Planar Front Illumination Light Guide with Micro Lenses
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Solution Overview
Problem
Existing planar front illumination systems for reflective displays face challenges such as air gaps being difficult to construct and maintain, leading to unwanted reflections, mechanical damage, and stray light leakage, which degrade optical performance and increase battery life impact in mobile devices.
Innovation Solution
A fully laminated front illumination system with a light guide plate featuring micro lenses on its inner or outer surface and a stepped index layer to confine light through total internal reflection, minimizing air gaps and reducing stray light, while being thin, lightweight, and cost-effective.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If air gaps are introduced to maximize refractive index difference for improved light extraction, then light extraction efficiency is improved, but mechanical stability and optical quality deteriorate due to unwanted reflections and difficulty in construction
Solution Approach 1:
A low refractive index adhesive layer is introduced as an intermediary between the light guide plate and the micro optical features. This adhesive layer serves as a mediator that maintains the refractive index difference necessary for effective light extraction while providing mechanical stability and eliminating air gaps that cause unwanted reflections and construction difficulties
Solution Approach 2:
The refractive index parameter is modified by replacing air (high refractive index difference) with a low refractive index adhesive material. This parameter change maintains sufficient optical contrast for effective light extraction while improving mechanical stability and eliminating the harmful effects of air gaps
2Illumination intensity
If air gaps are used to enhance light refraction and reflection, then optical performance improves, but stray light leakage increases degrading image quality
Solution Approach 1:
The low refractive index adhesive layer acts as an intermediary that controls the optical interface between the light guide plate and micro optical features. It maintains refraction efficiency while preventing stray light leakage by eliminating air gaps and providing a controlled optical pathway
3Illumination intensity
If micro optical features are exposed directly to air to maximize refractive power, then light extraction efficiency improves, but manufacturing complexity and cost increase
Solution Approach 1:
The adhesive layer is merged with the micro optical features during the molding process, combining the adhesive application and feature formation into a single manufacturing step. This integration simplifies production while maintaining the optical performance needed for effective light extraction
4Illumination intensity
If air gaps are introduced for optical performance, then light distribution improves, but device thickness and weight increase
Solution Approach 1:
A thin adhesive layer is used instead of air gaps to achieve light distribution. This thin film approach maintains optical performance while minimizing the increase in device thickness, as the adhesive layer can be applied as a thin coating during molding
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 provides uniform and efficient illumination with minimized artifacts, enhanced ruggedness, and reduced battery consumption by directing light inward while minimizing stray light, thus maintaining image quality and contrast.
Implementation Method 1
A layer having a lower index of refraction than the light guide plate is formed on the surface of the light guide plate to assist in confining the injected light in the light guide plate by total internal reflection
Implementation Method 2
Micro lenses are formed on the inner or outer surface of the light guide. The micro lenses direct the light conducted in the light guide toward the display
Data Source
AI summary
A system for illuminating a reflective display or other material from a planar front device and a method of manufacture thereof. The system includes a light guide plate that conducts light from an edge light source across the face of a reflective display. Micro lenses are formed on the inner or outer surface of the light guide and direct the light conducted in the light guide toward the display. A stepped index layer is formed on the surface of light guide plate containing the micro lenses. The stepped index layer has an index of refraction lower than an index of refraction of the light guide plate to assist in the total internal reflection of light injected into the light guide plate. A top layer protective coat or touch screen can be laminated to the outside of the light guide plate.