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 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 said seventh lens is an aspheric surface having at least one pole point in a position off the optical axis, an image-side surface of said first lens is concave in a paraxial region, said third lens is formed in a meniscus shape in a paraxial region, an image-side surface of said fifth lens is convex in a paraxial region, an object-side surface of said seventh lens is convex in a paraxial region, and the following conditional expressions (2), (3), and (4) are satisfied:
1.80<ν d 3/ν d 5<4.00 (2)
0.10<( T 5/ TTL )×100<0.40 (3)
10.00<ν d 4<29.00 (4)
where
νd3: an abbe number at d-ray of the third lens,
νd5: 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,
TTL: a total track length, and
νd4: an abbe number at d-ray of the fourth lens.
2. The imaging lens according to claim 1 , wherein the following conditional expression (5) is satisfied:
0.60<ν d 2/ν d 5<1.40 (5)
where
νd2: an abbe number at d-ray of the second lens, and
νd5: an abbe number at d-ray of the fifth lens.
3. The imaging lens according to claim 1 , wherein the following conditional expression (7) is satisfied:
−2.30<( D 2/ f 2)×100<−0.50 (7)
where
D2: a thickness along the optical axis of the second lens, and
f2: a focal length of the second lens.
4. 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.
5. The imaging lens according to claim 1 , wherein the following conditional expression (11) is satisfied:
1.55<| f 3/ f 7|<12.50 (11)
where
f3: a focal length of the third lens, and
f7: a focal length of the seventh lens.
6. 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.
7. 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.
8. An imaging lens comprising 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 said seventh lens is an aspheric surface having at least one pole point in a position off the optical axis, an image-side surface of said first lens is concave in a paraxial region, said third lens is formed in a meniscus shape in a paraxial region,
an object-side surface and an image-side surface of said fourth lens are plane surfaces in a paraxial region, an image-side surface of said fifth lens is convex in a paraxial region, an object-side surface of said seventh lens is convex in a paraxial region, and the following conditional expressions (2) and (4) are satisfied:
1.80<ν d 3/ν d 5<4.00 (2)
10.00<ν d 4<29.00 (4)
where
νd3: an abbe number at d-ray of the third lens,
νd5: an abbe number at d-ray of the fifth lens, and
νd4: an abbe number at d-ray of the fourth lens.
9. An imaging lens comprising 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 said seventh lens is an aspheric surface having at least one pole point in a position off the optical axis, an image-side surface of said first lens is concave in a paraxial region, said third lens is formed in a meniscus shape in a paraxial region,
an image-side surface of said fifth lens is convex in a paraxial region, an object-side surface of said seventh lens is convex in a paraxial region, and the following conditional expressions (2), (4), and (9) are satisfied:
1.80<ν d 3/ν d 5<4.00 (2)
10.00<ν d 4<29.00 (4)
1.00<( T 3/ TTL )×100<4.00 (9)
where
νd3: an abbe number at d-ray of the third lens,
νd5: an abbe number at d-ray of the fifth lens,
νd4: an abbe number at d-ray of the fourth 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
TTL: a total track length.