Imaging lens and imaging apparatus
The imaging lens includes only eight lenses consisting of, in order from an object side, a negative first lens, a negative second lens, a positive third lens convex toward an image side, a positive fourth lens convex toward an object side, a negative fifth lens, a positive sixth lens convex toward the image side, a positive seventh lens convex toward the object side, and a negative eighth lens, as lenses having refractive powers, in which predetermined conditional expressions are satisfied.
1. An imaging lens comprising:
only eight lenses consisting of, in order from an object side to an image side,
a first lens that has a negative refractive power,
a second lens that has a negative refractive power,
a third lens that has a positive refractive power and of which an image side surface is convex,
a fourth lens that has a positive refractive power and of which an object side surface is convex,
a fifth lens that has a negative refractive power,
a sixth lens that has a positive refractive power and of which an image side surface is convex,
a seventh lens that has a positive refractive power and of which an object side surface is convex, and
an eighth lens that has a negative refractive power, as lenses having refractive powers,
wherein in the sixth lens, an absolute value of a radius of curvature of the image side surface is smaller than an absolute value of a radius of curvature of an object side surface, and
wherein assuming that an Abbe number of the fifth lens at a d line is νd5, Conditional Expression (1) is satisfied, which is represented by
ν d 5<23 (1).
2. The imaging lens according to claim 1 ,
wherein in the third lens, an absolute value of a radius of curvature of the image side surface is smaller than an absolute value of a radius of curvature of an object side surface.
3. The imaging lens according to claim 1 ,
wherein in the fourth lens, an absolute value of a radius of curvature of an image side surface is larger than an absolute value of a radius of curvature of the object side surface.
4. The imaging lens according to claim 1 ,
wherein in the seventh lens, an absolute value of a radius of curvature of an image side surface is larger than an absolute value of a radius of curvature of the object side surface.
5. The imaging lens according to claim 1 ,
wherein assuming that a focal length of the first lens is f1 and a focal length of the imaging lens is f, Conditional Expression (4) is satisfied, which is represented by
−8< f 1/ f<− 0.5 (4).
6. The imaging lens according to claim 1 ,
wherein assuming that a composite focal length of the first lens and the second lens is f12 and a focal length of the imaging lens is f, Conditional Expression (5) is satisfied, which is represented by
−8< f 12/ f<− 0.5 (5).
7. The imaging lens according to claim 1 ,
wherein assuming that a composite focal length of the fourth lens and the fifth lens is f45 and a focal length of the imaging lens is f, Conditional Expression (6) is satisfied, which is represented by
f 45/ f<− 0.5 (6).
8. The imaging lens according to claim 1 ,
wherein assuming that a composite focal length of the second lens and the third lens is f23 and a focal length of the imaging lens is f, Conditional Expression (7) is satisfied, which is represented by
2< f 23/ f< 30 (7).
9. The imaging lens according to claim 1 ,
wherein assuming that a focal length of the sixth lens is f6 and a focal length of the imaging lens is f, Conditional Expression (8) is satisfied, which is represented by
0.5< f 6/ f (8).
10. The imaging lens according to claim 1 ,
wherein assuming that a focal length of the seventh lens is f7 and a focal length of the imaging lens is f, Conditional Expression (9) is satisfied, which is represented by
0.5< f 7/ f (9).
11. The imaging lens according to claim 1 ,
wherein assuming that a sum of a distance on an optical axis from an object side surface of the first lens to an image side surface of the eighth lens and a back focal length as an air conversion distance is TL and a focal length of the imaging lens is f, Conditional Expression (10) is satisfied, which is represented by
3< TL/f< 20 (10).
12. The imaging lens according to claim 1 ,
wherein assuming that a back focal length as an air conversion distance is Bf and a focal length of the imaging lens is f, Conditional Expression (11) is satisfied, which is represented by
0.5< Bf/f< 5 (11).
13. The imaging lens according to claim 1 ,
wherein assuming that an effective diameter of an image side surface of the eighth lens is ED8r and a back focal length as an air conversion distance is Bf, Conditional Expression (12) is satisfied, which is represented by
0.6<ED8 r /Bf<2.2 (12).
14. An imaging apparatus comprising:
the imaging lens according to claim 1 .
15. An imaging lens comprising:
only eight lenses consisting of, in order from an object side to an image side,
a first lens that has a negative refractive power,
a second lens that has a negative refractive power,
a third lens that has a positive refractive power and of which an image side surface is convex,
a fourth lens that has a positive refractive power and of which an object side surface is convex,
a fifth lens that has a negative refractive power,
a sixth lens that has a positive refractive power and of which an image side surface is convex,
a seventh lens that has a positive refractive power and of which an object side surface is convex, and
an eighth lens that has a negative refractive power, as lenses having refractive powers,
wherein in the sixth lens, an absolute value of a radius of curvature of the image side surface is smaller than an absolute value of a radius of curvature of an object side surface, and
wherein assuming that a distance on an optical axis between the second lens and the third lens is Db23 and a focal length of the imaging lens is f, Conditional Expression (2) is satisfied, which is represented by
0.8< Db 23/ f< 7 (2).
16. An imaging apparatus comprising:
the imaging lens according to claim 15 .
17. An imaging lens comprising:
only eight lenses consisting of, in order from an object side to an image side,
a first lens that has a negative refractive power,
a second lens that has a negative refractive power,
a third lens that has a positive refractive power and of which an image side surface is convex,
a fourth lens that has a positive refractive power and of which an object side surface is convex,
a fifth lens that has a negative refractive power,
a sixth lens that has a positive refractive power and of which an image side surface is convex,
a seventh lens that has a positive refractive power and of which an object side surface is convex, and
an eighth lens that has a negative refractive power, as lenses having refractive powers,
wherein in the sixth lens, an absolute value of a radius of curvature of the image side surface is smaller than an absolute value of a radius of curvature of an object side surface, and
wherein assuming that a composite focal length of the fourth lens, the fifth lens, and the sixth lens is f456 and a focal length of the imaging lens is f, Conditional Expression (3a) is satisfied, which is represented by
4.5< f 456/ f< 28 (3a).
18. An imaging apparatus comprising:
the imaging lens according to claim 17 .