Imaging lens and imaging apparatus equipped with the imaging lens
An imaging lens substantially includes six lenses, constituted by: a first lens having a negative refractive power; a second lens having a positive refractive power; a third lens having a positive refractive power; a fourth lens having a negative refractive power; a fifth lens having a positive refractive power; and a sixth lens having a negative refractive power, a concave surface toward an image side, and at least one inflection point in the surface toward the image side; provided in this order from an object side. The imaging lens satisfies a predetermined conditional formula.
1. An imaging lens consisting of six lenses, including:
a first lens having a negative refractive power;
a second lens having a positive refractive power;
a third lens having a positive refractive power;
a fourth lens having a negative refractive power;
a fifth lens having a positive refractive power; and
a sixth lens having a negative refractive power, a concave surface toward an image side, and at least one inflection point on the surface toward the image side; provided in this order from an object side;
the imaging lens satisfying the following conditional formula:
1 <f ·tan ω /R 6 r< 20 (1)
wherein f is the focal length of the entire system, ω is the half angle of view, and R6r is the paraxial radius of curvature of the surface of the sixth lens toward the image side, and
further satisfies the following conditional formula:
0.3<Db/f<1 (5)
wherein f is the focal length of the entire system, and Db is the distance between the first lens and the second lens along an optical axis.
2. The imaging lens as defined in claim 1 that further satisfies the following conditional formula:
−5 <f/f 6<−0.7 (3)
wherein f is the focal length of the entire system, and f6 is the focal length of the sixth lens.
3. The imaging lens as defined in claim 1 that further satisfies the following conditional formula:
Da/f <1 (4)
wherein f is the focal length of the entire system, and Da is the distance between the second lens and the third lens along an optical axis.
4. The imaging lens as defined in claim 1 that further satisfies the following conditional formula:
Dc/f <0.15 (6)
wherein f is the focal length of the entire system, and Dc is the distance between the fifth lens and the sixth lens along an optical axis.
5. The imaging lens as defined claim 1 that further satisfies the following conditional formula:
1.2 <f/f 5<5 (7)
wherein f is the focal length of the entire system, and f5 is the focal length of the fifth lens.
6. The imaging lens as defined in claim 1 that further satisfies the following conditional formula:
−0.55 <f/f 1<−0.1 (8)
wherein f is the focal length of the entire system, and f1 is the focal length of the first lens.
7. The imaging lens as defined in claim 1 , wherein:
a surface which has a radius of curvature with the smallest absolute value from among the lens surfaces of the first lens through the sixth lens is the surface of the fifth lens toward the image side, in the case that the surface of the fifth lens toward the image side is a convex surface.
8. The imaging lens as defined in claim 1 that further satisfies the following conditional formula:
1.5 <f ·tan ω /R 6 r <10 (1-1)
wherein f is the focal length of the entire system, ω is the half angle of view, and R6r is the paraxial radius of curvature of the surface of the sixth lens toward the image side.
9. The imaging lens as defined in claim 8 that further satisfies the following conditional formula:
1.5 <f ·tan ω /R 6 r <5 (1-2).
10. The imaging lens as defined in claim 1 that further satisfies the following conditional formula:
−0.25 <f/f 12<−0.05 (2-1)
wherein f is the focal length of the entire system, and f12 is the combined focal length of the first lens and the second lens.
11. The imaging lens as defined in claim 1 that further satisfies the following conditional formula:
−4 <f/f 6<−0.9 (3-1)
wherein f is the focal length of the entire system, and f6 is the focal length of the sixth lens.
12. The imaging lens as defined in claim 1 that further satisfies the following conditional formula:
Dc/f <0.1 (6-1)
wherein f is the focal length of the entire system, and Dc is the distance between the fifth lens and the sixth lens along an optical axis.
13. The imaging lens as defined in claim 1 , further comprising:
an aperture stop provided between the second lens and the third lens.
14. An imaging apparatus equipped with an imaging lens as defined in claim 1 .
15. An imaging lens consisting of six lenses, including:
a first lens having a negative refractive power;
a second lens having a positive refractive power;
a third lens having a positive refractive power;
a fourth lens having a negative refractive power;
a fifth lens having a positive refractive power; and
a sixth lens having a negative refractive power, a concave surface toward an image side, and at least one inflection point on the surface toward the image side; provided in this order from an object side;
the imaging lens satisfying the following conditional formula:
−0.3 <f/f 12<0 (2)
wherein f is the focal length of the entire system, and f12 is the combined focal length of the first lens and the second lens.
16. The imaging lens as defined in claim 15 that further satisfies the following conditional formula:
1 <f ·tan ω /R 6 r <20 (1)
wherein f is the focal length of the entire system, ω is the half angle of view, and R6r is the paraxial radius of curvature of the surface of the sixth lens toward the image side.
17. An imaging lens consisting of six lenses, including:
a first lens having a negative refractive power and a concave surface toward an object side;
a second lens having a positive refractive power;
a third lens having a positive refractive power;
a fourth lens having a negative refractive power;
a fifth lens having a positive refractive power; and
a sixth lens having a negative refractive power, a concave surface toward an image side, and at least one inflection point on the surface toward the image side; provided in this order from the object side.
18. The imaging lens as defined in claim 17 that further satisfies the following conditional formula:
1 <f ·tan ω /R 6 r <20 (1)
wherein f is the focal length of the entire system, ω is the half angle of view, and R6r is the paraxial radius of curvature of the surface of the sixth lens toward the image side.
19. The imaging lens as defined in claim 17 that further satisfies the following conditional formula:
−0.3 <f/f 12<0 (2)
wherein f is the focal length of the entire system, and f12 is the combined focal length of the first lens and the second lens.