Patent ID: 8351125

Claim:
A directional light distributing optical element, for receiving a light emitted by a light source comprising an optic axis, the directional light distributing optical element comprising: a light incident surface, for receiving the light and comprising a central axis; and a light emission curved surface, intersected with a first plane being vertical to the central axis to form a first curve, wherein the first curve has a plurality of first curve segments, each first curve segment comprises at least three first tangent points, and after passing each first tangent point along a connecting line of the light source and each first tangent point, the light exits along a first axis, an included angle formed between the first axis and the optic axis is greater than −15° and smaller than 15°, and each first tangent point satisfies a formula in the following: M x = tan ⁢ ⁢ θ = tan ⁡ ( sin - 1 ⁡ ( n 1 n 2 ⁢ sin ⁢ ⁢ A x ) ) wherein M x is a tangent slope at each first tangent point, θ is an included angle formed between the first axis and a normal line of each first tangent point, A x is an included angle formed between the connecting line of each first tangent point and the light source and the optic axis, n 1 is a refractive index of the directional light distributing optical element, and n 2 is a refractive index of an ambient environment in which the directional light distributing optical element is disposed.