Multiplexed Waveguide Gratings for Uniform Laser Illumination
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Solution Overview
Problem
Existing waveguide displays face challenges in achieving compact, wide-angle, full-color imaging with high efficiency due to alignment issues in multi-waveguide stacking and manufacturing tolerances, leading to low yield and inefficiencies in light utilization.
Innovation Solution
Implementing a single grating layer in waveguides that incorporates both transmissive and reflective gratings, multiplexed to support various optical functions, using holographic photopolymer dispersed liquid crystal (HPDLC) materials and alignment layers to optimize refractive index modulation and polarization response, and employing beam splitters for reduced banding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multi-waveguide stacking is used to achieve compact, wide-angle, full-color imaging, then display performance is improved, but alignment issues and manufacturing tolerances cause low yield
Solution Approach 1:
The patent merges multiple grating functions (transmissive and reflective gratings) into a single grating layer within one waveguide. This eliminates the need for multi-waveguide stacking while achieving compact, wide-angle, full-color imaging. The single grating layer integrates multiple optical functions that were previously requiring separate waveguides, thereby improving manufacturing yield by removing alignment issues between multiple waveguides.
Solution Approach 2:
The single grating layer is designed to perform multiple functions simultaneously: it acts as both a transmissive grating for coupling light into the waveguide and a reflective grating for extracting light to the viewer's eye. This multi-functionality reduces the overall device complexity and eliminates alignment requirements between separate waveguides, directly addressing the reliability issue while maintaining display performance.
2Adaptability or versatility
If multi-waveguide stacking is used to achieve compact, wide-angle, full-color imaging, then display performance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent combines multiple grating functions into a single grating layer, eliminating the need for multiple separate waveguides. This merging reduces manufacturing complexity by removing the alignment processes required between multiple waveguides while maintaining the display performance benefits of compact, wide-angle, full-color imaging.
Solution Approach 2:
The single grating layer is segmented into different functional regions: a first region with a first grating for coupling light into the waveguide and a second region with a second grating for extracting light. This segmentation allows each region to be optimized for its specific function while being manufactured as a single integrated structure, reducing overall manufacturing complexity.
3Ease of manufacture
If conventional waveguide structures are used, then manufacturing is simpler, but light utilization efficiency is low
Solution Approach 1:
The patent employs dynamic control of light paths through strategically positioned transmissive and reflective gratings. The first grating couples light into the waveguide while the second grating extracts light at optimal angles, dynamically managing light utilization throughout the waveguide length. This dynamic approach maximizes light utilization efficiency while maintaining manufacturing simplicity through the single-waveguide architecture.
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 enables wide-angle, full-color displays with improved light uniformity and efficiency by reducing manufacturing complexities and enhancing light utilization, while maintaining a generous eyebox and compact design.
Implementation Method 1
During the recording process, the monomers polymerize, and the mixture undergoes a photopolymerization-induced phase separation
Implementation Method 2
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 3
the in-coupled light can proceed to travel within the planar structure via total internal reflection (TIR)
Implementation Method 4
planar waveguides can be designed to utilize diffraction gratings to diffract and couple incident light into the waveguide structure
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
Data Source
AI summary
Multiplexed reflection and transmission gratings, and methods of their manufacture, are provided that improve uniformity with laser light, that is, reduced banding and other illumination artifacts occurring in waveguides. The mechanism for this can be the multiple reflections between the waveguide reflecting surfaces and the reflection hologram, which promote illumination averaging as beam propagation processes within a waveguide. In some gratings, a beam splitter layer overlapping the multiplexed gratings can be provided for the purposes of reducing banding in a laser-illuminated waveguide. The beam splitter can be provided by one or more dielectric layers. The beamsplitter can have sensitivity to one polarization. The beamsplitter can be sensitive to S-polarization. The beam splitter can be an anti-reflection coating optimized for normal incidence that becomes reflective at high TIR angles when immersed in glass or plastic.