Backlight System with Regional Luminance Control for LCDs
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Solution Overview
Problem
Conventional liquid crystal display devices with backlight systems face high power consumption and image quality issues due to the use of cold cathode fluorescent lamps, and the separation of backlight regions leads to inaccuracies in image display and increased power usage, especially with temperature and age-related changes in LEDs.
Innovation Solution
A liquid crystal display device with a backlight system divided into regions where light emission from each source is allowed to leak into adjacent areas, utilizing a maximum gradation detector, emission luminance calculator, luminance bitmap memory, image gain calculator, and multiplier to adjust image signals based on luminance distribution characteristics and position-specific gains, reducing power consumption while enhancing image quality.
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, 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 structures that caused brightness and color variations across regions.
Solution Approach 2:
The patent controls the emission luminance of each LED by adjusting the drive current parameter independently for each LED based on the image signal brightness. This parameter-based control replaces the physical segmentation approach, allowing precise luminance adjustment without light shielding walls, thereby maintaining image quality while reducing power consumption.
2Adaptability or versatility
If light shielding walls are used to separate backlight regions, then regional luminance control is achieved, but manufacturing complexity increases and alignment precision becomes critical
Solution Approach 1:
The light shielding walls are completely removed from the backlight device structure. Regional luminance control is achieved through electronic control of individual LED currents rather than physical separation, significantly simplifying the backlight device structure while maintaining the ability to control luminance in different regions independently.
Solution Approach 2:
The mechanical light shielding wall structure is replaced with an electronic control system that adjusts the drive current to each LED individually. This substitution eliminates complex mechanical alignment requirements and structural complexity while achieving the same regional luminance control function through electrical parameter adjustment.
3Use of energy by stationary object
If multiple divided regions are controlled entirely independently, then power consumption is reduced, but it becomes difficult to determine locations of adjacent regions and light leakage is prevented
Solution Approach 1:
The light shielding walls that created boundary definition problems are removed. The patent achieves independent regional control without physical separators, eliminating the difficulty of determining adjacent region locations while still enabling precise power consumption reduction through individual LED control.
Solution Approach 2:
Instead of using physical light shielding walls to define region boundaries, the patent uses the known geometric arrangement and optical characteristics of LEDs as a virtual model to calculate and control luminance distribution. This computational approach replaces physical boundary structures, eliminating alignment and boundary determination issues.
Data Source
AI summary
High quality images on liquid crystal panel can be obtained alleviating variations of the brightness and color among regions, in which backlight is divided when emission luminance of the backlight is controlled in each region based on image signal. 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 by using luminance bitmap held by luminance bitmap memory. An emission luminance calculator obtains an emission luminance of light to be emitted by each light source.