Wedge-Shaped Head-Up Display Cover for Ghost Image Elimination

Solution Overview

Problem

Conventional head-up display covers are either too thin and prone to damage or too thick, leading to light reflection issues that cause a ghost image on the windshield, making it difficult to prevent foreign objects from entering while maintaining visibility.

Innovation Solution

A cover with a wedge cross-section is designed to align the direct light path with the reflected light path, ensuring they overlap at the eye point, and the emitting surface is curved to redirect outside light away from the driver's view, preventing ghost images.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the cover is made thin, then the cover is easier to manufacture and less expensive, but the cover is prone to breaking and heat deformation

Engineering Contradiction:

Improveease of manufactureVSAvoiddurability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent changes the geometric parameters of the cover by introducing a wedge shape with specific thickness variations. The cover thickness transitions from a minimum value at the light exit surface to a maximum value at the opposite surface, creating an optimized thickness distribution that simultaneously achieves durability and optical performance

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the cover is made thick, then the cover is more durable and resistant to heat deformation, but light is reflected on inner surfaces causing a doubled virtual image

Engineering Contradiction:

ImprovedurabilityVSAvoidghost image

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent changes the geometric parameters of the cover by introducing a wedge shape with specific thickness variations. The cover thickness transitions from a minimum value at the light exit surface to a maximum value at the opposite surface, creating an optimized thickness distribution that simultaneously achieves durability and optical performance

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies curvature to the light exit surface of the cover, forming it as a convex curved surface. This curvature design redirects reflected light away from the driver's eye point, effectively eliminating the ghost image while maintaining adequate cover thickness for durability

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Object-affected harmful factors

If a thick cover is used, then foreign object protection is improved, but reflected light intensity increases causing a doubled virtual image

Engineering Contradiction:

Improveforeign object protectionVSAvoidreflected light

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The patent changes the geometric parameters of the cover by introducing a wedge shape with specific thickness variations. The cover thickness transitions from a minimum value at the light exit surface to a maximum value at the opposite surface, creating an optimized thickness distribution that simultaneously achieves durability and optical performance

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies curvature to the light exit surface of the cover, forming it as a convex curved surface. This curvature design redirects reflected light away from the driver's eye point, effectively eliminating the ghost image while maintaining adequate cover thickness for durability

Inventive Principle:

Principle #14Spheroidality (Curvature)

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 prevents foreign particles from entering while ensuring that direct and reflected light paths overlap, eliminating ghost images and improving durability and manufacturability of the cover.

Implementation Method 1

the substantially straight light path of the direct light from the arbitrary point on the display source through the cover without reflection is aligned with the reflected light path of the reflected light from the arbitrary point reflected twice on inner surfaces of the cover

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

the emitting surface near the windshield of the cover is formed in a curved shape so as to reflect outside light passing through the windshield to directions except a direction toward an eye point of a vehicle driver

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS7652825B2Cover for head-up display

Publication Date: 2010.01.26 YAZAKI CORP

AI summary

A display includes a case and a display source received in the case, and allows a virtual image of an image displayed on the display source projected on a windshield of a vehicle through an opening of the case to be superimposed on a foreground image through the windshield which is visually recognized at an eye point of the vehicle. A cover for the display is configured to prevent foreign particles from entering an inside of the case through the opening, and allows the image projected from the display source to pass therethrough. The cover has substantially a wedge cross section so as to align a substantially straight light path of direct light from an arbitrary point on the display source through the cover without reflection with a reflected light path of reflected light from the arbitrary point and reflected twice on inner surfaces of the cover.