Polygonal Optical Splitter for Eyebox Expansion in Wearable HUDs
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Solution Overview
Problem
Wearable heads-up displays face challenges in achieving a large eyebox without increasing bulk, which is essential for providing high-quality images while allowing users to see their external environment, as existing technologies often require bulky optical components to expand the eyebox.
Innovation Solution
The use of an optical splitter with a transparent polygonal structure that includes an input side to receive laser light and an output side with multiple facets, redirecting the light to create multiple spatially-separated virtual positions for the scanning laser projector, effectively expanding the eyebox by replicating the exit pupil over a larger area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional optical components are used to expand the eyebox, then the eyebox size is improved, but the device bulk increases
Solution Approach 1:
The optical splitter divides the single laser light path into multiple separate optical paths using multiple facets. Each facet directs light to a different spatial position, effectively segmenting the eyebox into multiple zones. This allows the eyebox to be expanded without requiring proportionally larger optical components, as the segmentation enables efficient use of the available optical path space.
Solution Approach 2:
The patent uses the polygonal structure with multiple facets to redirect light in different spatial directions, effectively utilizing three-dimensional space. By arranging facets at different angles and positions, the system creates multiple virtual image positions along the optical path, expanding the eyebox in multiple spatial dimensions simultaneously without increasing the overall device footprint.
2Area of stationary object
If multiple optical components are added to expand the eyebox, then the eyebox size is improved, but the device complexity increases
Solution Approach 1:
The patent combines multiple optical functions into a single integrated optical splitter component. The polygonal structure with multiple facets performs the work of what would traditionally require multiple separate mirrors or beam splitters. By merging these functions into one component, the eyebox is expanded while the overall device complexity is reduced compared to using multiple discrete optical elements.
Solution Approach 2:
The optical splitter serves multiple functions simultaneously: it acts as a beam splitter, a multi-facet mirror array, and a spatial light director all in one component. This multi-functionality allows the system to achieve eyebox expansion without adding proportional complexity, as one universal component replaces what would otherwise require several specialized components.
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 solution allows for a more aesthetically pleasing and compact wearable heads-up display with a larger eyebox, enabling users to see displayed content from a wider range of eye positions without compromising visual quality or external visibility.
Implementation Method 1
an optical splitter carried by the support structure and positioned in an optical path between the scanning laser projector and the holographic combiner, wherein the optical splitter includes a transparent polygonal structure that comprises: an input side oriented to receive laser light from the scanning laser projector and in-couple the laser light into a volume of the optical splitter; and an output side having at least N facets, where N is an integer greater than 1, each of the N facets oriented to out-couple a respective portion of the laser light from the volume of the optical splitter and direct the respective portion of the laser light along a respective optical path towards the holographic combiner
Implementation Method 2
Each of the N facets of the output side of the optical splitter may be oriented to direct a respective portion of the laser light from the scanning laser projector along a respective optical path towards the holographic combiner effectively from a different respective one of N spatially-separated virtual positions for the scanning laser projector
Implementation Method 3
the holographic combiner comprises at least one hologram positioned and oriented to receive the respective portions of the laser light from the N facets of the optical splitter and redirect each respective portion of the laser light towards a respective one of N exit pupils at the eye of the user
Data Source
AI summary
Systems, devices, and methods for optical splitters are described. An optical splitter includes a transparent polygonal structure having an input side to receive light from a light source and an output side that is segmented into multiple facets. Each facet is engineered to provide a respective planar surface that is oriented at a different angle in each of at least two spatial dimensions relative to the other facets in order to refract and route a respective portion of the light along a respective set of optical paths. The input side may be faceted as well to further refine the optical paths. A particular application of the polygonal structure in an optical splitter providing eyebox expansion by exit pupil replication in a scanning laser-based wearable heads-up display is described in detail.