Image pickup lens, image pickup apparatus and mobile terminal
The present invention provides an image pickup lens for forming a light flux from a subject into an image on an image pickup element, and the image pickup lens includes, in order from an object side thereof: an aperture stop; a first lens having a positive refractive power; a second lens having a negative refractive power and comprising a concave surface facing an image side of the image pickup lens; a third lens having a positive refractive power; and a fourth lens having a negative refractive power and comprising a concave surface facing the image side. The image pickup lens satisfies the predetermined condition according to a curvature radius of the surface facing the image side on the second lens, and a focal length of the image pickup lens.
1. An image pickup lens for forming a light flux from a subject into an image on an image pickup element, comprising, in order from an object side thereof:
an aperture stop;
a first lens having a positive refractive power;
a second lens having a negative refractive power and comprising a concave surface facing an image side of the image pickup lens;
a third lens having a positive refractive power; and
a fourth lens having a negative refractive power and comprising a concave surface facing the image side,
wherein the image pickup lens satisfies
0.2< r 4/ f≦ 0.52,
where r 4 is a curvature radius of the surface facing the image side on the second lens, and
f is a focal length of the image pickup lens.
2. The image pickup lens of claim 1 , wherein the surface facing the image side on the second lens is an aspherical surface such that a farther position on the aspherical surface from an optical axis has a smaller negative refractive power.
3. The image pickup lens of claim 1 , wherein the surface facing image side on the fourth lens is an aspherical surface such that a farther position on the aspherical surface from an optical axis has a smaller negative refractive power, the aspherical surface having an inflection point on a periphery of the fourth lens.
4. The image pickup lens of claim 1 , wherein a surface facing the image side on the third lens is an aspherical surface such that a farther position on the aspherical surface from an optical axis has a smaller positive refractive power.
5. The image pickup lens of claim 1 , satisfying
0.8 <f 12/ f< 3,
where f 12 is a composite focal length of the first lens and the second lens.
6. The image pickup lens of claim 1 , satisfying
−1.5< r 8/ r 6<−0.2,
where r 6 is a curvature radius of a surface facing the image side on the third lens, and
r 8 is a curvature radius of a surface facing the image side on the fourth lens.
7. The image pickup lens of claim 1 , satisfying
20< v 1− v 2<65,
where v 1 is an Abbe number of the first lens, and
v is an Abbe number of the second lens.
8. The image pickup lens of claim 1 , wherein at least one lens of the image pickup lens comprises a plastic.
9. An image pickup apparatus comprising:
a casing comprising a light-shielding material, and comprising an aperture where a light flux from a subject enters into;
the image pickup lens of claim 1 housed in the casing, for receiving a light flux passing through the aperture;
an image pickup element for receiving a light flux guided by the image pickup lens;
a substrate supporting the image pickup element; and
a connecting terminal formed on the substrate, for transmitting and receiving electrical signal.
10. The image pickup apparatus of claim 9 , wherein the image pickup apparatus has a height of less than 10 mm along an optical axis.
11. A mobile terminal comprising the image pickup apparatus of claim 9 .