Angularly Multiplexed Holographic Gratings for Wide Field of View Waveguides

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Solution Overview

Problem

Waveguide display devices, such as near-eye displays, suffer from a small field of view, and existing methods to increase this often result in increased size and luminance non-uniformity or require multiple layers of Bragg gratings, which thickens the device.

Innovation Solution

The use of angularly multiplexed holographic gratings, where multiple holograms with different angular diffraction peaks are spatially overlapped, increasing the angular bandwidth without increasing the thickness of the waveguide, allowing for a wider field of view.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If layered switchable Bragg gratings are used to create spatially separated diffraction elements, then the field of view is increased, but the thickness of the waveguide greatly increases

Engineering Contradiction:

Improvefield of viewVSAvoidthickness of waveguide

Core Design Contradiction:

Area of stationary objectVSLength of stationary object

Solution Approach 1:

Multiple holographic gratings are combined and spatially overlapped within a single waveguide layer, merging their diffraction functions into one integrated structure. This allows the waveguide to achieve the combined field of view of multiple gratings without requiring multiple separate layers, thus increasing the field of view while maintaining a thin profile.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

Instead of separating gratings in the vertical dimension (creating multiple layers that increase thickness), the invention overlays multiple gratings in the angular dimension. By encoding different gratings with distinct angular diffraction characteristics within the same physical layer, the system expands the field of view without increasing the waveguide thickness.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Area of stationary object

If spatially separated diffraction elements are used, then the combined field of view is greater than a single diffraction element, but output performance of the display is negatively affected

Engineering Contradiction:

Improvefield of viewVSAvoidoutput performance

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

Each holographic grating within the overlaid structure is designed with specific local optical properties tailored to its intended angular range. By optimizing each grating's diffraction efficiency and angular bandwidth for its specific function, the system maintains high output performance across the entire combined field of view while avoiding the performance degradation that occurs with spatially separated elements.

Inventive Principle:

Principle #3Local quality

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 approach enhances the field of view of near-eye display devices while maintaining a compact size, providing a larger angular bandwidth and reducing optical artifacts compared to single holographic recordings.

Implementation Method 1

angularly multiplexed holographic gratings, where multiple holograms with different angular diffraction peaks are spatially overlapped, increasing the angular bandwidth

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

a waveguide being configured to propagate light from the image source to a field of view of a user

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentUS11119318B2Multiplexed hologram tiling in a waveguide display

Publication Date: 2021.09.14 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

A near-eye display device includes an image source, a waveguide, and a controller. The waveguide is configured to propagate light received the image source to a user of the near-eye display device, and includes a holographic grating comprising a plurality of angularly multiplexed holograms. The controller is configured to control display of an image via the image source.