Imaging lens
An imaging lens includes a first lens having negative refractive power; an aperture stop; a second lens; a third lens; a fourth lens having negative refractive power; a fifth lens; and a sixth lens, arranged in this order from an object side to an image plane side. The fifth lens is formed in a shape so that a surface thereof on the object side is convex at a paraxial region thereof. The sixth lens is formed in a meniscus shape at a paraxial region thereof. The first lens and the sixth lens have specific Abbe's numbers.
1. An imaging lens comprising:
a first lens having negative refractive power;
an aperture stop;
a second lens;
a third lens;
a fourth lens having negative refractive power;
a fifth lens; and
a sixth lens, arranged in this order from an object side to an image plane side,
wherein said fifth lens is formed in a shape so that a surface thereof on the object side is convex at a paraxial region thereof,
said sixth lens is formed in a meniscus shape at a paraxial region thereof, and
said first lens has an Abbe's number ν1, and said sixth lens has an Abbe's number ν6, and said first lens is disposed away from the second lens by a distance D12 on an optical axis thereof so that the following conditional expressions are satisfied:
40<ν1<75,
10<ν6<40,
0.05< D 12/ f< 0.8,
where f is a focal length of a whole lens system.
2. The imaging lens according to claim 1 , 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:
0.001< D 23/ f< 0.3,
where f is a focal length of a whole lens system.
3. The imaging lens according to claim 1 , wherein said first lens is disposed away from the second lens by a distance D12 on an optical axis 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:
2< D 12/ D 23<30.
4. The imaging lens according to claim 1 , wherein said second lens and said third lens have a composite focal length f23 so that the following conditional expression is satisfied:
0.2< f 23/ f< 1,
where f is a focal length of a whole lens system.
5. The imaging lens according to claim 1 , wherein said sixth lens has a focal length f6 so that the following conditional expression is satisfied:
−5< f 6/ f<− 0.5,
where f is a focal length of a whole lens system.
6. The imaging lens according to claim 1 , wherein said fifth lens has a thickness T5 on an optical axis thereof and said sixth lens has a thickness T6 on an optical axis thereof so that the following conditional expression is satisfied:
0.5< T 5/ T 6<3.5.
7. An imaging lens comprising:
a first lens having negative refractive power;
an aperture stop;
a second lens;
a third lens;
a fourth lens having negative refractive power;
a fifth lens; and
a sixth lens, arranged in this order from an object side to an image plane side,
wherein said third lens is formed in a shape so that a surface thereof on the object side is convex at a paraxial region thereof,
said fifth lens is formed in a shape so that a surface thereof on the object side is convex at a paraxial region thereof,
said sixth lens is formed in a meniscus shape at a paraxial region thereof, and
said sixth lens has an Abbe's number ν6, and said first lens is disposed away from the second lens by a distance D12 on an optical axis thereof so that the following conditional expressions are satisfied:
10<ν6<40,
0.05< D 12/ f< 0.8,
where f is a focal length of a whole lens system.
8. The imaging lens according to claim 7 , 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:
0.001< D 23/ f< 0.3,
where f is a focal length of a whole lens system.
9. The imaging lens according to claim 7 , wherein said first lens is disposed away from the second lens by a distance D12 on an optical axis 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:
2< D 12/ D 23<30.
10. The imaging lens according to claim 7 , wherein said second lens and said third lens have a composite focal length f23 so that the following conditional expression is satisfied:
0.2< f 23/ f< 1,
where f is a focal length of a whole lens system.
11. The imaging lens according to claim 7 , wherein said sixth lens has a focal length f6 so that the following conditional expression is satisfied:
−5< f 6/ f<− 0.5,
where f is a focal length of a whole lens system.
12. The imaging lens according to claim 7 , wherein said fifth lens has a thickness T5 on an optical axis thereof and said sixth lens has a thickness T6 on an optical axis thereof so that the following conditional expression is satisfied:
0.5< T 5/ T 6<3.5.
13. An imaging lens comprising:
a first lens having negative refractive power;
an aperture stop;
a second lens;
a third lens;
a fourth lens;
a fifth lens; and
a sixth lens, arranged in this order from an object side to an image plane side,
wherein said third lens is formed in a shape so that a surface thereof on the object side is convex at a paraxial region thereof,
said fourth lens is formed in a meniscus shape at a paraxial region thereof,
said fifth lens is formed in a shape so that a surface thereof on the object side is convex at a paraxial region thereof,
said sixth lens is formed in a meniscus shape at a paraxial region thereof, and
said sixth lens has an Abbe's number ν6, and said second lens and said third lens have a composite focal length f23 so that the following conditional expressions are satisfied:
10<ν6<40,
0.2< f 23/ f< 1,
where f is a focal length of a whole lens system.
14. The imaging lens according to claim 13 , wherein said first lens is disposed away from the second lens by a distance D12 on an optical axis thereof so that the following conditional expression is satisfied:
0.05< D 12/ f< 0.8,
where f is a focal length of a whole lens system.
15. The imaging lens according to claim 13 , 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:
0.001< D 23/ f< 0.3,
where f is a focal length of a whole lens system.
16. The imaging lens according to claim 13 , wherein said first lens is disposed away from the second lens by a distance D12 on an optical axis 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:
2< D 12/ D 23<30.
17. The imaging lens according to claim 13 , wherein said sixth lens has a focal length f6 so that the following conditional expression is satisfied:
−5< f 6/ f<− 0.5,
where f is a focal length of a whole lens system.