Waveguide Projection Display with Dynamic Scattered Light Absorption
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Solution Overview
Problem
Waveguide-based projection display devices, particularly in vehicles, suffer from scattered light issues that can be disruptive, especially above the horizon at night, reducing the visibility of the road scene and potentially causing the driver to perceive a fog-like environment.
Innovation Solution
The implementation of a dynamic scattered light absorber, which adjusts based on eye tracking signals to shade the light output coupling surface of the waveguide, thereby restricting the beam of light rays to only the eyebox window, effectively blocking the scattered light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a waveguide is used to generate a large virtual display image in a small installation space, then the installation space is reduced, but scattered light increases significantly
Solution Approach 1:
The patent extracts and removes the harmful scattered light from the system by introducing a dedicated light absorption structure. The absorber is specifically positioned at the light output coupling surface of the waveguide to capture and eliminate scattered light before it reaches the user's eye, thereby resolving the contradiction between compact installation and scattered light reduction.
Solution Approach 2:
The patent introduces an intermediary light absorption structure between the waveguide's light output coupling surface and the user's eye. This mediator selectively absorbs scattered light while allowing the useful display image to pass through, thus resolving the contradiction by adding a component that mediates between the compact waveguide design and scattered light elimination.
2Area of stationary object
If the entire light output coupling surface of the waveguide is used, then the eyebox area is expanded, but scattered light covers the entire field of view
Solution Approach 1:
The patent applies local quality by making different regions of the light output coupling surface have different functions. The light absorption structure is selectively positioned in specific regions where scattered light is most problematic, while other regions continue to provide useful light output. This allows the eyebox to remain large while scattered light coverage is reduced in critical areas.
3Device complexity
If no light absorption structure is used, then the device complexity is low, but scattered light disrupts the road scene visibility
Solution Approach 1:
The patent converts the harmful scattered light into a beneficial situation by using a light absorption structure that selectively targets and removes only the scattered light components. The absorber is designed to capture stray light while preserving the main display image, thus converting the harmful scattered light problem into a controlled light management solution that maintains road scene visibility.
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 solution significantly reduces or eliminates the scattered light issue above the horizon, enhancing the driver's visibility and safety by minimizing the disruptive effects of scattered light, especially in low-light conditions.
Implementation Method 1
a light output coupling surface (4), configured with a large area for one-dimensional or two-dimensional eyebox expansion, for light that is coupled into the waveguide (3) laterally
Implementation Method 2
a dynamic scattered light absorber (10), configured to shade the light output coupling surface (4)—and therefore the scattered light emerging from the light output coupling surface (4)
Implementation Method 3
an at least partially transparent reflection pane (2), which is arranged in the field of view of a user and is configured to reflect a beam of light rays coupled out from the waveguide
Data Source
AI summary
A projection display device includes an imaging unit; a planar waveguide with a light decoupling face for a light beam bundle produced by the imaging unit; an at least partially transparent reflection plate arranged in the field of view of a user and configured to reflect a light beam bundle decoupled from the waveguide to an eyebox predetermined for the user's eyes; an eye-tracking device configured to determine an eyebox window which is currently occupied by the user's eyes; and a dynamic scattered light absorber, which, to shadow the light decoupling face in a surface portion which is dynamically adjustable depending on a signal of the eye-tracking device and which extends starting from at least one of the edges of the light decoupling surface, is configured to at least partially limit the decoupled light beam bundle to the current eyebox window.