Imaging lens and imaging apparatus equipped with the imaging lens
View Patent ↗An imaging lens consists of five lenses, including: a first lens having a positive refractive power with a convex surface toward the object side, a second lens having a negative refractive power, a third lens having a positive refractive power and a meniscus shape with a convex surface toward the object side, a fourth lens having a negative refractive power and a meniscus shape with a convex surface toward the image side, and a fifth lens having a negative refractive power with a concave surface toward the image side, the image-side surface thereof having at least one inflection point, and the first lens, the second lens, the third lens, the fourth lens, and the fifth lens being disposed in this order from the object side; wherein, the imaging lens satisfies a predetermined conditional formula.
1. An imaging lens consisting of five lenses, including:
a first lens, having a positive refractive power with a convex surface toward the object side;
a second lens, having a negative refractive power;
a third lens, having a positive refractive power and a meniscus shape with a convex surface toward the object side;
a fourth lens, having a negative refractive power and a meniscus shape with a convex surface toward the image side; and
a fifth lens, having a negative refractive power with a concave surface toward the image side, the image-side surface thereof having at least one inflection point, the first lens, the second lens, the third lens, the fourth lens, and the fifth lens being disposed in this order from the object side;
wherein, the imaging lens satisfies conditional formulae (1), (5-1), and (8) below:
1 <f 3 /f 1<4.2 (1),
0.9 <f/f 1<1.3 (5-1),
0.12 <D 7 /f <0.2 (8),
where,
f3 is the focal length of the third lens,
f1 is the focal length of the first lens,
f is the focal length of the entire system of the imaging lens, and
D 7 is the distance between the third lens and the fourth lens along the optical axis.
2. The imaging lens as defined in claim 1 , wherein the imaging lens further satisfies a conditional formula below:
0.8 <f ·tan ω/ R 5 r <10 (2),
where,
ω is a half angle of view, and
R 5 r is the paraxial radius of curvature of the image-side surface of the fifth lens.
3. The imaging lens as defined in claim 1 , wherein the imaging lens further satisfies a conditional fomula below:
−1<( R 3 f−R 3 r )/( R 3 f+R 3 r )<−0.3 (3),
where,
R 3 f is the paraxial radius of curvature of the object-side surface of the third lens, and
R 3 r is the paraxial radius of curvature of the image-side surface of the third lens.
4. The imaging lens as defined in claim 1 , wherein the imaging lens further satisfies a conditional formula below:
−1<( R 2 r−R 3 f )/( R 2 r+R 3 f )<0.5 (4),
where,
R 2 r is the paraxial radius of curvature of the image-side surface of the second lens, and
R 3 f is the paraxial radius of curvature of the object-side surface of the third lens.
5. The imaging lens as defined in claim 1 , wherein the imaging lens further satisfies a conditional formula below:
0.2 <f/f 3<0.6 (6).
6. The imaging lens as defined in claim 1 , wherein the imaging lens further satisfies a conditional formula below:
−1 <f/f 2<−0.2 (7),
where,
f2 is the focal length of the second lens.
7. The imaging lens as defined in claim 1 , wherein the imaging lens further satisfies a conditional formula below:
1.8 <f 3 /f 1<4.0 (1-1).
8. The imaging lens as defined in claim 1 , wherein the imaging lens further satisfies a conditional formula below:
1.5 <f ·tan ω /R 5 r <4.5 (2-1),
where,
ω is a half angle of view, and
R 5 r is the paraxial radius of curvature of the image-side surface of the fifth lens.
9. The imaging lens as defined in claim 1 , wherein the imaging lens further satisfies a conditional formula below:
−1<( R 3 f−R 3 r )/( R 3 f+R 3 r )<−0.4 (3-1),
where,
R 3 f is the paraxial radius of curvature of the object-side surface of the third lens, and
R 3 r is the paraxial radius of curvature of the image-side surface of the third lens.
10. The imaging lens as defined in claim 1 , wherein the imaging lens further satisfies a conditional fomula below:
−0.5<( R 2 r−R 3 f )/( R 2 r+R 3 f )<0.3 (4-1),
where,
R 2 r is the paraxial radius of curvature of the image-side surface of the second lens, and
R 3 f is the paraxial radius of curvature of the object-side surface of the third lens.
11. The imaging lens as defined in claim 1 , wherein the imaging lens further satisfies a conditional formula below:
0.25 <f/f 3<0.5 (6-1).
12. The imaging lens as defined in claim 1 , wherein the imaging lens further satisfies a conditional formula below:
−0.7 <f/f 2<−0.3 (7-1),
where,
f2 is the focal length of the second lens.
13. An imaging apparatus equipped with the imaging lens as defined in claim 1 .