Angular Selective Notch Filter Reflectors for Waveguide Displays
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Solution Overview
Problem
Conventional optical waveguide systems, particularly in augmented reality displays, suffer from inefficiencies in light propagation, leading to reduced luminance and secondary image formation due to flat angular response reflective coatings, which result in undesirable artefacts and decreased display efficiency.
Innovation Solution
The implementation of angularly selective notch filter optical reflectors within the optical waveguide substrate, where each reflector is configured to partially reflect and transmit light rays within a specific transflectance band, optimizing the angular response based on its order in the sequence, thereby minimizing unnecessary reflections and improving propagation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If flat angular response reflective coatings are used in optical waveguide systems, then light propagation is simplified and manufacturing is easier, but display efficiency decreases and secondary image formation occurs
Solution Approach 1:
The patent applies parameter changes by transitioning from flat angular response reflective coatings to angularly selective notch filter reflectors. This changes the angular response parameter of the reflectors, enabling them to selectively reflect specific angles of light while transmitting other angles. This resolves the contradiction by maintaining manufacturing feasibility while significantly improving display efficiency and eliminating secondary image formation through controlled angular selectivity.
Solution Approach 2:
The patent implements local quality by making each reflector have different angular response characteristics tailored to its specific position in the waveguide. Each reflector is designed with a specific transflectance band matched to the angular information required at that location. This localized optimization ensures that each reflector processes only the relevant angular information, improving overall display efficiency while maintaining manufacturing practicality through systematic design.
2Productivity
If angularly selective notch filter optical reflectors are implemented, then display efficiency and uniformity are enhanced, but device complexity increases
Solution Approach 1:
The patent manages device complexity through parameter changes by defining each reflector's angular response in terms of its transflectance band centered at a specific angle. This systematic parameterization allows complex angular selectivity to be achieved through controlled variations in reflector design parameters rather than fundamentally complex structures. The complexity is rendered manageable through the method for determining required angular responses based on ray tracing simulations.
Solution Approach 2:
The patent applies preliminary action by using computer simulations and ray tracing methods to determine the required angular response characteristics of each reflector before manufacturing. This preliminary design phase calculates the optimal transflectance band for each reflector based on the desired eye-box characteristics and waveguide geometry, allowing the complex angular selectivity to be predetermined and then implemented through standardized manufacturing processes.
3Ease of manufacture
If conventional reflective coatings are used, then manufacturing is simpler, but light propagation losses increase due to unnecessary reflections
Solution Approach 1:
The patent addresses light propagation losses through parameter changes by designing reflectors with angularly selective transflectance bands that match the specific angular information required at each position. This prevents unnecessary reflections of angular information that would otherwise be transmitted through the waveguide without being utilized. The parameter optimization ensures that each reflector only reflects the angular information needed, minimizing energy losses while maintaining manufacturing practicality.
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 configuration enhances display efficiency and uniformity, reduces secondary image formation, and improves overall light propagation by ensuring only relevant angular information is passed to the correct reflector, minimizing losses and artefacts.
Implementation Method 1
Each angular selective notch filter optical reflector can be configured both to partially reflect and partially transmit light rays having angles of incidence with respect to the reflector which are in a specific transflectance band of angles selected for the particular reflector
Implementation Method 2
angular selective notch filter optical reflectors...configured both to partially reflect and partially transmit light rays having angles of incidence
Data Source
AI summary
An optical device includes a range of angularly selective reflectors are contained within an optical waveguide substrate and substantially optimized according to their reflector order within the sequence of reflectors. This configuration of reflectors ensures that the required angular information is passed through to the correct reflector within the sequence. The angular response in addition reduces or eliminates formation of secondary images carried to successive reflectors, resulting in undesired artefacts.