Holographic VR Exit Pupil Replication for Wider Eyebox
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Solution Overview
Problem
Holographic displays face challenges with bulky and uncomfortable designs due to the need for the user's eye to remain at a specific exit pupil for image observation, limiting the flexibility and comfort of use.
Innovation Solution
The use of replicating lightguides and beam expanders in holographic displays to guide image light through total internal reflections, allowing image observation at multiple eyebox locations and expanding the effective exit pupil, combined with eye tracking systems to adjust image formation based on the user's eye position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If traditional holographic display optical paths are used, then image quality and depth of field are maintained, but the device becomes bulky and uncomfortable for wearable use
Solution Approach 1:
The patent implements a folded optical path where light travels through multiple optical components in a nested configuration within a compact housing. The optical path is folded back on itself multiple times, allowing the light to traverse a long optical distance while maintaining a small external footprint, effectively nesting the optical components within each other's spatial envelope
Solution Approach 2:
The patent transitions from a linear optical path to a three-dimensional folded path by introducing multiple reflections at different angles and planes. The light path is redirected through various dimensions within the device housing, utilizing vertical and lateral space efficiently to achieve compactness without sacrificing optical path length
2Illumination intensity
If the exit pupil is restricted to a specific location for proper image formation, then optical performance is optimized, but the user's eye position flexibility is limited
Solution Approach 1:
The patent divides the single exit pupil into multiple exit pupils positioned at different locations in space. Each exit pupil corresponds to a specific eye position, allowing the system to maintain optimal optical performance for multiple discrete viewing positions rather than requiring the user's eye to remain at a single fixed location
Solution Approach 2:
The patent implements a dynamic optical system that can adjust and switch between multiple exit pupil configurations. The system can adaptively redirect light to different exit pupil locations based on the detected eye position, providing real-time flexibility to maintain optimal illumination intensity across varying eye positions
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
Enables comfortable and flexible image observation across a range of eye positions, alleviating vergence-accommodation conflict and enhancing user experience by allowing image observation at multiple locations within the eyebox.
Implementation Method 1
The use of replicating lightguides and beam expanders in holographic displays to guide image light through total internal reflections
Implementation Method 2
beam expanders in holographic displays to guide image light through total internal reflections, allowing image observation at multiple eyebox locations and expanding the effective exit pupil
Data Source
AI summary
A holographic display includes an illuminator, a spatial light modulator (SLM) coupled to the illuminator, a beam redirector and an ocular lens coupled to the SLM. A controller is operably coupled to the SLM and the beam redirector and configured to provide exit pupils at eyebox locations where a holographic image may be observed. The exit pupils provided in a time-sequential manner, forming a grid of exit pupils/eyebox locations. An eye tracking system may be used to center the grid around the current eye pupil position, to provide a larger overall eyebox for viewing the holographically generated image.