Vehicle HUD Reflector Layout for Windshield Ghost Image Reduction
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Solution Overview
Problem
The existing display devices in vehicles suffer from the issue of light emitted by the display member being reflected not only by a separate reflector but also by the front windshield, leading to multiple virtual images being perceived by the occupant.
Innovation Solution
The display device employs a reflector with a reflective surface treated to enhance P-polarized light reflection, positioned to reflect light towards the occupant's eyepoint, and sets the angle of incidence of P-polarized light from the display member to minimize reflection by the windshield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a separate reflector is provided to reflect light from the display member, then the light can be directed toward the occupant's eyepoint, but the light may also be reflected by the front windshield causing multiple virtual images
Solution Approach 1:
The reflective surface is provided with local quality through reflection enhancing treatment specifically optimized for P-polarized light. This treatment creates different reflective properties in different regions of the optical system - the reflector has high reflectivity for P-polarized light while the windshield maintains lower reflectivity, allowing the system to differentiate between desired and unwanted reflections based on location and polarization state
Solution Approach 2:
The invention changes the polarization parameter of the light by using a display member that emits P-polarized light. This parameter change allows the reflector to efficiently reflect the light toward the eyepoint while the windshield reflects minimal amounts due to the polarization state and angle of incidence, thereby reducing multiple virtual images
2Reliability
If the display member emits P-polarized light and uses a reflector with reflection enhancing treatment, then P-polarized light reflection is improved, but the angle of incidence must be precisely controlled to minimize windshield reflection
Solution Approach 1:
The invention utilizes parameter changes by controlling the angle of incidence to be 69.7° or less, which optimizes the reflection efficiency of P-polarized light from the reflector while minimizing reflection from the windshield. This specific angle parameter ensures that the optical system achieves reliable light direction to the eyepoint without creating harmful multiple images
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 reduces the likelihood of multiple virtual images being perceived, ensuring clear visibility of the intended image without obstructing the driver's view, even when wearing sunglasses.
Implementation Method 1
a reflector provided between the display member and a windshield in a longitudinal direction of a vehicle, which reflects an emitted light from the display member toward an eyepoint of an occupant of the vehicle
Implementation Method 2
The reflector has a reflective surface provided with reflection enhancing treatment to reflect P-polarized light
Implementation Method 3
the emitted light of the display member may be reflected not only by the reflector but also by the front windshield
Data Source
AI summary
A display device may include a liquid crystal display and a reflector. The liquid crystal display emits light consisting of P-polarized light. The reflector may be provided between the liquid crystal display and the front windshield. The reflector reflects the emitted light OL from the liquid crystal display toward the driver's eyepoint EP. The reflector has a reflective surface provided with reflection enhancing treatment to reflect P-polarized light. The liquid crystal display may be positioned in a region where the angle of incidence α onto the front windshield of the emitted light OL is 69.7° or less.