LCD Black Non-Uniformity via Multi-Stage Gradation Conversion
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Solution Overview
Problem
Liquid crystal displays suffer from black non-uniformity due to disturbances in liquid crystal molecule orientation, which existing methods either fail to reduce or do so at the cost of reducing image contrast.
Innovation Solution
An image display apparatus and method that involves generating and processing image data using specific gradation conversion characteristics to control the emission brightness of light-emitting units, thereby reducing black non-uniformity while maintaining image contrast, by converting input gradation values into output gradation values through a series of data processing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the voltage applied to liquid crystal elements is increased to reduce black non-uniformity, then black non-uniformity is reduced, but the display brightness of black is increased and the contrast of the displayed image is reduced
Solution Approach 1:
The image data processing is divided into multiple conversion stages: first conversion unit applies gamma correction, second conversion unit performs black level adjustment, and third conversion unit applies tone mapping. This segmentation allows each unit to address specific aspects of the image data independently, enabling reduction of black non-uniformity while preserving overall image contrast.
Solution Approach 2:
The patent applies different processing characteristics to different parts of the image data: the lower limit of input gradation values is increased to a first gradation value to address black non-uniformity in dark regions, while the emission brightness of the backlight unit is corrected based on input image data to maintain contrast in brighter regions. This local quality approach allows differential treatment of different brightness regions.
2Illumination intensity
If local dimming is applied to enhance image contrast, then image contrast is enhanced, but black non-uniformity is not reduced
Solution Approach 1:
The patent merges multiple image processing techniques into a unified system: gamma correction, black level adjustment, tone mapping, and backlight brightness control are combined and applied in sequence. This merging allows the system to achieve both contrast enhancement and black non-uniformity reduction simultaneously, overcoming the limitation of local dimming alone.
Solution Approach 2:
The patent changes multiple parameters in the image processing chain: the lower limit of input gradation values is changed to a first gradation value, emission brightness values are corrected based on input image data, and a second gradation conversion characteristic is applied that reduces input gradation values equal to or lower than a second gradation value. These parameter changes work together to reduce black non-uniformity while maintaining contrast.
Data Source
AI summary
An image display apparatus, includes: a first conversion unit configured to generate first image data by applying a first gradation conversion characteristic to input image data; a light-emitting unit; a control unit configured to control an emission brightness of the light-emitting unit; a second conversion unit configured to generate second image data by correcting gradation values of the first image data based on the emission brightness of the light-emitting unit; a third conversion unit configured to generate third image data by applying a second gradation conversion characteristic to the second image data; and a display unit configured to display an image by transmitting light emitted from the light-emitting unit based on the third image data.