Molded Light Guide With TIR Cavities For LED Coupling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lighting structures using light guides and LEDs face challenges such as difficulty in coupling LED light into the edges of the light guide due to Lambertian emission, significant light attenuation with opaque reflector layers, and non-uniform light distribution across the top surface, leading to dark spots and inefficiencies.
Innovation Solution
The use of TIR structures and cavities formed along the perimeter of the light guide, with LEDs positioned within these cavities, allows for precise alignment and efficient light coupling, reducing light attenuation and achieving uniform light distribution through controlled light leakage, eliminating the need for opaque bezels and enhancing light guide flexibility and size variability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If LEDs are positioned along the perimeter of the light guide, then the light guide can be made thinner, but the light distribution across the top surface becomes non-uniform
Solution Approach 1:
The light guide is divided into multiple sections with cavities distributed throughout the volume, not just at the perimeter. Each cavity acts as an independent light coupling point, segmenting the light distribution function across the entire light guide volume to achieve uniform illumination while maintaining thin profile.
Solution Approach 2:
The invention transitions from two-dimensional perimeter positioning to three-dimensional volumetric distribution of cavities throughout the light guide. This dimensional change allows light to be coupled and distributed from multiple depth positions, enabling uniform top surface illumination in thinner structures.
2Productivity
If opaque reflector layers are used to reflect LED light back into the light guide, then light coupling efficiency improves, but significant light attenuation occurs
Solution Approach 1:
The invention replaces opaque metallic reflector layers with TIR (total internal reflection) optical structures formed directly in the light guide material. This substitution eliminates the need for separate reflector components and reduces light attenuation by utilizing the light guide's own optical properties rather than external reflective surfaces.
Solution Approach 2:
The TIR structures act as optical intermediaries that facilitate light redirection from LEDs into the light guide without the significant losses associated with opaque reflectors. The refractive index difference at the TIR interfaces provides efficient light coupling with minimal attenuation.
3Productivity
If TIR structures are formed above LED cavities, then light is reflected into the light guide, but dark spots are created over the light sources
Solution Approach 1:
The light guide is designed with spatially varying cavity distributions, with higher cavity density in regions that would otherwise be dark spots. This local quality adjustment ensures that areas directly over LEDs receive additional light coupling from nearby cavities, compensating for the shadowing effect of TIR structures and achieving uniform overall illumination.
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 solution achieves high LED light coupling efficiency of about 96% with improved uniformity and reduced light attenuation, enabling the creation of flexible and large-sized light guides with uniform illumination, suitable for various applications including backlighting and general lighting.
Implementation Method 1
The light guide comprises TIR structures above the cavities. Due to total internal reflection, the light generated by the light sources is reflected into the light guide
Data Source
Figure 1~6
Figure 2~3
AI summary
A thin plastic light guide is formed to have cavities on one surface and TIR (total internal reflection) structures directly above the cavities. LEDs mounted on a printed circuit board are positioned in the cavities. The cavity walls are shaped to refract the LED light and direct the LED light toward the TIR structures to most efficiently make use of the TIR structures. The TIR structures may have a cusp or cone shape. The top ceiling of the cavities may be shaped to direct light at the TIR structure so as to leak through the TIR structure and blend the light with light leaking through surrounding portions of the light guide. The LEDs may be distributed only near the edges of the light guide or over the entire back surface of the light guide. A diffuser sheet may be laminated over the light guide to further mix the light.