Patent ID: 8371735

Claim:
A multi-layer light guide apparatus receiving light from a light source, and a plurality optical paths are formed within the multi-layer light guide apparatus, each layer has a normal line, the apparatus comprising: a body having at least a first light-guide layer and a second light-guide layer, and the first light-guide layer has a first refractive index (n 1 ) and the second light-guide layer has a second refractive index (n 2 ), wherein the first refractive index is smaller than the second refractive index; a light incident surface being one side of the body, the light emitted from the light source simultaneously enters the first light-guide layer and the second light-guide layer from the light incident surface, and generating a first optical path and a second optical path; a light emission surface being a surface of the first light-guide layer, the light entering the light incident surface outputs from the light emission surface, wherein an angle is formed between the light incident surface and the light emission surface; a micro-structured layer formed on one surface of the second light-guide layer and one side opposite to the light emission surface, and a third optical path is formed as the light along the first optical path enters the micro-structured layer; wherein, when the second optical path passes through the first light-guide layer and the second light-guide layer, a first interface critical angle (θ C12 ) with respect to a normal line of the first light-guide layer is formed, and the first interface critical angle is: θ C ⁢ ⁢ 12 = sin - 1 ⁡ ( n 1 n 2 ) ; when the light along the second optical path passes through first light-guide layer, a first critical angle (θ C1 ) with respect to the normal line of the first light-guide layer is formed, and the first critical angle is: θ C ⁢ ⁢ 1 = sin - 1 ⁡ ( 1 n 1 ) ; and the first interface critical angle and the first critical angle are fulfilled with: 0<|θ C12 −θ C1 |≦35° wherein, the light propagates along the second optical path and the third optical path and outputs through the light emission surface.