Imaging lens and imaging device provided with the same
View Patent ↗An imaging lens substantially consists of five lenses consisting of, in order from the object side: a first lens having a positive refractive power and having a meniscus shape with the convex surface toward the object side; a second lens having a biconcave shape; a third lens having a positive refractive power and having a meniscus shape with the convex surface toward the image side; a fourth lens having a positive refractive power and having a convex surface toward the image side; and a fifth lens having a negative refractive power, wherein a predetermined conditional expression is satisfied.
1. An imaging lens consisting of five lenses consisting, in order from an object side:
a first lens having a positive refractive power and having a meniscus shape with a convex surface toward the object side;
a second lens having a biconcave shape in a vicinity of an optical axis;
a third lens having a positive refractive power and having a meniscus shape with a convex surface toward an image side in a vicinity of the optical axis;
a fourth lens having a positive refractive power and having a convex surface toward the image side; and
a fifth lens having a negative refractive power,
wherein the conditional expression below is satisfied:
0.4< f/f 4<2 (1),
where f is a focal length of the entire system, and f 4 is a focal length of the fourth lens.
2. The imaging lens as claimed in claim 1 , wherein the conditional expression below is further satisfied:
−3< f/f 5<−0.72 (3),
where f 5 is a focal length of the fifth lens.
3. The imaging lens as claimed in claim 2 , wherein the conditional expression below is further satisfied:
−2.5< f/f 5<−1 (3-1),
where f 5 is a focal length of the fifth lens.
4. The imaging lens as claimed in claim 3 , wherein the conditional expression below is further satisfied:
−2< f/f 5<−1.1 (3-2),
where f 5 is a focal length of the fifth lens.
5. The imaging lens as claimed in claim 1 , wherein the fifth lens has a concave surface toward the image side.
6. The imaging lens as claimed in claim 1 , wherein an image-side surface of the fifth lens has at least one inflection point.
7. The imaging lens as claimed in claim 1 , wherein the conditional expression below is further satisfied:
0.05<( L 4 f−L 4 r )/( L 4 f+L 4 r )<2 (4),
where L 4 f is a paraxial radius of curvature of an object-side surface of the fourth lens, and L 4 r is a paraxial radius of curvature of an image-side surface of the fourth lens.
8. The imaging lens as claimed in claim 7 , wherein the conditional expression below is further satisfied:
0.12<( L 4 f−L 4 r )/( L 4 f+L 4 r )<1 (4-1),
where L 4 f is a paraxial radius of curvature of the object-side surface of the fourth lens, and L 4 r is a paraxial radius of curvature of the image-side surface of the fourth lens.
9. The imaging lens as claimed in claim 1 , wherein the conditional expression below is further satisfied:
−3< f/f 2<−0.55 (5),
where f 2 is a focal length of the second lens.
10. The imaging lens as claimed in claim 9 , wherein the conditional expression below is further satisfied:
−2.5< f/f 2<−0.65 (5),
where f 2 is a focal length of the second lens.
11. The imaging lens as claimed in claim 1 , wherein the conditional expression below is further satisfied:
−2< f/f 23<−0.4 (6),
where f 23 is a combined focal length of the second lens and the third lens.
12. The imaging lens as claimed in claim 11 , wherein the conditional expression below is further satisfied:
−1.5< f/f 23<−0.55 (6-1),
where f 23 is a combined focal length of the second lens and the third lens.
13. The imaging lens as claimed in claim 1 , wherein the conditional expression below is further satisfied:
0.4< f ·tan ω/ L 5 r< 10 (7),
where ω is a half angle of view, and L 5 r is a paraxial radius of curvature of an image-side surface of the fifth lens.
14. The imaging lens as claimed in claim 13 , wherein the conditional expression below is further satisfied:
0.5< f ·tan ω/ L 5 r< 5 (7-1),
where ω is a half angle of view, and L 5 r is a paraxial radius of curvature of the image-side surface of the fifth lens.
15. The imaging lens as claimed in claim 1 , wherein the conditional expression below is further satisfied:
1.2< TTL /( f ·tan ω)<1.65 (8),
where TTL is a distance from an object-side surface of the first lens to an image plane, where a back focus portion of the distance is an equivalent air distance, and co is a half angle of view.
16. The imaging lens as claimed in claim 1 , wherein the conditional expression below is further satisfied:
0.5< f/f 4<1.7 (1-1),
where f 4 is a focal length of the fourth lens.
17. An imaging device comprising the imaging lens as claimed in claim 1 .
18. An imaging lens consisting of five lenses consisting, in order from an object side:
a first lens having a positive refractive power and having a meniscus shape with a convex surface toward the object side;
a second lens having a biconcave shape in a vicinity of an optical axis;
a third lens having a positive refractive power and having a meniscus shape with a convex surface toward an image side in a vicinity of the optical axis;
a fourth lens having a positive refractive power and having a convex surface toward the image side; and
a fifth lens having a negative refractive power, wherein the conditional expression below is satisfied:
−8< f ·tan ω/ L 4 r<− 0.4 (2),
where f is a focal length of the entire system, ω is a half angle of view, and L 4 r is a paraxial radius of curvature of an image-side surface of the fourth lens.
19. The imaging lens as claimed in claim 18 , wherein the conditional expression below is further satisfied:
0.4< f/f 4<2 (1),
where f is a focal length of the entire system, and f 4 is a focal length of the fourth lens.
20. The imaging lens as claimed in claim 18 , wherein the conditional expression below is further satisfied:
−6< f ·tan ω/ L 4 r<− 1.4 (2-1),
where ω is a half angle of view, and L 4 r is a paraxial radius of curvature of the image-side surface of the fourth lens.