Tilted Waveplate Light Source Unit for HUD Ghosting Reduction
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Solution Overview
Problem
Current image display devices for Head-Up Displays (HUDs) face challenges in providing high-quality virtual images that are not obstructed by glare and maintain safety for drivers, as existing technologies often result in image degradation due to ghosting effects and uneven luminance.
Innovation Solution
A light source unit comprising a display device, a reflective polarizing element, a reflecting member, and a waveplate, where the waveplate is tilted to prevent ghosting by ensuring that light not intended for the eyebox does not enter it, and the imaging optical system is telecentric at the first image side, with the light source unit emitting a substantially Lambertian light distribution to improve image quality and reduce size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If light is reflected multiple times through mirrors and polarizing elements, then the virtual image can be displayed, but ghosting effects and uneven luminance occur causing image degradation
Solution Approach 1:
The patent extracts and removes the harmful ghosting effects by introducing a waveplate that selectively blocks reflected light paths. The waveplate is positioned to intercept light that would otherwise create ghosting effects, allowing only the desired virtual image light to reach the viewer's eyebox.
Solution Approach 2:
The waveplate serves as an intermediary element between the reflective polarizing element and the reflecting member. It mediates the optical path by converting certain polarized light into a state that is blocked by the reflective polarizing element, thereby eliminating ghosting effects without affecting the main virtual image.
2Volume of moving object
If the light source unit size is reduced, then the device becomes more compact, but the luminance and chromaticity uniformity may deteriorate
Solution Approach 1:
The patent changes the optical parameters of the system by introducing the waveplate with specific tilt angles and polarization characteristics. This allows the light source unit to maintain compact size while achieving uniform luminance and chromaticity distribution across the virtual image through optimized optical path management.
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 enables high-quality, ghost-free virtual images that are visible to drivers without obstructing their line of sight, improving safety and reducing the size of the light source unit, while maintaining sufficient luminance and chromaticity uniformity across the image.
Implementation Method 1
The reflective polarizing element transmits a first polarized light and reflects a second polarized light
Implementation Method 2
The waveplate is interposed in a portion of an optical path between the reflective polarizing element and the reflecting member. The normal of the waveplate is tilted with respect to a direction of the optical path transmitted by the waveplate partway from the reflective polarizing element toward the reflecting member
Implementation Method 3
The reflecting member reflects, toward the reflective polarizing element, light transmitted by the reflective polarizing element
Data Source
AI summary
A light source unit includes a display device configured to display an image, a reflective polarizing element on which light emitted from the display device is incident, a reflecting member, and a waveplate. The reflective polarizing element transmits a first polarized light and reflects a second polarized light. The reflecting member reflects, toward the reflective polarizing element, light transmitted by the reflective polarizing element. The waveplate is interposed in a portion of an optical path between the reflective polarizing element and the reflecting member. The optical path is of light emitted from the display device, transmitted by the reflective polarizing element, reflected by the reflecting member, and reflected by the reflective polarizing element. A normal of the waveplate is tilted with respect to a direction of the optical path transmitted by the waveplate partway from the reflective polarizing element toward the reflecting member.