Stacked Multi-Layer Waveguides With Diffraction Gratings for Color Delivery
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Solution Overview
Problem
Existing augmented reality glasses face challenges in delivering polychromatic images efficiently across multiple color channels without requiring specific light polarization and using multiple waveguides, as existing solutions are limited to two color channels and impose polarization constraints.
Innovation Solution
A multi-layer waveguide system with stacked waveguide elements, each dedicated to a specific color band, utilizing diffraction gratings and achromatic half-wave plates to efficiently guide monochromatic light beams of varying wavelengths through total internal reflection, ensuring maximum efficiency and angular coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple waveguides are used to deliver polychromatic images for each color primary, then the field of view and image quality are improved, but the device complexity and manufacturing difficulty increase significantly
Solution Approach 1:
The patent combines multiple waveguides into a single integrated waveguide structure where multiple diffraction gratings are embedded within the same waveguide substrate. This merging approach allows multiple color channels to be delivered through one unified component rather than requiring separate waveguides for each color primary, thereby reducing device complexity while maintaining polychromatic image delivery capability
Solution Approach 2:
The single waveguide structure is designed to perform multiple functions simultaneously by embedding different diffraction gratings with specific pitch values for different wavelengths. This universal waveguide can handle multiple color channels (red, green, blue) and polarization states, eliminating the need for separate dedicated waveguides for each function
2Use of energy by moving object
If diffraction gratings are used for in-coupling, then the coupling efficiency is improved, but the wavelength range is limited requiring multiple gratings for polychromatic images
Solution Approach 1:
The diffraction grating structure is segmented into multiple regions with different pitch values within the same waveguide. Each segment is optimized for specific wavelength ranges, allowing the single grating structure to efficiently couple multiple color channels (blue, green, red) while maintaining high coupling efficiency for each wavelength band
Solution Approach 2:
Different regions of the diffraction grating are assigned different local properties (pitch values) optimized for specific wavelengths. The grating pitch varies locally across the structure to match the resonant conditions for different color channels, enabling each region to efficiently couple its designated wavelength range
3Loss of information
If polarization-selective wave retarders are used to route different color bands, then the color channel separation is improved, but the device complexity increases and polarization constraints are imposed
Solution Approach 1:
The patent changes the physical parameter of diffraction grating pitch rather than using polarization-selective retarders. By varying the pitch parameter across different regions of the grating, the system achieves wavelength-based routing without imposing polarization constraints, thereby reducing device complexity while maintaining effective color channel separation
4Speed
If multiple waveguides are stacked for each color band, then the angular efficiency and field of view are improved, but the manufacturing precision requirements increase
Solution Approach 1:
Multiple waveguide functions are merged into a single waveguide substrate with multiple embedded diffraction gratings. This eliminates the need for precise stacking and alignment of multiple separate waveguides, significantly reducing manufacturing precision requirements while maintaining the angular efficiency and field of view benefits of multi-channel waveguide systems
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 effectively delivers polychromatic images by optimizing color channel coupling and angular efficiency, overcoming limitations of previous technologies that are restricted to two color channels and polarization requirements.
Implementation Method 1
each waveguide element, except the one closer to the eye of a user, comprising a diffraction grating that can deviate only one of said n monochromatic light image in the waveguide element by total internal reflection
Implementation Method 2
said second output comprising an achromatic half-wave plate
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
It is proposed an optical device for delivering a polychromatic image to an eye box being an area positioned in front of an eye of a user wearing said optical device. The optical device is remarkable in that it comprises: • a light-engine for delivering said polychromatic image, said light engine being able to generate n different monochromatic light image beams [C 1,...,C i ,..., C n] , whom combination corresponds to said polychromatic image, each monochromatic light image C j being associated with a wavelength Ay, and wherein A i+1 > A £ for all the i E [1, n], and wherein the monochromatic light image beams C j is in a transverse electric mode if j is odd, and the monochromatic light image beams C j is in a transverse magnetic mode if j is even; • n-waveguide elements (502, 503, 504) that are stack on each other, n being an integer greater or equal to three, each waveguide element, except the one closer to the eye of a user, comprising a diffraction grating that can deviate only one of said n monochromatic light image in the waveguide element by total internal reflection, a first output that delivers deviated light toward said eye box, and a second output that delivers non-deviated light by a waveguide element to a subsequent waveguide element, wherein said second output comprising an achromatic half-wave plate (506, 507), and wherein the waveguide element that is closer to the eye of the user comprises also a diffraction grating that can deviate only one of said n monochromatic light image in the waveguide element by total internal reflection, and an output that delivers deviated light toward said eye box, wherein each diffraction grating of said optical device is associated with a different wavelength, and, wherein the arrangement order of said n-waveguide is done according to the wavelength value, from the smallest to the highest, the smallest waveguide element being positioned closer to the light engine.