Holographic Waveguide Backlight for Uniform Luminance
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Solution Overview
Problem
Traditional waveguide backlights face challenges in achieving uniform luminance and color due to wavelength-dependent absorption, polarization variations, and spatial nonuniformities caused by birefringent gratings, leading to inefficiencies and non-uniform illumination in display applications.
Innovation Solution
The implementation of holographic waveguide backlights with switchable Bragg gratings and strategically designed grating layers that diffract specific wavelengths and polarizations, combined with polarization control using waveplates and retarders, to achieve uniform and efficient light extraction and distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional waveguide backlights use conventional grating structures, then light extraction is achieved, but luminance uniformity and color consistency deteriorate due to wavelength-dependent absorption and polarization variations
Solution Approach 1:
The patent applies parameter changes by using switchable Bragg gratings that can dynamically adjust their diffraction properties. The gratings transition between diffracting and non-diffracting states through electrical control, enabling precise regulation of light extraction parameters to compensate for wavelength-dependent absorption and polarization variations, thereby achieving uniform luminance and color consistency.
Solution Approach 2:
The patent implements dynamics through switchable Bragg gratings that can change their optical properties in real-time. The gratings are electrically controlled to switch between active (diffracting) and inactive (non-diffracting) states, allowing dynamic adjustment of light extraction to maintain uniform illumination characteristics across different viewing conditions and wavelengths.
2Use of energy by moving object
If holographic polymer dispersed liquid crystal (HPDLC) mixtures are used to record volume phase gratings, then diffraction efficiency can be tuned from 0% to nearly 100%, but device complexity increases
Solution Approach 1:
The patent applies universality by using HPDLC mixtures that can serve multiple functions: they act as both the waveguide medium and the grating recording material. The same material system enables both light guidance through total internal reflection and light extraction through diffractive gratings, reducing the need for separate components and simplifying the overall device structure despite the advanced material properties.
Solution Approach 2:
The patent uses composite materials by combining photopolymerizable monomers with liquid crystals to create HPDLC mixtures. This composite material system provides both the refractive index modulation needed for high-contrast gratings and the electro-optic properties required for switchable operation, enabling diffraction efficiency tuning from 0% to nearly 100% while maintaining a relatively integrated structure.
3Adaptability or versatility
If multiple grating layers are used to encode multiple optical functions, then functional versatility improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies segmentation by dividing the optical functions into separate grating layers, each encoded with specific diffraction patterns for particular functions (e.g., input coupling, output extraction, beam steering). This modular approach allows each layer to be optimized for its specific function while maintaining overall system versatility, and enables independent fabrication and testing of individual layers before assembly.
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 results in a compact, highly uniform, and efficient holographic waveguide backlight that provides consistent luminance and color across a range of display applications, overcoming the limitations of traditional edge-lit solutions and ensuring high diffraction efficiency and reduced luminance and color nonuniformities.
Implementation Method 1
a light source optically coupled to the light guiding structure and configured to provide polarized light, the light undergoing total internal reflection within the light guiding structure
Implementation Method 2
at least one plurality of grating elements disposed in at least one grating layer for extracting light from the light guiding structure
Implementation Method 3
During the recording process, the monomers polymerize, and the mixture undergoes a photopolymerization-induced phase separation, creating regions densely populated by liquid crystal micro-droplets
Implementation Method 4
the mixture undergoes a photopolymerization-induced phase separation, creating regions densely populated by liquid crystal micro-droplets, interspersed with regions of clear polymer
Implementation Method 5
The resulting grating, which is commonly referred to as a switchable Bragg grating (SBG), has all the properties normally associated with volume or Bragg gratings but with much higher refractive index modulation ranges combined with the ability to electrically tune the grating over a continuous range of diffraction efficiency
Implementation Method 6
the liquid crystal molecules reorient themselves in response to an applied electric field, thereby changing the refractive index of the mixture
Data Source
AI summary
Systems and methods for holographic waveguide backlights in accordance with various embodiments of the invention are illustrated. One embodiment includes an optical illumination device including at least one waveguide, a source of light optically coupled to the at least one waveguide configured to emit light having a first polarization state, a first plurality of grating elements for diffracting the light having the first polarization state out of the at least one waveguide into a first set of output paths, a second plurality of grating elements for diffracting the light having the first polarization state light out of the at least one waveguide into a second set of output paths, and at least one input coupler configured to couple at least a portion of the light having the first polarization state towards the first and second pluralities of grating elements.