Imaging lens
An imaging lens includes a stop; a first lens; a second lens; a third lens having positive refractive power; a fourth lens; a fifth lens having positive refractive power; and a sixth lens, arranged in this order from an object side to an image plane side. The fourth lens is formed in a shape so that a surface thereof on the image plane side is convex near an optical axis thereof. The sixth lens is formed in a shape so that a surface thereof on the image plane side is concave near an optical axis thereof. The second lens is formed in a shape so that a surface thereof on the object side and a surface thereof on the image plane side have specific curvature radii.
1. An imaging lens comprising:
a stop;
a first lens;
a second lens;
a third lens having positive refractive power;
a fourth lens;
a fifth lens having positive refractive power; and
a sixth lens, arranged in this order from an object side to an image plane side,
wherein said fourth lens is formed in a shape so that a surface thereof on the image plane side is convex near an optical axis thereof,
said sixth lens is formed in a shape so that a surface thereof on the image plane side is concave near an optical axis thereof, and
said second lens is formed in a shape so that a surface thereof on the object side has a curvature radius R2f and a surface thereof on the image plane side has a curvature radius R2r, and said third lens has a focal length f3 so that the following conditional expressions are satisfied:
0.4< R 2 r/R 2 f< 0.8,
0.5< f 3/ f< 2.0,
where f is a focal length of a whole lens system.
2. The imaging lens according to claim 1 , wherein said first lens has a focal length f1 and said second lens has a focal length f2 so that the following conditional expression is satisfied:
−1.5 <f 1 /f 2<−0.4.
3. The imaging lens according to claim 1 , wherein said fifth lens has a focal length f5 and said sixth lens has a focal length f6 so that the following conditional expression is satisfied:
−2.0 <f 5 /f 6<−0.5.
4. An imaging lens comprising:
a first lens;
a second lens;
a third lens having positive refractive power;
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 first lens is formed in a shape so that a surface thereof on the object side is convex near an optical axis thereof,
said fourth lens is formed in a meniscus shape near the optical axis thereof,
said sixth lens is formed in a shape so that a surface thereof on the image plane side is concave near an optical axis thereof, and
said third lens has a focal length f3, said fourth lens has a focal length f4, said fifth lens has a focal length f5, and said sixth lens has a focal length f6 so that the following conditional expressions are satisfied:
0.5< f 3/ f< 2.0,
−5.0< f 4/ f<− 1.0,
−2.0< f 5/ f 6<−0.5,
where f is a focal length of a whole lens system.
5. The imaging lens according to claim 4 , wherein said first lens has a focal length f1 and said second lens has a focal length f2 so that the following conditional expression is satisfied:
−1.5 <f 1 /f 2<−0.4.
6. The imaging lens according to claim 4 , wherein said second lens is formed in a shape so that a surface thereof on the object side has a curvature radius R2f and a surface thereof on the image plane side has a curvature radius R2r so that the following conditional expression is satisfied:
0.4 <R 2 r/R 2 f< 0.8.
7. An imaging lens comprising:
a stop;
a first lens;
a second lens;
a third lens having positive refractive power;
a fourth lens;
a fifth lens having positive refractive power; and
a sixth lens, arranged in this order from an object side to an image plane side,
wherein said fourth lens is formed in a shape so that a surface thereof on the image plane side is convex near an optical axis thereof,
said sixth lens is formed in a shape so that a surface thereof on the image plane side is concave near an optical axis thereof, and
said second lens is formed in a shape so that a surface thereof on the object side has a curvature radius R2f and a surface thereof on the image plane side has a curvature radius R2r, and said fourth lens has a focal length f4 so that the following conditional expressions are satisfied:
0.4< R 2 r/R 2 f< 0.8,
−5.0< f 4/ f<− 1.0,
where f is a focal length of a whole lens system.
8. The imaging lens according to claim 7 , wherein said first lens has a focal length f1 and said second lens has a focal length f2 so that the following conditional expression is satisfied:
−1.5 <f 1 /f 2<−0.4.
9. The imaging lens according to claim 7 , wherein said third lens has a focal length f3 so that the following conditional expression is satisfied:
0.5 <f 3 /f< 2.0.
10. The imaging lens according to claim 7 , wherein said fifth lens has a focal length f5 and said sixth lens has a focal length f6 so that the following conditional expression is satisfied:
−2.0 <f 5 /f 6<−0.5.