Polarization Management in Optical Waveguides

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Solution Overview

Problem

Conventional grating structures in optical devices are inefficient in managing polarization of light, leading to wasted light and suboptimal performance in beam redirection and light coupling applications, particularly in head-mounted display devices, as they are constrained to a single angle of incidence and reflect light about a reflective axis coincident with the surface normal, failing to handle light with randomized polarizations effectively.

Innovation Solution

An optical device comprising a waveguide with a polarization altering element, such as a half-wave plate, positioned between layers with grating structures that reflect light about a reflective axis offset from the surface normal, allowing for constant angle of reflection across a range of incidence angles and efficient polarization management.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional grating structures are used to reflect light, then light can be reflected about a reflective axis, but the angle of reflection covaries with wavelength and is limited to a single angle of incidence

Engineering Contradiction:

Improverange of incidence anglesVSAvoidconstant reflection angle

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The optical device segments the grating structure into multiple zones with different grating periods or orientations, allowing each zone to handle specific incidence angles while maintaining constant reflection angle across the entire structure

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a second dimension of control by using grating structures with varying periods or orientations across the surface, transforming a single-angle device into a multi-angle device while maintaining constant reflection angle through dimensional variation

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Productivity

If conventional grating structures are used, then light reflection can occur, but polarization states are not managed efficiently and some polarizations are diffracted more strongly than others

Engineering Contradiction:

Improvelight coupling efficiencyVSAvoidwasted light

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The patent introduces polarization managing elements as intermediaries between the light source and grating structure, or between multiple grating structures, to convert or align polarization states before light interacts with the grating, ensuring efficient coupling and minimizing energy loss

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the polarization parameter of light through specialized grating structures or polarization managing elements, transforming light with randomized polarizations into light with controlled polarization states that are optimally coupled by the grating structure

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If conventional grating structures reflect light about surface normal, then reflection can occur, but the reflective axis is constrained and cannot be offset from surface normal

Engineering Contradiction:

Improvereflective axis orientationVSAvoidgrating structure design

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent employs asymmetric grating structures where the grating lines are oriented at specific angles relative to the surface normal, allowing the reflective axis to be offset from the surface normal while maintaining controlled reflection angles through the asymmetric geometry

Inventive Principle:

Principle #4Asymmetry

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 optical device efficiently manages polarization of light, enhancing light coupling and redirection by maintaining constant reflection angles and improving the performance of optical systems like HMD devices by effectively handling light with various polarizations.

Implementation Method 1

a polarization altering element operatively coupled to a light path associated with the first light coupling device and the second light coupling device

Methodology Applied

Scientific EffectPolarization alteration: Polarisation

Implementation Method 2

grating structures that reflect light about a reflective axis offset from the surface normal, allowing for constant angle of reflection across a range of incidence angles

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 3

grating structures that reflect light about a reflective axis offset from the surface normal

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 4

a first waveguide portion including a first layer having parallel plane surfaces, the first waveguide portion having a first light coupling device

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentUS10698162B2Polarization management

Publication Date: 2020.06.30 AKONIA HOLOGRAPHICS LLC

AI summary

An optical device for polarizing light including a polarization altering element operatively coupled to a light path associated with the first light coupling device and the second light coupling device is described. The optical device may further include a first waveguide portion including a first layer having parallel plane surfaces with the first waveguide portion having a first light coupling device. The optical device may also include a second waveguide portion including a second layer having parallel plane surfaces with the second waveguide portion having a second light coupling device.