AR Waveguide Returning Diffractive Element for Stray Light
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Solution Overview
Problem
Existing augmented reality devices face challenges in improving the contrast of the image output to the viewer due to stray light from the edges of the waveguide.
Innovation Solution
The implementation of a waveguide with an input diffractive optical element, an output diffractive optical element, and a returning diffractive optical element, which recycles unused light at the edge of the waveguide, reducing scatter and improving optical efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If light is transmitted through the waveguide to provide augmented reality, then the transparency of the waveguide is maintained, but stray light scatters at the edge of the waveguide reducing image contrast
Solution Approach 1:
The returning diffractive optical element converts the harmful stray light that would otherwise scatter at the waveguide edge into a beneficial resource by diffracting it back towards the output diffractive optical element. This回收利用 (recycling) of stray light improves image contrast by reducing unwanted scattered light while maintaining the transparency of the waveguide.
Solution Approach 2:
Instead of allowing stray light to be discarded at the waveguide edge, the returning diffractive optical element recovers this light and redirects it towards the output region. This recovery process improves optical efficiency and image contrast by ensuring that light which would have been wasted is instead reused to enhance the augmented reality image.
2Illumination intensity
If more light is coupled into the waveguide to improve brightness, then illumination intensity increases, but more light is lost to scatter at the edges
Solution Approach 1:
The returning diffractive optical element implements a recovery mechanism that captures light which would otherwise be lost at the waveguide edges and redirects it back into the useful optical path. This allows the system to maintain higher brightness levels without proportionally increasing light loss, as the returned light is reused rather than discarded.
Solution Approach 2:
The stray light that represents energy loss is converted into a beneficial resource by the returning diffractive optical element. By diffracting this stray light back towards the output, the system transforms what was previously wasted energy into useful illumination, improving overall optical efficiency.
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 enhances the contrast of the augmented reality image by minimizing stray light and improves optical efficiency by recycling light back into the output region.
Implementation Method 1
Light can be coupled into the waveguide by an input diffraction grating
Implementation Method 2
Light then propagates within the waveguide by total internal reflection
Implementation Method 3
an output diffraction grating couples light out of the waveguide and towards a viewer
Implementation Method 4
a returning diffractive optical element positioned in or on the waveguide configured to receive light from the output diffractive optical element and to diffract the received light so that it is returned towards the output diffractive optical element
Data Source
AI summary
An augmented reality device is provided and comprises a waveguide (306); an input diffractive optical element (301) positioned in or on the waveguide (306) configured to receive light from a projector and to couple the light into the waveguide (306) so that it is captured within the waveguide (306) by total internal reflection; an output diffractive optical element (304) positioned in or on the waveguide (306) configured to couple totally internally reflected light out of the waveguide (306) towards a viewer; and a returning diffractive optical element (307, 309, 312) positioned in or on the waveguide (306) configured to receive light from the output diffractive optical element (304) and to diffract the received light so that it is returned towards the output diffractive optical element (304).