Backlight LED Control for Display Color Uniformity
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Solution Overview
Problem
In liquid crystal display devices, the reduction in frame size leads to regions without phosphors overlapping with LEDs, causing uneven brightness and color issues due to direct transmission of primary light through these areas, resulting in color unevenness in the light output.
Innovation Solution
A lighting device configuration with end-side and center LEDs, where the wavelength converter extends along the LED arrangement, and a light source controller adjusts the light emission of end-side LEDs to be less than that of the center LEDs, ensuring that light entering the light guide plate is wavelength-converted, thereby minimizing color unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the frame size is reduced, then the device becomes more compact, but regions without phosphors overlap with LEDs causing color unevenness
Solution Approach 1:
The patent applies local quality by differentiating the light emission characteristics of end-side LEDs versus center LEDs. Specifically, the control unit reduces the light emission amount of end-side LEDs that correspond to regions without phosphors, while maintaining normal emission for center LEDs. This localized adjustment compensates for the color unevenness caused by direct LED light transmission in phosphor-free regions, thereby maintaining color uniformity despite reduced frame size.
2Illumination intensity
If end-side LEDs emit full light, then brightness is sufficient, but color unevenness occurs in regions without phosphors
Solution Approach 1:
The patent changes the light emission parameter (intensity) of specific LEDs based on their position. The control unit adjusts the driving current or duty cycle of end-side LEDs to reduce their light output in phosphor-free regions, while maintaining full intensity for center LEDs. This parameter adjustment eliminates color unevenness while preserving overall brightness through compensatory lighting control.
3Volume of moving object
If phosphors are removed from end regions, then device size is reduced, but primary light transmits directly causing color issues
Solution Approach 1:
The patent converts the harmful effect of direct LED light transmission in phosphor-free regions into a beneficial control mechanism. By identifying which LEDs correspond to phosphor-free regions, the system selectively reduces their emission intensity, transforming the potential color unevenness problem into a controlled lighting strategy that maintains overall color uniformity.
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 configuration effectively reduces color unevenness in the light output, maintaining high display quality even as frame size is reduced, by controlling light emission to compensate for regions without phosphors, ensuring consistent color tone across the display.
Implementation Method 1
a wavelength converter including a fluorescent substance excited by light emission from the LEDs to emit fluorescent light
Implementation Method 2
a light guide plate provided through the LEDs and the wavelength converter and configured to take in, through an end surface thereof, synthesized light of the light emitted from the LEDs and the light emitted from the fluorescent substance
Data Source
AI summary
A backlight unit includes LEDs, a light guide plate, a wavelength converter, and an LED controller. The LEDs include end-side LEDs arranged at ends in the direction of arrangement and a center LED arranged at the center in the direction of arrangement. The light guide plate includes a light entering end surface and a light exiting plate surface. The light entering end surface extends along the direction of arrangement. The wavelength converter extends along the direction of arrangement and is interposed among the LEDs and the light entering end surface. The wavelength converter includes a phosphor configured to wavelength-convert the light from the LEDs. The LED controller is configured to control the amount of light emitted by each LED per unit time such that the amount of light emitted by at least one of the end-side LEDs than the amount of light emitted by the center LED.