Beam-Splitter Waveguide for Dense Uniform Output Pupils
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Solution Overview
Problem
Compact planar optics in wearable displays face limitations in image quality, output pupil size and uniformity, field of view, and visual artifacts due to gaps in beam replication.
Innovation Solution
A pupil-replicating waveguide with a beam splitter positioned upstream of the output region to split the in-coupled beam into multiple portions, propagating toward opposing surfaces, thereby filling gaps and enhancing pupil replication density and illumination uniformity without reducing the input pupil size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If compact planar optics are used to reduce size and weight, then weight and compactness are improved, but image quality and output pupil uniformity deteriorate due to beam replication gaps
Solution Approach 1:
The waveguide is divided into distinct functional regions: input region with input coupler, output region with output coupler, and intermediate propagation region. This segmentation allows each region to be optimized independently for its specific function while maintaining overall system compactness.
Solution Approach 2:
The patent transitions from traditional 3D bulk optics to a 2D planar waveguide structure. Light propagation is confined to the planar waveguide layer, enabling compact form factor while maintaining optical performance through careful design of the planar geometry and coupling regions.
2Volume of moving object
If compact planar optics are used, then device size is reduced, but field of view and output pupil size are limited due to beam replication gaps
Solution Approach 1:
The input coupler is designed to pre-condition the incoming light beam by establishing proper propagation modes and angles before the light enters the waveguide core. This preliminary coupling action ensures that subsequent beam replication produces adequate pupil coverage and field of view.
Solution Approach 2:
The patent optimizes key parameters including waveguide thickness, coupling region dimensions, and grating parameters to control beam replication characteristics. By adjusting these parameters, the system achieves adequate output pupil size and field of view within a compact planar form factor.
3Quantity of substance
If beam replication is increased to improve pupil density, then output pupil density improves, but visual artifacts increase due to gaps in the replication process
Solution Approach 1:
The waveguide employs multiple beam replication to create multiple copies of the input beam, forming an expanded output pupil. By optimizing the replication process and ensuring adequate overlap between adjacent beam copies, the system achieves high pupil density while minimizing visual artifacts such as gaps or discontinuities in the reproduced image.
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 increases output pupil density and enhances illumination uniformity, reducing image artifacts and improving user comfort by accommodating various interpupillary distances and facial features.
Implementation Method 1
a beam splitter positioned upstream of the output region to split the in-coupled beam into multiple beam portions propagating toward opposing surfaces
Implementation Method 2
two opposing surfaces for guiding the beam in the waveguide by reflections therefrom
Data Source
AI summary
A waveguide, e.g. a pupil-replicating waveguide, is provided. The waveguide includes a substrate having two outer surfaces, for propagating a beam of light in the substrate by reflecting the beam from the outer surfaces. An output coupler, such as a diffraction grating in the substrate, is configured for diffracting the impinging beam out of the substrate. A beam splitter is disposed in the substrate between the outer surfaces upstream of the output coupler, so as to avoid substantially intersecting the output beam. The partial reflector is configured for splitting the impinging beam, increasing the number of beam portions in the waveguide, thereby improving output pupil density.