Patent ID: 7090388

Claim:
A light guide which receives an incident light from an incidence plane and emits the incident light from an emitting surface provided on a surface adjacent to the incidence plane, said light guide comprising: a total reflecting surface which guides the incident light within said light guide; a light extracting surface which reflects incident light toward said emitting surface where the incident light emits from said emitting surface; a re-incidence plane, which is formed so as to form a substantially V-shaped groove with said light extracting surface, and if not all of the incident light is reflected toward said emitting surface by said light extracting surface, said re-incidence plane receives incident light not reflected toward said emitting surface from said light extracting surface, and wherein said total reflecting surface, said light extracting surface, and said re-incidence plane are periodically formed on a surface opposite to said emitting surface, wherein a distance d defines a distance between a line through a vertex of said substantially V-shaped groove and parallel with said emitting surface and an intersection between said total reflecting surface adjacent to the substantially V-shaped groove and positioned at said incidence plane side and said light extracting surface, wherein a distance x defines a distance between the line through the vertex of said substantially V-shaped groove and parallel with said emitting surface and an intersection between said total reflecting surface adjacent to the substantially V-shaped groove and positioned at an opposite side of said incidence plane and said re-incidence plane, and wherein the surface opposite to said emitting surface has a region where x/d<1, and at least one of d and x is allowed to periodically change so that the intensity distribution of the light emitted from said emitting surface is uniform.