Method for controlling luminance of backlight unit

• US 8,085,237 B2
• Filed: 05/27/2005
• Issued: 12/27/2011
• Est. Priority Date: 05/28/2004
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Hong, Hee Jung
• Primary Examiner(s): Wang, Quan-Zhen
• Assistant Examiner(s): MA, CALVIN
• Application Number:
  US11/138,688
• Publication Number:
  US 20060007104A1
• Time in Patent Office: 2,405 Days
• Field of Search: 345/89, 345/102, 345/690, 315/224
• US Class Current: 345/102
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/066 for control of contrast
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines

Abstract

A method for controlling luminance of an edge type backlight unit having a plurality of lamps at opposite sides of a light-guiding plate is provided that includes: analyzing luminance data for each frame of an image before outputting the image; selecting a backlight luminance level from a Look-Up Table LUT that classifies the luminance according to the analyzed luminance data; outputting lamp on/off control signals according to the selected luminance level; and providing lamp on/off signals to respective lamps according to the lamp on/off control signals.

Claims

1. 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.

2. 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 that classifies the luminance according to the analyzed luminance data 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 the 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;

outputting lamp-dimming control signals according to the selected luminance level; and

providing lamp on/off signals to respective lamps according to the lamp on/off control signals from the Look-Up Table and the lamp-dimming control signals, 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 lamp on/off control signals from the Look-Up Table for 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.

3. The method of claim 2, wherein the lamp-dimming control signal applied in a pulse width modulation PWM method or an analog variable resistance control method.

4. The method of claim 3, wherein the lamp-dimming control signal is applied using a burst inverter, or using an analog inverter.