Waveguide HUD Prism Layout for Ambient Light Glare Control

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Solution Overview

Problem

Ambient light interference causes glare and reduces contrast in holographic images projected by waveguide head-up displays (HUDs) onto vehicle windshields, as it reflects off pupil replicators and overlaps with projected holograms in the eyebox.

Innovation Solution

A prism is arranged above the waveguide HUD with an angled upper surface relative to the waveguide, decoupling ambient light paths from the holograms by reflecting them outside the eyebox, while the holograms are projected along the normal of the waveguide, and an anti-reflective and filter coating are applied to further minimize interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If a pupil replicator is used to fill the eyebox with holograms, then the holographic image coverage is improved, but ambient light reflects off the pupil replicator into the eyebox causing glare and reducing contrast

Engineering Contradiction:

Improveeyebox coverageVSAvoidambient light reflection

Core Design Contradiction:

Area of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The patent segments the light paths by introducing a beam splitter that separates the path of projected holographic light from the path of ambient light. The beam splitter allows holograms to pass through to the eyebox while reflecting ambient light away, thus dividing the optical paths to prevent harmful reflections from entering the eyebox while maintaining full eyebox coverage

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The beam splitter acts as an intermediary element between the pupil replicator and the eyebox. It mediates the interaction between projected light and ambient light by selectively transmitting holographic light while deflecting ambient light, thereby solving the contradiction between maintaining eyebox coverage and preventing glare

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If the waveguide projects holograms along the normal of its upper surface, then the projection trajectory is simplified, but ambient light reflects directly back into the eyebox

Engineering Contradiction:

Improveprojection trajectoryVSAvoidambient light interference

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces asymmetry by angling the beam splitter at 45 degrees relative to the waveguide's upper surface. This asymmetric configuration changes the reflection angle of ambient light while maintaining the normal projection trajectory of holograms, thereby breaking the symmetry that causes direct reflection into the eyebox without complicating the overall projection path

Inventive Principle:

Principle #4Asymmetry

3Object-affected harmful factors

If anti-reflective and filter coatings are applied to the prism, then ambient light interference is reduced, but the device complexity increases

Engineering Contradiction:

Improveambient light interferenceVSAvoidcoating structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent changes the optical parameters of the beam splitter by applying anti-reflective coatings to reduce reflections at specific wavelengths and angles, and filter coatings to block ambient light spectra while transmitting holographic light. These parameter changes effectively reduce ambient light interference through optical property modification rather than structural complexity

Inventive Principle:

Principle #35Parameter changes

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

Effectively reduces glare and maintains image contrast by directing ambient light away from the eyebox, ensuring clear visibility of holographic projections.

Implementation Method 1

The upper surface of the prism is angled relative to the upper surface of the waveguide such that a first normal of the upper surface of the prism is different from a second normal of the upper surface of the waveguide

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

an anti-reflective and filter coating are applied to further minimize interference

Methodology Applied

Scientific EffectAnti-reflective coating: Anti-Reflective Coating

Implementation Method 3

a filter coating is configured as a triple bandpass filter

Methodology Applied

Scientific EffectOptical filtering: Filter (optical)

Data Source

PatentUS11880036B2Control of ambient light reflected from pupil replicator

Publication Date: 2024.01.23 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

A waveguide head-up display (HUD) includes a waveguide that includes a lower surface and an upper surface and is configured to receive an input and project, based on the input, at least one image from the upper surface and into an eyebox, and a prism arranged at least one of on and above the waveguide. The prism includes a lower surface facing the waveguide and configured to receive the at least one image and an upper surface opposite the lower surface configured to project the at least one image received via the lower surface of the prism. The upper surface of the prism is angled relative to the upper surface of the waveguide such that a first normal of the upper surface of the prism is different from a second normal of the upper surface of the waveguide.