Imaging lens
There is provided an imaging lens with excellent optical characteristics which satisfies demand of 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 an object-side surface being convex in a paraxial region, a second lens with negative refractive power having an object-side surface being convex in a paraxial region, a third lens with positive or negative refractive power in a paraxial region, a fourth lens with negative refractive power in a paraxial region, and a fifth lens with positive refractive power having an image-side surface being convex 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 an object-side surface being convex in a paraxial region,
a second lens with negative refractive power having an object-side surface being convex in a paraxial region,
a third lens with positive or negative refractive power in a paraxial region,
a fourth lens with negative refractive power in a paraxial region, and
a fifth lens with positive refractive power having an image-side surface being convex in a paraxial region,
wherein said third lens has an object-side surface being convex in the paraxial region, and following conditional expressions (1), (2), (3), and (6) are satisfied:
45.00<ν d 4<68.00 (1)
0.30< r 2/ r 8<2.00 (2)
3.00<( T 2/ f )×100<14.00 (3)
4.50< r 5/ D 3<31.00 (6)
where
νd4: an Abbe number at d-ray of the fourth lens,
r2: a paraxial curvature radius of an image-side surface of the first lens,
r8: a paraxial curvature radius of an image-side surface of the fourth lens,
T2: a distance along an optical axis from an image-side surface of the second lens to the object-side surface of the third lens,
f: a focal length of the overall optical system of the imaging lens,
r5: a paraxial curvature radius of the object-side surface of the third lens, and
D3: a thickness along the optical axis of the third lens.
2. The imaging lens according to claim 1 , wherein the following conditional expression (4) is satisfied:
10.50 <f 5 /D 5<41.00 (4)
where
f5: a focal length of the fifth lens, and
D5: a thickness along the optical axis of the fifth lens.
3. The imaging lens according to claim 1 , wherein the following conditional expression (5) is satisfied:
0.20 <r 3 /f <0.90 (5)
where
r3: a paraxial curvature radius of the object-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:
0.20 <r 6 /f <2.10 (7)
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.
5. The imaging lens according to claim 1 , wherein the following conditional expression (8) is satisfied:
−2.50 <r 7 /T 3<−0.80 (8)
where
r7: a paraxial curvature radius of an object-side surface of the fourth lens, and
T3: a distance along the optical axis from an image-side surface of the third lens to the object-side surface of the fourth lens.
6. The imaging lens according to claim 1 , wherein the following conditional expression (9) is satisfied:
−9.00 <r 10 /r 4<−1.50 (9)
where
r10: a paraxial curvature radius of the image-side surface of the fifth lens, and
r4: a paraxial curvature radius of the image-side surface of the second lens.
7. The imaging lens according to claim 1 , wherein the following conditional expression (10) is satisfied:
0.65 <r 8 /f 5≤2.64 (10)
where
r8: a paraxial curvature radius of the image-side surface of the fourth lens, and
f5: a focal length of the fifth lens.
8. The imaging lens according to claim 1 , wherein the following conditional expression (11) is satisfied:
−4.50 <r 10 /r 5<−0.50 (11)
where
r10: a paraxial curvature radius of the image-side surface of the fifth lens, and
r5: a paraxial curvature radius of the object-side surface of the third 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 having an object-side surface being convex in a paraxial region,
a third lens with positive or negative refractive power in a paraxial region,
a fourth lens with negative refractive power in a paraxial region, and
a fifth lens with positive refractive power having an image-side surface being convex in a paraxial region,
wherein said third lens has an object-side surface being convex in the paraxial region, and following conditional expressions (1), (2), (3), and (7) are satisfied:
45.00 <νd 4<68.00 (1)
0.30 <r 2 /r 8<2.00 (2)
3.00<( T 2 /f )×100<14.00 (3)
0.20 <r 6 /f <2.10 (7)
where
νd4: an Abbe number at d-ray of the fourth lens,
r2: a paraxial curvature radius of an image-side surface of the first lens,
r8: a paraxial curvature radius of an image-side surface of the fourth lens,
T2: a distance along an optical axis from an image-side surface of the second lens to the object-side surface of the third lens,
f: a focal length of the imaging lens, and
r6: a paraxial curvature radius of an image-side surface of the third lens.