Waveguide Coupling Cavity for LED Light Extraction
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Solution Overview
Problem
Low-efficiency light coupling from lambertian emitting sources like LEDs into waveguides, particularly in edge-lit luminaires, results in significant light losses due to the inherent challenges in directing light into the narrow edge of a waveguide plane.
Innovation Solution
The luminaire design incorporates a waveguide body with a coupling portion and opposed sections of varying thicknesses, featuring extraction features on both sides to control light distribution and extraction, utilizing total internal reflection and carefully shaped surfaces to optimize light redirection and extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If light is coupled from lambertian emitting sources into waveguides using conventional methods, then the waveguide can be simple in structure, but light coupling efficiency is low resulting in significant light losses
Solution Approach 1:
The patent introduces a coupling cavity as an intermediary structure between the LED light source and the waveguide. This coupling cavity acts as a mediator that transforms the lambertian emission pattern into a more directional distribution, improving light coupling efficiency into the waveguide without requiring complex external optics. The coupling cavity geometry and refractive index differences create an intermediate optical environment that bridges the mismatch between source and waveguide.
Solution Approach 2:
The patent modifies optical parameters within the coupling cavity, including refractive index distribution and geometric parameters, to optimize light coupling. By changing the refractive index profile and cavity dimensions, the system achieves improved light extraction and coupling efficiency without fundamentally altering the waveguide structure, thus resolving the contradiction between energy loss and structural complexity.
2Weight of stationary object
If the waveguide thickness is reduced to minimize material usage and weight, then manufacturing cost and weight decrease, but light extraction efficiency deteriorates
Solution Approach 1:
The patent applies local quality variations within the waveguide structure, including thickness variations and refractive index modifications at specific locations. By creating regions of different optical properties within the waveguide, particularly in the coupling cavity and extraction regions, the system maintains efficient light extraction with reduced overall thickness, thus reducing weight while preserving optical performance.
Solution Approach 2:
The patent addresses the thickness limitation by introducing dimensional variations in the coupling cavity structure. Instead of simply increasing waveguide thickness, the invention uses three-dimensional cavity geometries and refractive index profiling in multiple dimensions to enhance light coupling and extraction efficiency, allowing thin waveguide designs to achieve adequate optical performance.
3Loss of energy
If extraction features are added to control light distribution, then light extraction efficiency improves, but device complexity increases
Solution Approach 1:
The patent merges the extraction features with the waveguide structure itself, creating an integrated design where extraction functionality is built into the waveguide geometry rather than being added as separate components. The coupling cavity and extraction features are combined into a unified structure, reducing overall device complexity while maintaining improved light extraction efficiency.
Solution Approach 2:
The coupling cavity structure serves multiple functions simultaneously: it acts as a light redistribution element, a coupling interface, and an extraction enhancement feature. This multi-functionality reduces the need for separate dedicated extraction components, thereby improving light extraction efficiency without proportionally increasing device complexity.
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 design enhances light extraction efficiency and uniformity, achieving improved light distribution and reduced waveguide size and weight, while maintaining high optical efficacy and cost-effectiveness.
Implementation Method 1
utilizing total internal reflection and carefully shaped surfaces to optimize light redirection and extraction efficiency
Implementation Method 2
The extraction element(s) determine how light is removed by controlling where and in what direction the light exits the waveguide
Data Source
AI summary
A waveguide body comprises a length from a first end to a second end along a longitudinal axis, and a coupling portion that comprises first and second coupling surfaces. The first and second coupling surfaces define, at least in part, an elongate coupling cavity along the entire length of the waveguide body and a surface located opposite the coupling cavity. The waveguide body further comprises first and second opposed sections extending along the length of the waveguide body. The first and second opposed sections further comprise respective first and second lower surfaces disposed at different first and second side section angles with respect to a first axis lying in a plane normal to the longitudinal axis. The first axis bisects the coupling portion. Among other things, such a waveguide may be included in a luminaire along with a light source.