Local Dimming Block Compensation for LCD Halo Reduction
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Solution Overview
Problem
Existing local dimming methods for LCD devices suffer from luminance non-uniformity due to light leakage between adjacent blocks, leading to halo effects and degraded image quality, especially when displaying high gray patterns near dark areas.
Innovation Solution
A driving method that determines dimming values for each local dimming block by analyzing input image data, detects high gray areas, and compensates dimming values using spatial filtering with varying filter sizes and coefficients based on the distance between high gray areas and adjacent blocks to mitigate luminance non-uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If local dimming is applied by dividing the backlight unit into multiple blocks, then power consumption is reduced and contrast ratio is improved, but luminance non-uniformity occurs due to light leakage from adjacent blocks
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the dimming values of adjacent blocks based on the gray levels detected in each block. When a high gray area is detected near a block boundary, the dimming value of the adjacent block is increased to compensate for light leakage, thereby maintaining luminance uniformity while preserving the power-saving benefits of local dimming.
2Illumination intensity
If local dimming is applied by dividing the backlight unit into multiple blocks, then contrast ratio is improved, but halo effects occur due to luminance non-uniformity from light leakage
Solution Approach 1:
The patent dynamically changes the dimming parameters of adjacent blocks based on detected high gray areas. By increasing the dimming value of blocks adjacent to high gray areas, the patent compensates for light leakage and prevents halo effects, thereby maintaining high contrast ratio without the harmful visual artifacts.
Solution Approach 2:
The patent implements a feedback mechanism where the detected gray levels and high gray area positions are used to adjust the dimming values of adjacent blocks. This closed-loop control ensures that halo effects are compensated in real-time, maintaining image quality while preserving the contrast ratio benefits of local dimming.
3Device complexity
If simple block-based dimming is used, then processing complexity is reduced, but luminance non-uniformity cannot be compensated
Solution Approach 1:
The patent applies local quality by treating different blocks differently based on their specific characteristics. Instead of uniform dimming, the patent detects high gray areas in each block and applies localized compensation to adjacent blocks, thereby achieving luminance uniformity without requiring complex global processing.
Data Source
AI summary
A driving method for local dimming of a Liquid Crystal Display (LCD) device and an apparatus using the same are disclosed. The driving method includes determining a dimming value of each of a plurality of local dimming blocks into which a backlight unit is divided to be driven on a block basis by analyzing input image data on a block basis, detecting a high gray area concentrated with high gray levels from each local dimming block based on the analysis of the input image data, and generating position information about the high gray area according to a distance between the high gray area in the block and an adjacent block, and compensating the dimming value of each of the plurality of local dimming blocks by spatial filtering using a spatial filter having a different filter size or different filter coefficients for local dimming blocks according to the position information about the high gray area in the local dimming block.