PVH Combiner Rolling K-Vectors for Eye Tracking
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Solution Overview
Problem
Conventional eye tracking systems in artificial reality have limited angular bandwidth, leading to inaccurate tracking for users with high prescriptions, and are prone to inaccuracies due to physical and environmental stresses, and they often require large physical illumination sources that create unwanted artifacts.
Innovation Solution
The use of a polarization volume hologram (PVH) combiner with rolling k-vectors, fiducial regions, and segmented regions to improve angular coverage and calibration accuracy, and the utilization of virtual illumination sources generated by the PVH combiner to eliminate the need for physical illumination sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional combiner is used in the eye tracking system, then the system structure is simple, but the angular bandwidth is limited and tracking accuracy for users with high prescriptions deteriorates
Solution Approach 1:
The patent employs a PVH combiner with variable pitch regions where the grating pitch changes as a function of position across the combiner surface. This parameter change allows different regions to diffract light at different angles, thereby expanding the angular bandwidth to accommodate users with various prescriptions while maintaining a relatively simple overall device structure.
Solution Approach 2:
The PVH combiner is divided into multiple regions with locally optimized properties. Each region has a specific pitch value tailored to handle light from particular angular ranges or prescription strengths. This local quality approach ensures that each part of the combiner is optimized for its specific function, improving overall adaptability without uniformly increasing complexity.
2Illumination intensity
If physical illumination sources are used to generate glints for eye tracking, then the illumination is sufficient, but the system size increases and unwanted artifacts are created
Solution Approach 1:
The patent extracts the illumination function from separate physical illumination sources and integrates it into the PVH combiner structure itself. The combiner's variable pitch regions are designed to diffract ambient or weak illumination sources to create the necessary glints, thereby eliminating the need for dedicated physical illumination sources and reducing system size while maintaining sufficient glint brightness.
Solution Approach 2:
The PVH combiner serves multiple functions simultaneously: it acts as both the optical combiner for displaying content and as the illumination source for generating eye tracking glints. This multi-functionality eliminates the need for separate illumination components, reducing system size and eliminating artifacts associated with dedicated illumination sources.
3Reliability
If the combiner and imaging device are rigidly fixed, then the structure is stable, but physical and environmental stresses cause relative movement and tracking inaccuracy
Solution Approach 1:
The patent incorporates fiducial markers in the environment that are captured by the imaging device. These markers provide feedback information about the relative positions and orientations of the combiner and imaging device. This feedback is used to dynamically calibrate and correct the eye tracking system, maintaining high tracking accuracy even when physical or environmental stresses cause slight movements in the rigidly fixed structure.
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 PVH combiner with rolling k-vectors and segmented regions enhances eye tracking accuracy across a wide range of prescriptions and reduces system size by using virtual glints, improving user experience and system design.
Implementation Method 1
a polarization volume hologram (PVH) combiner that includes a liquid crystal (LC) layer having a non-uniform chiral concentration across a surface of the PVH combiner
Implementation Method 2
a PVH combiner with rolling k-vectors, fiducial regions, and segmented regions to improve angular coverage and calibration accuracy, and the utilization of virtual illumination sources generated by the PVH combiner
Implementation Method 3
a PVH combiner that includes fiducial regions and/or is segmented into regions having different diffraction directions can be used to calibrate an eye tracking system
Implementation Method 4
polarization volume hologram (PVH) combiner that includes a liquid crystal (LC) layer
Data Source
AI summary
Various embodiments set forth eye tracking systems. In some embodiments, an eye tracking system includes a polarization volume hologram (PVH) combiner having a rolling k-vector design that provides relatively wide coverage of users whose eyeglasses prescriptions can vary. The PVH combiner can further include (1) fiducial regions created by differential patterning that generate dark regions in images captured of an eye, and/or (2) multiple regions that diffract light at angles to produce different perspectives in the captured images. The dark regions and/or different perspectives can be used to calibrate eye tracking. In addition, the PVH combiner can include off-axis lens regions that generate glints for the eye tracking.