US Patent 7963680 Light emitting diode and lens for the same

A lens for a light emitting diode is formed with a material having a refractive index of n, and the lens includes a base, a first curved circumferential surface extending from the base, a curved center-edge surface extending from the first curved circumferential surface, and a curved centermost surface extending from the curved center-edge surface. The base includes a groove for receiving a light emitting chip therein. In the lens, a distance from a center of the base to a point of the curved center-edge surface is always shorter than the radius of curvature for the point of the curved center-edge surface. The curved centermost surface has a concave shape with respect to the base. In addition, when an obtuse angle formed between a main axis of the lens and a tangent line of a point of the curved centermost surface is A1, and an acute angle formed between a straight line linking the center of the base to the point of the curved centermost surface and the main axis of the lens is A2, the lens satisfies the equation: A1+A2<90+sin−1(1/n).