Waveguide Combiner With Separate HOE Plates for Larger Eyeboxes
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Solution Overview
Problem
Conventional mixed-reality head-mounted display (HMD) devices face challenges in optimizing the placement and sizing of holographic optical elements (HOEs) that reduce see-through quality and brightness, cause optical distortions, and limit the eyebox size due to HOEs being located within the user's visual field.
Innovation Solution
The use of separate in-coupling and out-coupling plates in the waveguide combiner, where the out-coupling plate is positioned in front of the user's eye and the in-coupling plate is outside the visual field, allowing for optimized HOE placement and coatings that enhance coupling efficiency and reduce light leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If HOEs are located within the user's visual field to enable in-coupling and out-coupling functions, then the device can achieve compact integration, but see-through quality and brightness are reduced
Solution Approach 1:
The patent divides the HOE system into separate in-coupling and out-coupling plates positioned at different locations. The in-coupling plate is placed outside the user's visual field while the out-coupling plate is positioned in front of the eye, allowing each plate to perform its function independently without compromising see-through quality.
Solution Approach 2:
The patent transitions from a two-dimensional planar arrangement of HOEs to a three-dimensional spatial separation. By positioning plates at different depths and locations (outside vs. inside visual field), the system achieves compact integration without blocking the user's view of the real world.
2Use of energy by moving object
If HOEs are positioned within the user's visual field for optimal coupling, then coupling efficiency is improved, but optical distortions increase
Solution Approach 1:
The patent extracts the in-coupling HOE from the user's visual field and places it outside, eliminating its contribution to optical distortions. The out-coupling HOE remains in front of the eye where it can maintain coupling efficiency without causing distorsions to the see-through view.
Solution Approach 2:
The waveguide acts as an intermediary that transports light from the in-coupling plate (outside visual field) to the out-coupling plate (in front of eye). This allows efficient light coupling while keeping the in-coupling element out of the direct visual path, preventing distortions.
3Adaptability or versatility
If multiple HOEs are placed in the waveguide for in-coupling and exit pupil expansion, then functional capabilities are enhanced, but eyebox size is limited
Solution Approach 1:
The patent segments the optical functions into separate plates: in-coupling HOE for light input and intermediate/out-coupling HOEs for exit pupil expansion. This separation allows each element to be optimally positioned and sized, achieving both enhanced functionality and larger eyebox.
Solution Approach 2:
By positioning the in-coupling plate outside the visual field and using a waveguide to transport light, the system gains spatial freedom to arrange HOEs in three dimensions. This enables exit pupil expansion in multiple directions without constraining the eyebox size.
4Adaptability or versatility
If additional HOEs are added for exit pupil expansion, then pupil coverage is improved, but obstructions in the visual field increase
Solution Approach 1:
The patent extracts the in-coupling HOE and intermediate HOEs from the user's direct visual field and places them outside or in non-obtrusive positions. The out-coupling HOE is positioned in front of the eye where it provides pupil expansion without blocking the see-through view of the real world.
Solution Approach 2:
The waveguide serves as an intermediary that carries light through the device without requiring additional HOEs in the user's visual path. This enables exit pupil expansion functionality while keeping the visual field clear of obstructions.
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 improves see-through quality, increases the eyebox size for wider interpupillary distance coverage, and minimizes obstructions, enhancing user comfort and display performance.
Implementation Method 1
the waveguide propagating virtual image light from the first plate to the second plate
Implementation Method 2
an internally-embedded in-coupling holographic optical element (HOE) configured for in-coupling light for virtual images into the waveguide combiner
Implementation Method 3
an internally-embedded in-coupling holographic optical element (HOE) configured for in-coupling light for virtual images into the waveguide combiner
Implementation Method 4
an internally embedded out-coupling HOE configured for out-coupling the virtual image light from the waveguide combiner to an eye of the user
Implementation Method 5
an internally embedded out-coupling HOE configured for out-coupling the virtual image light from the waveguide combiner to an eye of the user
Data Source
AI summary
A waveguide-based see-through combiner for mixed-reality head mounted display (HMD) devices uses input and output couplers comprising holographic optical elements (HOEs) to respectively in-couple light for virtual images from a display engine to the waveguide combiner and out-couple the virtual images to an HMD user's eyes. The in-coupling and out-coupling HOEs are respectively disposed on separate plates that are optically coupled by a waveguide. The plates and waveguide may be fabricated (e.g., molded) from an optically transparent polymeric material. The utilization of separate plates enables optimization for placement and sizing of the out-coupling HOE in front of the user's eye to thereby increase eyebox size for the virtual images and improves quality of the see-through experience.