Lens and bulb-type light emitting device lamp employing the lens

1. A lens for changing light distribution of incident illumination light and emitting the illumination light, the lens comprising:

a light incident surface comprising a first curved surface having a first curvature and a second curved surface having a second curvature, which is different from the first curvature;

a top surface; and

a side surface which is uneven,

wherein a majority of the transmitted through the first curved surface is emitted via the top surface, and a majority of the light incident on the second curved surface is emitted via the side surface, and

wherein the lens is rotationally symmetric with respect to a central axis and an outmost diameter of the lens is constant with respect to a height of the lens.

2. The lens of claim 1 , wherein the top surface is planar.

3. The lens of claim 1 , wherein first curved surface is centrally disposed with respect to the lens, and the second curved surface surrounds an outer perimeter of the first curved surface, and wherein an amount of light transmitted through the second curved surface is greater than an amount of light transmitted through the first curved surface.

4. The lens of claim 1 , wherein the first curved surface is centrally disposed with respect to the lens, and the second curved surface surrounds an outer perimeter of the first curved surface, and wherein the first curved surface is concave and the second curved surface is convex.

5. The lens of claim 1 , wherein the light incident surface faces the top surface.

6. The lens of claim 5 , wherein the first curved surface is concave and the second curved surface is convex.

7. The lens of claim 6 , wherein a radius of curvature of the first curved surface is smaller than a radius of curvature of the second curved surface.

8. The lens of claim 1 , wherein the first curved-surface is a concave surface which diverges light incident thereon, and

the second curved-surface is a convex surface which converges light incident thereon.

9. The lens of claim 8 , wherein the first curved-surface is a spherical surface whose radius of curvature R 1 satisfies an inequality below,

1.5 mm<R1<4 mm.

10. The lens of claim 8 , wherein the second curved-surface is a spherical surface whose radius of curvature R 2 satisfies an inequality below,

17 mm<R 2 <21 mm.

11. The lens of claim 1 , further comprising a planar bottom surface that connects the light incident surface and the side surface.

12. The lens of claim 1 , wherein incident light having a distribution angle within 180° is dispersed by the lens such that output light has a distribution angle equal to or greater than 300°.

13. A bulb-type light emitting device lamp comprising:

a light emitting device package comprising a light emitting device;

a body comprising a mount surface on which the light emitting device package is mounted, wherein the body is formed of a heat radiation material;

the lens of claim 1 , which is disposed such that light emitted from the light emitting device is incident on the incident surface; and

a cover which entirely covers the light emitting device package and the lens, wherein the cover is formed of a transparent material that is mixed with a diffusion material.

14. A lens for changing a distribution of incident light, the lens comprising:

a top surface which is planar;

a light incident surface, opposite the top surface, wherein the light incident surface comprises a first curved surface which is concave and has a first curvature and a second curved surface which is convex and has a second curvature, different form the first curvature;

a side surface which is prismatic;

wherein the first curved surface is centrally disposed with respect to the lens, and the second curved surface surrounds an outer perimeter of the first curved surface.

15. The lens of claim 14 , wherein a majority of light transmitted through the first curved surface is emitted via the top surface, and a majority of the light transmitted through the second curved surface is output via the side surface.

16. The lens of claim 14 , wherein a radius of curvature of the first curved surface is smaller than a radius of curvature of the second curved surface.

17. The lens of claim 14 , wherein an amount of light transmitted through the second curved surface is greater than an amount of light transmitted through the first curved surface.