Waveguide Combiner Assembly with Diffractive Virtual Image Focus
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Solution Overview
Problem
Conventional mixed-reality display systems employing waveguides require external lenses and protective elements, which increase parts count, cost, size, and weight, and cause issues like ghost images, reflections, and aberrations.
Innovation Solution
The optical combiner uses stacked waveguides with internal diffractive optical elements (DOEs) for in-coupling, intermediate expansion, and out-coupling, eliminating the need for external lenses by incorporating negative lens functionality into the out-coupling DOEs, which provide virtual image focus and minimize spectral dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external lenses and protective elements are used in waveguide-based mixed-reality display systems, then virtual image focus can be achieved, but parts count, cost, size, and weight increase
Solution Approach 1:
The patent combines the functions of external lenses and protective elements into the waveguide structure itself. The cover glass is integrated with the waveguide, and diffractive optical elements are embedded within the waveguide layers, eliminating the need for separate external lenses and protective elements while maintaining virtual image focus capability
Solution Approach 2:
The diffractive optical elements are nested within the multi-layer waveguide structure. The waveguide comprises multiple layers including input coupling layers, guide layers, and output coupling layers, with diffractive elements embedded in specific layers, creating a compact nested configuration that integrates multiple functions within the waveguide itself
2Reliability
If external lenses and protective elements are used in waveguide-based mixed-reality display systems, then virtual image focus can be achieved, but cost and weight increase
Solution Approach 1:
The patent merges the functions of external lenses and protective elements into the waveguide structure. The cover glass is integrated with the waveguide, and diffractive optical elements are embedded within the waveguide layers, eliminating the need for separate external lenses and protective elements while maintaining virtual image focus capability
Solution Approach 2:
The patent extracts and eliminates unnecessary external components (separate lenses and protective elements) from the system. By integrating these functions directly into the waveguide structure, the design removes redundant parts that contribute to weight, cost, and complexity while preserving the essential virtual image focus function
3Reliability
If external lenses are used in waveguide-based mixed-reality display systems, then virtual image focus can be achieved, but ghost images, reflections, and aberrations occur
Solution Approach 1:
The patent replaces traditional mechanical lens systems with diffractive optical elements. The diffractive elements use diffraction and interference of light to achieve focus and wavefront shaping without the reflective surfaces and mechanical structures of conventional lenses, thereby eliminating ghost images, reflections, and optical aberrations
Solution Approach 2:
The patent changes the optical approach from refraction-based lens systems to diffraction-based elements. By using diffractive optical elements with specific grating patterns and phase profiles, the system achieves virtual image focus through wavefront modulation rather than refractive focusing, avoiding the harmful optical effects associated with traditional lenses
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 design reduces parts count, cost, and weight while enhancing optical performance by increasing see-through transmission, uniformity, and contrast, and reducing ghost images and aberrations.
Implementation Method 1
The intermediate DOEs expand the exit pupil of the image light in a first direction and the out-coupling DOEs provide pupil expansion in a second direction relative to the input
Implementation Method 2
Each waveguide - one per RGB color component - includes an in-coupling DOE (diffractive optical element), an intermediate DOE, and an out-coupling DOE that are disposed on internal surfaces of the stacked waveguides
Implementation Method 3
Each of the out-coupling DOEs incorporates a diffractive lens functionality to render the out-coupled holographic images at a set depth on the mixed-reality display. In an illustrative non-limiting example, the out-coupling DOE may provide a half diopter of negative lens power to set the optical focus of the holographic images at 1.33 m
Data Source
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AI summary
An optical combiner, configured for use in a mixed-reality display system that combines holographic and real-world images, includes an assembly of see-through waveguides that are arranged in a stack to provide full color holographic images from constituent RGB (red, green, and blue) color components received from a holographic image source. Each waveguide - one per RGB color component - includes an in-coupling DOE (diffractive optical element), an intermediate DOE, and an out-coupling DOE that are disposed on internal surfaces of the stacked waveguides in the optical combiner. Each of the out-coupling DOEs incorporates a diffractive lens functionality to render the out-coupled holographic images at a set depth on the mixed-reality display. In an illustrative non-limiting example, the out-coupling DOE may provide a half diopter of negative lens power to set the optical focus of the holographic images at 1.33 m.