Patent ID: 8085237

Claim:
A method for controlling luminance of an edge type backlight unit having a plurality of lamps at opposite sides of a light-guiding plate, the method comprising: analyzing luminance data for each frame of an image before outputting the image; selecting a luminance level from a Look-Up Table and outputting lamp on/off control signals from the Look-Up Table according to the selected luminance level, wherein the Look-Up Table includes first, second and third luminance levels classified according to the analyzed luminance data and preset lamp on/off control signals that provide a number of lamps being turned-on for each of the three luminance levels, wherein the second luminance level is higher than the first luminance level and the third luminance level is higher than the second luminance level, wherein the number of lamps being turned-on for the each luminance level is different from the number of lamps being turned-on for each of other luminance levels; and providing lamp on/off signals to respective lamps according to the lamp on/off control signals from the Look-Up Table, wherein the lamps are of the same type, wherein the number of the lamps being turned on is adjusted according to the lamp on/off control signals from the Look-Up Table for the three luminance levels so that the number of lamps being turned-on for the each luminance level is different from the number of lamps being turned-on for each of other luminance levels, and the number of the lamps being turned on is different according to the three luminance levels, wherein a first number of the lamps turned-on at a first side of light-guiding plate is the same as a second number of the lamps turned-on at a second side of light-guiding plate for each of the three luminance levels, wherein when the first luminance level, there are turned-on at least one of the lamps placed at the first side and at least one of the lamps placed at the second side, wherein when the third luminance level, there are turned-on all the lamps placed at the first and second sides, and wherein a number of the lamps turned-on in the second luminance level is larger than that of the lamps turned-on in the first luminance level and smaller than that of the lamps turned-on in the third luminance level.