Reflective Waveguide Light Recycling Mirrors for Uniform AR Brightness
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Solution Overview
Problem
Reflective waveguides in augmented and mixed reality displays suffer from limited efficiency and luminance uniformity due to light depletion as it propagates through prism arrays, leading to decreased image brightness and gaps in the field of view.
Innovation Solution
Implementing light recycling structures within the waveguide, including multiple mirror arrays oriented to ensure efficient light reuse and alignment, with angular relationships and polarization-sensitive coatings to minimize stray light and image gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If light propagates through prism arrays in reflective waveguides, then the light path is expanded and field of view is increased, but light depletion occurs leading to decreased image brightness and gaps in the field of view
Solution Approach 1:
The patent implements light recycling mirrors that capture light which would otherwise be lost or depleted as it propagates through the waveguide. These mirrors redirect the depleted light back through the waveguide structure, allowing it to be reused for image formation. This recovering mechanism directly addresses the light depletion problem by retrieving and reutilizing light that would normally be discarded, thereby maintaining image brightness while preserving the expanded field of view.
2Productivity
If multiple mirror arrays are added to recycle light, then display efficiency and luminance uniformity are improved, but device complexity increases
Solution Approach 1:
The patent merges the light recycling function with the existing waveguide structure by integrating mirror arrays at strategic locations where light depletion occurs. Rather than adding completely separate systems, the recycling mirrors are combined with the waveguide's optical path, allowing the same structural elements to serve both waveguide guidance and light recycling functions. This merging approach improves display efficiency while minimizing the increase in device complexity.
3Reliability
If light recycling mirrors are positioned at specific angles, then louver effects and image gaps are reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent utilizes specific angular parameters for the light recycling mirrors to optimize their performance. By carefully selecting and adjusting the orientation angles of these mirrors, the system achieves proper light redirection that minimizes louver effects and image gaps. The angular relationships are designed to compensate for typical manufacturing tolerances, allowing standard manufacturing processes to produce the required precision without requiring excessively tight tolerances.
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
Improves display efficiency, enhances luminance uniformity across the viewing area, reduces fabrication complexity, and maintains a compact design by optimizing light recycling and reducing louver effects and image gaps.
Implementation Method 1
one or more light recycling mirrors configured to redirect light propagating through the waveguide for reuse in forming an image
Implementation Method 2
at least one of the one or more light recycling mirrors has an angularly selective coating configured to reflect light propagating through the waveguide while minimizing reflectance for see-through directions
Implementation Method 3
at least one of the one or more light recycling mirrors includes a coating configured to rotate a polarization state of light, such that the second mirror array reflects the rotated light
Data Source
AI summary
A waveguide includes a first configuration having an input coupler, an exit pupil expander, and an output coupler comprised of a first mirror array and a second mirror array. The first configuration further includes a light recycling mirror array disposed at an end opposite the exit pupil expander. Alternatively, or in addition to the first configuration, the waveguide includes a second configuration having a first light recycling mirror disposed at a first side of the exit pupil expander and a second light recycling mirror disposed at a second side of the exit pupil expander.