Refractive Cover for DBR LED Backlight Uniformity
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Solution Overview
Problem
Display devices face challenges in maintaining luminance uniformity and preventing the 'Mura effect' due to non-homogeneous backlight illumination, especially as they become thinner and the optical distance for light conversion decreases.
Innovation Solution
The implementation of a Distributed Bragg Reflector (DBR) Light Emitting Diode (LED) with a refractive cover having specific surface configurations to enhance light extraction efficiency and distribute light uniformly, eliminating the Mura effect while reducing the thickness of the backlight unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the optical distance is reduced to make the display thinner, then the display thickness decreases, but the luminance uniformity deteriorates and Mura effect becomes more visible
Solution Approach 1:
The patent segments the backlight unit into multiple independent point light sources (LEDs) arranged in an array, with each LED having its own refractive cover. This segmentation allows for precise control of light distribution from each point source, enabling uniform overall illumination even at reduced optical distances.
Solution Approach 2:
The patent employs refractive covers with curved surfaces (spheroidal or aspherical shapes) surrounding each LED point light source. These curved surfaces refract light in specific patterns to achieve high beam angles and uniform light distribution, compensating for the reduced optical distance and preventing Mura effect.
2Device complexity
If conventional LED structures are used, then the structure is simple, but light extraction efficiency is low and Mura effect occurs
Solution Approach 1:
The patent introduces refractive covers as intermediary optical elements between the LED point light sources and the liquid crystal panel. These covers act as mediators that reshape and distribute light, improving extraction efficiency and uniformity without significantly complicating the overall device structure.
Solution Approach 2:
The patent changes the optical parameters of the light distribution system by using refractive covers with specific curvature radii and refractive indices. This allows control over beam angles and light extraction efficiency, achieving uniform illumination while maintaining structural simplicity.
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 solution provides an ultra-slim backlight unit with uniform illumination, improving productivity and price competitiveness by enhancing light distribution and reducing the number of LEDs required, thus maintaining luminance uniformity without the Mura effect.
Implementation Method 1
a Distributed Bragg Reflector (DBR) Light Emitting Diode (LED) with light distribution of high beam angle
Implementation Method 2
a refractive cover capable of increasing light extraction efficiency through a simple dispensing process
Data Source
AI summary
A display device includes a backlight unit including: a substrate; a Light Emitting Diode (LED) disposed on a surface of the substrate; and a refractive cover configured to surround the LED. The refractive cover includes: a first refractive surface to: be spaced apart from the LED by a preset distance, be positioned on the upper surface of the substrate, be parallel to an axis of the LED or be inclined within one angle from the axis of the LED; a second refractive surface to be a curved surface in which an angle between a tangent line and the axis of the LED increases from a region connected to another upper portion of the first refractive surface toward a direction of the axis of the LED; and a third refractive surface to be connected to an portion of the second refractive surface and be perpendicular to the axis of the LED.