Patent ID: 7164842

Claim:
A backlighting device, comprising: a light guide plate having a first side, a second side opposite to said first side, and a surface extending between said first and second sides; and a point light source to generate light incident on said first side of said light guide plate; said light guide plate having a plurality of longitudinal diffraction microstructures formed on said surface of said light guide plate, and arranged and oriented according to a location of said point light source; said longitudinal diffraction microstructures being formed as ridges or grooves that are tapered away from said surface, and said microstructures, are varied gradually at least in size, position, density, or shape; wherein said microstructures extend in a direction along which said light is incident on said light guide plate, each of said microstructures having a height or depth from said surface, and an inclined face which is inclined with respect to said surface by an angle, said microstructures being spaced apart from each other by a distance, said microstructures being distributed with a density which changes gradually towards two sides from a light entrance region of said light guide plate as a center, said density being varied gradually by controlling said height or depth, said angle, or said distance so that when light is incident on said light guide plate from said point light source, said microstructures regulate and adjust the illuminance of bright and dark areas in said light guide plate so as to provide uniform brightness.