Local Dimming Brightness Compensation via Surrounding Luminance Analysis
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Solution Overview
Problem
In liquid crystal display apparatuses, local dimming techniques face challenges in accurately predicting backlight emission brightness per pixel, leading to image deterioration such as uneven brightness, decreased contrast, and halo effects due to physical device limitations, despite accurate prediction efforts.
Innovation Solution
The display apparatus incorporates a light modulating section, a radiating section, a control section, and a converting section that applies gradation conversion processing to adjust backlight emission brightness and transmittance based on surrounding luminosity, using human visual characteristics to compensate for image deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If local dimming is applied to reduce power consumption and improve contrast, then power efficiency and black level purity are improved, but image deterioration such as uneven brightness, contrast loss, and halo effects occur at boundaries between light emitting areas
Solution Approach 1:
The screen is divided into multiple light emitting areas (zones) that can be independently controlled. Each zone's backlight brightness is adjusted separately based on the display content within that zone, enabling localized power savings while maintaining overall image quality. This segmentation allows the system to apply dimming only where necessary rather than uniformly across the entire screen.
Solution Approach 2:
Different brightness levels are applied to different regions of the screen based on local display content requirements. The system identifies dark regions and applies stronger dimming there, while maintaining higher brightness in regions requiring detail visibility. This local quality approach optimizes power consumption in dark areas without sacrificing image quality in bright or detail-critical areas.
2Illumination intensity
If backlight brightness is reduced in dark areas to improve contrast, then black level purity is improved, but brightness uniformity deteriorates at boundaries between light and dark areas
Solution Approach 1:
The system performs preliminary analysis of the display content to identify dark regions before applying backlight dimming. By predicting which areas will be dark and pre-adjusting the backlight accordingly, the system avoids the need for aggressive dimming that would cause boundary artifacts. This preliminary action allows for smoother transitions and maintains brightness uniformity while still achieving pure black levels in appropriate areas.
3Manufacturing precision
If accurate per-pixel backlight prediction is implemented to correct brightness, then image quality is improved, but computational complexity and algorithm difficulty increase significantly
Solution Approach 1:
Instead of performing complex per-pixel calculations, the system segments the screen into larger light emitting areas and performs simplified calculations at the zone level. This segmentation reduces the computational burden significantly while still achieving acceptable brightness accuracy. The system calculates required brightness adjustments for each zone rather than individually for each pixel, dramatically reducing computation requirements.
Solution Approach 2:
The system uses a simpler, less computationally expensive algorithm that provides sufficient accuracy for practical purposes. Rather than implementing a complex physics-based model that would require significant computational resources, the patent employs a pragmatic approach that achieves acceptable results with minimal computation, effectively trading theoretical perfection for practical efficiency.
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
This approach effectively compensates for image deterioration caused by uneven brightness and contrast issues, enhancing display quality by utilizing human visual characteristics to adjust brightness and transmittance, thereby improving the local dimming technique's effectiveness.
Implementation Method 1
modulates the transmittance of illumination light by means of the liquid crystal display element and changes brightness to display an image
Implementation Method 2
radiates illumination light on a back face of a liquid crystal display element by means of an illuminating apparatus
Data Source
AI summary
Disclosed is a display device capable of compensating unevenness in brightness caused by physical restrictions of a display device or degradation in image quality caused by a partial reduction in contrast occurring in the local dimming technology using human visual characteristics. A liquid crystal panel (101) modulates illuminating light in accordance with the transmittance, and displays images on a screen. A backlight (102) emits the illuminating light to the liquid crystal panel (101) such that amounts of the illuminating light differ for each light emitting area of the screen. A backlight control unit (106) controls emission brightness of the backlight (102) for each light emitting area. A local gradation converting unit (104) performs gradation conversion on an image signal, and acquires a brightness value for each pixel after the conversion. A backlight driving unit (107) controls the transmittance for each pixel on the basis of the acquired brightness values after the conversion. The local gradation converting unit sets conversion characteristics for pixels to be processed in the image signal such that the brightness values of the pixels to be processed are low as the lightness of the periphery of the pixels to be processed is high, and performs gradation conversion using the set conversion characteristics.