Waveguide Edge Film and Nanostructures for Reflection Reduction
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Solution Overview
Problem
Augmented reality headsets face issues with reflections from the edge surface of waveguides, which can lead to ghost images and reduced contrast due to spurious reflected light, compromising the integrity of the displayed content.
Innovation Solution
The implementation of a reflectivity-reducing film, such as an absorptive or photovoltaic film, on the edge surface of the waveguide, along with nanostructures that create a gradient in effective refractive index, to minimize reflections and improve image contrast. This film is formed using a curable material on a dissolvable substrate to avoid stress on the waveguide surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a reflectivity-reducing film is applied to the edge surface of the waveguide, then reflections are reduced and image contrast is improved, but the waveguide surface may experience stress and deformation
Solution Approach 1:
A stress-relief layer is introduced as an intermediary between the reflectivity-reducing film and the waveguide surface. This intermediate layer absorbs and distributes the stress generated by the reflectivity-reducing film, preventing stress concentration on the waveguide surface and avoiding shape deformation while maintaining the anti-reflection function.
Solution Approach 2:
The refractive index of the stress-relief layer is specifically optimized to create a gradient transition between the waveguide core and cladding regions. By adjusting the refractive index parameter of the stress-relief layer, the patent achieves both stress management and enhanced optical performance, reducing reflections without compromising waveguide integrity.
2Reliability
If the waveguide core index is increased to improve light confinement, then light confinement is improved, but reflections from the edge surface increase
Solution Approach 1:
The waveguide structure is segmented into multiple functional layers: a core layer for light confinement, a stress-relief layer for stress management and additional optical optimization, and a reflectivity-reducing film for edge surface reflection control. This segmentation allows each layer to independently optimize its function without compromising the others.
Solution Approach 2:
The patent employs a composite structure combining materials with different refractive indices and mechanical properties. The core layer uses high-index material for light confinement, while the stress-relief layer uses a material with intermediate refractive index to provide both mechanical stress relief and optical optimization, creating a composite system that simultaneously achieves light confinement and reflection reduction.
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 effectively reduces reflections from the edge surface, enhancing the contrast and integrity of the displayed images by converting reflected light into electrical energy, which can be stored, thereby reducing power consumption and maintaining the shape and functionality of the waveguide.
Implementation Method 1
a photovoltaic film disposed on the edge surface and configured to reduce a reflectivity of the edge surface
Implementation Method 2
nanostructures that create a gradient in effective refractive index, to minimize reflections
Data Source
AI summary
An augmented reality system can include a waveguide having an edge surface that extends between opposing light-guiding surfaces. The waveguide can guide light toward the edge surface. The waveguide can include a reflectivity-reducing film, such as an absorptive film or a photovoltaic film, disposed on the edge surface. To form the reflectivity-reducing film, curable material can be disposed onto a dissolvable film. The curable material can be cured while disposed on the dissolvable film such that the cured material forms a reflectivity-reducing structure on the dissolvable film. The dissolvable film can be dissolved such that the reflectivity-reducing structure remains intact as a reflectivity-reducing film that can be adhered to the edge surface, such as with a primer layer. The edge surface can include nanostructures, sized smaller than half a wavelength of the guided light, that can reduce a reflectivity of the edge surface.