Optical Waveguide Combiner with Embedded Mirrors for Eye-Box Expansion
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Solution Overview
Problem
Existing optical systems in XR displays face challenges in providing a comfortably large eye motion box (EMB) for virtual images while maintaining a compact, lightweight, and energy-efficient design, without introducing image artifacts.
Innovation Solution
An optical waveguide combiner with embedded dielectric partially reflective mirrors, configured to reflect and transmit light at specific angular ranges, expanding the virtual image into a user's EMB with high RGB resolution and low adulteration, using a laser display engine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a combiner is configured with a relatively large, expanded aperture to fill the EMB, then the user can comfortably view virtual images without precise eye alignment, but the device size and weight increase
Solution Approach 1:
The output coupler is segmented into multiple discrete facets arranged in an array, each facet handling a specific angular range of light. This segmentation allows the combiner to achieve aperture expansion functionality without requiring a single large aperture, thereby reducing overall device weight while maintaining comfortable EMB coverage for the user.
Solution Approach 2:
The patent transitions from a conventional single-aperture combiner design to a faceted array structure that expands functionality in the angular dimension. By distributing light coupling across multiple facets at different orientations, the system achieves effective aperture expansion in angular space without proportionally increasing physical mass.
2Ease of operation
If a combiner uses a large, expanded aperture to transmit multiple virtual image duplicates, then the EMB is filled for comfortable viewing, but the device complexity increases
Solution Approach 1:
The output coupler is divided into multiple discrete facets, each responsible for a specific angular range. This segmentation simplifies the overall design by breaking down the complex function of aperture expansion into manageable, repeating unit structures that can be systematically arranged.
Solution Approach 2:
The patent varies the orientation parameters of individual facets within the array to achieve different angular reflection ranges. By controlling facet tilt angles and orientations, the system optimizes light coupling efficiency for each angular band, achieving effective EMB coverage with a structured yet manageable complexity level.
3Reliability
If the facets reflect light with high reflectivity in a first angular range, then virtual images are effectively coupled into the EMB, but light transmission in other angular ranges is reduced
Solution Approach 1:
The angular spectrum of incident light is segmented into different ranges, with each facet optimized to reflect specific angular ranges while transmitting others. This angular segmentation allows high reflectivity for virtual image coupling in designated ranges while maintaining light transmission in complementary ranges, resolving the energy trade-off.
Solution Approach 2:
Different facets within the array possess different local optical properties, specifically different reflectivity characteristics tailored to their assigned angular ranges. This local differentiation enables each facet to optimize its function for its specific angular band, achieving high virtual image coupling efficiency without compromising overall light transmission across all angles.
4Reliability
If the facets are designed for high reflectivity in specific angular ranges, then virtual images are effectively reflected, but manufacturing precision requirements increase
Solution Approach 1:
The segmentation into discrete facets with standardized geometries allows for modular manufacturing. Each facet can be fabricated using the same precision processes, and the modular nature enables quality control to be applied to individual units rather than requiring ultra-precise monolithic fabrication, thereby managing manufacturing precision requirements.
Solution Approach 2:
The patent employs controlled variations in facet orientation parameters to achieve the desired angular reflectivity ranges. By designing facets with specific, standardized orientation angles, the system achieves reliable angular selectivity while maintaining manufacturing feasibility through repeatable fabrication processes for each facet type.
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 effectively expands the EMB to accommodate virtual images with high resolution and low image artifacts, meeting ergonomic, technical, and financial constraints.
Implementation Method 1
the facets are configured to reflect with relatively large reflectivity incident light in a first range of incident angles into the user EMB
Implementation Method 2
In a second range of incident angles different from the first range, the facets are configured to have relatively low reflectivity and transmit light in substantially the same laser wavelength band with relatively large transmittance
Implementation Method 3
an optical waveguide combiner having an output coupler comprising an array of embedded dielectric partially reflective mirrors
Data Source
AI summary
An optical waveguide combiner having an output coupler comprising an array of embedded partially reflective dielectric mirrors expanding and coupling a virtual, optionally color, image generated by a laser display engine into a user EMB, wherein the dielectric mirrors are configured having a wavelength band for each lasing band of the laser display engine that includes wavelengths of light in the lasing band and in a range of wavelengths over which the lasing band is expected to drift, a reflectivity angular range exhibiting a first reflectivity, a transmittance angular range exhibiting a second reflectivity less than the first reflectivity, and a see-thru angular transmittance range having high transmittance for natural light incident on the facets.