Imaging lens and imaging apparatus
An imaging lens composed of six lenses 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 when refractive indices of the third lens to the sixth lens are taken as Nd3 to Nd6 respectively, the imaging lens satisfies conditional expressions (1): Nd3<1.7, (2): Nd4<1.6, (3):Nd5<1.6 and (4): Nd6<1.89.
1. An imaging lens, substantially 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:
Nd3<1.7 (1)
Nd4<1.6 (2)
Nd5<1.6 (3)
Nd6<1.89 (4)
where
Nd3: refractive index of the material of the third lens with respect to the d-line,
Nd4: refractive index of the material of the fourth lens with respect to the d-line,
Nd5: refractive index of the material of the fifth lens with respect to the d-line, and
Nd6: refractive index of the material of the sixth lens with respect to the d-line,
wherein the imaging lens satisfies a conditional expression given below:
−3.0<f1/f2<−0.2 (19)
where
f1: focal length of the first lens, and
f2: focal length of the second lens.
2. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
1.0<( R 1 f+R 1 r )/( R 1 f−R 1 r ) (5)
where
R1f: paraxial radius of curvature of the object side surface of the first lens, and
R1r: paraxial radius of curvature of the image side surface of the first lens.
3. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
0.3 < f 4 / f 5 (6)
where
f4: focal length of the fourth lens, and
f5: focal length of the fifth lens.
4. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
f 5/ f< 3.4 (7)
where
f5: focal length of the fifth lens, and
f: focal length of the entire system.
5. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
0.3< f 56/f (8)
where
f56: combined focal length of the fifth lens and the sixth lens, and
f: focal length of the entire system.
6. An imaging lens equipped with the imaging lens as claimed in claim 1 .
7. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
0.0< R/ 1 f/f (10)
where
R1f: paraxial radius of curvature of the object side surface of the first lens, and
f: focal length of the entire system.
8. 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 (11)
where
f1: focal length of the first lens, and
f: focal length of the entire system.
9. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
−0.15<( R 2 f+R 2 r )/( R 2 f−R 2 r ) (12)
where
R2f: paraxial radius of curvature of the object side surface of the second lens, and
R2r: paraxial radius of curvature of the image side surface of the second lens.
10. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
0.1 <f 12/ f <4.0 (13)
where
f12: combined focal length of the first lens and the second lens, and
f: focal length of the entire system.
11. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
0.5 <f 4/ f <5.0 (14)
where
f4: focal length of the fourth lens, and
f: focal length of the entire system.
12. 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.
13. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
−3.0<( R 5 f+R 5 r )/( R 5 f−R 5 r )<−0.1 (16)
where
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.
14. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
0.2 <f 2/ f <3.0 (17)
where
f2: focal length of the second lens, and
f: focal length of the entire system.
15. 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 (18)
where
D3: center thickness of the second lens
Db23: air space on the optical axis between the second lens and the third lens, and
f: focal length of the entire system.
16. The imaging lens as claimed in claim 1 , wherein the imaging lens satisfies a conditional expression given below:
vd3<30 (20)
where
vd3: Abbe number of the material of the third lens with respect to the d-line.
17. The imaging lens as claimed in claim 1 , wherein the fourth lens is a biconvex lens.
18. An imaging lens, substantially 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:
Nd3<1.7 (1)
Nd4<1.6 (2)
Nd5<1.6 (3)
Nd6<1.89 (4)
where
Nd3: refractive index of the material of the third lens with respect to the d-line,
Nd4: refractive index of the material of the fourth lens with respect to the d-line,
Nd5: refractive index of the material of the fifth lens with respect to the d-line, and
Nd6: refractive index of the material of the sixth lens with respect to the d-line,
wherein the imaging lens satisfies a conditional expression given below:
0.2 <Db 12/ f <3.0 (21)
where
Db12: air space on the optical axis between the first lens and the second lens, and
f: focal length of the entire system.