Single Waveguide RGB Diffractive Optical Elements
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Solution Overview
Problem
Current virtual reality and augmented reality devices face limitations in Field of View (FoV) due to the need for multiple waveguides when using diffraction gratings, which complicates manufacturing and increases costs.
Innovation Solution
A diffractive waveguide system that uses multiple diffraction optical elements (DOEs) to split and recombine RGB optical signals in a single waveguide, expanding the pupil and achieving a large Field of View (FoV) of 45 x 30°, by employing an incoupling grating, expansion gratings, and out-coupling gratings with distinct periods and orientations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If diffraction gratings are used to spread light by wavelength to increase FoV, then the Field of View is improved, but multiple separate waveguides are required which complicates manufacturing
Solution Approach 1:
The patent combines multiple waveguides into a single integrated waveguide structure. The first and second waveguides are merged into one waveguide with different propagation paths, eliminating the need for separate waveguide assemblies while maintaining the ability to guide different wavelengths independently through spatial separation of light paths.
Solution Approach 2:
The patent segments the light paths within the single waveguide by using diffraction gratings to separate different wavelengths into distinct propagation paths. The first diffraction grating separates light into a first wavelength range that propagates along a first path, while other wavelengths propagate along a second path, enabling wavelength-specific guidance within a unified structure.
2Area of stationary object
If multiple waveguides are used to support RGB wavelengths, then the Field of View is improved, but manufacturing tolerances become much tighter and costs increase
Solution Approach 1:
The patent merges multiple waveguide functions into a single waveguide structure, reducing the total number of components that require precise manufacturing. By consolidating the waveguiding function into one element with internally separated light paths, the system reduces cumulative tolerance errors that would arise from assembling multiple separate waveguides.
Solution Approach 2:
The patent applies local quality by implementing wavelength-specific diffraction gratings at specific locations within the waveguide. The first diffraction grating is positioned to affect only the first wavelength range, while other portions of the waveguide handle other wavelengths, allowing each region to be optimized for its specific function without affecting the entire system's tolerances.
3Area of stationary object
If multiple waveguides are used to expand image content in the waveguide, then the Field of View is improved, but additional manufacturing steps requiring high accuracy are added
Solution Approach 1:
The patent combines multiple waveguide expansion functions into a single waveguide structure with integrated diffraction gratings. The first and second waveguides are merged into one element that performs both waveguiding and image expansion functions, eliminating the need for separate assembly steps for multiple waveguide components.
Solution Approach 2:
The patent makes the single waveguide multi-functional by enabling it to simultaneously perform waveguiding for multiple wavelengths, image expansion, and field of view expansion. The diffraction gratings integrated into the waveguide structure provide both wavelength separation and beam expansion functions, reducing the number of specialized components needed.
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 solution allows for a large FoV of RGB content in a single waveguide, simplifying manufacturing and reducing costs by eliminating the need for multiple waveguides while maintaining high image quality and accuracy.
Implementation Method 1
a first diffraction optical element configured to diffract the light based on wavelength such that a first wavelength range of the light is diffracted into a first propagation path
Implementation Method 2
a waveguide configured to guide the light from an input of the waveguide to an output of the waveguide
Data Source
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AI summary
An optical device for combining RGB optical signals in a single waveguide. The device includes a plurality of DOEs. A first DOE is configured to receive an optical signal at input propagation angles and to diffract the optical signal based on spectrum such that predominately one spectrum of light is diffracted in a first direction and path and predominately a second spectrum of light is diffracted in a second different direction and path. The first DOE is configured to diffract light into a second DOE. The second DOE is configured to diffract light into a third DOE. The third DOE is configured to diffract light into an eye box keeping output propagation angles substantially parallel to the input propagation angles. A summation of grating vectors for each of the paths is substantially equal to zero.