Optical Device Ray Control Structure for Light Leakage Reduction
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Solution Overview
Problem
Optical devices with lightguides face challenges in achieving uniform light distribution and adequate display quality due to light leakage and non-uniform illumination, particularly when light enters at angles below the critical angle, leading to reduced contrast and visibility.
Innovation Solution
Incorporating optically functional layers, such as low-refractive index layers and air cavities, to control light propagation and extraction, ensuring total internal reflection and minimizing stray light, thereby enhancing light distribution and display quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a layer of lower refractive index than the lightguide is provided on the upper surface or bottom surface of the lightguide, then light extraction efficiency is improved, but light leakage occurs near the end face when rays enter at angles smaller than the critical angle
Solution Approach 1:
The patent applies different refractive index characteristics to different regions of the lightguide structure. A lower refractive index layer is provided on the light-extracting surface to improve light extraction efficiency, while a higher refractive index cladding layer is provided at the end face region to prevent light leakage. This local differentiation of optical properties resolves the contradiction between light extraction and light leakage prevention.
Solution Approach 2:
The lightguide structure is segmented into distinct functional regions: a lightguide body, a lower refractive index layer for light extraction, and a higher refractive index cladding layer at the end face for light confinement. This segmentation allows each region to perform its specific function optimally without interfering with other functions.
2Illumination intensity
If light enters the lightguide at angles smaller than the critical angle, then light coupling is achieved, but light passes through the adhesive layer causing non-uniform illumination and reduced contrast
Solution Approach 1:
The higher refractive index cladding layer is provided in advance at the end face region to prevent light leakage before it can occur. This preliminary protective measure ensures that even when light enters at angles smaller than the critical angle, the cladding layer prevents it from passing through the adhesive layer, thereby maintaining illumination uniformity and contrast.
3Loss of energy
If the optical pattern density is reduced, then transparency is improved, but bright spots are formed producing stray light at the viewing angle
Solution Approach 1:
The patent applies different optical properties to different regions: the lightguide body maintains an open structure with low pattern density for high transparency, while the end face region is covered with a higher refractive index cladding layer that prevents stray light formation. This local differentiation allows the system to achieve both transparency and stray light control.
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 uniform light distribution and improved display quality by efficiently guiding and extracting light, reducing light loss and maintaining high contrast and visibility.
Implementation Method 1
rays which enter the low-refractive index layer at an angle smaller than the critical angle exist near the end face. These rays are not controlled by the configuration for light guiding and light extraction control that is provided in the optical device
Implementation Method 2
Incorporating optically functional layers, such as low-refractive index layers and air cavities, to control light propagation and extraction
Data Source
Figure 1A
Figure 1B
Figure 2A(a)~2A(b)
AI summary
With a simple configuration, an optical device which realizes uniform light distribution and adequate display quality is provided. An optical device includes: a light guiding layer; a first optically functional layer provided on at least one of a first principal face and a second principal face of the light guiding layer; and a ray control structure, at an end of the light guiding layer on a light-incident side, being provided on a surface of the first optically functional layer that is on an opposite side to the light guiding layer. The ray control structure reduces light which is incident from an edge of the light guiding layer to the first optically functional layer at an angle smaller than a critical angle.