Imaging lens
An imaging lens includes a first lens having positive refractive power; 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, arranged in this order from an object side to an image plane side. The imaging lens has a total of nine lenses. The eighth lens has at least one aspheric surface. The ninth 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 the shape so that the surface thereof on the image plane side has a specific paraxial curvature radius.
1. An imaging lens comprising:
a first lens having positive refractive power;
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, 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 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.
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.
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 TB 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 has a focal length f9 so that the following conditional expression is satisfied:
−2< f 9/ f<− 0.2.
7. An imaging lens comprising:
a first lens;
a second lens;
a third lens;
a fourth lens having positive refractive power;
a fifth lens;
a sixth lens;
a seventh lens;
an eighth lens; and
a ninth lens, 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 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.
8. The imaging lens according to claim 7 , 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.
9. The imaging lens according to claim 7 , 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.
10. 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:
−6< f 3/ f 2<−0.2.
11. The imaging lens according to claim 7 , wherein said seventh lens has a thickness T7 near an optical axis thereof, and said eighth lens has a thickness TB near an optical axis thereof so that the following conditional expression is satisfied:
0.5< T 8/ T 7<4.
12. The imaging lens according to claim 7 , 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.
13. An imaging lens comprising:
a first lens;
a second lens;
a third lens;
a fourth lens having positive refractive power;
a fifth lens;
a sixth lens;
a seventh lens;
an eighth lens; and
a ninth lens, arranged in this order from an object side to an image plane side,
wherein said imaging lens has a total of nine lenses,
said ninth 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 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.
14. The imaging lens according to claim 13 , 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.
15. The imaging lens according to claim 13 , 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.
16. The imaging lens according to claim 13 , 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.
17. The imaging lens according to claim 13 , wherein said seventh lens has a thickness T7 near an optical axis thereof,
and said eighth lens has a thickness TB near an optical axis thereof so that the following conditional expression is satisfied:
0.5< T 8/ T 7<4.
18. The imaging lens according to claim 13 , wherein said ninth lens has a focal length f9 so that the following conditional expression is satisfied:
−2< f 9/ f<− 0.2.
19. The imaging lens according to claim 13 , wherein said first lens has an Abbe's number vdl so that the following conditional expression is satisfied:
35< vdl< 80.