Waveguide HUD Glare Reduction Using Circular Polarization
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Solution Overview
Problem
Existing display systems, such as head-up displays (HUDs), face issues with glare from ambient light, particularly in vehicles, which can distract users and affect visibility by reflecting into the viewing window, such as windshields.
Innovation Solution
Incorporating a circular polarizer in conjunction with a waveguide that has a transmissive-reflective and reflective surface, where the circular polarizer applies circular polarization to ambient light entering the waveguide, ensuring it undergoes an odd number of reflections, thus changing its polarization direction, preventing it from being transmitted back to the viewer, while allowing polarized light from the display system to pass through.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a waveguide is used to expand the viewing window for the picture generating unit, then the viewing window is expanded, but glare from ambient light is transmitted back to the viewer
Solution Approach 1:
A circular polarizer is introduced as an intermediary component between the waveguide and the viewer. This polarizer selectively blocks circularly polarized ambient light that has undergone odd reflections in the waveguide, while allowing the picture light to pass through. The circular polarizer acts as a mediator that distinguishes between desired picture light and harmful glare based on polarization state.
Solution Approach 2:
The invention exploits changes in the polarization parameter of light as it traverses the waveguide. Ambient light entering the waveguide undergoes polarization changes due to reflections, and the circular polarizer is configured to block light with specific polarization states. By utilizing polarization parameter changes, the system distinguishes between picture light and ambient glare.
2Object-affected harmful factors
If a circular polarizer is added to block glare, then glare reduction is achieved, but device complexity increases
Solution Approach 1:
The circular polarizer serves multiple functions simultaneously: it blocks glare from ambient light while allowing picture light to pass through. By designing the waveguide to create specific polarization states for picture light, the circular polarizer becomes a multi-functional component that performs both glare rejection and image transmission, reducing the need for additional separate components.
Solution Approach 2:
The waveguide structure itself is designed to generate specific polarization states for the picture light through its internal reflections. This self-service approach means the waveguide automatically prepares the picture light in a polarization state that is compatible with the circular polarizer, eliminating the need for additional polarization control components.
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
Effectively reduces glare from ambient light without compromising the functionality of the waveguide as a viewing window expander, ensuring clear visibility of the displayed information for the user.
Implementation Method 1
a circular polarizer arranged in cooperation with the first surface such that ambient light incident upon the first surface is circularly polarized
Implementation Method 2
The waveguide is arranged to guide the circularly polarized ambient light by internal reflection between the pair of surfaces
Implementation Method 3
partially transmitting the spatially-modulated light out of the waveguide, at a plurality of locations on the waveguide, to form a substantially continuous viewing window
Data Source
AI summary
A method and system for reducing the effects of glare in a system comprising a picture generating unit, such as a holographic projector. The system may be a head-up display (HUD), which is configured to display a picture to a viewer, without requiring the user to look away from their usual viewpoint. The HUD system may be comprised within a vehicle. The glare in the system may be caused by light being incident on a surface comprising a screen or a window, through which the user looks at their usual viewpoint. The surface may comprise a windshield in a vehicle. The light that causes the glare may be ambient light. The method and system are provided for reducing the effects of glare in a system that comprises a waveguide in conjunction with the picture generating unit. The waveguide may be operable to act as an exit pupil expander.