Single Waveguide RGB Architecture Using Low Index Mediums
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Solution Overview
Problem
Conventional wearable heads-up displays (WHUDs) using multiple waveguides for RGB display light are bulky and heavy, and low refractive index waveguides struggle to direct all RGB components into an exit pupil with a sufficient field of view, limiting their optical specifications.
Innovation Solution
A single waveguide with a low refractive index (n=1.6 or less) uses multidimensional gratings to direct RGB display light along different paths within a total internal reflection volume, employing an incoupler and outcoupler grating, and intermediate gratings to redirect red, green, and blue components effectively, allowing all wavelengths to be accommodated within the waveguide's refractive space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple waveguides are used for RGB display light, then the field of view and optical specifications are improved, but the device becomes bulky and heavy
Solution Approach 1:
The patent combines multiple waveguides (red, green, blue) into a single integrated waveguide structure. The waveguide receives RGB display light from a light engine and uses intermediate multidimensional gratings to separate and redirect different wavelength components along different paths to the user's eye, eliminating the need for multiple separate waveguide assemblies and reducing overall device weight and bulk.
Solution Approach 2:
The patent employs intermediate multidimensional gratings that operate in multiple dimensions to redirect light paths within the single waveguide. These gratings create separate propagation paths for different wavelength components (red, green, blue) by diffracting light at different angles and positions, effectively using spatial dimensionality to accommodate multiple color channels in a compact structure.
2Weight of moving object
If low refractive index waveguides are used, then the device becomes compact and lightweight, but the ability to direct all RGB components into the exit pupil is limited
Solution Approach 1:
The patent uses intermediate multidimensional gratings to create multiple light paths within the low refractive index waveguide. By diffracting light in multiple dimensions and angles, the gratings compensate for the limited refractive space, enabling all RGB wavelength components to be redirected to the exit pupil despite the lower refractive index material.
Solution Approach 2:
The patent changes the grating parameters (period, orientation, depth) of the intermediate multidimensional gratings to optimize light redirection for different wavelength components. By adjusting these parameters, the system achieves effective separation and routing of red, green, and blue light paths within the constraints of low refractive index material.
3Adaptability or versatility
If high refractive index materials are used, then the optical specifications are improved, but the device becomes bulkier and heavier
Solution Approach 1:
The patent merges multiple waveguide functions into a single low refractive index waveguide, using intermediate multidimensional gratings to achieve the optical separation and routing that would traditionally require multiple separate high-index waveguide components. This integration reduces the overall device volume while maintaining optical performance.
Solution Approach 2:
The patent changes the approach from relying on high refractive index material properties to using grating-based light manipulation. By changing the operational parameters from material-dependent total internal reflection to grating-dependent diffraction, the system achieves effective light control in low-index materials without requiring bulky high-index 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
This approach enables a compact and lightweight WHUD to direct substantially all RGB wavelengths to the user's eye, enhancing the field of view and optical specifications while avoiding the limitations of high-index materials.
Implementation Method 1
light from a projector, micro-display, or other light engine of the WHUD enters a waveguide of the combiner through an incoupler, propagates along the waveguide via total internal reflection (TIR), and exits the waveguide through an outcoupler
Implementation Method 2
a diffractive waveguide, and an incoupler and outcoupler that are each optically coupled to the diffractive waveguide. In operation, the incoupler receives the display light from the light engine and directs the received display light into the diffractive waveguide and to one or more intermediate multidimensional gratings
Data Source
AI summary
A virtual image is displayed to a user via a light engine (211) to generate a display light representing the virtual image, a diffractive waveguide (235), and an incoupler (231) and outcoupler (234) that are each optically coupled to the diffractive waveguide (235). In operation, the incoupler (231) receives the display light from the light engine (211) and directs the received display light into the diffractive waveguide (235) and to one or more multidimensional intermediate gratings (232. 233). The multidimensional intermediate gratings (232, 233) redirect the display light through the diffractive waveguide (235) to the outcoupler (234), which in turn redirects at least a portion of the display light out of the diffractive waveguide (235) to an eye (291, 293) of the user.