Electromagnetic Tracking Stylus for Surface-Independent 6D Input

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Solution Overview

Problem

Conventional input devices with a pen/stylus form factor have limited positional tracking in two dimensions, restricting their utility in three-dimensional spaces like VR and AR applications, and often require a special surface for tracking, limiting portability and flexibility.

Innovation Solution

An electromagnetic (EM) pose tracking system is employed in a stylus or pen form factor device, allowing six-degree-of-freedom pose tracking without line-of-sight requirements and without needing a special writing surface, using a base station and a stylus with EM coils and secondary sensors for enhanced flexibility and precision.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional pen/stylus input devices are used, then the device maintains a simple form factor, but the positional tracking is limited to two dimensions

Engineering Contradiction:
Improvepositional tracking capabilityVSAvoidapplication compatibility
Core Design Contradiction:
Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent transitions from 2D positional tracking to 6D pose tracking by incorporating electromagnetic coils that can detect position and orientation in three-dimensional space. The EM tracking system measures three positional coordinates (x, y, z) and three rotational angles (pitch, yaw, roll), enabling full six-degree-of-freedom tracking capability.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent replaces mechanical or optical tracking systems with an electromagnetic tracking system. Instead of using mechanical encoders, optical markers, or special surfaces, the invention uses electromagnetic coils and magnetic fields to achieve contactless, three-dimensional pose tracking in VR and AR applications.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If conventional pen/stylus devices require a special surface for tracking, then tracking precision can be maintained, but portability and flexibility are reduced

Engineering Contradiction:
Improvetracking precisionVSAvoidportability and flexibility
Core Design Contradiction:
Measurement precisionVSEase of operation

Solution Approach 1:

The patent extracts the tracking dependency from the writing surface by using electromagnetic fields instead of surface-based tracking methods. The EM tracking system operates independently of the surface material, allowing the stylus to be tracked in mid-air or on any surface without requiring special magnetic or optical properties in the writing surface.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The electromagnetic tracking system provides universal compatibility across different surfaces and environments. The same stylus device can be used on various surfaces (paper, glass, air) and in different applications (2D drawing, 3D modeling, VR, AR) without requiring surface-specific adaptations or special writing surfaces.

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If electromagnetic tracking components are added to the stylus, then three-dimensional tracking capability is achieved, but device complexity increases

Engineering Contradiction:
Improvethree-dimensional tracking capabilityVSAvoidinternal component structure
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent combines multiple tracking functions into a single electromagnetic coil assembly. The same EM coils that generate the magnetic field for tracking also serve as sensors for detecting position and orientation, eliminating the need for separate transmitter and receiver components within the stylus.

Inventive Principle:
Principle #5Merging (Combining)

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

Enables precise, three-dimensional input capabilities in VR and AR applications, maintaining a portable and flexible user experience by supporting tracking on various surfaces and environments.

Implementation Method 1

an electromagnetic coil configured to generate EM pose data indicating a relative pose between a transmitter module and the coil

Methodology Applied
Scientific EffectElectromagnetic field: Electromagnetic Induction

Data Source

PatentEP3864497B1Writing device with electromagnetic tracking
Publication Date: 2025.07.02 GOOGLE LLC
  • EP3864497B1 patent drawingFigure 1
  • EP3864497B1 patent drawingFigure 2~3
  • EP3864497B1 patent drawingFigure 4

AI summary

An electromagnetic (EM) pose tracking system includes a computer input device having a pen or stylus form factor. In some embodiments, a base station device includes one of the transmitter (Tx) or receiver (Rx) module for the EM pose tracking system while the computer input device includes the other of the TX and receiver modules. The EM pose tracking system employs the Tx and Rx modules to collect EM pose data indicating a relative pose between the Tx and Rx modules. Based on the EM pose data, the EM pose tracking system (or a computer device working with the EM pose tracking system) identifies a pose (position, orientation, or both position and orientation) of the computer input device.