Holographic Waveguide Layout for Interference-Resistant Image Display
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Solution Overview
Problem
Existing waveguides for displaying images in glass surfaces face challenges such as high manufacturing costs for large-format applications, susceptibility to interference due to dirt or water on outer interfaces, and limited usable pane formats when surrounding substrates are tinted.
Innovation Solution
A waveguide design that uses total internal reflections at the interface between layers to reduce interference susceptibility, allows the input-coupled beam to incident multiple times on the image hologram for broader illumination, and features an efficiency curve that increases deflection efficiency with each incidence to achieve a more homogeneous reconstructed image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If light guidance is achieved through total internal reflection at outer interfaces, then light guidance is simple to implement, but susceptibility to interference from dirt or water increases
Solution Approach 1:
The patent introduces an intermediate layer with refractive index n2 between the waveguide layer (n1) and the environment (n3). This intermediary layer acts as a buffer that reduces the sensitivity of total internal reflection to surface contaminants. The critical angle condition is modified to depend on the interface between n1 and n2 rather than directly on the outer surface, making the light guidance less susceptible to interference from dirt or water on the outer interface.
2Manufacturing precision
If microstructures are integrated for light guidance, then light guidance precision is improved, but manufacturing costs increase quadratically with area
Solution Approach 1:
The patent extracts the light guidance function from complex microstructures and implements it through the refractive index difference at the waveguide layer's outer interface. By removing the need for expensive microstructures and relying instead on the inherent optical properties of the layered structure, the manufacturing cost is reduced while maintaining light guidance precision.
3Device complexity
If the waveguide uses a single beam incidence on the image hologram, then the device complexity is reduced, but the image illumination coverage is insufficient for large extents
Solution Approach 1:
The patent employs periodic total internal reflections of the light beam within the waveguide layer. The beam undergoes multiple sequential reflections at the waveguide-intermediate layer interface, creating a periodic interaction with the image hologram along the propagation direction. This periodic action allows a single input beam to illuminate large extents of the image hologram without increasing device complexity.
4Manufacturing precision
If the deflection efficiency is uniform across all beam incidences, then the manufacturing precision is simplified, but the reconstructed image homogeneity deteriorates
Solution Approach 1:
The patent applies local quality by varying the deflection efficiency of the image hologram at different locations along the propagation direction. The image hologram is designed with spatially varying properties such that regions corresponding to earlier beam incidences have lower deflection efficiency while later regions have higher efficiency. This compensates for the decreasing beam intensity and achieves homogeneous image reconstruction.
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 efficient and interference-resistant light guidance in waveguides, allowing for the reconstruction of large and homogeneous images in glass surfaces, even with tinted substrates, while reducing manufacturing costs.
Implementation Method 1
the input-coupled beam is reflected by one or more reflections, in particular by one or more total internal reflections at the interface between the first and second layers
Implementation Method 2
the guided beam is incident on the image hologram, on which the guided beam is at least partially deflected for the reconstruction of the exposed image
Data Source
AI summary
A waveguide for displaying an image includes a transparent base body having a coupling-in region and a coupling-out region which is spaced apart therefrom in a first direction. The coupling-out region has an image hologram having an imprinted image. The coupling-in region deflects at least some of the radiation originating from a light source such that the deflected part propagates as a coupled-in beam bundle in the base body by reflection as far as the coupling-out region and impinges on the image hologram. The image hologram deflects at least part of the impinging beam bundle in order to reconstruct the imprinted image such that the deflected part exits the base body via the front face or rear face such that the imprinted image is perceptible for a viewer.