Imaging lens and imaging apparatus including the same
View Patent ↗The imaging lens substantially consists of a first lens having a biconvex shape, a second lens having a negative refractive power, a third lens having a negative refractive power and a convex surface that faces the object side, a fourth lens having a positive refractive power, and a fifth lens having a negative refractive power, of which at least one of the object-side surface and the image-side surface has at least one inflection point, in this order from the object side; and wherein conditional expression (1A): −0.38<f/f45<−0.01 is satisfied. This conditional expression is related to the focal length f of the entire system and the combined focal length f45 of the fourth lens and the fifth lens.
1. An imaging lens substantially consisting of five lenses, including:
a first lens of being a biconvex shape;
a second lens having a negative refractive power;
a third lens having a negative refractive power and a convex surface that faces the object side;
a fourth lens having a positive refractive power;
a fifth lens having a negative refractive power, of which at least one surface of an object-side surface and an image-side surface has at least one inflection point, in this order from the object side; and
wherein conditional expressions (1A) and (2) below are satisfied:
−0.38< f/f 45<−0.01 (1A), where
f: the focal length of the entire system, and
f45: the combined focal length of the fourth lens and the fifth lens, and
1.7<( R 2 f−R 2 r )/( R 2 f+R 2 r ) (2), where
R2f: the paraxial radius of curvature of the object-side surface of the second lens, and
R2r: the paraxial radius of curvature of the image-side surface of the second lens.
2. The imaging lens of claim 1 , wherein the fifth lens is of a biconcave shape.
3. The imaging lens of claim 1 , wherein conditional expression below is further satisfied:
−0.27< f/f 45<−0.015 (1A-1).
4. The imaging lens of claim 1 , wherein conditional expression is further satisfied:
−0.25< f/f 45<−0.02 (1 A -2).
5. The imaging lens of claim 1 , wherein the second lens is of a biconcave shape.
6. The imaging lens of claim 1 , wherein the fourth lens is of a meniscus shape having a convex surface that faces the image side.
7. The imaging lens of claim 1 , wherein an aperture stop is provided between the object-side surface of the first lens L1 and the object-side surface of the second lens L2.
8. The imaging lens of claim 1 , wherein conditional expression below is further satisfied:
0< f/f 4<1.9 (3), where
f4: the focal length of the fourth lens.
9. The imaging lens of claim 1 , wherein conditional expression below is further satisfied:
1.7<( R 2 f−R 2 r )/( R 2 f+R 2 r )<4 (2-1), where
R2f: the paraxial radius of curvature of the object-side surface of the second lens, and
R2r: the paraxial radius of curvature of the image-side surface of the second lens.
10. The imaging lens of claim 1 , wherein conditional expression below is further satisfied:
1.8<( R 2 f−R 2 r )/( R 2 f+R 2 r )<3.5 (2-2), where
R2f: the paraxial radius of curvature of the object-side surface of the second lens, and
R2r: the paraxial radius of curvature of the image-side surface of the second lens.
11. The imaging lens of claim 1 , wherein conditional expression below is further satisfied:
0< f/f 4<1.8 (3-1), where
f4: the focal length of the fourth lens.
12. The imaging lens of claim 1 , wherein conditional expression below is further satisfied:
0< f/f 4<1.75 (3-2), where
f4: the focal length of the fourth lens.
13. An imaging apparatus, including the imaging lens of claim 1 .
14. The imaging lens substantially consisting of five lenses, including:
a first lens of being a biconvex shape;
a second lens having a negative refractive power;
a third lens having a negative refractive power and a convex surface that faces the object side;
a fourth lens having a positive refractive power;
a fifth lens having a biconcave shape, of which at least one surface of an object-side surface and an image-side surface has at least one inflection point, in this order from the object side; and
wherein conditional expressions (1B) and (2) below are satisfied:
f/f 45<0 (1B), where
f: the focal length of the entire system, and
f45: the combined focal length of the fourth lens and the fifth lens, and
1.7<( R 2 f−R 2 r )/( R 2 f+R 2 r ) (2), where
R2f: the paraxial radius of curvature of the object-side surface of the second lens, and
R2r: the paraxial radius of curvature of the image-side surface of the second lens.
15. The imaging lens of claim 14 , wherein conditional expression below is further satisfied:
−2< f/f 45<0 (1B-1).
16. The imaging lens of claim 14 , wherein conditional expression below is further satisfied:
−1< f/f 45<0 (1B-2).
17. An imaging apparatus, including: The the imaging lens of claim 14 .