Head-Up Display Lens Layout for Distortion and Stray Light Control

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Solution Overview

Problem

Existing head-up displays face challenges in reducing size while minimizing distortion and inhibiting stray light from outside sources, which affects the clarity and visibility of projected images.

Innovation Solution

The head-up display incorporates a projection optical system with a first lens and a first optical element, such as a mirror, disposed in a specific order along the optical path, where the first lens is inclined with respect to a reference beam to condense and diffuse light, and a telephoto arrangement is used to reduce the size of the display while preventing stray light entry.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If a conventional head-up display configuration is used, then the display can project images on the windshield, but the device size is large and distortion occurs

Engineering Contradiction:

Improvehead-up display sizeVSAvoidimage distortion

Core Design Contradiction:

Volume of moving objectVSManufacturing precision

Solution Approach 1:

The optical system is divided into multiple discrete optical elements (lens and optical element) with specific functions. The lens handles light condensation while the optical element handles diffusion, separating functions to optimize each component's performance and reduce overall system size while maintaining image quality

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces inclination of the lens with respect to the reference beam, adding an angular dimension to the optical path design. This dimensional change allows compact arrangement of optical components while controlling distortion through precise angular positioning

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Volume of moving object

If the head-up display size is reduced, then compactness is improved, but stray light from outside sources increases

Engineering Contradiction:

Improvehead-up display sizeVSAvoidstray light

Core Design Contradiction:

Volume of moving objectVSObject-affected harmful factors

Solution Approach 1:

Different regions of the optical system are assigned different functional properties. The lens has light-condensing properties in specific regions while the optical element provides diffusion in others. This local differentiation allows selective control of light paths to block stray light while maintaining compact dimensions

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent converts potentially harmful stray light into useful reflected light by strategically positioning the optical element to diffuse outside light into the viewpoint region. This transforms the harmful effect of outside light into a beneficial contribution to image visibility

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Ease of manufacture

If the first lens is positioned perpendicular to the reference beam, then alignment is simple, but stray light cannot be effectively inhibited

Engineering Contradiction:

Improvelens alignmentVSAvoidstray light

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The lens is positioned at an asymmetric angle relative to the reference beam rather than perpendicular alignment. This asymmetric positioning creates specific angular relationships that exploit geometric optics to redirect stray light away from the viewpoint region while maintaining manufacturability through defined angular specifications

Inventive Principle:

Principle #4Asymmetry

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

This configuration results in a smaller head-up display with reduced distortion and effective inhibition of stray light, ensuring clear and undistorted virtual images for the observer, even under outside light conditions.

Implementation Method 1

a first lens configured to condense light

Methodology Applied

Scientific EffectLight condensation: Focusing

Implementation Method 2

a first optical element configured to diffuse light

Methodology Applied

Scientific EffectLight diffusion: Scattering

Data Source

PatentUS12196959B2Head-up display and moving body with head-up display mounted thereon

Publication Date: 2025.01.14 PANASONIC AUTOMOTIVE SYST CO LTD

AI summary

A head-up display is configured to project an image on a transparent reflection member to cause an observer to visually recognize a virtual image, and includes a display device configured to display the image, and a projection optical system configured to project the image displayed by the display device as the virtual image for the observer. The projection optical system is configured to form an image as an intermediate image, and includes a first lens configured to condense light, and a first optical element configured to diffuse light. The first lens and the first optical element are disposed in this order along an optical path from the display device. The first lens is inclined with respect to a reference beam which is defined as a beam reaching a center of a viewpoint region of the observer and corresponding to a center of the virtual image.