Backlight Control for Peak Luminance in Display Devices
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Solution Overview
Problem
Liquid crystal display devices face challenges in improving image quality, contrast ratio, viewing angle, response speed, power consumption, and manufacturing costs, particularly in achieving high peak luminance without increasing faint light emission during black display.
Innovation Solution
The implementation of a display device with multiple subframe periods in a frame period, where the gray level is expressed through time integration of instantaneous luminances, and a scale factor is used to adjust the integrated luminance based on gray level data distribution, allowing for increased peak luminance without increasing faint light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the luminance of the backlight is increased to increase the peak luminance, then the peak luminance is improved, but the faint light emission at the time of black display is also increased, which reduces the contrast ratio
Solution Approach 1:
The patent applies periodic action by dividing the frame period into multiple subframe periods and controlling the backlight to operate intermittently during these subframes. The backlight is turned on during specific subframes corresponding to high gray level regions and turned off during other subframes, creating a periodic on-off pattern that achieves peak luminance enhancement without continuous backlight operation, thereby preventing increased faint light emission during black display periods.
Solution Approach 2:
The patent segments the frame period into multiple subframe periods and applies different luminance control strategies to different regions of the display. By segmenting the time domain into subframes and the spatial domain into high gray level and other regions, the system can selectively increase peak luminance in specific regions during specific subframes while maintaining low luminance in other regions and times, thus resolving the contradiction between peak luminance and black display quality.
2Illumination intensity
If intermittent driving of the backlight is controlled in accordance with average picture level (APL) to improve peak luminance modulation, then the peak luminance is improved, but the time for displaying a black image is shortened when the image is generally dark, causing afterimages and reducing moving image quality
Solution Approach 1:
The patent applies local quality by implementing region-specific luminance control within the display frame. The backlight control is localized to regions with high gray level data, while regions with low gray level data maintain normal or reduced backlight operation. This localized approach allows peak luminance enhancement in specific areas without requiring reduced black display time across the entire screen, thereby preventing afterimages and maintaining moving image quality.
3Ease of operation
If hold-type display driving is used to maintain luminance for one frame period, then the display simplicity is maintained, but afterimages occur and the moving image quality is reduced
Solution Approach 1:
The patent resolves the contradiction between display simplicity and moving image quality by introducing periodic backlight control within the hold-type driving framework. The backlight operates periodically during specific subframe periods rather than continuously, creating a pulsed illumination pattern that reduces afterimage effects while maintaining the overall hold-type display architecture. This periodic modulation within the simple hold-driven structure improves moving image quality without requiring complex driving schemes.
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 enhances image quality, contrast ratio, and viewing angle while reducing power consumption and manufacturing costs by effectively managing luminance and reducing afterimages.
Implementation Method 1
a liquid crystal display device has a liquid crystal layer including a plurality of liquid crystal cells
Data Source
AI summary
A display device in which the image quality is improved by control of the peak luminance. A plurality of instantaneous luminances are expressed by performing signal writing to each pixel plural times within one frame period. The gray level is expressed by controlling time integration levels of the plurality of instantaneous luminances. Moreover, the time integration level is increased as the level of gray level data of the pixel is higher, and the time integration level is increased as the average value of gray level data of an image to be displayed is smaller.