Hologram Focus Accommodation via Switchable Polarization Retarders

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Solution Overview

Problem

Current focus accommodation systems in waveguide displays for augmented and virtual reality are inadequate due to size, complexity, power consumption, and latency issues, leading to viewing fatigue as they struggle to adjust focus quickly enough to match eye movement and real-world distances, causing conflict between stereopsis and focus cues.

Innovation Solution

A focus accommodation system utilizing switchable polarization retarders and polarization sensitive gratings to dynamically adjust the focal length of holograms displayed on waveguide displays, allowing for variable focus and multi-focus settings to align with user perception, combined with a light controller to manage environmental light and reduce latency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a mechanical mechanism is used to adjust focus, then focus accommodation can be achieved, but the system becomes too large, complex, and power-consuming for wearable display devices

Engineering Contradiction:

Improvefocus accommodationVSAvoidmechanical mechanism

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces mechanical focus adjustment mechanisms with an optical system using switchable polarization retarders and polarization-sensitive gratings. This substitution eliminates moving parts, reducing size, complexity, and power consumption while maintaining focus accommodation capability through optical path modulation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system changes the polarization state of light using switchable retarders to dynamically adjust focal length. By modulating the polarization parameter of light and interacting with polarization-sensitive gratings, the system achieves variable focus without mechanical movement.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If a fixed focal distance lens is used, then the virtual image appears at a fixed distance, but the user experience diminishes when viewing real objects at different distances

Engineering Contradiction:

Improvefixed focal distanceVSAvoidviewing distance

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The patent transforms the fixed focal length lens into a dynamic variable focus system. By using switchable polarization retarders that can be activated in different combinations, the system provides multiple focal lengths (e.g., 25cm, 50cm, 100cm, infinity), enabling adaptation to different viewing distances while maintaining image stability.

Inventive Principle:

Principle #15Dynamics

3Speed

If current focus accommodation techniques are used in waveguide displays, then some focus adjustment is possible, but latency and performance issues arise that cannot keep up with eye movement

Engineering Contradiction:

Improvefocus adjustment speedVSAvoidfocus accommodation

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The replacement of mechanical focus adjustment with an optical modulation system using polarization-retarder-and-grating combinations enables instantaneous focus changes. The switchable retarders can be activated/deactivated electronically at high speeds, eliminating mechanical inertia and achieving focus adjustment speeds that can keep up with natural eye movements.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 system effectively resolves the conflict between stereopsis and focus cues, providing a comfortable viewing experience by allowing holograms to appear at arbitrary focal lengths, reducing vergence discomfort and enhancing user immersion in augmented and virtual reality environments.

Implementation Method 1

switchable polarization retarders that rotate a polarization of light of the generated image

Methodology Applied

Scientific EffectPolarization rotation: Polarisation

Implementation Method 2

polarization sensitive gratings alternatingly interspersed with the switchable polarization retarders... Each of the switchable polarization retarders is combined with an associated polarization sensitive grating to form lenses

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentUS10274732B2Hologram focus accommodation

Publication Date: 2019.04.30 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

In implementations of hologram focus accommodation, a focus accommodation system is implemented for variable focus of a generated image, such as a hologram, that is displayed for viewing on a waveguide display. The focus accommodation system includes switchable polarization retarders that rotate a polarization of light of the generated image, where the light passes through the switchable polarization retarders along an imaging path in which the generated image is viewable. The focus accommodation system also includes polarization sensitive gratings alternatingly interspersed with the switchable polarization retarders. Each of the polarization sensitive gratings are configurable to diffract the light in a first polarization state and transmit the light in a second polarization state. The variable focus is adjustable to a focal distance at which a user perceives viewing the generated image as displayed by the waveguide display.