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 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 positive refractive power in a paraxial region, a fourth lens, a fifth lens with negative refractive power in a paraxial region, a sixth lens with positive refractive power 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, 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 with positive refractive power in a paraxial region,
a fourth lens,
a fifth lens with negative refractive power in a paraxial region,
a sixth lens with positive refractive power having an object-side surface being convex 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 following conditional expressions (1), (2a), and (17′) are satisfied:
40.00 <νd 5<72.00 (1)
4.50≤| r 10 |/f <40.00 (2a)
1.61 <=r 5 /f <=3.11 (17′)
where
νd5: an abbe number at d-ray of the fifth lens,
r10: a paraxial curvature radius of an image-side surface of the fifth lens,
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.
2. The imaging lens according to claim 1 , wherein an image-side surface of said third lens is concave in the paraxial region.
3. The imaging lens according to claim 1 , wherein an image-side surface of said sixth lens is concave in the paraxial region.
4. The imaging lens according to claim 1 , wherein the following conditional expression (3) is satisfied:
9.00 <νd 3<39.00 (3)
where
νd3: an abbe number at d-ray of the third lens.
5. The imaging lens according to claim 1 , wherein the following conditional expression (4) is satisfied:
1.50 <T 6 /T 5<8.00 (4)
where
T6: a distance along the optical axis from an image-side surface of the sixth lens to an object-side surface of the seventh lens, and
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.
6. The imaging lens according to claim 1 , wherein the following conditional expression (5) is satisfied:
−8.50 <f 5 /f <−1.50 (5)
where
f5: a focal length of the fifth 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 (6) is satisfied:
1.45 <f 2 /f 7<4.50 (6)
where
f2: a focal length of the second lens, and
f7: a focal length of the seventh lens.
8. The imaging lens according to claim 1 , wherein the following conditional expression (7) is satisfied:
6.00 <r 4 /T 2<14.00 (7)
where
r4: a paraxial curvature radius of an image-side surface of the second lens, and
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.
9. The imaging lens according to claim 1 , wherein the following conditional expression (8) is satisfied:
1.00 <r 6 /f <12.00 (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.
10. The imaging lens according to claim 1 , wherein the following conditional expression (9) is satisfied:
0.30 <r 12 /f <3.50 (9)
where
r12: a paraxial curvature radius of an image-side surface of the sixth lens, and
f: a focal length of the overall optical system of the imaging lens.