LED Backlight Duty Ratio Normalization for LCD Flicker Reduction
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Solution Overview
Problem
Liquid crystal display devices using light-emitting diodes for backlighting experience image distortion and severe flickering due to inadequate light emission in areas with varying brightness, particularly during local dimming, which affects display quality.
Innovation Solution
A liquid crystal display device and method that utilize a plurality of light-emitting blocks with a timing controller and look-up tables to normalize and adjust the duty ratio and amplitude of optical data signals based on the initial brightness of each block, maintaining color coordinates and reducing flickering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If local dimming is performed to increase contrast ratio and reduce power consumption, then power consumption and contrast ratio are improved, but light emission in bright portions becomes insufficient causing image distortion
Solution Approach 1:
The backlight unit is divided into multiple light-emitting blocks that can be independently controlled. This segmentation allows different regions to have different brightness levels, enabling local dimming to reduce power consumption in dark areas while maintaining sufficient brightness in bright areas, thereby preventing image distortion.
Solution Approach 2:
Different light-emitting blocks are assigned different duty ratios based on the local brightness requirements of the displayed image. This local quality adjustment ensures that each region receives appropriate light emission, improving contrast ratio in dark regions while preventing insufficient brightness in bright regions.
2Illumination intensity
If local boosting is performed to increase brightness in specific light-emitting blocks, then brightness is improved, but severe flickering occurs due to color differences in the same image
Solution Approach 1:
The patent applies gamma correction and uses look-up tables to normalize duty ratios, transforming the brightness parameters of optical data signals in a coordinated manner across all light-emitting blocks. This parameter transformation ensures that brightness adjustments through local boosting do not cause color shifts or flickering, as all blocks undergo consistent parameter transformation.
3Use of energy by stationary object
If duty ratio is adjusted to control light emission intensity, then power consumption is reduced, but color coordinates are not maintained causing display quality degradation
Solution Approach 1:
Gamma correction and look-up table normalization are applied to transform duty ratio parameters while preserving color coordinates. This parameter transformation allows duty ratio adjustment for power savings while maintaining accurate color reproduction through mathematical normalization.
Solution Approach 2:
The system uses pre-calculated look-up tables that store normalized duty ratio values, providing a feedback mechanism that ensures color accuracy is maintained during duty ratio adjustments. The look-up tables act as a reference that guides the transformation process to preserve color coordinates.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution improves display quality by maintaining color coordinates and reducing flickering, even during local boosting, by adjusting the optical data signals to match the brightness of each light-emitting block, thereby enhancing the overall image quality.
Implementation Method 1
a liquid crystal layer that has dielectric anisotropy that is interposed between the first display panel and the second display panel. An electric field is formed between the pixel electrode and the common electrode, and the intensity of the electric field is adjusted to control the amount of light passing through the liquid crystal panel
Implementation Method 2
as the light source, light-emitting diodes (LEDs) have drawn attention. A backlight unit using light-emitting diodes as a light source
Data Source
AI summary
A liquid crystal display device and a method of driving the same are provided for one or more embodiments. The liquid crystal display device includes: a liquid crystal panel including a plurality of display blocks and displaying an image in response to image signals; a plurality of light-emitting blocks emitting light to the liquid crystal panel and corresponding to the plurality of display blocks; a first look-up table including a normalized value obtained by normalizing an initial duty ratio corresponding to the brightness of the image to a maximum duty ratio corresponding to the maximum brightness of the image; and a timing controller receiving the normalized value corresponding to each of the light-emitting blocks from the first look-up table and using the normalized value to provide an optical data signal corresponding to each of the light-emitting blocks.