Partially Curved Lightguide with Embedded Collimators
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Solution Overview
Problem
Conventional eyewear display systems have a limited eyebox due to typical ophthalmic lens sizes, restricting variance in eye location for viewing augmented or mixed reality displays, and require thick substrates to achieve a larger eyebox, which is not feasible in a thin form factor.
Innovation Solution
A partially curved lightguide with embedded collimators and a flat pupil replication region is used, collimating light within the lightguide rather than before entry, eliminating bulky optics and enabling a thinner, more efficient AR display form factor similar to traditional eyeglasses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional ophthalmic lens sizes are used, then the device can maintain a thin form factor, but the eyebox is limited and restricts variance in eye location
Solution Approach 1:
The lightguide is divided into distinct functional regions: a curved lightguide portion for light propagation and a flat pupil replication region for eyebox expansion. This segmentation allows each region to be optimized independently - the curved portion maintains thin form factor while the flat region provides the necessary optical path length for pupil replication without increasing overall substrate thickness
Solution Approach 2:
The patent transitions from a purely curved lightguide design to a hybrid design that incorporates a flat region. This dimensional change enables the lightguide to perform multiple functions - the curved portion guides light efficiently while the flat portion replicates the exit pupil, achieving both thin form factor and large eyebox without requiring increased substrate thickness
2Area of stationary object
If a larger eyebox is achieved using thick substrates, then eye location variance is improved, but the device cannot maintain a thin form factor
Solution Approach 1:
The lightguide is divided into distinct functional regions: a curved lightguide portion for light propagation and a flat pupil replication region for eyebox expansion. This segmentation allows each region to be optimized independently - the curved portion maintains thin form factor while the flat region provides the necessary optical path length for pupil replication without increasing overall substrate thickness
Solution Approach 2:
The patent employs a curved lightguide portion that utilizes total internal reflection to guide light efficiently through a thin substrate. The curvature is optimized to maintain sufficient optical path length for pupil replication while keeping the overall form factor thin, demonstrating that curved geometry can achieve both compact size and functional requirements
3Device complexity
If light is collimated before entering the lightguide, then the lightguide structure can be simplified, but bulky optics are required which increases form factor
Solution Approach 1:
The collimating function is performed preliminarily within the lightguide itself through the curved portion's total internal reflection mechanism, before the light reaches the flat pupil replication region. This eliminates the need for separate external collimating optics while maintaining the thin form factor, as the lightguide structure itself performs the collimation function
Solution Approach 2:
The patent merges the collimating function with the lightguide structure itself. The curved lightguide portion performs both light guidance and collimation functions simultaneously, eliminating the need for separate collimating optics. This integration achieves the same optical performance with reduced component count and smaller form factor
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 provides a wider eyebox and more efficient AR display with a thinner form factor, accommodating a larger range of users while minimizing bulkiness and manufacturing costs.
Implementation Method 1
the light beams are 'guided' through the substrate, typically by multiple instances of total internal reflection (TIR), to then be directed out of the lightguide
Data Source
AI summary
Techniques for implementing a partially curved lightguide with pupil replicators are disclosed. A partially curved lightguide includes an embedded collimator with surfaces that act to collimate light for display prior to the light encountering a surface in a pupil expansion region of an exit pupil expander. By collimating the light within the lightguide rather than collimating the light prior to entering the lightguide, the requisite volume of a form factor of an AR display is minimized by eliminating select collimating optics and thus enabling a less bulky volume of the AR display in the region of the light source. Using techniques disclosed herein, a partially curved lightguide with pupil replicators is achievable in an eyewear display system having a form factor similar to traditional eyeglasses and curved, thin lenses.