Air Cavity LED Backlight Unit for Thin LCD Displays
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Solution Overview
Problem
Existing backlight units for LCDs face challenges in achieving adequate illuminance and uniformity while maintaining a thin profile, as refractive optical principles become insufficient as the thickness decreases below 12 mm, and the increased efficiency of LEDs requires new optical architectures to prevent hot spots and ensure display quality in thinner designs.
Innovation Solution
A low-profile, side-lit, hollow cavity LED backlight assembly using an array of LEDs with light transported via a reflective baffle and an optical conditioning stack, including specular and diffuse bottom reflectors and localized optical lenses, to ensure spatial uniformity and illuminance across the LCD display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the thickness of the backlight unit is reduced below 12 mm, then the device becomes thinner and more compact, but the refractive optical principles become insufficient to maintain adequate illuminance uniformity and display quality
Solution Approach 1:
The patent changes the optical parameter from refractive index (n>1) to air cavity (n=1), fundamentally altering how light is guided and distributed. This parameter change enables the system to achieve uniform illuminance in ultra-thin configurations where traditional refractive optics fail, as the air cavity eliminates refraction-related uniformity issues while maintaining light transport efficiency.
Solution Approach 2:
The patent extracts the refractive optical elements (lenses, diffusers) from the traditional backlight architecture and replaces them with an air cavity structure. This extraction removes the source of refraction-induced non-uniformity while preserving the light-guiding function through total internal reflection at the air-cavity boundaries, enabling thin-profile designs with superior uniformity.
2Use of energy by moving object
If the number of LEDs is reduced due to increased LED efficacy, then energy efficiency improves and cost decreases, but new optical architectures are required to prevent hot spots and maintain display quality
Solution Approach 1:
The patent changes the optical medium parameter from solid/refractive material to air cavity, which fundamentally alters light propagation characteristics. This parameter change creates a simpler optical architecture that naturally distributes light more evenly, preventing hot spots even with fewer LEDs, thereby reducing overall system complexity despite improved energy efficiency.
Solution Approach 2:
The air cavity acts as an intermediary medium between the LEDs and the display panel, mediating light transport through total internal reflection. This intermediary structure simplifies the optical path compared to traditional multi-element refractive systems, reducing complexity while maintaining uniform illuminance distribution across the display surface.
3Length of moving object
If traditional refractive lenses are used in ultra-thin designs, then the backlight unit achieves thin profile, but the refractive optical principles cease to yield acceptable uniformity
Solution Approach 1:
The patent changes the refractive index parameter from >1 (solid materials) to exactly 1 (air), eliminating refraction effects that cause non-uniformity in thin designs. The air cavity maintains light guidance through total internal reflection at its boundaries, achieving both thin profile and uniform illuminance where traditional refractive optics fail.
Solution Approach 2:
Instead of using refractive materials to guide light (traditional approach), the patent inverts the approach by using an air cavity (lower refractive index) surrounded by higher index materials. This inversion exploits total internal reflection at the air interface rather than refraction within the material, achieving superior uniformity in ultra-thin configurations.
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 achieves excellent spatial uniformity and illuminance in both lateral and longitudinal directions, maintaining display quality in thinner designs with a thickness of 10 mm or less, while reducing manufacturing costs and weight, and ensuring compatibility with modern LED efficacy.
Implementation Method 1
light transported via a reflective baffle
Implementation Method 2
optical conditioning stack
Implementation Method 3
specular and diffuse bottom reflectors
Data Source
AI summary
A light-emitting diode (LED) backlight unit includes first and second curved bottom floor reflectors exhibiting mirror image symmetry along a center line extending in a latitudinal direction, first and second sides disposed along a longitudinal direction, the first and second bottom floor reflectors disposed therebetween, first and second back reflectors disposed on distal ends of the first and second bottom floor reflectors, respectively, away from the center line, and LEDs disposed in or adjacent to the first and second back reflectors. A curvature of the first and second bottom floor reflectors respectively reach a maximum near the center line.