Angularly Selective Dimming Element for AR Waveguide Rainbow Suppression

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Solution Overview

Problem

Pupil-expansion waveguide displays with diffractive coupling structures in augmented reality (AR) headsets suffer from a 'rainbow effect' due to see-through artifacts, where diffractive structures cause multicolored glare when looking at bright light sources from certain angles, degrading the image quality of the see-through view.

Innovation Solution

An optical device with a light source, an optical combiner featuring a diffractive element, and an angularly selective dimming element disposed at the combiner's side facing the real world, which attenuates light intensity with incidence angles between 60° to 90°, reducing the rainbow effect while maintaining the brightness of the desired see-through image.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If diffractive coupling structures are used in waveguide displays, then field of view and eye-box size are improved, but rainbow effect and see-through artifacts occur

Engineering Contradiction:

Improveeye-box sizeVSAvoidrainbow effect

Core Design Contradiction:

Area of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The dimming element introduces spatially varying optical properties across the waveguide surface, creating angular-selective attenuation zones that selectively suppress rainbow effect while preserving see-through image quality in specific viewing regions

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The dimming element acts as an intermediary optical component between the diffractive coupling structures and the user's eye, mediating the interaction by selectively attenuating harmful diffracted light while allowing desired see-through light to pass through

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If conventional dimming elements are used to reduce rainbow effect, then rainbow effect is suppressed, but brightness of see-through image is significantly reduced

Engineering Contradiction:

Improverainbow effectVSAvoidsee-through image brightness

Core Design Contradiction:

Object-affected harmful factorsVSIllumination intensity

Solution Approach 1:

The dimming element creates non-uniform optical attenuation across different angular ranges, applying strong attenuation to oblique angles where rainbow effect occurs while maintaining high transmission for normal angles where see-through images are viewed

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The dimming element's optical properties are engineered to change dramatically with incidence angle, transitioning from high transmission at normal angles to high attenuation at oblique angles, thereby selectively suppressing rainbow effect while preserving see-through brightness

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If angularly selective dimming is implemented, then image quality of see-through view is improved, but device complexity increases

Engineering Contradiction:

Improveimage qualityVSAvoidoptical combiner structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The dimming element is integrated directly onto the waveguide surface, merging the dimming function with the existing optical combiner structure rather than adding separate discrete components, thereby reducing overall device complexity

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The dimming element serves multiple functions simultaneously: it acts as both a diffractive optical element for beam steering and an angular-selective attenuator for rainbow suppression, eliminating the need for separate functional components

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 suppresses the rainbow effect by significantly attenuating obliquely incident light with high incidence angles, thereby enhancing the image quality of the see-through view without significantly reducing the brightness of the desired see-through image.

Implementation Method 1

configured to receive a light from the real world and significantly attenuate an intensity of the light having an incidence angle in a predetermined range

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Implementation Method 2

The optical combiner includes at least one diffractive element. The optical combiner is configured to direct the image light to an eye-box of the optical device

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentUS11435585B1Angularly selective dimming element, method of fabricating the same and optical device containing the same

Publication Date: 2022.09.06 META PLATFORMS TECHNOLOGIES LLC

AI summary

An optical device having suppressed rainbow effect is provided. The optical device includes a light source configured to generate an image light, an optical combiner coupled with the light source and configured to direct the image light to an eye-box of the optical device, and a dimming element disposed at the optical combiner. The optical combiner includes at least one diffractive element. The optical combiner has a first side facing the eye-box and an opposing second side facing a real world, and the dimming element is disposed at the second side of the optical combiner. The dimming element is configured to receive a light from the real world and significantly attenuate an intensity of the light having an incidence angle in a predetermined range.