Imaging lens and imaging device provided with the same
View Patent ↗An imaging lens substantially consists of six lenses consisting of, in order from the object side: a first lens having a biconvex shape; a second lens having a negative refractive power; a third lens having a positive refractive power; a fourth lens having a positive refractive power; a fifth lens having a negative refractive power and having a concave surface toward the object side; and a sixth lens having a negative refractive power and having a concave surface toward the object side.
1. An imaging lens substantially consisting of six lenses consisting of, in order from an object side:
a first lens having a biconvex shape;
a second lens having a negative refractive power;
a third lens having a positive refractive power;
a fourth lens having a positive refractive power;
a fifth lens having a negative refractive power and having a concave surface toward the object side; and
a sixth lens having a negative refractive power and having a concave surface toward the object side,
wherein the condition expression below is satisfied:
−1< f×P 45<0 (4),
where f is a focal length of the entire system, and P45 is a refractive power of an air lens formed by an image-side surface of the fourth lens and an object-side surface of the fifth lens, where the refractive power of the air lens is calculated according to the equation (P) below:
P
45
=
1
-
Nd
4
L
4
r
+
Nd
5
-
1
L
5
f
-
(
1
-
Nd
4
)
×
(
Nd
5
-
1
)
×
D
9
L
4
r
×
L
5
f
(
P
)
where Nd4 is a refractive index with respect to the d-line of the fourth lens, Nd5 is a refractive index with respect to the d-line of the fifth lens, L4r is a paraxial radius of curvature of an image-side surface of the fourth lens, L5f is a paraxial radius of curvature of an object-side surface of the fifth lens, and D9 is an air space along the optical axis between the fourth lens and the fifth lens.
2. The imaging lens as claimed in claim 1 , wherein the sixth lens has a concave surface toward an image side.
3. The imaging lens as claimed in claim 1 , wherein the fifth lens has a convex surface toward an image side.
4. The imaging lens as claimed in claim 1 , wherein the second lens has a concave surface toward an image side.
5. The imaging lens as claimed in claim 1 , wherein the condition expression below is further satisfied:
0.7< f/f 1<5 (1),
where f is a focal length of the entire system, and f1 is a focal length of the first lens.
6. The imaging lens as claimed in claim 1 , wherein the condition expression below is further satisfied:
1.18< f/f 4<5 (2),
where f is a focal length of the entire system, and f4 is a focal length of the fourth lens.
7. The imaging lens as claimed in claim 1 , wherein the condition expression below is further satisfied:
−1.6<( L 6 r+L 6 f )/( L 6 r−L 6 f )<−0.7 (3),
where L6f is a paraxial radius of curvature of an object-side surface of the sixth lens, and L6r is a paraxial radius of curvature of an image-side surface of the sixth lens.
8. The imaging lens as claimed in claim 1 , wherein the condition expression below is further satisfied:
0< f 6/ f 5<0.11 (5),
where f5 is a focal length of the fifth lens, and f6 is a focal length of the sixth lens.
9. The imaging lens as claimed in claim 1 , wherein the condition expression below is further satisfied:
−3< f/f 5<−0.05 (6),
where f is a focal length of the entire system, and f5 is a focal length of the fifth lens.
10. The imaging lens as claimed in claim 1 , wherein the condition expression below is further satisfied:
−3< f/f 6<−1.47 (7),
where f is a focal length of the entire system, and f6 is a focal length of the sixth lens.
11. The imaging lens as claimed in claim 1 , wherein the condition expression below is further satisfied:
0.5< f ·tan ω/ L 6 r< 20 (8),
where f is a focal length of the entire system, ω is a half angle of view, and L6r is a paraxial radius of curvature of an image-side surface of the sixth lens.
12. The imaging lens as claimed in claim 1 , wherein the condition expression below is further satisfied:
0.5<( L 1 r+L 1 f )/( L 1 r−L 1 f )<1 (9),
where L1f is a paraxial radius of curvature of an object-side surface of the first lens, and L1r is a paraxial radius of curvature of an image-side surface of the first lens.
13. The imaging lens as claimed in claim 5 , wherein the condition expression below is further satisfied:
1.1< f/f 1<3 (1-1).
14. The imaging lens as claimed in claim 6 , wherein the condition expression below is further satisfied:
1.21< f/f 4<5 (2-1).
15. The imaging lens as claimed in claim 7 , wherein the condition expression below is further satisfied:
−0.92<( L 6 r+L 6 f )/( L 6 r−L 6 f )<−0.7 (3-1).
16. The imaging lens as claimed in claim 1 , wherein the condition expression below is further satisfied:
−0.88< f×P 45<0 (4-1).
17. The imaging lens as claimed in claim 8 , wherein the condition expression below is further satisfied:
0.035< f 6/ f 5<0.08 (5-1).
18. The imaging lens as claimed in claim 9 , wherein the condition expression below is further satisfied:
−0.19< f/f 5<−0.055 (6-1).
19. An imaging device comprising the imaging lens as claimed in claim 1 .