Display Backlight Luminance Control for Contrast Optimization
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Solution Overview
Problem
Liquid crystal display (LCD) panels face challenges in achieving high contrast ratios due to light leakage, especially when displaying black images, as existing local dimming methods are ineffective for both bright and dark images, leading to reduced image quality.
Innovation Solution
A method for driving light source blocks in a display apparatus, where a block representative value is determined based on a parameter corresponding to the total luminance of a frame, allowing each light source block to adjust its luminance within a range between the block mean and maximum values, ensuring effective local dimming for both bright and dark images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the luminance of light source blocks is set based on the mean value of corresponding pixel data, then bright images are displayed well, but dark images look too dark
Solution Approach 1:
The patent applies dynamics by making the light source block luminance adaptive rather than static. The control unit dynamically adjusts the luminance of each light source block based on the luminance characteristics of the image data in its corresponding region. This allows the system to automatically adapt to different image conditions (bright or dark scenes) and optimize display quality accordingly, resolving the contradiction between displaying bright and dark images effectively.
2Illumination intensity
If the luminance of light source blocks is set based on the maximum value of corresponding pixel data, then local dimming is not effective, but bright images are displayed with high luminance
Solution Approach 1:
The patent applies local quality by dividing the display into multiple regions corresponding to different light source blocks, and applying different luminance control strategies to each region based on its local image characteristics. Instead of using a global maximum value for all blocks, each block's luminance is independently controlled according to the luminance distribution in its specific region, thereby maintaining both high luminance where needed and effective local dimming where appropriate.
3Illumination intensity
If LCD panel transmissivity is minimized to display black images, then light leakage occurs, but contrast ratio is reduced
Solution Approach 1:
The patent applies segmentation by dividing the backlight unit into multiple independently controllable light source blocks that correspond to different regions of the display. This segmentation allows selective dimming of specific blocks rather than requiring the entire backlight to be dimmed for black images. By controlling individual blocks, the system can reduce light leakage in specific dark regions while maintaining contrast ratio through localized luminance adjustment rather than global dimming.
Data Source
AI summary
A display apparatus includes light source blocks driven as follows in displaying at least one frame (possibly every frame). An image to be displayed includes image pixels. Each light source block corresponds to an image pixels block which is a block of image pixels to be displayed directly opposite to the light source block. For each image pixels block, a block mean value and a block maximum value are determined. A parameter is determined which corresponds to a total luminance of the frame. For each image pixels block, a block representative value is determined which corresponds to the parameter, the block representative value being within a range between the block mean value and the block maximum value inclusive. During the frame, each light source block is driven to provide a luminance which is an increasing function of the corresponding block representative value.