Imaging lens including seven lenses of +--+0+, +--+-+-, +---+- or +--++- refractive powers
There is provided an imaging lens with excellent optical characteristics which satisfies demand of wide field of view, low profile and low F-number. An imaging lens comprising in order from an object side to an image side, a first lens with positive refractive power having a convex object-side surface in a paraxial region, a second lens with negative refractive power in a paraxial region, a third lens with negative refractive power in a paraxial region, a fourth lens with positive or negative refractive power in a paraxial region, a fifth lens, a sixth lens with positive refractive power in a paraxial region, and a seventh lens with negative refractive power having a concave image-side surface in a paraxial region, 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 a convex object-side surface in a paraxial region,
a second lens with negative refractive power in a paraxial region,
a third lens with negative refractive power in a paraxial region,
a fourth lens with positive or negative refractive power in a paraxial region,
a fifth lens,
a sixth lens with positive refractive power, and having a convex object-side surface, in a paraxial region, and
a seventh lens with negative refractive power having a concave image-side surface in a paraxial region, wherein the following conditional expressions (1), (2) and (3) are satisfied:
0.55< vd 2/ vd 3<1.50 (1)
0.30< r 2/ f< 2.70 (2)
1.85<| r 13|/ f (3)
where
vd2: an abbe number at d-ray of the second lens,
vd3: an abbe number at d-ray of the third lens,
r2: a paraxial curvature radius of an image-side surface of the first lens,
f: a focal length of the overall optical system of the imaging lens, and
r13: a paraxial curvature radius of an object-side surface of the seventh lens.
2. The imaging lens according to claim 1 , wherein the following conditional expression (5) is satisfied:
f 3/ f<− 3.50 (5)
where
f3: a focal length of the third lens, and
f: a focal length of the overall optical system of the imaging lens.
3. The imaging lens according to claim 1 , wherein the following conditional expression (6) is satisfied:
0.60< r 4/ f< 1.20 (6)
where
r4: a paraxial curvature radius of an image-side surface of the second lens, and
f: a focal length of the overall optical system of the imaging lens.
4. The imaging lens according to claim 1 , wherein the following conditional expression (7) is satisfied:
1.50<| r 5|/ f< 6.80 (7)
where
r5: a paraxial curvature radius of an object-side surface of the third lens, and
f: a focal length of the overall optical system of the imaging lens.
5. The imaging lens according to claim 1 , wherein the following conditional expression (8) is satisfied:
0.90<| r 6|/ f< 9.00 (8)
where
r6: a paraxial curvature radius of an image-side surface of the third lens, and
f: a focal length of the overall optical system of the imaging lens.
6. An imaging lens comprising, in order from an object side to an image side,
a first lens with positive refractive power having a convex object-side surface in a paraxial region,
a second lens with negative refractive power in a paraxial region,
a third lens with negative refractive power in a paraxial region,
a fourth lens with positive or negative refractive power in a paraxial region,
a fifth lens,
a sixth lens with positive refractive power in a paraxial region, and
a seventh lens with negative refractive power having a concave image-side surface in a paraxial region, wherein the following conditional expressions (1), (2), (3), and (4) are satisfied:
0.55< vd 2/ vd 3<1.50 (1)
0.30< r 2/ f< 2.70 (2)
1.85<| r 13|/ f (3)
0.65< T 2/ T 4<3.00 (4)
where
vd2: an abbe number at d-ray of the second lens,
vd3: an abbe number at d-ray of the third lens,
r2: a paraxial curvature radius of an image-side surface of the first lens,
f: a focal length of the overall optical system of the imaging lens,
r13: a paraxial curvature radius of an object-side surface of the seventh lens,
T2: a distance along an optical axis from an image-side surface of the second lens to an object-side surface of the third lens, and
T4: a distance along an optical axis from an image-side surface of the fourth lens to an object-side surface of the fifth lens.