Light Guide Plate LED In-Coupling Hole Geometry for Lumen Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In lighting devices using a light guide plate and multiple side-emitting LEDs, closely spaced in-coupling holes lead to light leakage and absorption or scattering, resulting in degraded lumen efficiency due to light entering adjacent holes.
Innovation Solution
The design features holes with at least two side facets and a corner formed by converging side facets, allowing light to be split into sub-beams that are more perpendicular to their originating facets, reducing the likelihood of light entering adjacent holes through total internal reflection (TIR), and includes out-coupling structures like edges or mirrors to direct light efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If in-coupling holes are closely spaced to increase LED density, then the lighting device can accommodate more LEDs in a smaller area, but light from one LED leaks into adjacent holes and gets absorbed or scattered, degrading lumen efficiency
Solution Approach 1:
The hole is segmented into multiple side facets (at least two) with a corner formed by converging facets. This segmentation divides the light from a single LED into multiple sub-beams, each traveling in different directions. By orienting these sub-beams at angles that cause total internal reflection at adjacent hole facets, light leakage into neighboring holes is prevented while maintaining high LED density.
Solution Approach 2:
The corner region of each hole is given special geometric configuration where two side facets converge. This local geometric modification creates specific light reflection paths at the corner that redirect light away from adjacent holes. The localized corner structure with controlled facet angles enables TIR to occur at adjacent holes, preventing light absorption by neighboring LEDs while preserving the closely-spaced hole arrangement.
2Productivity
If holes are arranged in a densely packed linear array to maximize space utilization, then the lighting device achieves compact design, but light leakage between adjacent holes increases by approximately 10%, reducing overall luminous efficiency
Solution Approach 1:
The hole geometry is made asymmetric by introducing a corner formed by converging side facets rather than using symmetric circular or regular polygonal shapes. This asymmetric corner configuration creates preferential light reflection paths that exploit the geometric asymmetry to redirect light away from adjacent holes through total internal reflection, thereby reducing light leakage while maintaining dense packing.
Solution Approach 2:
The solution addresses the two-dimensional light propagation problem by introducing angular dimensionality through the corner geometry. The converging facets create light sub-beams that propagate at different angles, adding a directional dimension to light control. This angular control enables TIR at adjacent holes by orienting sub-beams at critical angles, effectively using dimensional transformation to prevent light leakage in the densely packed array.
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 configuration significantly reduces light loss by increasing the probability of total internal reflection at adjacent holes, enhancing the luminous efficiency of the lighting device and ensuring uniform, collimated light output.
Implementation Method 1
light from a LED arranged in the hole may be split up in sub-beams, each of which is more or less perpendicular to its originating side facet, allowing control of the direction of the light to prevent light from entering adjacent holes... light coupled into the light guide plate through the in-coupling side facet of one hole generally (if ever) hits the side facet(s) of the adjacent hole at larger angles of incidence... thereby increasing the probability of total internal reflection (TIR) at the side facet of the adjacent hole so that the light does not enter that hole
Data Source
Figure 1a~1b
Figure 2a~3a
Figure 3b~3c
AI summary
The present invention relates to lighting device (10). The lighting device comprises a light guide plate (12), and at least one array of light emitting diodes (LEDs) (14), which LEDs are accommodated in holes arranged in the light guide plate, wherein each hole has: at least two side facets (18) through which light from the LEDs is to be laterally coupled into the light guide plate, and at least one corner (20) formed by two converging side facets of the at least two side facets. This promotes TIR at adjacent light sources and therefore diminishes losses due to absorption or scattering at adjacent holes.