Imaging lens
There is provided an imaging lens with excellent optical characteristics which satisfies demand of a low profile and a low F-number. An imaging lens comprises in order from an object side to an image side, a first lens with positive refractive power being formed in a meniscus shape having an object-side surface being convex in a paraxial region, a second lens with positive refractive power in a paraxial region, a third lens with negative refractive power in a paraxial region, a fourth lens with positive refractive power in a paraxial region, a fifth lens having aspheric surfaces on both sides, and a sixth lens with negative refractive power having an image-side surface being concave 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 being formed in a meniscus shape having an object-side surface being convex in a paraxial region,
a second lens with positive refractive power in a paraxial region,
a third lens with negative refractive power in a paraxial region,
a fourth lens with positive refractive power in a paraxial region,
a fifth lens having aspheric surfaces on both sides, and
a sixth lens with negative refractive power having an image-side surface being concave in a paraxial region, wherein the following conditional expressions (1), (2) and (4) are satisfied:
0.30 <f 1/ f 4<1.85 (1)
−3.30 <r 6/ f<− 0.70 (2)
1.50<( T 2/ f 2)×100<5.50 (4)
where
f1: a focal length of the first lens,
f4: a focal length of the fourth lens,
r6: a paraxial curvature radius of an image-side surface of the third lens,
f: a focal length of the overall optical system of the imaging 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, and
f2: a focal length of the second lens.
2. The imaging lens according to claim 1 , wherein the following conditional expression (5) is satisfied:
−12.50 <r 6 /r 12<−3.20 (5)
where
r6: a paraxial curvature radius of an image-side surface of the third lens, and
r12: a paraxial curvature radius of an image-side surface of the sixth lens.
3. The imaging lens according to claim 1 , wherein the following conditional expression (6) is satisfied:
−3.50 <r 8 /r 11<−1.10 (6)
where
r8: a paraxial curvature radius of an image-side surface of the fourth lens, and
r11: a paraxial curvature radius of an object-side surface of the sixth lens.
4. The imaging lens according to claim 1 , wherein the following conditional expression (7) is satisfied:
0.40 <r 2 /r 4 /r 6<1.20 (7)
where
r2: a paraxial curvature radius of an image-side surface of the first lens,
r4: a paraxial curvature radius of an image-side surface of the second lens, and
r6: a paraxial curvature radius of an image-side surface of the third lens.
5. The imaging lens according to claim 1 , wherein the following conditional expression (8) is satisfied:
3.75<| r 3 |/f< 70.00 (8)
where
r3: a paraxial curvature radius of an object-side surface of the second lens, and
f: a focal length of the overall optical system of the imaging lens.