10.
8. The imaging lens according to claim 1 , wherein said fourth lens has a focal length f 4 so that the following conditional expression is satisfied:
−3 <f 4/ f <−1.
9. The imaging lens according to claim 1 , wherein said fourth lens has a focal length f 4 and said sixth lens has a focal length f 6 so that the following conditional expression is satisfied:
−1.3 <f 4/ f 6<−0.6.
10. The imaging lens according to claim 1 , wherein said second lens group has a focal length F 2 and said sixth lens has a focal length f 6 so that the following conditional expression is satisfied:
−1.5 <f 6/ F 2<−0.1.