Radial Pupil-Replicating Lightguide for VR Eyebox Expansion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing VR displays are bulky and heavy due to the requirement for a fixed position of the projector relative to the eye, and they often suffer from blind zones in the field of view.
Innovation Solution
A pupil-replicating lightguide with in-coupling and out-coupling gratings that expand and redirect image light to create multiple exit pupil replicas, allowing for a more compact design and eliminating blind zones by using a perimeter grating to reflect light back into the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed position of the projector relative to the eye is used, then the display can function properly, but the device becomes bulky and heavy
Solution Approach 1:
The patent transitions from a fixed one-dimensional projector positioning to a two-dimensional lightguide plane where multiple exit pupils are distributed across the surface. This dimensional change allows the eye to move freely within a larger eyebox area while maintaining proper optical function, eliminating the need for precise fixed positioning and reducing overall device bulk.
Solution Approach 2:
The patent creates multiple copies of the exit pupil across the lightguide surface through radial pupil replication. These pupil replicas allow the user's eye to access the optical path from multiple positions, effectively replacing the need for a single fixed projector position and enabling a more compact, lightweight design.
2Reliability
If a fixed position of the projector relative to the eye is used, then the display can function properly, but the device becomes bulky
Solution Approach 1:
The patent distributes multiple exit pupils across a two-dimensional lightguide surface, transforming the optical architecture from a single-point projector to an area-based light distribution system. This enables compact integration while maintaining proper display function across a larger eyebox.
Solution Approach 2:
The patent combines multiple optical functions (projection, light guiding, pupil expansion, and eyebox enlargement) into a single integrated lightguide component. This merging eliminates the need for separate bulky projector and optical alignment mechanisms, achieving compact device volume.
3Device complexity
If conventional light routing is used, then the display structure is simple, but blind zones appear in the field of view
Solution Approach 1:
The patent employs asymmetric grating arrangements and non-uniform pupil distribution patterns within the lightguide to optimize light routing coverage. The asymmetric design ensures that light is directed appropriately across the entire field of view, eliminating blind zones while maintaining manageable structural complexity.
Solution Approach 2:
The patent divides the lightguide into multiple functional zones with different grating configurations to address different regions of the field of view. This segmentation allows targeted optimization of light routing in each zone, ensuring complete coverage without requiring overly complex uniform structures throughout.
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 a compact and efficient VR display that relaxes the requirement for precise eye positioning and eliminates blind zones, enhancing user comfort and visual experience.
Implementation Method 1
A first grating is supported by the slab for in-coupling the light into the slab
Implementation Method 2
a slab of a transparent material for guiding light in the slab
Implementation Method 3
A second grating is supported by the slab for at least one of: splitting the light in the slab, redirecting the light in the slab, or out-coupling the light from the slab
Implementation Method 4
using a perimeter grating to reflect light back into the system
Data Source
AI summary
A pupil-replicating waveguide usable in a VR display may have a slab of transparent material, an input grating coupler supported by the slab at the center of the slab, with output gratings supported by the slab and surrounding the input grating coupler. The input grating coupler couples image light into the slab, which propagates in the slab by total internal reflections. The out-coupling grating or gratings spread the image light all around the input grating, providing a wide beam of image light illuminating the eyebox of the VR display.