Backlight Global Mode Mixer for Passive Display Brightness
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Solution Overview
Problem
Passive displays, such as LCDs and electrophoretic displays, lack the ability to emit light, limiting their practical applications due to reliance on external light sources, which affects their brightness and efficiency.
Innovation Solution
A plate waveguide with a global mode mixer is used to convert light from a first directional mode to a second directional mode, enhancing light extraction efficiency and enabling the use of brighter or more efficient backlights for passive displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If passive displays use external light sources for illumination, then they can function, but their brightness and efficiency are limited
Solution Approach 1:
The patent changes the parameters of light propagation by introducing a waveguide with specific refractive index characteristics and geometric dimensions. The waveguide parameters (refractive index ratio, thickness) are optimized to enable efficient light coupling and directional emission, transforming the limited external light source into an efficient illumination system that achieves high brightness without excessive energy consumption.
Solution Approach 2:
The waveguide acts as an intermediary between the external light source and the display. It receives light from the external source, guides it through total internal reflection, and converts it into directional emission patterns. This intermediary structure enables efficient light utilization and directional control, resolving the contradiction between brightness and energy efficiency.
2Productivity
If light is guided in specific directional modes within the waveguide, then light extraction efficiency improves, but the device structure becomes more complex
Solution Approach 1:
The patent applies local quality by creating specific regions within the waveguide with different refractive indices. The core region has a higher refractive index than the cladding, creating localized optical properties that enable selective light guidance and extraction. This localized refractive index variation achieves high light extraction efficiency without requiring complex overall device structure.
Solution Approach 2:
The patent utilizes parameter changes in the refractive index distribution within the waveguide to control light propagation modes. By optimizing the refractive index ratio and spatial distribution, the system achieves efficient light extraction through specific directional modes without introducing complex structural elements, thus resolving the contradiction between productivity and device complexity.
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 improves light extraction efficiency, allowing passive displays to emit brighter light, effectively functioning like active displays by converting light within the waveguide to optimize scattering and emission.
Implementation Method 1
A plate waveguide may be used to guide light in a plurality of directional modes
Implementation Method 2
The global mode mixer is configured to convert a portion of the light guided in a first directional mode into light guided in a second directional mode
Data Source
AI summary
Examples disclosed herein include a plate light guide configured to guide light along a length of a light guide. The light guided along the length of the light guide propagates in at least two directional modes: a first directional mode and a second directional mode. Light guided in a first directional mode has one or both of a transverse component that is greater than and a vertical component that is less than respective transverse and vertical components of light guided in the second directional mode. Also included is a global mode mixer. The global mode mixer extends along the length of the light guide length and is configured to convert a portion of the light guided in a first directional mode into a second directional mode. A scattering element preferentially scatters light in the second directional mode out of the light guide.