Hollow Core Electromagnetic Coil for AR/VR Tracking
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Solution Overview
Problem
Conventional electromagnetic (EM) coils used in virtual and augmented reality tracking systems are heavy due to solid ferrite cores, leading to user discomfort, susceptibility to dislocation, and accuracy issues from impacts.
Innovation Solution
A hollow-core EM coil design using a lightweight core substrate with high magnetic permeability thin metal foil wrappings, such as amorphous or nanocrystalline metal foils, to generate a 3D EM field, reducing weight while maintaining performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a solid ferrite core is used in the EM coil, then the EM sensitivity is improved, but the weight of the coil increases
Solution Approach 1:
The patent applies porous materials by using a hollow-core structure instead of a solid ferrite core. The hollow core is wrapped with high magnetic permeability metal foil, creating a structure that maintains magnetic field generation capability while significantly reducing the amount of magnetic material used, thus reducing weight while preserving EM sensitivity.
Solution Approach 2:
The patent uses composite materials by combining a non-magnetic hollow core structure with high magnetic permeability metal foil wrappings. This composite approach allows the lightweight hollow core to provide structural support while the thin metal foil layers provide the necessary magnetic properties, achieving a balance between weight reduction and magnetic performance.
2Reliability
If a solid ferrite core is used in the EM coil, then the EM field generation capability is maintained, but the susceptibility to dislocation from drop impacts increases
Solution Approach 1:
The hollow-core structure with void space inside provides shock absorption capability during drop impacts. The empty space allows the core to deform slightly without transmitting full impact forces to the coil windings and mounting structure, reducing dislocation risk while maintaining EM field generation through the metal foil wrappings.
Solution Approach 2:
The hollow-core design inherently provides cushioning against impact forces before they can cause damage. The void space acts as a pre-designed shock absorption zone that mitigates impact forces during drop events, protecting the coil structure and maintaining positional stability beforehand.
3Reliability
If a solid ferrite core is used in the EM coil, then the magnetic permeability is sufficient, but the user comfort is reduced due to increased weight
Solution Approach 1:
The hollow-core structure removes unnecessary magnetic material from the center of the coil, dramatically reducing weight. The metal foil wrappings on the hollow core provide sufficient magnetic permeability for EM field generation, while the reduced weight significantly improves user comfort during extended wear.
Solution Approach 2:
The composite structure combines a lightweight hollow core with thin high magnetic permeability metal foil layers. This allows the device to achieve the necessary magnetic properties for reliable tracking while keeping the overall weight low enough to maintain user comfort during prolonged use.
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 hollow-core EM coil achieves similar EM field generation and sensing performance to conventional coils but with significant weight reduction, enhancing user comfort and impact resistance.
Implementation Method 1
The core substrate is wrapped in three orthogonal directions with strips of thin metal foil, which may be excited with corresponding alternating current (AC) signals to generate a three-dimensional EM field, or which may be used to generate voltages representative of a position and/or orientation of the hollow-core EM coil within a generated 3D EM field. The thin metal foil is composed of a metal with high magnetic permeability
Implementation Method 2
The thin metal foil is composed of a metal with high magnetic permeability (that is, a magnetic permeability higher than pure iron), such as an amorphous metal foil or nanocrystalline metal foil. The combination of the lightweight nature of the hollow core and the thin and lightweight nature of the thin metal foil while providing high magnetic permeability allows the hollow-core EM coil to provide similar EM field generation or EM field sensing performance
Data Source
AI summary
An augmented reality/virtual reality (AR/VR) system employs a tracking system for tracking one or more components of the AR/VR system using a generated electromagnetic (EM) field. The tracking system employs an EM coil for generating the EM field or, alternatively, sensing the EM field. The EM coil includes a core substrate and thin metal foil wrapped around the core substrate in three orthogonal axes. The EM coil is effectively “hollow” in that it weighs less than a conventional solid ferrite or ferrous core of comparable dimensions, either through the use of one or more openings formed in the core substrate, the use of a material less dense than ferrite or ferrous materials, the formation of the core substrate as a hollow framework, or a combination thereof. The resulting EM coil thus weighs less than conventional solid-core EM coils, thereby reducing user fatigue and the possibility of misalignment of the EM coil as a result from a drop impact of the device implementing the EM coil.