Region-Divided Backlight Luminance Control for LCD Power Reduction
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Solution Overview
Problem
Conventional liquid crystal display devices with backlight systems face issues of high power consumption and image quality degradation due to temperature dependence and age deterioration of LEDs, especially when using region-separated backlight configurations, which also struggle with accurate pixel placement and uniform luminance control.
Innovation Solution
A liquid crystal display device with a region-divided backlight system that allows light emission from each region to leak into others, using a maximum gradation detector, image gain calculator, multiplier, and emission luminance calculator to adjust regional image signals and luminance, reducing power consumption and improving image quality by controlling luminance non-uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the backlight device is divided into multiple regions with light shielding walls to control emission luminance independently, then power consumption is reduced and local brightness control is improved, but brightness and color vary among regions causing image quality degradation
Solution Approach 1:
The light shielding walls are removed entirely from the backlight device. Instead of physically separating regions, the patent controls each LED's emission luminance independently through individual current control, eliminating the harmful light blocking effect while maintaining regional control capability.
Solution Approach 2:
The patent controls the emission luminance of each LED by adjusting the drive current parameter individually. This allows independent control of brightness in each region without physical separation, maintaining color and brightness uniformity across the display while achieving power consumption reduction through localized dimming.
2Ease of operation
If light shielding walls are used to separate backlight regions, then regional luminance control is achieved, but manufacturing accuracy requirements increase and pixel placement becomes difficult
Solution Approach 1:
The light shielding walls that created manufacturing difficulties are completely removed. Regional luminance control is achieved through electrical control of individual LED currents rather than physical separation, eliminating the need for high manufacturing precision in wall placement.
Solution Approach 2:
The mechanical light shielding wall system is replaced with an electrical control system. Instead of using physical barriers to define regions, the patent uses electronic control of LED drive currents to achieve regional luminance control, simplifying manufacturing and improving pixel placement accuracy.
3Illumination intensity
If multiple LEDs are used with different brightness and color characteristics, then color rendering is improved, but variations in brightness and color among regions increase
Solution Approach 1:
The patent applies local quality control by adjusting the drive current of each LED individually based on its specific characteristics. This allows each LED to contribute optimally to the overall color rendering while maintaining uniform brightness and color across all regions through compensatory current adjustment.
Solution Approach 2:
The patent compensates for LED variations by adjusting the drive current parameter for each LED individually. This electrical parameter control allows LEDs with different brightness and color characteristics to work together harmoniously, achieving both good color rendering and uniformity across regions.
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
The solution reduces power consumption and enhances image quality by allowing light leakage between regions, improving brightness and color uniformity, and reducing the need for precise region alignment, thus addressing the limitations of conventional systems.
Implementation Method 1
The liquid crystal in the panel is switched between an OFF state and an ON state according to applied voltage. When in the OFF state, the liquid crystal panel interrupts light, while, in the ON state, the liquid crystal panel transmits light.
Implementation Method 2
a light emitting diode (LED) is used as a backlight. The emission luminance of the LED changes according to the brightness of the image signal.
Implementation Method 3
the backlight having a structure in which light emitted from each of the light sources of the plurality of regions is allowed to leak to regions other than the respective light source region
Data Source
AI summary
A backlight device is divided into multiple regions, and has a configuration in which light emitted from a light source of each of the regions is allowed to leak to other regions. A maximum gradation detector detects a maximum gradation of a regional image signal displayed on each of the regions of the liquid crystal panel. An image gain calculator obtains a gain to be multiplied to each regional image signal. An emission luminance calculator obtains an emission luminance of light to be emitted by each light source, by using an operation expression according to the emission luminance of light to be emitted by the backlight device. At this time, if the emission luminance takes a negative value as a result of calculation, the emission luminance calculator makes a correction so that the emission luminance can take a value equal to or greater than 0.