Headset Magnetic Tracking for Hemisphere Ambiguity Resolution
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Solution Overview
Problem
Existing augmented and virtual reality systems face challenges in accurately and efficiently localizing the position and orientation of objects, particularly due to high latency and low resolution in conventional localization methods, which can lead to motion sickness and unstable virtual content rendering.
Innovation Solution
The use of an electromagnetic tracking system with compact electromagnetic field emitters and sensors, combined with inertial measurement units, to determine the position and orientation of objects with high accuracy and low latency, and a method to optimize sensor data processing by using a lower frequency for accurate sensors to correct noisy data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional localization methods are used in AR systems, then the system complexity is reduced, but the localization precision and frame rate deteriorate
Solution Approach 1:
The system divides the localization function into two independent modules: an electromagnetic tracking system for high-precision position and orientation detection, and an inertial measurement unit for continuous motion tracking. This segmentation allows each module to specialize in its strength, achieving high localization precision without requiring a completely complex integrated system.
Solution Approach 2:
The patent introduces a correction mechanism where the lower-frequency electromagnetic tracking data serves as an intermediary to correct and ground the higher-frequency inertial sensor data. This intermediary correction process resolves accumulated errors in the inertial system without requiring the inertial system itself to be overly complex.
2Productivity
If high-frequency sensor data is processed continuously, then the localization update rate is improved, but the computational resources and energy consumption increase
Solution Approach 1:
The system dynamically adjusts the processing frequency of different sensor types based on their characteristics. The inertial measurement unit operates at high frequency to provide continuous updates, while the electromagnetic tracking system operates at lower frequency but provides correction ground truth. This dynamic frequency assignment maintains high localization update rates while optimizing energy consumption by not processing all sensors at maximum frequency continuously.
3Stability of the object's composition
If inertial measurement units are used for continuous tracking, then the localization smoothness is improved, but the accumulated error increases
Solution Approach 1:
The electromagnetic tracking system provides periodic feedback to correct the accumulated errors in the inertial measurement unit. The EM tracker's accurate but lower-frequency measurements serve as ground truth that resets and corrects the drift in the continuous inertial data, maintaining both smoothness and accuracy over time.
Solution Approach 2:
The system performs preliminary correction by using the electromagnetic tracking data to establish accurate reference positions before the inertial errors accumulate significantly. This preliminary grounding of the inertial system prevents large error accumulation while maintaining continuous smooth tracking.
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 approach enables precise and efficient localization of objects in augmented reality systems, reducing latency and improving the stability of virtual content rendering, thereby enhancing the user experience.
Implementation Method 1
emitting, at a hand-held controller of the system, one or more magnetic fields. The method further includes detecting, by one or more sensors positioned within a headset of the system, the one or more magnetic fields
Data Source
Figure 1
Figure 2A~2B
Figure 2C~2D
AI summary
Embodiments resolve hemisphere ambiguity at a system comprising sensors. A hand-held controller of the system emits magnetic fields. Sensors positioned within a headset of the system detect the magnetic fields. A first position and orientation of the hand-held controller is determined within a first hemisphere with respect to the headset based on the magnetic fields. A second position and orientation of the hand-held controller is determined within a second hemisphere, diametrically opposite the first hemisphere, with respect to the headset based on the magnetic fields. A normal vector is determined with respect to the headset, and a position vector identifying a position of the hand-held controller with respect to the headset in the first hemisphere. A dot-product of the normal vector and the position vector is calculated, and the first position and orientation of the hand-held controller is determined to be accurate when a result of the dot-product is positive.