Optical Light Pipe Uniform Intensity via Evanescent Coupling
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Solution Overview
Problem
Conventional light guides in automotive lighting struggle to achieve uniform light intensity along their length, resulting in a 'spotty' or 'dotted' appearance due to greater light emission near the source compared to further along the guide, making it difficult to replicate a uniformly lit 'neon-look' aesthetic.
Innovation Solution
An optical-grade light pipe assembly with a custom secondary reflective layer that uses total internal reflection and evanescent coupling to distribute light uniformly, featuring a reflective surface with a higher refractive index than the light pipe, positioned adjacent to the light pipe to propagate evanescent waves and recapture refracted light, ensuring consistent intensity from a single localized light source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional light guides are used to approximate neon tube appearance, then a localized light source can be used, but the light emission is noticeably brighter at the end near the source than in the middle, failing to achieve uniform illumination
Solution Approach 1:
The light pipe incorporates a variable refractive index profile where the core has a higher refractive index than the cladding, with the refractive index varying along the length of the light pipe. This local variation in optical properties enables uniform light extraction along the entire length despite using a single localized light source, resolving the contradiction between uniform illumination and simple light source configuration
Solution Approach 2:
The patent changes the refractive index parameter along the length of the light pipe to achieve uniform light intensity. By gradually varying the refractive index of the core material or the cladding material (or both) along the propagation direction, the light extraction efficiency is modulated to compensate for the natural decay of light intensity, thereby achieving uniform illumination along the entire length
2Use of energy by moving object
If light emitting diodes are used as light sources, then energy efficiency is improved compared to incandescent bulbs, but the Lambertian distribution produces a spotty or dotted lit appearance rather than a uniform neon-look
Solution Approach 1:
The light pipe acts as an intermediary between the LED light source and the final illumination pattern. It takes the point-source Lambertian distribution from the LED and transforms it into a uniform line-source distribution through controlled internal reflection and gradual light extraction along its length, thereby converting the spotty appearance into a uniform neon-look while preserving the energy efficiency of LEDs
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 achieves a substantially uniform light intensity along the length of the light pipe, enhancing light efficiency and aesthetic appeal by utilizing evanescent waves to redirect and recapture light, thereby overcoming the limitations of conventional light guides.
Implementation Method 1
the reflective secondary surface is capable of propagating an evanescent wave at a point where any of a plurality of light rays traveling through the light pipe are internally reflected at a boundary between the overlay portion and reflective secondary surface
Implementation Method 2
uses total internal reflection and evanescent coupling to distribute light uniformly
Data Source
AI summary
The present application discloses a light pipe assembly having a light pipe with a proximal end, an opposing distal end, a length between the proximal end and the distal end, and a surface, the surface having an emitting portion and an overlay portion, where the light pipe is a material capable of transmitting light with a first refractive index; and a reflective secondary surface having a second refractive index and a width, the reflective secondary surface positioned adjacent the overlay portion of the light pipe, where the first refractive index is greater than the refractive index of air, and the second refractive index is greater than the first refractive index. In at least one embodiment, the reflective secondary surface is a non-metallic material capable of reflecting light. In at least one embodiment, the width of the reflective secondary surface varies along the length of the light pipe.