Imaging lens
There is provided a compact and high-resolution imaging lens at a low cost. The imaging lens comprises in order from an object side to an image side, a first lens having positive refractive power and a convex surface facing the object side near an optical axis, a second lens having negative refractive power and a meniscus shape having the convex surface facing the object side near the optical axis, a third lens having the positive or the negative refractive power, a fourth lens having the convex surface facing the image side near the optical axis, a fifth lens having the positive refractive power, a sixth lens having the positive refractive power, and a seventh lens having the negative refractive power and a concave surface facing the image side near the optical axis, the image side surface of said seventh lens is formed as an aspheric surface which changes to the convex surface at a peripheral area, the object-side surface of said fifth lens has the convex surface facing the object side near the optical axis, all lenses are single lenses arranged with an interval between lenses adjacent to each other, and below conditional expressions (1), (2) and (3) are satisfied: 1.50< Nd 1<1.60 (1) −8.0< f 2/ f <−2.0 (2) 0.3< t 2/ t 3<3.3 (3) where Nd1: refractive index at d-ray of the first lens, f: focal length of the overall optical system, f2: focal length of the second lens, t2: distance along the optical axis from the image-side surface of the second lens to the object-side surface of the third lens, and t3: distance along the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens.
1. An imaging lens comprising in order from an object side to an image side,
a first lens having positive refractive power and a convex surface facing the object side near an optical axis,
a second lens having negative refractive power and a meniscus shape having a convex surface facing the object side near the optical axis,
a third lens having positive or negative refractive power,
a fourth lens having a convex surface facing the image side near the optical axis,
a fifth lens having positive refractive power,
a sixth lens having positive refractive power, and
a seventh lens having negative refractive power and a concave surface facing the image side near the optical axis, wherein an image side surface of said seventh lens is formed as an aspheric surface which changes to a convex surface at a peripheral area, an object-side surface of said fifth lens has a convex surface facing the object side near the optical axis, all lenses are single lenses arranged with an interval between lenses adjacent to each other, and below conditional expressions (1), (2), (3), and (16′) are satisfied:
1.50< Nd 1<1.60 (1)
−8.0< f 2/ f <−2.0 (2)
0.3< t 2/ t 3<3.3 (3)
where
Nd1: refractive index at d-ray of the first lens,
f: focal length of the overall optical system,
f2: focal length of the second lens,
t2: distance along the optical axis from the image-side surface of the second lens to the object-side surface of the third lens, and
t3: distance along the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens, and
f34: composite focal length of the third lens and the fourth lens.
2. The imaging lens according to claim 1 , wherein said fourth lens has negative refractive power near the optical axis.
3. The imaging lens according to claim 1 , wherein a below conditional expression (5) is satisfied:
−10.0<( r 9 +r 10)/( r 9 −r 10)<−0.5 (5)
where
r9: paraxial curvature radius of the object-side surface of the fifth lens, and
r10: paraxial curvature radius of the image-side surface of the fifth lens.
4. The imaging lens according to claim 1 , wherein a below conditional expression (6) is satisfied:
1.0<| f 23|/ f< 4.5 (6)
where
f: focal length of the overall optical system of the imaging lens, and
f23: composite focal length of the second lens and the third lens.
5. The imaging lens according to claim 1 , wherein a below conditional expression (7) is satisfied:
0.01< t 3/ f< 0.15 (7)
where
f: focal length of the overall optical system of the imaging lens, and
t3: distance along the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens.
6. The imaging lens according to claim 1 , wherein below conditional expressions (8) and (9) are satisfied:
50< vd 1<60 (8)
15< vd 2<25 (9)
where
vd1: abbe number at d-ray of the first lens, and
vd2: abbe number at d-ray of the second lens.
7. The imaging lens according to claim 1 , wherein a below conditional expression (10) is satisfied:
15< vd 4<25 (10)
where
vd4: abbe number at d-ray of the fourth lens.
8. The imaging lens according to claim 1 , wherein below conditional expressions (11), (12) and (13) are satisfied:
50< vd 5<60 (11)
50< vd 6<60 (12)
50< vd 7<60 (13)
where
vd5: abbe number at d-ray of the fifth lens,
vd6: abbe number at d-ray of the sixth lens, and
vd7: abbe number at d-ray of the seventh lens.
9. An imaging lens comprising in order from an object side to an image side,
a first lens having positive refractive power and a convex surface facing the object side near an optical axis,
a second lens having negative refractive power and a meniscus shape having a convex surface facing the object side near the optical axis,
a third lens having positive or negative refractive power,
a fourth lens having a convex surface facing the image side near the optical axis,
a fifth lens having positive refractive power,
a sixth lens having positive refractive power, and
a seventh lens having negative refractive power and a concave surface facing the image side near the optical axis, wherein the image side surface of said seventh lens is formed as an aspheric surface which changes to a convex surface at a peripheral area, all lenses are single lenses arranged with an interval between lenses adjacent to each other, and below conditional expressions (4) and (11) are satisfied:
3.0 <f 567/ f< 10.0 (4)
50< vd 5<60 (11)
where
f: focal length of the overall optical system of the imaging lens, and
f567: composite focal length of the fifth lens, the sixth lens and the seventh lens, and
vd5: abbe number at d-ray of the fifth lens.
10. The imaging lens according to claim 9 , wherein said fourth lens has negative refractive power near the optical axis.
11. The imaging lens according to claim 9 , wherein a below conditional expression (5) is satisfied:
−10.0<( r 9 +r 10)/( r 9 −r 10)<−0.5 (5)
where
r9: paraxial curvature radius of the object-side surface of the fifth lens, and
r10: paraxial curvature radius of the image-side surface of the fifth lens.
12. The imaging lens according to claim 9 , wherein a below conditional expression (6) is satisfied:
1.0<| f 23|/ f< 4.5 (6)
where
f: focal length of the overall optical system of the imaging lens, and
f23: composite focal length of the second lens and the third lens.
13. The imaging lens according to claim 9 , wherein a below conditional expression (7) is satisfied:
0.01< t 3/ f< 0.15 (7)
where
f: focal length of the overall optical system of the imaging lens, and
t3: distance along the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens.
14. The imaging lens according to claim 9 , wherein below conditional expressions (8) and (9) are satisfied:
50< vd 1<60 (8)
15< vd 2<25 (9)
where
vd1: abbe number at d-ray of the first lens, and
vd2: abbe number at d-ray of the second lens.
15. The imaging lens according to claim 9 , wherein a below conditional expression (10) is satisfied:
15< vd 4<25 (10)
where
vd4: abbe number at d-ray of the fourth lens.
16. The imaging lens according to claim 9 , wherein below conditional expressions (11), (12) and (13) are satisfied:
50< vd 6<60 (12)
50< vd 7<60 (13)
where
vd6: abbe number at d-ray of the sixth lens, and
vd7: abbe number at d-ray of the seventh lens.