Baffled Micro-Optical Elements for Thin LCD Backlight Uniformity
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Solution Overview
Problem
Existing backlight units for LCDs face challenges in achieving uniformity and illuminance as they transition to thinner designs, with previous optical architectures failing to maintain adequate luminance and spatial uniformity due to Fresnel reflections and increased LED efficiency, which worsens non-uniformities as thickness decreases below 12 mm.
Innovation Solution
The implementation of baffled micro-optical elements with diffuse reflective coatings and conical reflectors that utilize total internal reflection and highly diffusive materials to redirect light, ensuring uniform illumination by preventing Fresnel reflections and optimizing light distribution, featuring a cup reflector to gather lateral light and a circumferential ledge for additional scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional refractive lenses are used in backlight units, then light distribution can be achieved, but Fresnel reflections cause non-uniformities that worsen as thickness decreases below 12 mm
Solution Approach 1:
The patent converts the harmful Fresnel reflections into beneficial effects by using highly reflective coatings (95-99% reflectivity) on the bottom surface and lateral walls of the optical element. These coatings capture the reflected light that would otherwise cause non-uniformities and redirect it constructively toward the display surface, transforming the harmful reflection phenomenon into a useful light redistribution mechanism that maintains uniformity in thin backlight units.
Solution Approach 2:
The patent changes the optical parameters of the system by transitioning from purely refractive optics to a hybrid approach combining reflection and refraction. By introducing reflective surfaces with specific reflectivity parameters (95-99%) and configuring the optical element with specific geometric parameters (height 0.5-2 mm, base width matching LED diameter), the system achieves improved light distribution uniformity in thinner configurations without suffering from Fresnel reflection artifacts.
2Loss of energy
If LED efficiency is increased to reduce the number of LEDs, then energy consumption decreases, but hot spots and non-uniformities increase
Solution Approach 1:
The patent introduces an intermediary optical element with reflective coatings that acts as a mediator between the high-efficiency LED source and the display surface. This optical element with highly reflective surfaces (95-99%) redistributes the intense light from efficient LEDs, capturing lateral reflections and redirecting them to fill in hot spots, thereby maintaining energy efficiency while achieving uniform light distribution across the display.
3Ease of manufacture
If the number of LEDs is reduced to lower cost, then manufacturing cost decreases, but achieving adequate illuminance becomes more difficult
Solution Approach 1:
The patent replaces the mechanical approach of using numerous LEDs to achieve adequate illuminance with an optical system based on reflection and refraction principles. By using highly reflective coatings (95-99%) and optimizing the geometric configuration of the optical element, the system achieves superior light extraction and distribution efficiency, allowing fewer LEDs to produce adequate illuminance while improving 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 solution achieves improved uniformity and illuminance in thinner backlight units, maintaining high spatial uniformity and optical efficiency, even at reduced thicknesses, by effectively managing light distribution and minimizing non-uniformities caused by Fresnel reflections.
Implementation Method 1
baffled micro-optical elements with diffuse reflective coatings and conical reflectors that utilize total internal reflection
Implementation Method 2
conical reflectors that utilize total internal reflection and highly diffusive materials to redirect light
Data Source
AI summary
A light-emitting diode (LED) backlight unit includes a housing, an LED array disposed on a bottom surface of the housing, an optical film stack disposed on the LED array, and a baffled micro-optical element (BMOE) disposed between the LED array and the optical film stack. The thickness of the backlight unit is 12 mm or less, a first portion of light emitted from each LED of the LED array is configured to directly contact the optical film stack and a second portion of light emitting from each LED of the LED array is configured to be reflected off of the BMOE and onto the optical film stack, and the first and second portions of light combine to create surface illuminance on the optical film stack having a uniformity greater than 70%.