Light Guide Outcoupling Elements for Display Uniformity
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Solution Overview
Problem
Light guides used in displays often exhibit visual artifacts such as hot spots and rainbow-like features due to non-uniform light emission, which existing technologies fail to address effectively without increasing the thickness of the layer assembly or reducing brightness.
Innovation Solution
Divide the outcoupling elements into groups with unique blaze angles and angular distributions, allowing for partial mixing of light to minimize or diminish visual artifacts like hot spots and rainbow-like features without using additional optical layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If outcoupling elements are used to couple out light from the light guide, then light emission is achieved, but visual artifacts such as hot spots and rainbow-like features appear due to non-uniform light emission
Solution Approach 1:
The outcoupling elements are divided into multiple groups, where each group has a different blaze angle. This segmentation allows different angular distributions of light to be generated, which when mixed together, reduce the formation of hot spots and rainbow-like features while maintaining overall light emission.
Solution Approach 2:
Different regions of the light guide are assigned outcoupling elements with locally optimized blaze angles. This creates local variations in light outcoupling characteristics that, when combined, produce a more uniform overall light distribution and minimize visual artifacts.
2Illumination intensity
If additional optical layers are added to reduce visual artifacts, then luminance uniformity improves, but the thickness of the layer assembly increases
Solution Approach 1:
The light guide itself is modified to include outcoupling elements with different blaze angles, allowing it to self-correct the non-uniform light emission and eliminate visual artifacts without requiring additional optical layers. The light guide performs the function of both light transport and uniformity correction.
3Object-affected harmful factors
If additional optical layers are added to reduce visual artifacts, then hot spots and rainbow-like features are reduced, but the brightness of the display is reduced
Solution Approach 1:
The light guide structure itself is designed to minimize visual artifacts through the use of multiple outcoupling element groups with different blaze angles, eliminating the need for additional optical layers that would otherwise reduce brightness. This self-correcting mechanism preserves display brightness while reducing artifacts.
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 luminance uniformity and reduces visual artifacts, enhancing the viewing experience by ensuring light is emitted more uniformly and reducing the appearance of hot spots and rainbow-like features, while maintaining the thickness and brightness of the display.
Implementation Method 1
light coupled into the light guide on at least one of the lateral faces and propagating so as to be totally internally reflected within the light guide prior to entering or impinging on an outcoupling element
Implementation Method 2
total internal reflection is disturbed by refraction and/or reflection
Implementation Method 3
total internal reflection is disturbed by refraction and/or reflection
Data Source
AI summary
A light guide which has two main faces, each having at least one surrounding edge; the main faces connected by lateral faces at the edges. The light guide includes three-dimensionally shaped light outcoupling elements on a main face and/or within the volume enclosed by the main and lateral faces. The outcoupling elements are distributed according to a predetermined pattern. Light coupled into the light guide propagates by total internal reflection unless entering or impinging on an outcoupling element and for outcoupling, one of the two main faces is preferred over the other. The outcoupling elements are divided into groups, each group being complementary to the other groups. Group members each have a common blaze angle and a common outcoupling property, which differ from those of the members of the other groups, which results in light being outcoupled with different angular distributions, thereby reducing visible artifacts.