Waveguide Display Grating System for Eye Box Expansion
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Solution Overview
Problem
Waveguide-based display systems face challenges in maintaining image quality and reducing distortion, particularly in ensuring that the entire virtual image is visible to the user over a wider area without significant banding effects, which can affect the perceived image quality.
Innovation Solution
The system employs an optical waveguide with an incoupling grating, an intermediate grating, and an exit grating, coupled with an actuator generating acoustic waves that propagate through the waveguide, allowing multiple collimated input beams to form a virtual image by diffraction, with the gratings' widths being larger than the beam diameters, enabling beam splitting and expansion to create a wider exit beam area, and the actuator shifts interference fringes to minimize banding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If waveguide-based display systems use traditional optical components to transport light, then the image can be displayed, but the eye box area is limited and the user cannot see the image over a wider area
Solution Approach 1:
The waveguide is divided into multiple functional zones with distinct gratings: an incoupling grating for beam entry, intermediate gratings for beam distribution and TIR transport, and an exit grating for beam output. This segmentation allows each zone to be optimized independently, expanding the overall eye box area while maintaining manageable complexity in each individual component.
Solution Approach 2:
The system transitions from traditional single-path light transport to multi-dimensional beam manipulation by using gratings with widths substantially larger than beam diameters. This enables beams to be split and distributed across multiple spatial regions within the waveguide, effectively expanding the eye box in lateral dimensions beyond the original beam width.
2Area of stationary object
If the waveguide structure is configured to expand beam width for wider visibility, then the eye box area increases, but image distortion and banding effects worsen
Solution Approach 1:
Different regions of the waveguide are assigned different grating structures with specific local properties. The incoupling grating has a first width, intermediate gratings have a second width substantially larger than the beam diameter, and the exit grating has a third width. This local differentiation allows optimal beam manipulation in each zone while maintaining overall image quality and minimizing distortion and banding effects.
Solution Approach 2:
The system changes the grating width parameter across different zones of the waveguide. By making the intermediate grating width substantially larger than the beam diameter, the system enables effective beam splitting and distribution without causing significant distortion. The specific parameter relationships (width ratios) are optimized to balance eye box expansion with image quality preservation.
3Area of stationary object
If multiple beams are split and distributed across wider areas, then the eye box expands, but interference patterns and banding effects become more pronounced
Solution Approach 1:
The intermediate gratings act as intermediary elements between the incoupling and exit gratings. These intermediate gratings with increased width serve as mediators that distribute beams across multiple TIR regions, enabling eye box expansion while the specific grating design and spacing minimize harmful interference patterns and banding effects through controlled beam manipulation.
4Area of stationary object
If traditional diffraction gratings are used for beam expansion, then the eye box area increases, but significant banding effects reduce perceived image quality
Solution Approach 1:
The waveguide employs a composite optical structure combining multiple grating types (incoupling, intermediate, and exit gratings) with different width parameters and functional properties. This composite approach integrates the benefits of each grating type while minimizing their individual drawbacks, achieving both wide eye box coverage and acceptable image quality with reduced banding effects.
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 ensures a wider field of view for the virtual image with improved image quality by reducing distortion and banding effects, allowing the user to see the image clearly over a larger area without perceivable interference patterns.
Implementation Method 1
an actuator coupled to the optical waveguide arranged to generate acoustic waves, wherein the generated acoustic waves are incident on, and propagate through, the optical waveguide
Implementation Method 2
the incoupling grating is arranged to couple each beam into the intermediate grating
Implementation Method 3
the intermediate grating is arranged to split that beam at the splitting regions to provide multiple substantially parallel versions of that beam
Implementation Method 4
the exit grating is arranged to diffract the multiple versions of that beam outwardly, the multiple input beams thus causing multiple exit beams to exit the waveguide which form a version of the virtual image
Implementation Method 5
Waveguide-based display systems typically transport light from a light engine to the eye via a TIR (Total Internal Reflection) mechanism in a waveguide
Data Source
AI summary
A display system comprises an optical waveguide, an actuator and a light engine. The light engine generates multiple input beams which form a virtual image. An incoupling grating of the optical waveguide couples each beam into an intermediate grating of the waveguide, in which that beam is guided onto multiple splitting regions. The intermediate grating splits that beam at the splitting regions to provide multiple substantially parallel versions of that beam. Those multiple versions are coupled into an exit grating of the waveguide, in which the multiple versions are guided onto multiple exit regions. The exit grating diffracts the multiple versions of that beam outwardly. The multiple input beams thus cause multiple exit beams to exit the waveguide which form a version of the virtual image. The actuator is coupled to the waveguide and is arranged to generate acoustic waves, which are incident on, and propagate through, the optical waveguide.