Single Plate Waveguide with Separate Input Gratings for Color Uniformity
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Solution Overview
Problem
Single plate surface relief grating (SRG) waveguide-based head-mounted displays suffer from low optical efficiency and poor color uniformity due to shared input gratings for multiple colors, narrow laser source spectrum, and limited pupil size, leading to increased power consumption and spatial color nonuniformity.
Innovation Solution
The use of separate input and expansion gratings for each color channel, optimized projection lenses, and micro-LED arrays with distinct pixel configurations for red, green, and blue channels, allowing for improved light coupling and color uniformity within a compact single plate waveguide architecture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single plate waveguide with shared input gratings is used for multiple colors, then the device complexity is reduced, but the optical efficiency and color uniformity deteriorate
Solution Approach 1:
The patent divides the waveguide system into separate color channels, each with its own dedicated input grating and expansion grating. This segmentation allows each grating to be optimized for specific wavelengths, improving optical efficiency and color uniformity while maintaining a compact single-plate structure through careful spatial arrangement of the separated components.
2Manufacturing precision
If laser sources with narrow spectrum are used, then the color purity is improved, but the optical efficiency and color uniformity deteriorate
Solution Approach 1:
The patent applies local quality by designing expansion gratings with spatially varying properties tailored to each color channel. Each expansion grating has locally optimized parameters (period, depth, orientation) matched to its specific wavelength range, allowing efficient coupling of narrow-spectrum laser light while maintaining color uniformity across the display field.
3Volume of moving object
If the pupil size is limited by MEMS mirrors and relay optics, then the device compactness is improved, but the spatial color uniformity deteriorates
Solution Approach 1:
The patent addresses the pupil size limitation by introducing expansion gratings that diffract light into multiple orders, effectively creating virtual pupils in different spatial locations. This dimensional approach allows a compact physical pupil while achieving uniform color across the expanded field of view through the diffractive optical element.
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 configuration enhances optical efficiency and color uniformity, reducing power consumption and spatial color variations, while maintaining a compact design, resulting in a more effective and user-friendly mixed reality display system.
Implementation Method 1
an optical waveguide, optical waveguides
Implementation Method 2
surface relief grating (SRG) waveguide-based head-mounted displays
Data Source
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AI summary
Display systems with a single plate optical waveguide and independently adjustable micro display arrays and related methods are provided. A method includes coupling: a first light portion received from the first micro display array to a first input grating region of the optical waveguide, a second light portion received from the second micro display array to a second input grating region of the optical waveguide, and a third light portion received from the third micro display array to a third input grating region of the optical waveguide. The method further includes directing: a first diffracted portion of the first light portion to a first expansion grating, a second diffracted portion of the second light portion to a second expansion grating, and a third diffracted portion of the third light portion to a third expansion grating. The method further includes using a single output grating outputting combined light.