Luminance Equalizer Sheet Corner Low Transmittance for LED Backlight Uniformity
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Solution Overview
Problem
LED backlight devices in liquid crystal display devices often result in non-uniform luminance across the display screen due to secondary LED light sources at the corners being brighter than other areas, making it difficult to achieve uniform illumination.
Innovation Solution
A display device with a luminance equalizer sheet that includes corner low transmittance areas with lower light transmittance than other areas, positioned opposite to the secondary LED light sources, to adjust and equalize luminance distribution, combined with a control unit for local dimming control to manage light emission from first and second light sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If secondary LED light sources are added at the four corners of the mounting substrate, then the corner portions become brighter, but the luminance uniformity across the display screen deteriorates because the corners become excessively bright compared to other portions
Solution Approach 1:
The patent applies local quality by creating corner low transmittance areas with different optical properties than the rest of the luminance equalizer sheet. Specifically, the corner regions have lower light transmittance to compensate for the excessive brightness from corner LED light sources, while other regions maintain higher transmittance. This spatially varying transmittance property allows different parts of the display screen to receive appropriate light amounts, achieving overall luminance uniformity.
2Illumination intensity
If all LED light sources (main and secondary) are turned on simultaneously, then the overall brightness of the display screen increases, but the luminance distribution becomes non-uniform with excessively bright corners
Solution Approach 1:
The luminance equalizer sheet acts as an intermediary between the LED light sources and the display screen. It includes corner low transmittance areas that selectively reduce light transmission from the corner LED light sources while allowing light from other LED light sources to pass through with higher transmittance. This intermediary structure balances the luminance contribution from all LED light sources, achieving uniform luminance distribution across the display screen when all lights are on.
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 ensures uniform luminance across the entire display screen by adjusting light transmission through the luminance equalizer sheet and controlling light emission from the control unit, effectively mitigating the brightness difference caused by secondary LED light sources at the corners.
Implementation Method 1
the second portions of the luminance equalizer sheet forming corner low transmittance areas with lower light transmittance than a portion of the luminance equalizer sheet other than the first portions and the second portions
Data Source
AI summary
A display device comprises a plurality of light sources, a luminance equalizer sheet and a display. The light sources include a plurality of first light sources arranged in an array on an arrangement region and a plurality of second light sources arranged at corner portions of the arrangement region, respectively. The luminance equalizer sheet is arranged opposite the light sources to equalize luminance, the luminance equalizer sheet including first portions that face the first light sources, respectively, and second portions that face the second light sources, respectively, the second portions being different from the first portions. The display is arranged opposite the luminance equalizer sheet and disposed on an opposite side of the luminance equalizer sheet relative to the light sources. The second portions of the luminance equalizer sheet form corner low transmittance areas with lower light transmittance than a portion of the luminance equalizer sheet other than the first portions and the second portions.