Time-sequenced grating pairings for wide FOV waveguide displays

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Waveguide displays, such as near-eye displays, face limitations in field of view due to angular bandwidth constraints, with existing solutions like multiple waveguide layers or switchable gratings resulting in reduced angular bandwidth and potential flicker issues, making it difficult to achieve a practical field of view beyond 30 degrees.

Innovation Solution

The use of grating configurations with pairings of non-output and output diffraction gratings, along with multiplexed K-vectors, to generate multiple field of view tiles through time-sequenced activation of grating pairings, allowing for increased angular bandwidth and reduced crosstalk, thereby expanding the field of view beyond traditional limitations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple waveguide layers are used to increase field of view, then the field of view range is improved, but the waveguide thickness increases making it too thick for consumer products

Engineering Contradiction:

Improvefield of view rangeVSAvoidwaveguide thickness

Core Design Contradiction:

Adaptability or versatilityVSLength of stationary object

Solution Approach 1:

The patent uses dynamically switchable Bragg gratings that can be activated or deactivated electronically. This allows a single waveguide layer to provide multiple field of view ranges by switching between different grating configurations, eliminating the need for multiple physical layers while maintaining adaptability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the optical parameters of the waveguide by using switchable Bragg gratings with different periodicities and orientations. By electronically controlling which gratings are active, the effective optical path and field of view can be adjusted without changing the physical thickness of the waveguide.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If switchable gratings are used to expand field of view, then the field of view range is improved, but angular bandwidth per grating decreases to less than 10 degrees

Engineering Contradiction:

Improvefield of view rangeVSAvoidangular bandwidth

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent segments the field of view into multiple tiles, each handled by a specific grating pairing. By having multiple non-output gratings work with multiple output gratings in different time periods, the system achieves a wide overall field of view while each individual grating maintains sufficient angular bandwidth for its designated tile.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses time-sequential activation of different grating pairings to generate different field of view tiles. Each grating pairing is activated during its designated time period, allowing the system to provide wide field of view coverage through periodic switching while maintaining high angular bandwidth during each activation cycle.

Inventive Principle:

Principle #19Periodic action

3Ease of manufacture

If Bragg gratings with limited angular bandwidth are used, then manufacturing is simplified, but the field of view is limited to around 30 degrees

Engineering Contradiction:

Improvegrating fabricationVSAvoidfield of view

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent makes individual Bragg gratings multi-functional by having them serve different purposes at different time periods. The same physical grating structure can be used in different pairings to generate different field of view tiles, allowing standard Bragg gratings to achieve wide overall field of view through temporal multiplexing.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent combines multiple Bragg gratings with different angular characteristics into a unified time-sequential system. By merging the functionality of multiple gratings that each cover limited angular ranges into a coordinated switching system, the overall field of view exceeds 30 degrees while maintaining the manufacturing simplicity of individual Bragg gratings.

Inventive Principle:

Principle #5Merging (Combining)

4Adaptability or versatility

If multiple gratings are activated simultaneously to increase field of view, then field of view coverage is improved, but crosstalk between pairings degrades image quality

Engineering Contradiction:

Improvefield of view coverageVSAvoidimage quality

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent activates different grating pairings in periodic time-sequential intervals rather than simultaneously. Each grating pairing is activated during its designated time period to generate a specific field of view tile, and inactive pairings are deactivated to prevent crosstalk. This temporal separation maintains image quality while achieving wide field of view coverage through rapid switching.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent uses dynamic control of grating activation states to prevent crosstalk. By electronically controlling which gratings are active at any given moment and switching between configurations rapidly, the system achieves wide field of view coverage while maintaining sharp image quality through dynamic suppression of unwanted diffraction from inactive gratings.

Inventive Principle:

Principle #15Dynamics

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 effectively increases the field of view of waveguide displays to greater than 10 degrees, reducing the need for multiple layers and minimizing flicker, while ensuring high diffraction efficiency and image quality by activating specific grating pairings during designated time periods.

Implementation Method 1

light is coupled into a waveguide mode by an input diffractive element and coupled out to the eye by a second diffractive element

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

crown glass such as N-BK7 has a refractive index of approximately 1.52 which makes the critical angle for supporting total internal reflection approximately 42.2° in glass

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 3

If Bragg Gratings are used to couple light into and out of the waveguide

Methodology Applied

Scientific EffectBragg diffraction: Bragg Diffraction

Data Source

PatentUS9164290B2Grating configurations for a tiled waveguide display

Publication Date: 2015.10.20 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

Grating configurations are described for creating time sequenced field of view (FOV) tiles for a waveguide display. Pairings of non-output diffraction gratings and output diffraction gratings are activated to create a number of FOV tiles in a time sequence, for example in a frame update period for the image. Examples of a non-output grating are an input grating and a fold grating. For a set of at least three gratings used to make the pairings, each non-output grating is paired with each output grating. The number of pairings, and so the number of FOV tiles, is equal to a product of the total number of non-output gratings and the total number of output gratings. At least one diffraction grating in the pairing is an active pairing. Also described is a multiplexed diffraction grating including multiplexed K-vectors which increases the overall angular bandwidth for both incidence and diffraction.