Waveguide Combiner Facet Array for Expanded Eye Box in Mixed Reality
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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 causing 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 image resolution and low adulteration by image artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the combiner is configured with a relatively large, expanded aperture to fill the EMB, then the user can comfortably see virtual images without aligning the eye, 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 portion of the virtual image. This segmentation allows the combiner to achieve expanded aperture functionality through distributed small facets rather than requiring a single large aperture, thereby reducing overall device weight while maintaining eye box comfort.
Solution Approach 2:
The patent transitions from a conventional single-plane aperture approach to a three-dimensional arrangement of facets within the waveguide. By distributing reflective facets throughout the waveguide volume and using angular separation to direct light, the system achieves expanded effective aperture without proportionally increasing physical dimensions and weight.
2Area of stationary object
If the combiner uses a large expanded aperture to transmit multiple duplicates of virtual images, then the EMB is filled for comfortable viewing, but the device becomes less compact and more complex
Solution Approach 1:
The waveguide structure serves multiple functions simultaneously: it guides light from the display engine, contains the array of output coupler facets, provides structural support, and acts as the combiner element itself. This multi-functionality reduces the need for separate components, thereby decreasing device complexity while achieving large effective output aperture.
Solution Approach 2:
The patent merges the output coupler facets directly into the waveguide structure, eliminating the need for separate mounting mechanisms and alignment systems. The facets are integrated within the waveguide material or bonded to its internal surfaces, simplifying the overall optical system architecture while maintaining large aperture functionality.
3Use of energy by moving object
If the facets reflect light with high reflectivity in a first angular range, then virtual images are coupled into the EMB, but light transmission in other angular ranges is reduced
Solution Approach 1:
The output coupler facets are designed with angularly selective reflectivity, where each facet reflects light efficiently only within a specific angular range corresponding to the virtual image path. For other angular ranges (ambient light paths), the facets maintain high transmittance. This local angular quality control allows simultaneous optimization of virtual image coupling and ambient light transmission without compromising either function.
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 provides an expanded EMB for clear virtual images with minimal artifacts, achieving ergonomic, technical, and financial advantages by optimizing the optical system's design.
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.