Imaging lens
An imaging lens includes, in order from an object side to an image side, a first lens L 1 having negative refractive power, a second lens L 2 having positive refractive power, a third lens L 3 having positive refractive power, a fourth lens L 4 , a fifth lens L 5 , a sixth lens L 6 , a seventh lens L 7 , and an eighth lens L 8 having negative refractive power, wherein said eighth lens L 8 has an aspheric image-side surface having at least one inflection point.
1. An imaging lens comprising, in order from an object side to an image side,
a first lens having negative refractive power,
a second lens having positive refractive power,
a third lens having positive refractive power,
a fourth lens,
a fifth lens,
a sixth lens,
a seventh lens, and
an eighth lens having negative refractive power,
wherein said eighth lens has an aspheric image-side surface having at least one inflection point, and
wherein the following conditional expression is satisfied:
−3.0< f 8/ f<− 0.3
where
f: a focal length of the overall optical system of the imaging lens, and
f8: a focal length of the eighth lens.
2. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied:
−10.0< f 1/ f 2<−0.8
where
f1: a focal length of the first lens, and
f2: a focal length of the second lens.
3. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied:
0.05< D 12/ f< 0.20
where
f: a focal length of the overall optical system of the imaging lens, and
D12: a distance along the optical axis between the first lens and the second lens.
4. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied:
1.0< f 2/ f 3<6.5
where
f2: a focal length of the second lens, and
f3: a focal length of the third lens.
5. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied:
0.3< f 3/ f< 3.5
where
f: a focal length of the overall optical system of the imaging lens, and
f3: a focal length of the third lens.
6. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied:
0.2< R 4 r/f< 1.0
where
f: a focal length of the overall optical system of the imaging lens, and
R4r: a curvature radius of an image-side surface of the fourth lens.
7. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied:
0.08< D 45/ f< 0.20
where
f: a focal length of the overall optical system of the imaging lens, and
D45: a distance along the optical axis between the fourth lens and the fifth lens.
8. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied:
0.5< D 56/ D 67<4.0
where
D56: a distance along the optical axis between the fifth lens and the sixth lens, and
D67: a distance along the optical axis between the sixth lens and the seventh lens.
9. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied:
0.2< R 8 f/f< 1.8
where
f: a focal length of the overall optical system of the imaging lens, and
R8f: a curvature radius of an object-side surface of the eighth lens.