Retroreflective Windshield Screen for Head-Up Display Light Efficiency

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Solution Overview

Problem

Existing windshield image display systems have low light efficiency due to the scattering of light energy, particularly in situations with strong outside luminosity, as they rely on reflective diffuser films that do not effectively direct light towards the user's line of sight.

Innovation Solution

A partially transparent and partially retroreflective screen is used, with retroreflective portions separated by transparent areas, featuring cube corner protrusions or microbead coatings, allowing for efficient retroreflection of projected images while maintaining transparency and reducing light scattering.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a reflective diffuser film is used to project images on the windshield, then the image can be displayed on the windshield, but the light efficiency is low due to scattering of light energy

Engineering Contradiction:

Improvelight efficiencyVSAvoidlight energy scattering

Core Design Contradiction:

Illumination intensityVSLoss of energy

Solution Approach 1:

The screen is segmented into multiple retroreflective elements (cube corner protrusions or microbeads) distributed across the windshield surface, with each element independently retroreflecting light towards the user's pupils. This segmentation allows selective retroreflection while maintaining transparency in non-retroreflective areas, improving light efficiency compared to a complete diffuser film coverage.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the screen have different optical properties: retroreflective portions (with cube corner protrusions or microbeads) direct light efficiently towards the user, while transparent portions maintain visibility of the outer scene. This local differentiation of optical properties optimizes light efficiency in the retroreflective zones while preserving transparency where needed.

Inventive Principle:

Principle #3Local quality

2Ease of operation

If a wide diffusion cone is used to capture the user's line of sight, then the image is visible to the user, but light energy is scattered across the angular space reducing efficiency

Engineering Contradiction:

Improveimage visibilityVSAvoidlight energy scattering

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

Instead of using a wide diffusion cone that scatters light in many directions, the patent inverts the approach by using retroreflective elements that actively direct light back towards the source (projector) and the user's pupils. This inversion of the light scattering principle into retroreflection concentrates light energy into a useful direction, improving efficiency while maintaining visibility.

Inventive Principle:

Principle #13The other way round (Inversion)

3Illumination intensity

If the screening rate by retroreflective portions is increased, then light efficiency improves, but transparency of the windshield is reduced

Engineering Contradiction:

Improvelight efficiencyVSAvoidtransparency area

Core Design Contradiction:

Illumination intensityVSQuantity of substance

Solution Approach 1:

The patent applies partial retroreflection rather than complete coverage, with retroreflective portions occupying only a portion of the screen surface. This partial action provides sufficient light efficiency improvement while preserving transparency in the remaining areas, avoiding the extreme of complete retroreflective coverage which would eliminate transparency.

Inventive Principle:

Principle #16Partial or excessive action

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 achieves higher light efficiency by directing projected light towards the user's pupils, enhancing visibility of overlaid images on the windshield without significantly altering external light, thus improving viewing comfort and reducing the impact of strong outside luminosity.

Implementation Method 1

Methodology Applied

Scientific EffectRetroreflection: Retroreflector

Implementation Method 2

transparent portions separated by transparent areas... maintaining transparency and reducing light scattering

Methodology Applied

Scientific EffectLight transmission: Light

Data Source

PatentUS10585280B2Method of manufacturing a screen comprising transparent portions and retroreflective portions

Publication Date: 2020.03.10 COMMISSARIAT A LENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES

AI summary

The invention relates to a method of manufacturing a screen comprising transparent portions and retroreflective portions distributed over all or part of the surface thereof.