Imaging lens and imaging apparatus equipped with the imaging lens
View Patent ↗An imaging lens, substantially consisting of six lenses, composed of a first lens having a positive refractive power and a meniscus shape 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 and a biconcave shape, and a sixth lens having a negative refractive power, disposed in order from the object side.
1. An imaging lens consisting of six lenses:
a first lens having a positive refractive power and a meniscus shape 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 and a biconcave shape; and
a sixth lens having a negative refractive power, disposed in order from the object side,
wherein the imaging lens further satisfies a conditional expression given below:
−5.3<( L 4 r+L 4 f )/( L 4 r − L 4 f )<−3 (4)
where:
L 4 f: paraxial radius of curvature of the object side surface of the fourth lens
L 4 r: paraxial radius of curvature of the image side surface of the fourth lens.
2. The imaging lens as claimed in claim 1 , wherein the fourth lens has a meniscus shape with a concave surface on the object side.
3. The imaging lens as claimed in claim 1 , wherein the sixth lens has a meniscus shape with a concave surface on the image side.
4. The imaging lens as claimed in claim 1 , wherein the second lens has a biconcave shape.
5. The imaging lens as claimed in claim 1 , wherein the third lens has a convex surface on the object side.
6. The imaging lens as claimed in claim 1 , wherein the imaging lens further satisfies a conditional expression given below:
0.7< f/f 1<5 (1)
where:
f: focal length of the entire system
f 1 : focal length of the first lens.
7. The imaging lens as claimed in claim 1 , wherein the imaging lens further satisfies a conditional expression given below:
0< f/f 3<1.5 (2)
where:
f: focal length of the entire system
f 3 : focal length of the third lens.
8. The imaging lens as claimed in claim 1 , wherein the imaging lens further satisfies a conditional expression given below:
−2.4< f·P 34<−1 (3)
where:
f: focal length of the entire system
P 34 : refractive power of air lens formed by the image side surface of the third lens and the object side surface of the fourth lens, and can be obtained by a formula (P) given below:
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 : refractive index of the third lens with respect to the d-line
Nd 4 : refractive index of the fourth lens with respect to the d-line
L 3 r: paraxial radius of curvature of the image side surface of the third lens
L 4 f: paraxial radius of curvature of the object side surface of the fourth lens
D 7 : air distance on the optical axis between the third lens and the fourth lens.
9. The imaging lens as claimed in claim 1 , wherein the imaging lens further satisfies a conditional expression given below:
−2.6<( L 5 r+L 5 f )/( L 5 r − L 5 f )<3.8 (5)
where:
L 5 f: paraxial radius of curvature of the object side surface of the fifth lens
L 5 r: paraxial radius of curvature of the image side surface of the fifth lens.
10. The imaging lens as claimed in claim 1 , wherein the imaging lens further satisfies a conditional expression given below:
−0.67< f 4/ f 5<−0.35 (6)
where:
f 4 : focal length of the fourth lens
f 5 : focal length of the fifth lens.
11. The imaging lens as claimed in claim 1 , wherein the imaging lens further satisfies a conditional expression given below:
0.5< f ·tanω/ L 6 r< 20 (7)
where:
f: focal length of the entire system
ω: half angle of view
L 6 r: paraxial radius of curvature of the image side surface of the sixth lens.
12. The imaging lens as claimed in claim 1 , wherein a stop is disposed on the object side of the object side surface of the second lens.
13. The imaging lens as claimed in claim 6 , wherein the imaging lens further satisfies a conditional expression given below:
0.8< f/f 1<3 (1-1).
14. An imaging lens consisting of six lenses:
a first lens having a positive refractive power and a meniscus shape 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 and a biconcave shape; and
a sixth lens having a negative refractive power, disposed in order from the object side,
wherein the imaging lens further satisfies a conditional expression given below:
0.3< f/f 3<1.2 (2-1)
where:
f: focal length of the entire system
f 3 : focal length of the third lens.
15. The imaging lens as claimed in claim 8 , wherein the imaging lens further satisfies a conditional expression given below:
−1.9< f·P 34<−1.1 (3-1).
16. The imaging lens as claimed in claim 1 , wherein the imaging lens further satisfies a conditional expression given below:
−4.6<( L 4 r+L 4 f )/( L 4 r − L 4 f )<−3.65 (4-1).
17. The imaging lens as claimed in claim 9 , wherein the imaging lens further satisfies a conditional expression given below:
−1.4<( L 5 r+L 5 f )/( L 5 r − L 5 f )<2.3 (5-1).
18. The imaging lens as claimed in claim 11 , wherein the imaging lens further satisfies a conditional expression given below:
1< f·tanω / L 6 r< 5 (7-1).
19. An imaging apparatus equipped with the imaging lens as claimed in claim 1 and further comprising an electronic imaging sensor.
20. An imaging apparatus equipped with the imaging lens as claimed in claim 14 and further comprising an electronic imaging sensor.