Imaging lens
There is provided an imaging lens with high-resolution which satisfies the wide field of view, the low-profileness and the low F-number in well balance, and excellently corrects aberrations. An imaging lens comprises in order from an object side to an image side, a first lens having negative refractive power, an aperture stop, a second lens, a third lens being a double-aspheric lens, a fourth lens having positive refractive power, and a fifth lens being a double-sided aspheric lens, wherein a below expression is satisfied: −0.07<( N 1−1)/( r 1× f )×1000<0.07 where N1: refractive index at d-ray of the first lens, r1: curvature radius of the object-side surface of the first lens, f: focal length of the overall optical system.
1. An imaging lens comprising in order from an object side to an image side,
a first lens having negative refractive power,
an aperture stop,
a second lens,
a third lens being a double-aspheric lens,
a fourth lens having positive refractive power, and
a fifth lens being a double-sided aspheric lens, wherein a below conditional expression (1) is satisfied:
−0.07<( N 1−1)/( r 1× f )×1000<0.07 (1)
where
N1: refractive index at d-ray of the first lens,
r1: curvature radius of the object-side surface of the first lens (mm),
f: focal length of the overall optical system (mm).
2. The imaging lens according to claim 1 , wherein said second lens has positive refractive power and an image-side surface thereof is a convex surface near the optical axis.
3. The imaging lens according to claim 1 , wherein said fifth lens has negative refractive power and has at least one off-axial pole point on the image-side surface thereof.
4. The imaging lens according to claim 1 , wherein said third lens has at least one off-axial pole point on the object-side surface or the image-side surface thereof.
5. The imaging lens according to claim 1 , wherein a below conditional expression (2) is satisfied:
0.8<| r 9|/ f< 7.0 (2)
where
r9: curvature radius of the object-side surface of the fifth lens (mm).
6. The imaging lens according to claim 1 , wherein a below conditional expression (3) is satisfied:
−0.07<( N 2−1)/( r 3× f )×1000<90.0 (3)
where
N2: refractive index at d-ray of the second lens,
r3: curvature radius of the object-side surface of the second lens (mm).
7. The imaging lens according to claim 1 , wherein a below conditional expression (4) is satisfied:
0.6< f 2/ f< 1.5 (4)
where
f2: focal length of the second lens (mm).
8. The imaging lens according to claim 1 , wherein a below conditional expression (5) is satisfied:
2.5<| f 3|/ f (5)
where
f3: focal length of the third lens (mm).
9. The imaging lens according to claim 1 , wherein a below conditional expression (6) is satisfied:
0.5< f 4/ f< 1.1 (6)
where
f4: focal length of the fourth lens (mm).
10. The imaging lens according to claim 1 , wherein a below conditional expression (7) is satisfied:
−1.2< f 5/ f<− 0.5 (7)
where
f5: focal length of the fifth lens (mm).
11. The imaging lens according to claim 1 , wherein a below conditional expression (8) is satisfied:
20<( vd 1+ vd 2)/2− vd 3<50 (8)
where
vd1: abbe number at d-ray of the first lens,
vd2: abbe number at d-ray of the second lens,
vd3: abbe number at d-ray of the third lens.
12. The imaging lens according to claim 1 , wherein a below conditional expression (9) is satisfied:
20<| vd 4− vd 5|<50 (9)
where
vd4: abbe number at d-ray of the fourth lens,
vd5: abbe number at d-ray of the fifth lens.
13. The imaging lens according to claim 1 , wherein the image-side surface of said fourth lens is convex near the optical axis, and a below conditional expression (10) is satisfied:
2.3< r 7/ r 8<14.0 (10)
where
r7: curvature radius of the object-side surface of the fourth lens (mm),
r8: curvature radius of the image-side surface of the fourth lens (mm).
14. The imaging lens according to claim 1 , wherein the image-side surface of said fifth lens is concave near the optical axis, and a below conditional expression (11) is satisfied:
0.2< r 10/ f< 0.7 (11)
where
r10: curvature radius of the image-side surface of the fifth lens (mm).
15. The imaging lens according to claim 1 , wherein a below conditional expression (12) is satisfied:
20<( t 1/ f )×100<35 (12)
where
t1: distance along the optical axis from the image-side surface of the first lens to the object-side surface of the second lens.
16. The imaging lens according to claim 1 , wherein the image-side surface of said first lens is concave near the optical axis, and a below conditional expression (13) is satisfied:
−1.3<( r 2×2)/ f 1<−0.8 (13)
where
r2: curvature radius of the image-side surface of the first lens (mm),
f1: focal length of the first lens (mm).
17. The imaging lens according to claim 1 , wherein a below conditional expression (14) is satisfied:
0.2< d 2/ f< 0.5 (14)
where
d2: thickness along the optical axis of the second lens (mm).
18. The imaging lens according to claim 1 , wherein a below conditional expression (15) is satisfied:
0.30< d 4/ f< 0.65 (15)
where
d4: thickness along the optical axis of the fourth lens (mm).
19. The imaging lens according to claim 1 , wherein a below conditional expression (16) is satisfied:
1.0< f 12/ f< 2.0 (16)
where
f12: composite focal length of the first lens and the second lens (mm).