Imaging lens
An imaging lens includes a first lens having positive refractive power; a second lens having negative refractive power; a third lens having positive refractive power; a fourth lens having positive refractive power; 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 ninth lens is formed in a shape so that a surface thereof on the image plane side has an aspherical shape having an inflection point.
1. An imaging lens comprising:
a first lens having positive refractive power;
a second lens having negative refractive power;
a third lens having positive refractive power;
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, and
said ninth lens is formed in a shape so that a surface thereof on the image plane side has an aspherical shape having an inflection point.
2. The imaging lens according to claim 1 , wherein said seventh lens has a thickness T7 on an optical axis thereof, and said eighth lens has a thickness T8 on an optical axis thereof so that the following conditional expression is satisfied:
0.5< T 8/ T 7<4.
3. The imaging lens according to claim 1 , wherein said eighth lens is disposed away from the ninth lens by a distance D89 on an optical axis thereof so that the following conditional expression is satisfied:
0.05< D 89/ f< 0.15,
where f is a focal length of a whole lens system.
4. 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.
5. 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.
6. The imaging lens according to claim 1 , wherein said first lens is arranged so that a surface thereof on the object side is away from an image plane by a distance TL on an optical axis thereof so that the following conditional expression is satisfied:
1.0< TL/f< 1.5,
where f is a focal length of a whole lens system.
7. The imaging lens according to claim 1 , wherein said first lens is arranged so that a surface thereof on the object side is away from an image plane by a distance TL on an optical axis thereof so that the following conditional expression is satisfied:
1.0< TL/H max<1.8,
where Hmax is a maximum image height of the image plane.
8. An imaging lens comprising:
a first lens having positive refractive power;
a second lens having negative refractive power;
a third lens having positive refractive power;
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 ninth lens is formed in a shape so that a surface thereof on the image plane side has an aspherical shape having an inflection point, and
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.
9. The imaging lens according to claim 8 , wherein said seventh lens has a thickness T7 on an optical axis thereof, and said eighth lens has a thickness T8 on an optical axis thereof so that the following conditional expression is satisfied:
0.5< T 8/ T 7<4.
10. The imaging lens according to claim 8 , wherein said eighth lens is disposed away from the ninth lens by a distance D89 on an optical axis thereof so that the following conditional expression is satisfied:
0.05< D 89/ f< 0.15.
11. 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.
12. The imaging lens according to claim 8 , wherein said first lens is arranged so that a surface thereof on the object side is away from an image plane by a distance TL on an optical axis thereof so that the following conditional expression is satisfied:
1.0< TL/f< 1.5.
13. The imaging lens according to claim 8 , wherein said first lens is arranged so that a surface thereof on the object side is away from an image plane by a distance TL on an optical axis thereof so that the following conditional expression is satisfied:
1.0< TL/H max<1.8,
where Hmax is a maximum image height of the image plane.
14. An imaging lens comprising:
a first lens having positive refractive power;
a second lens having negative refractive power;
a third lens having positive refractive power;
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 ninth lens is formed in a shape so that a surface thereof on the image plane side has an aspherical shape having an inflection point, and
said first lens is arranged so that a surface thereof on the object side is away from an image plane by a distance TL on an optical axis thereof so that the following conditional expression is satisfied:
1.0< TL/f< 1.5,
where f is a focal length of a whole lens system.
15. The imaging lens according to claim 14 , wherein said seventh lens has a thickness T7 on an optical axis thereof, and said eighth lens has a thickness T8 on an optical axis thereof so that the following conditional expression is satisfied:
0.5< T 8/ T 7<4.
16. The imaging lens according to claim 14 , wherein said eighth lens is disposed away from the ninth lens by a distance D89 on an optical axis thereof so that the following conditional expression is satisfied:
0.05< D 89/ f< 0.15.
17. 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.
18. 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.
19. The imaging lens according to claim 14 , wherein said first lens is arranged so that a surface thereof on the object side is away from an image plane by a distance TL on an optical axis thereof so that the following conditional expression is satisfied:
1.0< TL/H max<1.8,
where Hmax is a maximum image height of the image plane.