Light-Expanding Waveguide Couplers for Low-Dispersion Near-Eye Displays
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Solution Overview
Problem
Designing electronic devices with near-eye displays, such as virtual and augmented reality headsets, is challenging due to the unsightly and bulky components that often fail to achieve desired optical performance levels.
Innovation Solution
The use of a waveguide-based optical system with a non-diffractive input coupler, a cross coupler that performs an even number of diffractions to mitigate chromatic dispersion, and an output coupler that expands light in two dimensions, utilizing surface relief gratings or holographic phase gratings to redirect light to an eye box without color separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional optical components are used in near-eye displays, then the display can be constructed, but the components become bulky and unsightly while failing to achieve desired optical performance
Solution Approach 1:
The patent transitions from traditional bulk optical components to thin-film optical elements deposited on transparent substrates. The optical system uses multiple layers of dielectric films with varying refractive indices arranged in specific patterns to achieve complex optical functions (beam steering, focusing, chromatic dispersion compensation) within a thin profile, enabling near-eye displays with improved form factor and optical performance
Solution Approach 2:
The patent employs composite optical structures consisting of multiple dielectric material layers with different refractive indices (e.g., high-index materials like TiO2 or SiO2 alternated with low-index materials like air or fluorinated polymers). These composite thin-film structures enable precise control of light propagation, achieving desired optical performance while maintaining thin component profiles suitable for near-eye displays
2Adaptability or versatility
If light is coupled into the waveguide and expanded, then the field of view and optical bandwidth are expanded, but chromatic dispersion causes color separation
Solution Approach 1:
The patent introduces a chromatic dispersion compensation element as an intermediary optical component within the waveguide system. This element, positioned between the light source and the output coupler, actively compensates for chromatic dispersion by introducing opposite dispersion characteristics, thereby preventing color separation while maintaining the expanded field of view and optical bandwidth
Solution Approach 2:
The patent utilizes diffractive optical elements with specifically designed grating structures where the diffraction angle and dispersion characteristics can be tuned by changing grating period, orientation, and depth. By optimizing these parameters, the system achieves wavelength-independent beam steering and compensates for chromatic dispersion across the visible spectrum, enabling broad field of view without color separation
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 system achieves an expanded field of view and optical bandwidth while maintaining uniform intensity and minimizing chromatic dispersion, resulting in a more aesthetically pleasing and optically efficient near-eye display.
Implementation Method 1
a waveguide, an input coupler on the waveguide, a cross coupler on the waveguide, and an output coupler on the waveguide
Implementation Method 2
The cross coupler may expand the light coupled into the waveguide in a first direction. The cross coupler may perform an even number of diffractions on the light
Implementation Method 3
The output coupler may receive the light from the cross coupler. The output coupler may expand the light in a second direction perpendicular to the first direction while coupling the light out of the waveguide
Data Source
AI summary
An electronic device may include a display that generates light for an optical system that redirects the light towards an eye box. The optical system may include a waveguide, a non-diffractive input coupler, a cross coupler, and an output coupler. The cross coupler may expand the light in a first direction. The cross coupler may perform an even number of diffractions on the light and may couple the light back into the waveguide at an angle suitable for total internal reflection. The output coupler may expand the light in a second direction while coupling the light out of the waveguide. The cross coupler may include surface relief gratings or holographic gratings embedded within the waveguide or formed in a separate substrate. The optical system may direct the light towards the eye box without chromatic dispersion and while supporting an expanded field of view and optical bandwidth.