Imaging lens and imaging apparatus equipped with the imaging lens
View Patent ↗An imaging lens consists of five lenses, including: a fist lens having a biconvex shape with the surface having the radius of curvature with the smaller absolute value toward the object side, a second lens having a negative refractive power and a concave surface toward the image side, a third lens having 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 and a meniscus shape with a concave surface toward the image side, the image-side surface thereof having at least one inflection point, disposed in this order from the object side.
1. An imaging lens consisting of five lenses, including:
a first lens having a biconvex shape with a surface having the radius of curvature with the smaller absolute value toward the object side;
a second lens having a negative refractive power with a concave surface toward the image side;
a third lens having 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 and a meniscus shape with a concave surface toward the image side, the image-side surface thereof having at least one inflection point, disposed in this order from the object side, wherein
the imaging lens satisfies conditional formula below:
−0.3<( R 2 r−R 3 f )/( R 2 r+R 3 f )<−0.05 (5-1),
where,
R 2 r : the paraxial radius of curvature of the image-side surface of the second lens, and
R 3 f : the paraxial radius of curvature of the object-side surface of the third lens.
2. The imaging lens as defined in claim 1 that further satisfies conditional formula below:
−0.6< f/f 45<−0.1 (1),
where,
f: the focal length of the entire system, and
f 45 : the combined focal length of the fourth lens and the fifth lens.
3. The imaging lens as defined in claim 1 that further satisfies conditional formula below:
0.5< f ·tan ω/ R 5 r< 10 (2),
where,
f: the focal length of the entire system,
ω: a half angle of view, and
R 5 r : the paraxial radius of curvature of the image-side surface of the fifth lens.
4. The imaging lens as defined in claim 1 that further satisfies conditional formula below:
1< f 3/ f 1<10 (3),
where,
f 3 : the focal length of the third lens, and
f 1 : the focal length of the first lens.
5. The imaging lens as defined in claim 1 that further satisfies conditional formula below:
−1<( R 3 f−R 3 r )/( R 3 f+R 3 r )<0 (4),
where,
R 3 r : the paraxial radius of curvature of the image-side surface of the third lens.
6. The imaging lens as defined in claim 1 that further satisfies the conditional formula below:
0.8< f/f 1<1.5 (6),
where,
f: the focal length of the entire system, and
f 1 : the focal length of the first lens.
7. The imaging lens as defined in claim 1 that further satisfies conditional formula below:
0.1 <f/f 3<0.6 (7),
where,
f: the focal length of the entire system, and
f 3 : the focal length of the third lens.
8. The imaging lens as defined in claim 1 that further satisfies conditional formula below:
−1< f/f 2<−0.2 (8),
where,
f: the focal length of the entire system, and
f 2 : the focal length of the second lens.
9. The imaging lens as defined in claim 1 that further satisfies the conditional formula below:
0.05< D 7/ f< 0.2 (9),
where,
f: the focal length of the entire system, and
D 7 : the distance between the third lens and the fourth lens along the optical axis.
10. The imaging lens as defined in claim 1 that further satisfies the conditional formula below:
−0.42< f/f 45<−0.23 (1-1),
where,
f: the focal length of the entire system, and
f 45 : the combined focal length of the fourth lens and the fifth lens.
11. The imaging lens as defined in claim 1 that further satisfies conditional formula below:
1.5< f ·tan ω/ R 5 r< 4.5 (2-1),
where,
f: the focal length of the entire system,
ω: a half angle of view, and
R 5 r : the paraxial radius of curvature of the image-side surface of the fifth lens.
12. The imaging lens as defined in claim 1 that further satisfies the conditional formula below:
2.5< f 3/ f 1<8 (3-1),
where,
f: 3 : the focal length of the third lens, and
f 1 : the focal length of the first lens.
13. The imaging lens as defined in claim 1 that further satisfies the conditional formula below:
−0.8<( R 3 f−R 3 r )/( R 3 f+R 3 r )<−0.2 (4-1),
where,
R 3 r : the paraxial radius of curvature of the image-side surface of the third lens.
14. The imaging lens as defined in claim 1 that further satisfies the conditional formula below:
0.9< f/f 1<1.4 (6-1),
where,
f: the focal length of the entire system, and
f 1 : the focal length of the first lens.
15. The imaging lens as defined in claim 1 that further satisfies the conditional formula below:
0.15< f/f 3<0.4 (7-1),
where,
f: the focal length of the entire system, and
f 3 : the focal length of the third lens.
16. The imaging lens as defined in claim 1 that further satisfies the conditional formula below:
−0.8< f/f 2<−0.5 (8-1),
where,
f: the focal length of the entire system, and
f 2 : the focal length of the second lens.
17. An imaging apparatus equipped with the imaging lens as defined in claim 1 .