Imaging lens and imaging apparatus equipped with the imaging lens
View Patent ↗An imaging lens consisting essentially of six lenses, composed of, in order from the object side, a first lens having a positive refractive power with a convex surface on the object side, 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 with a concave surface on the image side, and a sixth lens having a negative refractive power, in which predetermined conditional expressions are satisfied.
1. An imaging lens, consisting of six lenses, composed of, in order from the object side:
a first lens having a positive refractive power with a convex surface on the object side;
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 with a concave surface on the image side; and
a sixth lens having a negative refractive power,
wherein the following conditional expressions are satisfied:
0< f/f 1<1.22 (1)
−0.68< f/f 2<0 (2)
−0.15< f/L 6 f< 0.9 (3)
where:
f is the focal length of the entire system;
f 1 is the focal length of the first lens;
f 2 is the focal length of the second lens; and
L 6 f is the paraxial radius of curvature of the object side surface of the sixth lens.
2. The imaging lens of claim 1 , wherein the sixth lens has a concave surface on the image side.
3. The imaging lens of claim 1 , wherein the fourth lens has a meniscus shape with a concave surface on the object side.
4. The imaging lens of claim 1 , wherein the second lens has a meniscus shape with a convex surface on the object side.
5. The imaging lens of claim 1 , wherein the fifth lens has a biconcave shape.
6. The imaging lens of claim 1 , wherein the third lens has a convex shape on the object side.
7. The imaging lens of claim 1 , wherein the following conditional expression is further satisfied:
0.15< f/f 3<3 (4)
where f 3 is the focal length of the third lens.
8. The imaging lens of claim 1 , wherein the following conditional expression is further satisfied:
0.65< f/f 4<3 (5)
where f 4 is the focal length of the fourth lens.
9. The imaging lens of claim 1 , wherein the following conditional expression is further satisfied:
−3< f/f 6<−0.5 (6)
where f 6 is the focal length of the sixth lens.
10. The imaging lens of claim 1 , wherein the following conditional expression is further satisfied:
0.5<( L 1 r+L 1 f )/( L 1 r−L 1 f )<3 (7)
where:
L 1 f is the paraxial radius of curvature of the object side surface of the first lens; and
L 1 r is the paraxial radius of curvature of the image side surface of the first lens.
11. The imaging lens of claim 1 , wherein the following conditional expression is further satisfied:
−7.5<( L 4 r+L 4 f )/( L 4 r−L 4 f )<0 (9)
where:
L 4 f is the paraxial radius of curvature of the object side surface of the fourth lens; and
L 4 r is the paraxial radius of curvature of the image side surface of the fourth lens.
12. The imaging lens of claim 1 , wherein the following conditional expression is further satisfied:
−1.4< f·P 34<0 (10)
where P 34 is the refractive power of the air lens formed between the image side surface of the third lens and the object side surface of the fourth lens, and the refractive power of the air lens may be obtained by the following formula (P):
P
34
=
1
-
Nd
3
L
3
r
+
Nd
4
-
1
L
4
f
-
(
1
-
Nd
3
)
×
(
Nd
4
-
1
)
×
D
7
L
3
r
×
L
4
f
(
P
)
where:
Nd 3 is the refractive index of the third lens with respect to the d-line;
Nd 4 is the refractive index of the fourth lens with respect to the d-line;
L 3 r is the paraxial radius of curvature of the image side surface of the third lens;
L 4 f is the paraxial radius of curvature of the object side surface of the fourth lens; and
D 7 is the air space between the third lens and the fourth lens on the optical axis.
13. The imaging lens of claim 1 , wherein the following conditional expression is further satisfied:
0.5< f ·tan ω/ L 6 r< 20 (11)
where:
ω is the maximum half angle of view when an object at infinity is in focus; and
L 6 r is the paraxial radius of curvature of the image side surface of the sixth lens.
14. The imaging lens of claim 1 , wherein the following conditional expression is further satisfied:
0.31< f/f 1<1.2 (1-1).
15. The imaging lens of claim 1 , wherein the following conditional expression is further satisfied:
−0.68< f/f 2<−0.1 (2-1).
16. The imaging lens of claim 1 , wherein the following conditional expression is further satisfied:
−0.1< f/L 6 f< 0.9 (3-1).
17. The imaging lens of claim 7 , wherein the following conditional expression is further satisfied:
0.15< f/f 3<1.7 (4-1)
where f 3 is the focal length of the third lens.
18. The imaging lens of claim 8 , wherein the following conditional expression is further satisfied:
0.68< f/f 4<2.1 (5-1)
where f 4 is the focal length of the fourth lens.
19. An imaging apparatus equipped with the imaging lens of claim 1 .
20. An imaging lens, consisting of six lenses, composed of, in order from the object side:
a first lens having a positive refractive power with a convex surface on the object side;
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 with a concave surface on the image side; and
a sixth lens having a negative refractive power,
wherein the following conditional expressions are satisfied:
0< f/f 1<1.22 (1)
−0.68< f/f 2<0 (2)
−0.15< f/L 6 f< 1.25 (3)
where:
f is the focal length of the entire system;
f 1 is the focal length of the first lens;
f 2 is the focal length of the second lens; and
L 6 f is the paraxial radius of curvature of the object side surface of the sixth lens,
wherein the following conditional expression is further satisfied:
−0.55<( L 5 r+L 5 f )/( L 5 r−L 5 f )<1
where:
L 5 f is the paraxial radius of curvature of the object side surface of the fifth lens; and
L 5 r is the paraxial radius of curvature of the image side surface of the fifth lens.