Imaging lens
An imaging lens includes a first lens; a second lens; a third lens; a fourth lens; a fifth lens; a sixth lens; a seventh lens; an eighth lens; and a ninth lens having negative refractive power, arranged in this order from an object side to an image plane side. The imaging lens has a total of nine lenses. The first lens is formed in a shape so that a surface thereof on the image plane side has an aspherical shape. The ninth lens is formed in a shape so that a surface thereof on the image plane side has an aspherical shape.
1. An imaging lens comprising:
a first lens;
a second lens;
a third lens;
a fourth lens;
a fifth lens;
a seventh lens;
an eighth lens; and
a ninth lens having negative refractive power, arranged in this order from an object side to an image plane side,
wherein said imaging lens has a total of nine lenses,
said first lens is formed in a shape so that a surface thereof on the image plane side has an aspherical shape, and
said ninth lens is formed in a shape so that a surface thereof on the image plane side has an aspherical shape.
2. The imaging lens according to claim 1 , wherein said first lens, said second lens, and said third lens have a composite focal length f123 so that the following conditional expression is satisfied:
0.5< f 123/ f< 2.5,
where f is a focal length of a whole lens system.
3. The imaging lens according to claim 1 , wherein said seventh lens, said eighth lens, and said ninth lens have a composite focal length f789 so that the following conditional expression is satisfied:
f 789<0.
4. 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:
−6< f 3/ f 2<−0.2.
5. The imaging lens according to claim 1 , wherein said seventh lens has a thickness T7 near an optical axis thereof, and said eighth lens has a thickness T8 near an optical axis thereof so that the following conditional expression is satisfied:
0.5< T 8/ T 7<4.
6. The imaging lens according to claim 1 , wherein said ninth lens is formed in the shape so that the surface thereof on the image plane side has a paraxial curvature radius R9r so that the following conditional expression is satisfied:
0.2< R 9 r/f< 0.6,
where f is a focal length of a whole lens system.
7. The imaging lens according to claim 1 , wherein said ninth lens has a focal length f9 so that the following conditional expression is satisfied:
−2< f 9/ f<− 0.2,
where f is a focal length of a whole lens system.
8. An imaging lens comprising:
a first lens;
a second lens;
a third lens;
a fourth lens;
a fifth lens;
a sixth lens;
a seventh lens;
an eighth lens; and
a ninth lens having negative refractive power, arranged in this order from an object side to an image plane side,
wherein said imaging lens has a total of nine lenses,
said eighth lens has at least one aspheric surface,
said ninth lens is formed in a shape so that a surface thereof on the image plane side has an aspherical shape, and
said seventh lens, said eighth lens, and said ninth lens have a composite focal length f789 so that the following conditional expression is satisfied:
f 789<0.
9. The imaging lens according to claim 8 , wherein said first lens, said second lens, and said third lens have a composite focal length f123 so that the following conditional expression is satisfied:
0.5< f 123/ f< 2.5,
where f is a focal length of a whole lens system.
10. The imaging lens according to claim 8 , 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:
−6< f 3/ f 2<−0.2.
11. The imaging lens according to claim 8 , wherein said seventh lens has a thickness T7 near an optical axis thereof, and said eighth lens has a thickness T8 near an optical axis thereof so that the following conditional expression is satisfied:
0.5<T8/T7<4.
12. The imaging lens according to claim 8 , wherein said ninth lens is formed in the shape so that the surface thereof on the image plane side has a paraxial curvature radius R9r so that the following conditional expression is satisfied:
0.2< R 9 r/f< 0.6,
where f is a focal length of a whole lens system.
13. The imaging lens according to claim 8 , wherein said ninth lens has a focal length f9 so that the following conditional expression is satisfied:
−2< f 9/ f<− 0.2,
where f is a focal length of a whole lens system.
14. An imaging lens comprising:
a first lens;
a second lens;
a third lens;
a fourth lens;
a fifth lens;
a sixth lens;
a seventh lens;
an eighth lens; and
a ninth lens having negative refractive power, arranged in this order from an object side to an image plane side,
wherein said imaging lens has a total of nine lenses,
said eighth lens has at least one aspheric surface,
said ninth lens is formed in a shape so that a surface thereof on the image plane side has an aspherical shape, and
said seventh lens has a thickness T7 near an optical axis thereof, and said eighth lens has a thickness T8 near an optical axis thereof so that the following conditional expression is satisfied:
0.5< T 8/ T 7<4.
15. The imaging lens according to claim 14 , wherein said first lens, said second lens, and said third lens have a composite focal length f123 so that the following conditional expression is satisfied:
0.5< f 123/ f< 2.5,
where f is a focal length of a whole lens system.
16. The imaging lens according to claim 14 , wherein said seventh lens, said eighth lens, and said ninth lens have a composite focal length f789 so that the following conditional expression is satisfied:
f 789<0.
17. 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:
−6< f 3/ f 2<−0.2.
18. The imaging lens according to claim 14 , wherein said ninth lens is formed in the shape so that the surface thereof on the image plane side has a paraxial curvature radius R9r so that the following conditional expression is satisfied:
0.2< R 9 r/f< 0.6,
where f is a focal length of a whole lens system.
19. The imaging lens according to claim 14 , wherein said ninth lens has a focal length f9 so that the following conditional expression is satisfied:
−2< f 9/ f<− 0.2,
where f is a focal length of a whole lens system.
20. The imaging lens according to claim 14 , wherein said first lens has an Abbe's number νd1 so that the following conditional expression is satisfied:
35<ν d 1<80.