Light guide apparatus and fabrication method thereof

A light guide apparatus having a first layer and a second layer;

• said first layer having a first planar surface and a second planar opposing surface, a first side and a second side;
• said first layer comprising:
• a first optically transparent section comprising a first optical medium having a first index of refraction;
• the first optically transparent section including the first planar surface;
• and
• a second optically transparent section comprising a second optical medium having a second index of refraction, an interface between the first optically transparent section and the second optically transparent section defining a first continuous prismatic shape;
• the first continuous prismatic shape being a first array of prisms, each element of the first array being a prism;
• the second optically transparent section including the second planar opposing surface;
• said second layer having a third planar surface and a fourth planar opposing surface;
• said second layer comprising:
• a third optically transparent section comprising a third optical medium having a third index of refraction;
• the third optically transparent section including the third planar surface;
• and a fourth optically transparent section comprising a fourth optical medium having a fourth index of refraction, an interface between the third optically transparent section and the fourth optically transparent section defining a second continuous prismatic shape;
• the second continuous prismatic shape being a second array of prisms, each element of the second array being a prism;
• the fourth optically transparent section including the fourth planar opposing surface;
• wherein the fourth planar surface of said another layer is disposed on the first planar surface of the first layer;
• wherein the interface between the third optically transparent section and a fourth optically transparent section, the third index of refraction and the fourth index of refraction are configured such that light impinging on the first planar surface is refracted into the fourth planar surface and, after impinging the interface between the third optically transparent section and the fourth optically transparent section, is returned to the first optically transparent section;
• wherein each prism of the first array of prisms is asymmetric and has a negatively inclined facet that is inclined with respect to a normal to the second planar opposing surface;
• wherein the negatively inclined facet of each prism of the first array of prisms forms an acute angle with another facet of the prism and forms an obtuse angle with a base of the prism so that an entire projection of the negatively inclined facet on said second planar opposing surface lies outside the base of the prism;
• wherein at least one of the first side and the second side configured to receive light from a light source;
• and
• wherein light experiences total internal reflection at said first planar surface, impinges on the negatively inclined facets of the first array of prisms, and emerges from said second planar opposing surface substantially collimated within a predetermined angle.