Imaging lens and imaging apparatus
An imaging lens substantially consists of six lenses, composed of a negative first lens, a positive second lens, a negative third lens, a positive fourth lens, a positive fifth lens, and a negative sixth lens, disposed in order from the object side, and satisfies, when the distance between the first lens and the second lens is taken as Db12, the center thickness of the second lens is taken as D3, the focal length of the second lens is taken as f2, the focal length of the entire system is taken as f, the paraxial radius of curvature of the object side surface of the first lens is taken as R1f, and the paraxial radius of curvature of the image side surface of the first lens is taken as R1r, conditional expressions given below: 1.0<( Db 12+ D 3)/ f (1) f 2/ f <1.68 (2) 1.1<( R 1 f+R 1 r )/( R 1 f−R 1 r )<2.2 (3-3)
1. An imaging lens, consisting of six lenses,
composed of a first lens having a negative refractive power, a second lens having a positive refractive power, a third lens having a negative refractive power, a fourth lens having a positive refractive power, a fifth lens having a positive refractive power, and a sixth lens having a negative refractive power, disposed in order from the object side, wherein the imaging lens satisfies conditional expressions given below:
1.1<( R 1 f+R 1 r )/( R 1 f−R 1 r )<2.0 (3-4)
0.0< f 4/ f< 2.45 (5)
19<ν d 6<30 (6-8)
−2.5<( R 5 f+R 5 r )/( R 5 f−R 5 r )<−0.25 (11)
where
R1f: paraxial radius of curvature of the object side surface of the first lens,
R1r: paraxial radius of curvature of the image side surface of the first lens,
f4: focal length of the fourth lens,
f: focal length of the entire system, and
νd6: Abbe number of the material of the sixth lens with respect to the d-line,
R5f: paraxial radius of curvature of the object side surface of the fifth lens, and
R5r: paraxial radius of curvature of the image side surface of the fifth lens.
2. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
20<ν d 6<30 (6-7).
3. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
19<ν d 6<26 (6-5).
4. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
Nd 6<1.89 (25)
where
Nd6: refractive index of the material of the sixth lens with respect to the d-line.
5. The imaging lens as claimed in claim 4 , wherein the imaging lens satisfies a conditional expression given below:
Nd 6<1.86 (25-1).
6. The imaging lens as claimed in claim 4 , wherein the imaging lens satisfies a conditional expression given below:
1.58< Nd 6<1.89.
7. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
0.19< Db 23/ f< 1.0 (21-3)
where
Db23: air space on the optical axis between the second lens and the third lens.
8. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
ν d 4<60
where
νd4: Abbe number of the material of the fourth lens with respect to the d-line.
9. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
f 2/ f< 1.68 (2)
where
f2: focal length of the second lens.
10. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
f 12/ f< 2.5 (8)
where
f12: combined focal length of the first lens and the second lens.
11. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
f 5/ f< 5.0 (9)
where
f5: focal length of the fifth lens.
12. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
−4.0<( R 6 f+R 6 r )/( R 6 f−R 6 r ) (12)
where
R6f: paraxial radius of curvature of the object side surface of the sixth lens, and
R6r: paraxial radius of curvature of the image side surface of the sixth lens.
13. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
0.0< R 1 f/f (13).
14. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
−3.0< f 1/ f <− 0 . 5 (14)
where
f1: focal length of the first lens.
15. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
0.1< f 12/ f 3456<2.0 (15)
where
f12: combined focal length of the first lens and the second lens, and
f3456: combined focal length of the third lens to the sixth lens.
16. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
0.2<( D 3+ Db 23)/ f< 3.0 (16)
where
D3: center thickness of the second lens,
Db23: air space on the optical axis between the second lens and the third lens.
17. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
−3.0< f 1/ f 2<−0.2 (17)
where
f1: focal length of the first lens, and
f2: focal length of the second lens.
18. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
ν d 3<30 (18)
where
νd3: Abbe number of the material of the third lens with respect to the d-line.
19. An imaging apparatus, comprising the imaging lens as claimed in claim 1 .