Imaging lens and imaging apparatus equipped with the imaging lens
View Patent ↗An imaging lens is essentially constituted by seven lenses, including: a positive first lens having a convex surface toward the object side; a second lens, of which at least one surface is of an aspherical shape; a third lens, of which at least one surface is of an aspherical shape; a fourth lens, of which at least one surface is of an aspherical shape; a positive fifth lens of a meniscus shape with a convex surface toward the image side; a sixth lens, of which at least one surface is of an aspherical shape; and a negative seventh lens having a concave surface toward the image side, provided in this order from the object side. The imaging lens satisfies a predetermined conditional formula.
1. An imaging lens consisting essentially of seven lenses, including:
a first lens having a positive refractive power and a convex surface toward the object side;
a second lens, of which at least one surface is of an aspherical shape;
a third lens, of which at least one surface is of an aspherical shape;
a fourth lens, of which at least one surface is of an aspherical shape;
a fifth lens having a positive refractive power and is of a meniscus shape with a convex surface toward the image side;
a sixth lens, of which at least one surface is of an aspherical shape; and
a seventh lens having a negative refractive power and a concave surface toward the image side, provided in this order from the object side;
the imaging lens satisfying the following conditional formula:
−1.25< f/f 7<−0.5 (1)
wherein f is the focal length of the entire system, and f 7 is the focal length of the seventh lens.
2. An imaging lens as defined in claim 1 that further satisfies the following conditional formula:
−0.6< f/f 6<0.3 (2)
wherein f 6 is the focal length of the sixth lens.
3. An imaging lens as defined in claim 1 that further satisfies the following conditional formula:
0< f/f 3<0.35 (3)
wherein f 3 is the focal length of the third lens.
4. An imaging lens as defined in claim 1 that further satisfies the following conditional formula:
0.5< f ·tan ω/ L 7 r< 10 (4)
wherein ω is the half value of a maximum angle of view when focused on an object at infinity, and L 7 r is the paraxial radius of curvature of the surface of the seventh lens toward the image side.
5. An imaging lens as defined in claim 1 , wherein:
the second lens has a negative refractive power.
6. An imaging lens as defined in claim 1 , wherein:
the third lens has a positive refractive power.
7. An imaging lens as defined in claim 1 , wherein:
the fourth lens has a negative refractive power.
8. An imaging lens as defined in claim 1 , wherein:
the seventh lens is of a meniscus shape having a convex surface toward the object side.
9. An imaging lens as defined in claim 1 , wherein:
the first lens is of a meniscus shape having a convex surface toward the object side.
10. An imaging lens as defined in claim 1 , wherein:
the sixth lens is of a meniscus shape having a convex surface toward the object side.
11. An imaging lens as defined in claim 1 , wherein:
the fourth lens is of a biconcave shape.
12. An imaging lens as defined in claim 1 that further satisfies the following conditional formula:
0.15<( L 7 f−L 7r)/( L 7 f+L 7 r )<0.55 (5)
wherein L 7 r is the paraxial radius of curvature of the surface of the seventh lens toward the image side, and L 7 f is the paraxial radius of curvature of the surface of the seventh lens toward the object side.
13. An imaging lens as defined in claim 1 that further satisfies the following conditional formula:
−1.24< f/f 7<−0.7 (1-1).
14. An imaging lens as defined in claim 1 that further satisfies the following conditional formula:
−0.45< f/f 6<0.15 (2-1)
wherein f 6 is the focal length of the sixth lens.
15. An imaging lens as defined in claim 1 that further satisfies the following conditional formula:
1.5< f ·tan ω/ L 7 r< 5 (4-1)
wherein ω is the half value of a maximum angle of view when focused on an object at infinity, and L 7 r is the paraxial radius of curvature of the surface of the seventh lens toward the image side.
16. An imaging lens as defined in claim 1 that further satisfies the following conditional formula:
0.3<( L 7 f−L 7 r )/( L 7 f+L 7 r )<0.55 (5-1)
wherein L 7 r is the paraxial radius of curvature of the surface of the seventh lens toward the image side, and L 7 f is the paraxial radius of curvature of the surface of the seventh lens toward the object side.
17. An imaging lens as defined in claim 1 that further satisfies the following conditional formula:
−1.2< f/f 7<−0.8 (1-2).
18. An imaging lens as defined in claim 1 that further satisfies the following conditional formula:
−0.3< f/f 6<0.1 (2-2)
wherein f 6 is the focal length of the sixth lens.
19. An imaging lens as defined in claim 1 , wherein:
the first lens and the second lens are cemented together; and
the joint surface between the first lens and the second lens is of an aspherical shape.
20. An imaging apparatus equipped with an imaging lens as defined in claim 1 .