Position-Textured HUD Diffuser for Uniform Image Brightness

Solution Overview

Problem

Conventional head-up displays in vehicles face issues with brightness uniformity, particularly in the center of the virtual image, due to proximity to light sources and non-uniform light distribution, leading to increased complexity and cost with existing solutions like local dimming and bulk optical elements.

Innovation Solution

A diffuser with varying scattering properties as a function of position is used to scatter light uniformly across the field of view, optimizing brightness uniformity without requiring a two-dimensional array of LEDs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a two-dimensional array of LEDs with local dimming is used to improve brightness uniformity, then brightness uniformity is improved, but device complexity and cost increase

Engineering Contradiction:

Improvebrightness uniformityVSAvoiddevice complexity

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The patent applies local quality by varying the scattering properties of different regions of the diffuser. Specifically, the diffuser has a first region with a first scattering coefficient and a second region with a second scattering coefficient that is different from the first. This allows different parts of the diffuser to scatter light differently, compensating for the non-uniform light distribution from the LED array and achieving brightness uniformity without complex control systems.

Inventive Principle:

Principle #3Local quality

2Device complexity

If conventional uniform diffuser material is used, then device complexity is low, but brightness uniformity in the virtual image deteriorates

Engineering Contradiction:

Improvedevice complexityVSAvoidbrightness uniformity

Core Design Contradiction:

Device complexityVSIllumination intensity

Solution Approach 1:

The patent applies local quality by varying the scattering properties of different regions of the diffuser. Specifically, the diffuser has a first region with a first scattering coefficient and a second region with a second scattering coefficient that is different from the first. This allows different parts of the diffuser to scatter light differently, compensating for the non-uniform light distribution from the LED array and achieving brightness uniformity without complex control systems.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent applies parameter changes by modifying the scattering coefficient parameter of the diffuser material across different regions. The scattering coefficient varies spatially, with the first region having a different scattering coefficient than the second region. This parameter variation enables the diffuser to correct the non-uniform light distribution and achieve uniform brightness in the virtual image.

Inventive Principle:

Principle #35Parameter changes

3Illumination intensity

If bulk optical elements such as lenses and reflectors are used to improve brightness uniformity, then brightness uniformity is improved, but device complexity and volume increase

Engineering Contradiction:

Improvebrightness uniformityVSAvoidpackage volume

Core Design Contradiction:

Illumination intensityVSVolume of stationary object

Solution Approach 1:

The patent applies local quality by varying the scattering properties of different regions of the diffuser. Specifically, the diffuser has a first region with a first scattering coefficient and a second region with a second scattering coefficient that is different from the first. This allows different parts of the diffuser to scatter light differently, compensating for the non-uniform light distribution from the LED array and achieving brightness uniformity without complex control systems.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent applies parameter changes by modifying the scattering coefficient parameter of the diffuser material across different regions. The scattering coefficient varies spatially, with the first region having a different scattering coefficient than the second region. This parameter variation enables the diffuser to correct the non-uniform light distribution and achieve uniform brightness in the virtual image.

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

Enhances brightness uniformity across the virtual image without additional complexity or cost, achieving consistent brightness perception for the driver.

Implementation Method 1

The surface has a texture that varies with position on the surface. The texture scatters the light such that the brightness of the light over the field of view of the head-up display as seen by the human driver is more uniform

Methodology Applied

Scientific EffectLight scattering: Scattering

Data Source

PatentUS12578513B2Diffuser to improve uniformity of head-up display image brightness

Publication Date: 2026.03.17 PANASONIC AUTOMOTIVE SYSTEMS AMERICA LLC

AI summary

A backlighting arrangement is for a head up display that presents a virtual image to a human driver of a motor vehicle. The arrangement includes a light source emitting light with a non-uniform brightness over a field of view of the human driver. A diffuser includes a surface through which the light emitted by the light source passes. The surface has a texture that varies with position on the surface. The texture scatters the light such that the brightness of the light over a field of view of the human driver is more uniform after passing through the diffuser at a given average brightness than it would be with a diffuser configured to scatter light independent of position after passing through the diffuser.