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<1.6 (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,
a second lens,
a third lens,
a fourth lens having negative refractive power,
a fifth lens having positive refractive power,
a sixth lens, and
a seventh lens, wherein said fourth lens has a convex surface facing the image side near the optical axis, and the following conditional expressions (2a), (3), (13) and (16) are satisfied:
−7.1< f 2/ f<− 2.5 (2a)
0.3< t 2/ t 3<3.3 (3)
50<ν d 7<60 (13)
2.5<| f 34|/ f< 12.0 (16)
where
f: a focal length of the overall optical system,
f2: a focal length of the second lens,
f34: a composite focal length of the third lens and the fourth lens,
t2: a distance along the optical axis from an image-side surface of the second lens to an object- side surface of the third lens,
t3: a distance along the optical axis from an image-side surface of the third lens to an object-side surface of the fourth lens, and
vd7: an abbe number at d-ray of the seventh lens.
2. The imaging lens according to claim 1 , wherein the following conditional expression (4) is satisfied:
3.0< f 567/ f< 10.0 (4)
where
f567: a composite focal length of the fifth lens, the sixth lens, and the seventh lens.
3. The imaging lens according to claim 1 , wherein the following conditional expression (5) is satisfied:
−10.0<( r 9+ r 10)/( r 9− r 10)<−0.5 (5)
where
r9: a paraxial curvature radius of an object-side surface of the fifth lens, and
r10: a paraxial curvature radius of an image-side surface of the fifth lens.
4. The imaging lens according to claim 1 , wherein the following conditional expression (6) is satisfied:
1.0<| f 23|/ f< 4.5 (6)
where
f23: a composite focal length of the second lens and the third lens.
5. The imaging lens according to claim 1 , wherein the following conditional expression
0.01< t 3/ f< 0.15 (7)
is satisfied.
6. The imaging lens according to claim 1 , wherein the following conditional expression (14) is satisfied:
0.05< d 1/ f< 0.30 (14)
where
d1: a thickness along the optical axis of the first lens.
7. The imaging lens according to claim 1 , wherein the following conditional expression (15) is satisfied:
1.0< f 12/ f< 3.0 (15)
where
f12: a composite focal length of the first lens and the second lens.
8. The imaging lens according to claim 1 , wherein the following conditional expression (17) is satisfied:
1.7< f 5/ f< 4.5 (17)
where
f5: a focal length of the fifth lens.
9. The imaging lens according to claim 1 , wherein the following conditional expression (18) is satisfied:
0.1< r 1/ r 2<0.7 (18)
where
r1: a paraxial curvature radius of an object-side surface of the first lens, and
r2: a paraxial curvature radius of an image-side surface of the first lens.
10. An imaging lens comprising in order from an object side to an image side,
a first lens having positive refractive power,
a second lens,
a third lens,
a fourth lens having negative refractive power,
a fifth lens having positive refractive power,
a sixth lens, and
a seventh lens, wherein said second lens has a convex surface facing the object side near the optical axis, said fourth lens has a convex surface facing the image side near the optical axis, and the following conditional expression (2a) and (16) are satisfied:
−7.1< f 2/ f<− 2.0 (2a)
2.5<| f 34|/ f< 12.0 (16)
where
f: a focal length of the overall optical system,
f2: a focal length of the second lens, and
f34: a composite focal length of the third lens and the fourth lens.
11. The imaging lens according to claim 10 , wherein the following conditional expression (3) is satisfied:
0.3< t 2/ t 3<3.3 (3)
where
t2: a distance along the optical axis from an image-side surface of the second lens to an object-side surface of the third lens, and
t3: a distance along the optical axis from an image-side surface of the third lens to an object-side surface of the fourth lens.
12. The imaging lens according to claim 10 , wherein the following conditional expression (4) is satisfied:
3.0< f 567/ f< 10.0 (4)
where
f567: a composite focal length of the fifth lens, the sixth lens, and the seventh lens.
13. The imaging lens according to claim 10 , wherein the following conditional expression (5) is satisfied:
−10.0<( r 9+ r 10)/( r 9− r 10)<−0.5 (5)
where
r9: a paraxial curvature radius of an object-side surface of the fifth lens, and
r10: a paraxial curvature radius of an image-side surface of the fifth lens.
14. The imaging lens according to claim 10 , wherein the following conditional expression (6) is satisfied:
1.0<| f 23|/ f< 4.5 (6)
where
f23: a composite focal length of the second lens and the third lens.
15. The imaging lens according to claim 10 , wherein the following expression (7) is satisfied:
0.01< t 3/ f< 0.15 (7)
where t3: a distance along the optical axis from an image-side surface of the third lens to an object-side surface of the fourth lens.
16. The imaging lens according to claim 10 , wherein the following conditional expression (14) is satisfied:
0.05< d 1/ f< 0.30 (14)
where
d1: a thickness along the optical axis of the first lens.
17. The imaging lens according to claim 10 , wherein the following conditional expression (15) is satisfied:
1.0< f 12/ f< 3.0 (15)
where
f12: a composite focal length of the first lens and the second lens.
18. The imaging lens according to claim 10 , wherein the following conditional expression (17) is satisfied:
1.7< f 5/ f< 4.5 (17)
where
f5: a focal length of the fifth lens.
19. The imaging lens according to claim 10 , wherein the following conditional expression (18) is satisfied:
0.1< r 1/ r 2<0.7 (18)
where
r1: a paraxial curvature radius of an object-side surface of the first lens, and
r2: a paraxial curvature radius of an image-side surface of the first lens.