A backlight unit to effectively prevent generation of double images, having a frame, a plurality sets of light sources, at least one isolator and one diffuser. The light source sets are located within the frame and are individually driven periodically. The isolator is disposed at the bottom of the frame between adjacent light source sets. The diffuser is located on top of the frame over the light source sets and the isolator with a height larger than or equal to half the distance between the diffuser and the bottom of the frame.