Imaging lens and imaging apparatus
View Patent ↗Provided are an imaging lens, which has a small F number and in which various aberrations are satisfactorily corrected, and an imaging apparatus including the imaging lens. The imaging lens includes, in order from an object side: a first lens that has a biconcave shape; a second lens that is convex toward an image side and has a positive refractive power; a third lens that has a biconvex shape; a fourth lens that has a negative refractive power; a fifth lens that has a positive refractive power; and a sixth lens that has a negative refractive power. Assuming that L1f and L1r are paraxial radii of curvature of an object side surface and an image side surface of the first lens, Conditional Expression (1) is satisfied. 0.1<( L 1 f+L 1 r )/( L 1 f−L 1 r )<0.8 (1)
1. An imaging lens comprising, in order from an object side:
a first lens that has a biconcave shape;
a second lens that is convex toward an image side and has a positive refractive power;
a third lens that has a biconvex shape;
a fourth lens that has a negative refractive power;
a fifth lens that has a positive refractive power; and
a sixth lens that has a negative refractive power,
wherein the following conditional expression is satisfied,
0.1<( L 1 f+L 1 r )/( L 1 f−L 1 r )<0.8 (1),
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.
2. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied,
0.55< TH sum/ LL< 0.9 (2),
where THsum is a sum of center thicknesses of the lenses of the whole system, and
LL is a distance on an optical axis from the object side surface of the first lens to an image side surface of the sixth lens.
3. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied,
0.1< f 3/ f 2<0.8 (3),
where f2 is a focal length of the second lens, and
f3 is a focal length of the third lens.
4. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied,
−0.2<( L 3 f+L 3 r )/( L 3 f−L 3 r )<0.1 (4),
where L3f is a paraxial radius of curvature of an object side surface of the third lens, and
L3r is a paraxial radius of curvature of an image side surface of the third lens.
5. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied,
−20< L 2 r/L 2 f< 0.5 (5),
where L2f is a paraxial radius of curvature of an object side surface of the second lens, and
L2r is a paraxial radius of curvature of an image side surface of the second lens.
6. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied,
−2< f/f 1<−0.6 (6),
where f is a focal length of the whole system, and
f1 is a focal length of the first lens.
7. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied,
2< TTL/f< 5 (7),
where TTL is a distance on the optical axis from the object side surface of the first lens to a focal point on the image side in a case where a back focal length is set as an air conversion length, and
f is a focal length of the whole system.
8. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied,
1.5< LL/f< 4 (8),
where LL is a distance on the optical axis from the object side surface of the first lens to the image side surface of the sixth lens, and
f is a focal length of the whole system.
9. The imaging lens according to claim 1 ,
wherein a material of a plurality of lenses among the first to sixth lenses is resin, and
wherein the following conditional expression is satisfied,
−0.2< f×ΣΦp< 0.35 (9),
where f is a focal length of the whole system, and
ΣΦp is a sum of refractive powers as an inverse of a focal length of all the lenses of which materials are resin.
10. The imaging lens according to claim 1 , wherein an aperture stop is disposed between the image side surface of the second lens and the image side surface of the third lens.
11. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied.
0.2<( L 1 f+L 1 r )/( L 1 f−L 1 r )<0.65 (1-1)
12. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied,
0.6< TH sum/ LL< 0.85 (2-1),
where THsum is a sum of center thicknesses of the lenses of the whole system, and
LL is a distance on the optical axis from the object side surface of the first lens to the image side surface of the sixth lens.
13. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied,
0.2< f 3/ f 2<0.65 (3-1),
where f2 is a focal length of the second lens, and
f3 is a focal length of the third lens.
14. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied,
−0.17<( L 3 f+L 3 r )/( L 3 f−L 3 r )<0.05 (4-1),
where L3f is a paraxial radius of curvature of the object side surface of the third lens, and
L3r is a paraxial radius of curvature of the image side surface of the third lens.
15. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied,
−10< L 2 r/L 2 f< 0.1 (5-1),
where L2f is a paraxial radius of curvature of the object side surface of the second lens, and
L2r is a paraxial radius of curvature of the image side surface of the second lens.
16. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied,
−1.5< f/f 1<−0.7 (6-1),
where f is a focal length of the whole system, and
f1 is a focal length of the first lens.
17. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied,
2.5< TTL/f< 0.5 (7-1),
where TTL is a distance on the optical axis from the object side surface of the first lens to the focal point on the image side in a case where a back focal length is set as an air conversion length, and
f is a focal length of the whole system.
18. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied,
2< LL/f< 3.5 (8-1),
where LL is a distance on the optical axis from the object side surface of the first lens to the image side surface of the sixth lens, and
f is a focal length of the whole system.
19. The imaging lens according to claim 1 ,
wherein a material of a plurality of lenses among the first to sixth lenses is resin, and
wherein the following conditional expression is satisfied,
−0.15< f×ΣΦp< 0.3 (9-1),
where f is a focal length of the whole system, and
ΣΦp is a sum of refractive powers as an inverse of a focal length of all the lenses of which materials are resin.
20. An imaging apparatus comprising the imaging lens according to claim 1 .