Light Homogenization via Partially Reflective Waveguide Element

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Solution Overview

Problem

Optical waveguides often suffer from spatially-inhomogeneous power distribution due to total internal reflection, leading to performance deficits in TIR devices such as head-mounted displays, resulting in reduced image resolution and non-uniform brightness.

Innovation Solution

Incorporating a partially reflective element with a reflective axis parallel to the waveguide surface normal, configured to reflect light at varying reflectivities based on incidence angles, within the waveguide structure to homogenize light distribution, utilizing grating structures like holograms or diffractive optical elements to achieve uniform intensity profiles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If total internal reflection is used to guide light in the waveguide, then light propagation efficiency is improved, but spatially-inhomogeneous power distribution occurs leading to non-uniform brightness

Engineering Contradiction:

Improvelight propagation efficiencyVSAvoiduniformity of brightness

Core Design Contradiction:

Use of energy by moving objectVSIllumination intensity

Solution Approach 1:

The patent introduces a light homogenizing element with spatially varying properties within the waveguide. This element has different reflectivity or scattering characteristics at different locations to compensate for the non-uniform light distribution caused by total internal reflection, thereby achieving uniform brightness across the output while maintaining efficient light propagation

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The light homogenizing element acts as an intermediary component between the light source and the output. It mediates the non-uniform light distribution by selectively scattering or reflecting light at different positions within the waveguide, transforming the inhomogeneous power distribution into a uniform intensity profile without blocking overall light transmission

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If light is propagated through the waveguide with mode inhomogeneity, then the waveguide structure is simple, but the point spread function broadens reducing image resolution

Engineering Contradiction:

Improvewaveguide structure complexityVSAvoidimage resolution

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent modifies the optical parameters of light propagation within the waveguide by introducing the light homogenizing element. This element changes the distribution parameters of light intensity and phase to reduce mode inhomogeneity effects, thereby narrowing the point spread function and improving image resolution while keeping the waveguide structure relatively simple

Inventive Principle:

Principle #35Parameter changes

3Illumination intensity

If a light homogenizing element is added to homogenize light distribution, then brightness uniformity is improved, but device complexity increases

Engineering Contradiction:

Improveuniformity of brightnessVSAvoidwaveguide structure complexity

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The light homogenizing element is implemented as a thin film or coating applied to the waveguide surface or embedded within the waveguide structure. This thin-film approach achieves light homogenization with minimal additional bulk and structural complexity, maintaining a compact and simple overall device design while effectively uniforming brightness distribution

Inventive Principle:

Principle #30Flexible shells and thin films

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 minimizes the point spread function of the output beam, enhancing image resolution and brightness by homogenizing light across the waveguide, thereby improving the overall performance of TIR devices like head-mounted displays.

Implementation Method 1

Optical waveguides have a physical structure that guides electromagnetic waves in the optical spectrum (e.g., light). An optical waveguide can use total internal reflection (TIR) to guide light to an output.

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

The partially reflective element may be configured to reflect light incident on the partially reflective element at a first reflectivity for a first set of incidence angles and to reflect light incident on the partially reflective element at a second reflectivity for a second set of incident angles

Methodology Applied

Scientific EffectPartial reflection: Reflection

Implementation Method 3

utilizing grating structures like holograms or diffractive optical elements to achieve uniform intensity profiles

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentUS20230350208A1Light homogenization

Publication Date: 2023.11.02 AKONIA HOLOGRAPHICS LLC

AI summary

An optical reflective device for homogenizing light including a waveguide having a first and second waveguide surface and a partially reflective element is disclosed. The partially reflective element may be located between the first waveguide surface and the second waveguide surface. The partially reflective element may have a reflective axis parallel to a waveguide surface normal. The partially reflective element may be configured to reflect light incident on the partially reflective element at a first reflectivity for a first set of incidence angles and reflect light incident on the partially reflective element at a second reflectivity for a second set of incident angles.