A backlight unit includes a substrate, a plurality of light emitting diodes disposed at corners of a polygon or arranged side by side on the substrate, and a plurality of lenses coupled to the light emitting diodes for directing the lights emitted from the light emitting diodes in a predetermined direction. The light emitting diodes are comprised of at least three light emitting diodes capable of cooperating with each other to create a white light. Each of the lenses has an asymmetrical irradiation characteristic such that the lenses allow the lights to be irradiated on a predetermined target region and uniformly mixed with each other. The lenses are designed and oriented to irradiate the lights in an elliptical shape close to a rectangle toward a top portion of the backlight unit.