Liquid Crystal Display Local Dimming Grayscale Saturation Control
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Solution Overview
Problem
The image quality of liquid crystal displays is degraded due to grayscale saturation caused by local dimming methods, which result in high gray levels appearing at the same brightness, limiting the improvement of contrast ratios.
Innovation Solution
A liquid crystal display system that includes a backlight unit with individually controllable blocks and a local dimming control circuit that calculates and adjusts pixel gain values based on grayscale saturation levels to compensate for luminance reductions, thereby correcting the pixel gain values and improving image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If local dimming method is applied to improve contrast ratio, then luminance control is improved, but grayscale saturation occurs causing image quality degradation
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the pixel gain value based on the grayscale saturation level. When grayscale saturation is detected, the system modifies the pixel gain parameter to compensate for the saturation effect, thereby maintaining image quality while preserving the luminance control benefits of local dimming.
Solution Approach 2:
The patent implements a feedback mechanism where the grayscale saturation level is continuously monitored and used to adjust the pixel gain value. This closed-loop control ensures that image quality is maintained by automatically compensating for saturation effects that occur during local dimming operation.
2Illumination intensity
If pixel gain value is increased to compensate for luminance reduction, then brightness compensation is achieved, but grayscale saturation becomes more serious
Solution Approach 1:
The patent uses feedback control where the pixel gain value is dynamically adjusted based on the measured grayscale saturation level. Instead of using a fixed gain value, the system continuously monitors saturation and adjusts the gain accordingly, preventing excessive saturation while maintaining brightness compensation.
Solution Approach 2:
The patent transforms the static pixel gain value into a dynamic parameter that changes based on the grayscale saturation level. This dynamic adjustment allows the system to optimize both brightness compensation and saturation control in real-time, rather than using a fixed gain value that cannot adapt to varying conditions.
3Illumination intensity
If all light sources of backlight unit are turned on for non-dimming, then luminance is sufficient, but power consumption increases and contrast ratio improvement is limited
Solution Approach 1:
The patent applies segmentation by dividing the backlight unit into multiple independently controllable blocks. This allows selective activation of light sources in different blocks based on the displayed image content, enabling local dimming to reduce power consumption while maintaining sufficient luminance in bright areas.
Solution Approach 2:
The patent implements local quality control by applying different luminance levels to different blocks of the backlight unit based on the local image content. This allows the system to optimize power consumption by dimming blocks displaying dark content while maintaining full luminance in blocks displaying bright content, thereby improving contrast ratio without excessive power consumption.
Data Source
AI summary
A liquid crystal display includes a liquid crystal display panel, a backlight unit including a plurality of light sources, the backlight unit providing light to a back surface of the liquid crystal display panel, a backlight driving circuit that individually drives a plurality of previously determined blocks each including the light sources based on a dimming value of each of the blocks, and a local dimming control circuit that calculates a pixel gain value compensating for a luminance reduction resulting from the dimming value of each block and corrects the pixel gain value based on a grayscale saturation level of each block.