Imaging lens and imaging apparatus
View Patent ↗An imaging lens is constituted by, in order from the object side to the image side: a negative first lens having a concave surface toward the image side; a positive second lens having a convex surface toward the image side; a negative third lens having a concave surface toward the image side; a positive biconvex fourth lens; a positive biconvex fifth lens; and a negative sixth lens having a concave surface toward the object side. Conditional Formula (1) related to the combined focal length f12 of the first lens and the second lens and the focal length f of the entire lens system is satisfied: −5< f 12/ f <−2 (1).
1. An imaging lens consisting of, in order from an object side to an image side:
a first lens having a negative refractive power and a concave surface toward the image side;
a second lens having a positive refractive power and a convex surface toward the image side;
a third lens having a negative refractive power and a concave surface toward the image side;
a fourth lens having a positive refractive power and is of a biconvex shape;
a fifth lens having a positive refractive power and is of a biconvex shape; and
a sixth lens having a negative refractive power and a concave surface toward the object side; and
Conditional Formula (1) below being satisfied:
−5< f 12/ f<− 2 (1)
wherein f12 is a combined focal length of the first lens and the second lens, and f is a focal length of the entire imaging lens.
2. The imaging lens as defined in claim 1 , in which Conditional Formula (1-1) below is satisfied:
−4.7< f 12/ f<− 2.3 (1-1).
3. The imaging lens as defined in claim 1 , in which Conditional Formula (2) below is satisfied:
2<| R 3|/ f (2)
wherein R3 is a radius of curvature of a surface of the second lens toward the object side.
4. The imaging lens as defined in claim 3 , in which Conditional Formula (2-1) below is satisfied:
−300< R 3/ f<− 2 (2-1).
5. The imaging lens as defined in claim 1 , in which Conditional Formula (3) below is satisfied:
−2.1< f 1/ f<− 1.3 (3)
wherein f1 is the focal length of the first lens.
6. The imaging lens as defined in claim 5 , in which Conditional Formula (3-1) below is satisfied:
−2.0< f 1/ f<− 1.4 (3-1).
7. The imaging lens as defined in claim 1 , in which Conditional Formula (4) below is satisfied:
−3.5< R 4/ f<− 2.0 (4)
wherein R4 is a radius of curvature of a surface of the second lens toward the image side.
8. The lens as defined in claim 7 , in which Conditional Formula (4-1) below is satisfied:
−3.2< R 4/ f<− 2.2 (4-1).
9. The imaging lens as defined in claim 1 , in which Conditional Formula (5) below is satisfied:
0.9< f 45/ f< 1.3 (5)
wherein f45 is a combined focal length of the fourth lens and the fifth lens.
10. The imaging lens as defined in claim 9 , in which Conditional Formula (5-1) below is satisfied:
0.9< f 45/ f< 1.2 (5-1).
11. The imaging lens as defined in claim 9 , in which Conditional Formula (6) below is satisfied:
1.5< f 4/ f< 3.0 (6)
wherein f4 is the focal length of the fourth lens.
12. The imaging lens as defined in claim 11 , in which Conditional Formula (6-1) below is satisfied:
1.6< f 4/ f< 2.6 (6-1).
13. The imaging lens as defined in claim 11 , in which Conditional Formula (7) below is satisfied:
1.4< f 5/ f< 2.2 (7).
wherein f5 is the focal length of the fifth lens.
14. The imaging lens as defined in claim 9 , in which Conditional Formula (7) below is satisfied:
1.4< f 5/ f< 2.2 (7)
wherein f5 is the focal length of the fifth lens.
15. The imaging lens as defined in claim 14 , in which Conditional Formula (7-1) below is satisfied:
1.45< f 5/ f< 2.1 (7-1).
16. The imaging lens as defined in claim 1 , in which a material of at least one of the fourth lens and the fifth lens satisfies Conditional Formula (8) below:
dN/dT< 0 (8),
wherein dN/dT is a relative temperature coefficient of a refractive index of the material with respect to a wavelength of 632.8nm within a temperature range from 20° C. to 40° C.
17. An imaging apparatus equipped with an imaging lens as defined in claim 1 .