Mixed Waveguide Display with Volume Bragg Grating and Mirror
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Solution Overview
Problem
Current display systems, such as augmented reality head-mounted devices, face challenges in providing a wide field of view and high-quality images due to limitations in waveguide coverage and the formation of ghost images and optical lines patterns caused by multiplexed volume Bragg gratings, leading to reduced user experience with visual discomfort and artifacts.
Innovation Solution
The implementation of a waveguide system with multiple volume Bragg gratings having the same horizontal period, coupled with a 100% reflective mirror or mirror array, allows each color to be coupled out at the same angle, reducing image blurriness and ghost images, while selecting two or more wavelengths for each color at the projector matches the spectral response to the waveguide, enhancing field of view coverage across the entire wavelength spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple volume Bragg gratings are used to expand field of view coverage, then field of view coverage is improved, but ghost images and optical lines patterns are formed causing image quality degradation
Solution Approach 1:
The patent divides the waveguide into multiple discrete coupling regions, each containing a specific volume Bragg grating structure. Each grating is independently designed with specific orientation and wavelength characteristics, allowing selective coupling of different wavelength ranges to different regions of the eye, thereby preventing overlapping light paths that cause ghost images while maintaining expanded field of view coverage
Solution Approach 2:
The patent applies different grating structures, orientations, and wavelength selectivities to different local regions of the waveguide. Each coupling region is optimized for specific wavelengths and viewing angles, creating spatially varying optical properties that prevent uniform ghost image formation across the entire field of view while maintaining high-quality image delivery in each local region
2Device complexity
If conventional waveguide systems are used, then device simplicity is maintained, but image quality deteriorates due to spectral lines and artifacts
Solution Approach 1:
The patent modifies key optical parameters including grating orientation angles, wavelength selectivity ranges, and coupling region positions to optimize image quality. By carefully tuning these parameters, the system achieves high manufacturing precision in terms of image delivery quality while maintaining a relatively simple integrated waveguide structure without requiring complex external optical 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 increases the field of view coverage, reduces image artifacts, and improves image quality by eliminating ghost images and optical lines, resulting in a more comfortable and immersive user experience with augmented reality systems.
Implementation Method 1
a first volume Bragg grating having a first grating vector configured to couple light into the waveguide and a second volume Bragg grating having a second grating vector configured to couple light out of the waveguide
Implementation Method 2
The light from the light source may then be reflected by a 100% reflective mirror or mirror array
Implementation Method 3
a waveguide for propagating the display light to an eye box
Data Source
AI summary
A display system includes a wearable eyewear arrangement with a projector for propagating display light associated with an image and a waveguide for propagating the display light to an eye box. The waveguide includes volume Bragg gratings (VBGs), which may be in groups of three or more gratings with same horizontal period allowing each color to be coupled out from the waveguide by the same type of grating, thus, at the same angle, reducing or eliminating image blurriness and ghost images while allowing a smaller size waveguide. A 100% reflective mirror or mirror array is used for broad spectrum reflection into the waveguide for light input. Selection of two or more wavelengths for each color at the projector provides spectral response matching to the waveguide allowing wider field of view (FOV) coverage for the entire wavelength spectrum.