Closed-Loop Light Guide for Uniform Display Illumination
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Solution Overview
Problem
Front light illumination systems for reflective display devices using light guides face challenges in achieving uniform illumination due to exponential decrease in luminous flux with distance, leading to inefficient use of light and poor optical output ratio, and existing solutions either require complex design variations or result in low light extraction efficiency.
Innovation Solution
A light guide system where unused light is recycled by returning it to the injection area within a closed loop, allowing re-injection in the same direction of propagation, enhancing light coupling and extraction efficiency, and featuring light extraction perpendicular to the injection plane for uniform illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the light extraction efficiency is increased to improve illumination intensity, then the illumination intensity is improved, but the illumination uniformity deteriorates due to exponential decrease in luminous flux with distance
Solution Approach 1:
The light guide is divided into multiple segments with different extraction efficiencies. The first light guide portion has a first light extraction efficiency and the second light guide portion has a second light extraction efficiency, allowing different regions to serve different illumination functions while maintaining overall uniformity
Solution Approach 2:
Different portions of the light guide are assigned different light extraction efficiencies tailored to their specific positions and functions. The first portion extracts light at a higher rate for intense illumination areas, while the second portion extracts light at a lower rate to maintain uniformity in other regions
2Ease of manufacture
If the light extraction efficiency is made constant along the guide to simplify design, then the ease of manufacture is improved, but the optical output ratio deteriorates due to exponential loss of luminous flux
Solution Approach 1:
The light guide is segmented into multiple portions with different extraction efficiencies, allowing the system to overcome exponential loss while maintaining manufacturing simplicity. Each segment can be manufactured with standard techniques but with different extraction properties
Solution Approach 2:
The light extraction efficiency parameter is changed along the length of the light guide, transitioning from a first extraction efficiency in the first portion to a second extraction efficiency in the second portion, optimizing energy utilization while maintaining manufacturability
3Stability of the object's composition
If the light extraction efficiency varies continuously along the guide to compensate for exponential decrease, then the illumination uniformity is improved, but the device complexity increases due to continuous geometry alteration
Solution Approach 1:
Instead of continuous variation, the light extraction efficiency is varied in discrete segments. The light guide is divided into first and second portions with distinct extraction efficiencies, achieving uniformity without the complexity of continuous geometry alteration
Solution Approach 2:
Different segments of the light guide have locally optimized extraction efficiencies that are constant within each segment but differ between segments, providing uniform illumination while avoiding the complexity of continuous variation
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 approach significantly improves light coupling and illumination uniformity, increasing the optical output ratio and maintaining a compact design suitable for both reflective and transmissive display devices.
Implementation Method 1
The light guide is structured to allow gradual extraction of the light that is propagating in the direction of the underlying display device. The structures provided in the light guide for extracting the light are called 'light extractors'.
Implementation Method 2
the light guide takes the form of a loop closed onto itself at the light injection area... the light is extracted from the light guide along a perpendicular direction to a plane defined by the direction of injection of light into the guide
Data Source
AI summary
Lighting system for a data display device (12, 20), wherein said lighting system includes a light guide (1; 22) including an area (2; 26) into which the light produced by at least one light source (4) is injected, said injection area (2; 26) is extended by an area (8; 24) for extracting the light propagating inside the guide (1; 22) to light the display device (12; 20), said extraction area (12, 20) is provided with light extractors (10), the light guide (1; 22) takes the form of a loop closed on itself at the light injection area (2; 26) to allow the light originating from the light source (4) and which was not extracted from the light guide (1; 22) in the extraction area (8; 24) to continue to travel inside the light guide (1; 22) and to return to the starting point thereof at the light injection area (2; 26), the data display device (12; 20) is arranged inside the loop, and the lighting system is characterized in that the light is extracted from the light guide (1; 22) in a perpendicular direction to a plane (P1) defined by the direction (X-X) of injection of light into the guide (1), and by a generating line (Y-Y) of the loop.