Imaging lens including seven lenses of +−+0+−−, +−+0−+−or +−+0++−refractive powers
There is provided an imaging lens with excellent optical characteristics which satisfies demand of wide field of view, low-profileness and low F-number. An imaging lens comprises, in order from an object side to an image side, a first lens with positive refractive power having an object-side surface being convex in a paraxial region, a second lens with negative refractive power in a paraxial region, a third lens, a fourth lens being a double-sided aspheric lens, a fifth lens, a sixth lens having an image-side surface being concave in a paraxial region, and a seventh lens with negative refractive power having an image-side surface being concave in a paraxial region, wherein the image-side surface of the seventh lens is an aspheric surface having at least one pole point in a position off the optical axis, and predetermined conditional expressions are satisfied.
1. An imaging lens comprising in order from an object side to an image side,
a first lens with positive refractive power,
a second lens,
a third lens,
a fourth lens being a double-sided aspheric lens, an object-side surface and an image-side surface of said fourth lens being plane surfaces in a paraxial region,
a fifth lens,
a sixth lens, and
a seventh lens with negative refractive power having an image-side surface being concave in a paraxial region, wherein the image-side surface of said seventh lens is an aspheric surface having at least one pole point in a position off the optical axis, and following conditional expression (1) is satisfied:
10.00 <vd 2<29.00 (1)
where
vd2: an abbe number at d-ray of the second lens.
2. The imaging lens according to claim 1 , wherein an object-side surface of said third lens is convex in a paraxial region.
3. The imaging lens according to claim 1 , wherein an object-side surface of said seventh lens is convex in a paraxial region.
4. The imaging lens according to claim 1 , wherein the following conditional expression (6) is satisfied:
0.60 <vd 3 /vd 6<1.40 (6)
where
vd3: an abbe number at d-ray of the third lens, and
vd6: an abbe number at d-ray of the sixth lens.
5. The imaging lens according to claim 1 , wherein the following conditional expression (8) is satisfied:
0.30<( D 5/| f 5|)×100<6.50 (8)
where
D5: a thickness along the optical axis of the fifth lens, and f5: a focal length of the fifth lens.
6. The imaging lens according to claim 1 , wherein the following conditional expression (10) is satisfied:
0.10| f 3 /f 5|<2.10 (10)
where
f3: a focal length of the third lens, and f5: a focal length of the fifth lens.
7. The imaging lens according to claim 1 , wherein the following conditional expression (12) is satisfied:
0.50 <r 2 /f <2.10 (12)
where
r2: a paraxial curvature radius of an image-side surface of the first lens, and f: a focal length of the overall optical system of the imaging lens.
8. The imaging lens according to claim 1 , wherein the following conditional expression (13) is satisfied:
−8.50 <r 10 /f <−0.70 (13)
where
r10: a paraxial curvature radius of an image-side surface of the fifth lens, and f: a focal length of the overall optical system of the imaging lens.
9. The imaging lens according to claim 1 , wherein the following conditional expression (14) is satisfied:
0.30 <r 13 /f <1.55 (14)
where
r13: a paraxial curvature radius of an object-side surface of the seventh lens, and
f: a focal length of the overall optical system of the imaging lens.
10. The imaging lens according to claim 1 , wherein an object-side surface of said first lens is convex in a paraxial region.
11. The imaging lens according to claim 1 , wherein said second lens has negative refractive power in a paraxial region.
12. The imaging lens according to claim 1 , wherein an image-side surface of said sixth lens is concave in a paraxial region.
13. The imaging lens according to claim 1 , wherein the following conditional expressions (2) and (3) are satisfied:
1.80 <vd 3 /vd 5<4.00 (2)
0.10<( T 5/TTL)×100<0.40 (3)
where
vd3: an abbe number at d-ray of the third lens,
vd5: an abbe number at d-ray of the fifth lens,
T5: a distance along the optical axis from an image-side surface of the fifth lens to an object-side surface of the sixth lens, and
TTL: a total track length.