Imaging lens and imaging device provided with the same
View Patent ↗An imaging lens with five lenses arranged as, in order from the object side, a first lens with a positive refractive power and a meniscus shape with a convex surface directed toward the object side, a second lens with a biconcave shape, a third lens with a negative refractive power and a meniscus shape with a convex surface toward the image side, a fourth lens with a positive refractive power, and a fifth lens with a negative refractive power, where an image-side surface of the fifth lens includes a concave surface and at least one inflection point, and a predetermined conditional expression is satisfied that achieves a high imaging performance from a central angle of view to a peripheral angle of view, while achieving reduction of an entire length of the lens.
1. An imaging lens with five lenses, consisting of, ordered as follows 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;
a third lens having a negative refractive power and having a meniscus shape with a convex surface toward an image side;
a fourth lens having a positive refractive power; and
a fifth lens having a negative refractive power, wherein an image-side surface of the fifth lens includes a concave surface and at least one inflection point,
wherein the conditional expression below is satisfied:
0.2< f/f 4<1.38 (1),
where f is a focal length of the entire system, and f4 is a focal length of the fourth lens, and
wherein the conditional expression below is further satisfied:
−0.6<( L 1 r+L 2 f )/( L 1 r−L 2 f )<0.11 (3),
where L1r is a paraxial radius of curvature of an image-side surface of the first lens, and L2f is a paraxial radius of curvature of an object-side surface of the second lens.
2. The imaging lens as claimed in claim 1 , wherein the conditional expression below is further satisfied:
−0.86<( L 1 f−L 1 r )/( L 1 f+L 1 r )<−0.1 (2),
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.
3. The imaging lens as claimed in claim 2 , wherein the conditional expression below is further satisfied:
−0.85<( L 1 f−L 1 r )/( L 1 f+L 1 r )<−0.5 (2-1),
where L1f is a paraxial radius of curvature of the object-side surface of the first lens, and L1r is a paraxial radius of curvature of the image-side surface of the first lens.
4. The imaging lens as claimed in claim 3 , wherein the conditional expression below is further satisfied:
−0.84<( L 1 f−L 1 r )/( L 1 f+L 1 r )<−0.6 (2-2),
where L1f is a paraxial radius of curvature of the object-side surface of the first lens, and L1r is a paraxial radius of curvature of the image-side surface of the first lens.
5. The imaging lens as claimed in claim 1 , wherein the conditional expression below is further satisfied:
0.2< f/f 34<1.3 (4),
where f34 is a combined focal length of the third lens and the fourth lens.
6. The imaging lens as claimed in claim 5 , wherein the conditional expression below is further satisfied:
0.6< f/f 34<1.28 (4-1),
where f34 is a combined focal length of the third lens and the fourth lens.
7. The imaging lens as claimed in claim 1 , wherein the conditional expression below is further satisfied:
0.21< f/L 1 r< 1 (5),
where L1r is a paraxial radius of curvature of an image-side surface of the first lens.
8. The imaging lens as claimed in claim 1 , wherein the conditional expression below is further satisfied:
1.1< f/f 1234<1.42 (6),
where f1234 is a combined focal length of the first to the fourth lenses.
9. The imaging lens as claimed in claim 8 , wherein the conditional expression below is further satisfied:
1.2< f/f 1234<1.42 (6-1),
where f1234 is a combined focal length of the first to the fourth lenses.
10. 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 L5r is a paraxial radius of curvature of an image-side surface of the fifth lens.
11. The imaging lens as claimed in claim 10 , 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 L5r is a paraxial radius of curvature of the image-side surface of the fifth lens.
12. The imaging lens as claimed in claim 1 , wherein the conditional expression below is further satisfied:
1.3< TTL /( f ·tan ω)<1.9 (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.
13. The imaging lens as claimed in claim 1 , wherein the fourth lens has a meniscus shape with a convex surface toward the image side.
14. The imaging lens as claimed in claim 1 , wherein the fifth lens has a meniscus shape with a concave surface toward the image side.
15. The imaging lens as claimed in claim 1 , wherein the conditional expression below is further satisfied:
0.6< f/f 4<1.34 (1-1).
16. The imaging lens as claimed in claim 1 , wherein the conditional expression below is further satisfied:
−0.45<( L 1 r+L 2 f )/( L 1 r−L 2 f )<0.105 (3-1),
where L1r is a paraxial radius of curvature of the image-side surface of the first lens, and L2f is a paraxial radius of curvature of the object-side surface of the second lens.
17. An imaging device comprising the imaging lens as claimed in claim 1 .
18. An imaging lens with five lenses, consisting of, ordered as follows 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;
a third lens having a negative refractive power and having a meniscus shape with a convex surface toward an image side;
a fourth lens having a positive refractive power; and
a fifth lens having a negative refractive power, wherein an image-side surface of the fifth lens includes a concave surface and at least one inflection point,
wherein the conditional expression below is satisfied:
0.2< f/f 4<1.38 (1),
where f is a focal length of the entire system, and f4 is a focal length of the fourth lens, and
wherein the conditional expression below is further satisfied:
0.23< f/L 1 r< 0.8 (5-1),
where L1r is a paraxial radius of curvature of the image-side surface of the first lens.
19. An imaging lens with five lenses, consisting of, ordered as follows 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;
a third lens having a negative refractive power and having a meniscus shape with a convex surface toward an image side;
a fourth lens having a positive refractive power; and
a fifth lens having a negative refractive power, wherein an image-side surface of the fifth lens includes a concave surface and at least one inflection point,
wherein the conditional expression below is satisfied:
1< f/f 4<1.32 (1-2)
where f is a focal length of the entire system, and f4 is a focal length of the fourth lens.