Imaging lens
An imaging lens includes a first lens having negative refractive power; a stop; a second lens having positive refractive power; a third lens having negative refractive power; and a fourth lens having positive refractive power, arranged in the order from an object side to an image plane side. The first lens has an object-side surface and an image plane-side surface, curvature radii of which are both negative. The second lens has an object-side surface and an image plane-side surface, curvature radii of which are both positive. The third lens has an object-side surface and an image plane-side surface, curvature radii of which are both negative. The fourth lens has an object-side surface, a curvature of which is positive.
1. An imaging lens comprising:
a first lens having negative refractive power;
a stop;
a second lens having positive refractive power;
a third lens having negative refractive power; and
a fourth lens having positive refractive power 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 concave and a surface thereof on the image plane side is convex,
said second lens is formed in a shape so that a surface thereof on the object side is convex and a surface thereof on the image plane side is concave,
said third lens is formed in a shape so that a surface thereof on the object side is concave and a surface thereof on the image plane side is convex,
said fourth lens is formed in a shape so that a surface thereof on the object side is convex, and
said first lens has a focal length f 1 and said second lens has a focal length f 2 so that the following conditional expression is satisfied:
−8.0< f 1/ f 2<−4.0.
2. An imaging lens comprising:
a first lens having negative refractive power;
a stop;
a second lens having positive refractive power;
a third lens having negative refractive power; and
a fourth lens having positive refractive power 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 concave and a surface thereof on the image plane side is convex,
said second lens is formed in a shape so that a surface thereof on the object side is convex and a surface thereof on the image plane side is concave,
said third lens is formed in a shape so that a surface thereof on the object side is concave and a surface thereof on the image plane side is convex,
said fourth lens is formed in a shape so that a surface thereof on the object side is convex, and
said second lens has the surface on the object side having a curvature radius R 2 f and the surface on the image plane side having a curvature radius R 2 r so that the following conditional expression is satisfied:
0.05< R 2 f/R 2 r< 0.15.
3. An imaging lens comprising:
a first lens having negative refractive power;
a stop;
a second lens having positive refractive power;
a third lens having negative refractive power; and
a fourth lens having positive refractive power 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 concave and a surface thereof on the image plane side is convex,
said second lens is formed in a shape so that a surface thereof on the object side is convex and a surface thereof on the image plane side is concave,
said third lens is formed in a shape so that a Surface thereof on the object side is concave and a surface thereof on the image plane side is convex,
said fourth lens is formed in a shape so that a surface thereof on the object side is convex, and
said first lens and said second lens have a composite focal length f 12 , and said third lens and said fourth lens have a composite focal length f 34 so that the following conditional expression is satisfied:
0.05< f 12/ f 34<0.20.
4. An imaging lens comprising:
a first lens having negative refractive power;
a stop;
a second lens having positive refractive power;
a third lens having negative refractive power; and
a fourth lens having positive refractive power 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 concave and a surface thereof on the image plane side is convex,
said second lens is formed in a shape so that a surface thereof on the object side is convex and a surface thereof on the image plane side is concave,
said third lens is formed in a shape so that a surface thereof on the object side is concave and a surface thereof on the image plane side is convex,
said fourth lens is formed in a shape so that a surface thereof on the image plane side is convex, and
said first lens has a focal length f 1 and said second lens has a focal length f 2 so that the following conditional expression is satisfied:
−8.0< f 1/ f 2<−4.0.
5. The imaging lens according to claim 1 , wherein said first lens has the surface on the object side having a curvature radius R 1 f and the surface on the image plane side having a curvature radius R 1 r so that the following conditional expression is satisfied:
0.5< R 1 f/R 1 r< 0.95.
6. The imaging lens according to claim 1 , wherein said second lens has the surface on the object side having a curvature radius R 2 f and the surface on the image plane side having a curvature radius R 2 r so that the following conditional expression is satisfied:
0.05< R 2 f/R 2 r< 0.15.
7. The imaging lens according to claim 1 , wherein said first lens and said second lens have a composite focal length f 12 , and said third lens and said fourth lens have a composite focal length f 34 so that the following conditional expression is satisfied:
0.05< f 12/ f 34<0.20.
8. The imaging lens according to claim 1 , wherein said second lens and said third lens have a composite focal length f 23 and f is a focal length of a whole lens system so that the following conditional expression is satisfied:
1.5< f 23/ f< 2.5.
9. The imaging lens according to claim 1 , wherein said first lens has an Abbe's number νd 1 , said second lens has an Abbe's number νd 2 , said third lens has an Abbe's number νd 3 , and said fourth lens has an Abbe's number νd 4 so that the following conditional expressions are satisfied:
45<ν d 1,ν d 2,ν d 4<75
20<ν d 3<40.
10. The imaging lens according to claim 2 , wherein said first lens has the surface on the object side having a curvature radius R 1 f and the surface on the image plane side having a curvature radius R 1 r so that the following conditional expression is satisfied:
0.5< R 1 f/R 1 r< 0.95.
11. The imaging lens according to claim 2 , wherein said first lens has a focal length f 1 and said second lens has a focal length f 2 so that the following conditional expression is satisfied:
−8.0< f 1/ f 2<−4.0.
12. The imaging lens according to claim 2 , wherein said first lens and said second lens have a composite focal length f 12 , and said third lens and said fourth lens have a composite focal length f 34 so that the following conditional expression is satisfied:
0.05< f 12/ f 34<0.20.
13. The imaging lens according to claim 12 , wherein said second lens and said third lens have a composite focal length f 23 and f is a focal length of a whole lens system so that the following conditional expression is satisfied:
1.5< f 23/ f< 2.5.
14. The imaging lens according to claim 2 , wherein said first lens has an Abbe's number νd 1 , said second lens has an Abbe's number νd 2 , said third lens has an Abbe's number νd 3 , and said fourth lens has an Abbe's number νd 4 so that the following conditional expressions are satisfied:
45<ν d 1,ν d 2,ν d 4<75
20<ν d 3<40.
15. The imaging lens according to claim 3 , wherein said first lens has the surface on the object side having a curvature radius R 1 f and the surface on the image plane side having a curvature radius R 1 r so that the following conditional expression is satisfied:
0.5< R 1 f/R 1 r< 0.95.
16. The imaging lens according to claim 3 , wherein said first lens has a focal length f 1 and said second lens has a focal length f 2 so that the following conditional expression is satisfied:
−8.0< f 1/ f 2<−4.0.
17. The imaging lens according to claim 3 , wherein said second lens has the surface on the object side having a curvature radius R 2 f and the surface on the image plane side having a curvature radius R 2 r so that the following conditional expression is satisfied:
0.05< R 2 f/R 2 r< 0.15.
18. The imaging lens according to claim 3 , wherein said second lens and said third lens have a composite focal length 123 and f is a focal length of a whole lens system so that the following conditional expression is satisfied:
1.5< f 23/ f< 2.5.
19. The imaging lens according to claim 3 , wherein said first lens has an Abbe's number νd 1 , said second lens has an Abbe's number νd 2 , said third lens has an Abbe's number νd 3 , and said fourth lens has an Abbe's number νd 4 so that the following conditional expressions are satisfied:
45<ν d 1,ν d 2,ν d 4<75
20<ν d 3<40.
20. The imaging lens according to claim 4 , wherein said first lens has the surface on the object side having a curvature radius R 1 f and the surface on the image plane side having a curvature radius R 1 r so that the following conditional expression is satisfied:
0.5< R 1 f/R 1 r< 0.95.
21. The imaging lens according to claim 4 , wherein said second lens has the surface on the object side having a curvature radius R 2 f and the surface on the image plane side having a curvature radius R 2 r so that the following conditional expression is satisfied:
0.05< R 2 f/R 2 r< 0.15.
22. The imaging lens according to claim 4 , said first lens and said second lens have a composite focal length f 12 , and said third lens and said fourth lens have a composite focal length f 34 so that the following conditional expression is satisfied:
0.05< f 12/ f 34<0.20.
23. The imaging lens according to claim 4 , wherein said second lens and said third lens have a composite focal length f 23 and f is a focal length of a whole lens system so that the following conditional expression is satisfied:
1.5< f 23/ f< 2.5.
24. The imaging lens according to claim 4 , wherein said first lens has an Abbe's number νd 1 , said second lens has an Abbe's number νd 2 , said third lens has an Abbe's number νd 3 , and said fourth lens has an Abbe's number νd 4 so that the following conditional expressions are satisfied:
45<ν d 1,ν d 2,ν d 4<75
20<ν d 3<40.