Face-Lit Waveguide Illumination with Elongated Coupling Elements
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Solution Overview
Problem
Conventional edge-lit waveguide illumination systems face challenges in efficiently coupling light from large light sources into waveguides and require access to the waveguide's edges for light input.
Innovation Solution
A face-lit waveguide illumination system is developed, featuring a waveguiding substrate with elongated light coupling elements attached to its broad-area surface. Compact light sources, such as LEDs, are positioned to illuminate the terminal ends of these elements, optimizing light injection and distribution across the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If edge-lit waveguide illumination systems are used, then light can be input through the waveguide edges, but light coupling efficiency from large light sources is poor and accessibility to edges is required
Solution Approach 1:
The patent inverts the conventional edge-lit approach by implementing face-lit illumination. Instead of coupling light into the waveguide edges, light sources are positioned to illuminate the broad-area face of the waveguide substrate directly. This inversion allows large light sources to be efficiently coupled into the waveguide without requiring access to edges, thereby resolving the contradiction between ease of operation and light coupling efficiency.
Solution Approach 2:
The patent transitions from one-dimensional edge coupling to two-dimensional face illumination. By distributing light sources across the broad-area face of the waveguide substrate rather than confining coupling to the edges, the system achieves improved light coupling efficiency while maintaining ease of operation. This dimensional change allows large light sources to be effectively utilized.
2Device complexity
If conventional edge-lit systems are used, then structure is simpler, but light distribution uniformity across broad-area surfaces is poor
Solution Approach 1:
The patent segments the illumination function by incorporating multiple light sources across the broad-area face of the waveguide substrate. This segmentation allows different regions of the waveguide face to be illuminated independently, enabling uniform light distribution across the entire broad-area surface. The segmented approach maintains relatively simple system structure while achieving improved illumination uniformity.
3Reliability
If face-lit waveguide illumination systems are implemented, then light coupling efficiency improves, but device complexity increases due to additional optical elements
Solution Approach 1:
The patent merges the light source and waveguide substrate into an integrated assembly. The broad-area face of the waveguide substrate serves dual functions as both the illumination surface and the light guiding medium. This merging eliminates the need for separate coupling optics and intermediate components, thereby improving light coupling efficiency while avoiding excessive increase in device complexity.
Solution Approach 2:
The waveguide substrate's broad-area face serves its own illumination function without requiring external coupling optics. By directly illuminating the face of the waveguide substrate with light sources positioned in proximity, the system achieves efficient light coupling using the waveguide substrate itself as the primary optical element, thereby reducing overall 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
The system achieves improved light coupling efficiency and uniformity, allowing for effective redistribution of light from various sources across broad-area surfaces, such as in wide-area luminaires and LCD display backlights.
Implementation Method 1
a waveguiding substrate and one or more elongated light coupling elements attached to a broad-area surface of the substrate
Implementation Method 2
One or more compact light sources, such as Light Emitting Diodes (LEDs), may be positioned to illuminate a terminal end of each elongated light coupling element
Data Source
AI summary
A backlight unit for LCD displays including a planar light transmissive sheet with first and second broad-area surfaces and parallel first and second edges. The sheet guides light from the first edge to the second edge using total internal reflection. A patterned light extraction area with microstructures is located at a distance from the first edge, with a light mixing area located in between. A reflector is positioned adjacent to one broad-area surface. A side-emitting LED strip, comprising a flexible printed circuit with a linear array of LED packages, is optically coupled to the first edge. The LED packages' light-emitting surfaces are oriented perpendicular to the circuit's major surface and have at least one dimension greater than the sheet's thickness. The circuit's major surface is parallel to and in contact with one of the sheet's broad-area surfaces.