Segmented Light Guide Extraction for Uniform LCD Backlighting
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Solution Overview
Problem
Conventional edge-lit illumination systems face challenges in efficiently coupling, decoupling, and distributing light, leading to optical losses and suboptimal performance in achieving desired angular distribution and uniformity.
Innovation Solution
A thin, flexible sheet of optically transmissive material is illuminated by compact solid-state sources, featuring discrete surface microstructures patterned for light extraction, utilizing a UV-curable ink with light-scattering particles to distribute light from both surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional edge-lit illumination systems are used, then light can be guided through planar light guides, but light coupling and distribution efficiency is poor leading to optical losses
Solution Approach 1:
The light extraction pattern is segmented into multiple discrete surface microstructures distributed across the light guide surface. Each microstructure acts as an independent light extraction element, collectively improving light distribution efficiency while reducing optical losses through enhanced light coupling.
Solution Approach 2:
Surface microstructures are strategically positioned at specific locations on the light guide to optimize local light extraction properties. This localized modification enhances light distribution efficiency in critical regions while maintaining overall system performance.
2Illumination intensity
If conventional edge-lit illumination systems are used, then light guiding is possible, but achieving desired angular distribution and uniformity is difficult
Solution Approach 1:
The light extraction pattern is divided into discrete surface microstructures that can be independently optimized for angular distribution. This segmentation allows precise control over light emission characteristics without requiring complex overall system configuration.
Solution Approach 2:
The surface microstructures modify local optical parameters (refractive index, surface curvature) to control light extraction angles. By adjusting these parameters at the micro-scale, desired angular distribution and uniformity are achieved without increasing system-level complexity.
3Productivity
If discrete surface microstructures are added to extract light, then light extraction efficiency improves, but manufacturing complexity increases
Solution Approach 1:
The surface microstructures are designed with optimized parameters (size, shape, spacing, material properties) that balance light extraction efficiency with manufacturability. These parameter optimizations enable the complex light extraction pattern to be produced using standard manufacturing processes.
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
Enhances light extraction and distribution efficiency, achieving uniform illumination with reduced energy waste and improved performance.
Implementation Method 1
The thin and flexible sheet is configured for guiding light between opposing edges using optical transmission and a total internal reflection
Implementation Method 2
The light scattering material is disposed in optical contact with the surface and configured for extracting light from the thin and flexible sheet
Data Source
AI summary
A backlight for an LCD display has an optically transmissive sheet with first and second broad-area surfaces, four edges, a light mixing region adjacent to a first edge, and a light extraction region. The mixing region has smooth planar surfaces for guiding light via total internal reflection. Light extraction features are distributed across the extraction region with increasing density toward the opposing edge. A flexible LED strip extends parallel to the first edge, with a flexible circuit and side-emitting LED packages of less than 2 mm in height. The LED packages have light emitting surfaces perpendicular to the circuit's major surface. A metallic housing partially encases the LED array with a linear channel providing light passage to the mixing region. At least one extraction feature has a surface relief microstructure separated from other features and edges by smooth planar portions of the sheet.