Planar Refractive Waveguide Backlight for LCD Uniformity
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Solution Overview
Problem
Conventional direct and edge backlight systems for LCDs face issues with thickness and luminescence, with direct backlights being too thick and edge backlights providing insufficient brightness due to reduced light sources and light propagation challenges.
Innovation Solution
A compact backlight system utilizing a substantially planar refractive waveguide with injection and extraction features that optically couple light, allowing for enhanced lateral spreading, mixing, and luminance through total internal reflection, with varying extraction densities to optimize light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a direct backlight system with an integrating cavity is used, then light uniformity is improved, but the system thickness increases
Solution Approach 1:
The patent transitions from a conventional direct backlight system with an integrating cavity (three-dimensional volume for light mixing) to a planar waveguide system (two-dimensional surface for light propagation). The waveguide uses total internal reflection at its surfaces to guide light laterally across the display area, eliminating the need for a thick integrating cavity while maintaining light uniformity through surface-based light distribution.
Solution Approach 2:
The patent employs a thin planar waveguide structure that acts as a light-guiding film. This waveguide is significantly thinner than conventional integrating cavities, yet it achieves light mixing and uniform distribution through its extended lateral dimensions and optical reflection properties, effectively replacing the thick cavity with a thin film solution.
2Length of stationary object
If an edge backlight system with a light guide is used, then system thickness is reduced, but luminescence intensity decreases
Solution Approach 1:
The patent divides the light source into multiple discrete LED sources positioned at regular intervals across the waveguide rather than using a single edge light source. This segmentation allows light to be injected at multiple locations simultaneously, increasing overall luminescence intensity while maintaining the thin profile of the waveguide structure.
Solution Approach 2:
The patent uses multiple identical LED light sources distributed across the waveguide, each replicating the light injection function. This copying approach ensures uniform light distribution and high luminescence intensity across the entire display area, as each LED segment contributes to the overall brightness while maintaining the thin form factor.
3Illumination intensity
If multiple light sources are distributed across the waveguide, then luminescence intensity is improved, but device complexity increases
Solution Approach 1:
The planar waveguide structure serves multiple functions simultaneously: it guides light from multiple LED sources, mixes light laterally through total internal reflection, distributes light uniformly across the display area, and maintains a thin profile. This multi-functionality reduces the need for separate components, thereby managing device complexity despite using multiple light sources.
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 provides a thinner and more luminous backlight system with uniform light distribution, addressing the thickness and brightness limitations of conventional systems while maintaining scalability and efficient heat management.
Implementation Method 1
an injection feature is proximate to one or more of the second major face and the first major face and within the viewing region to optically couple the light into the waveguide such that the light becomes waveguided light
Implementation Method 2
enhanced lateral spreading, mixing, and luminance through total internal reflection
Implementation Method 3
A plurality of extraction features is proximate to one or more of the second major face and the first major face and within the viewing region to optically couple the waveguided light out of the waveguide
Data Source
AI summary
A backlight system for a liquid crystal display includes a substantially planar, refractive waveguide having a first major face and a second major face opposite the first major face. The waveguide includes a viewable region corresponding to a viewable area of the liquid crystal display. The system further includes a light source positioned proximate to the second major face and within the viewing region for producing light. An injection feature is proximate to one or more of the second major face and the first major face and within the viewing region to optically couple the light into the waveguide such that the light becomes waveguided light. A plurality of extraction features is proximate to one or more of the second major face and the first major face and within the viewing region to optically couple the waveguided light out of the waveguide.