Stylus Location Sensing with Magnetometer Background Compensation
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Solution Overview
Problem
Existing stylus location sensing methods require a large number of coils to provide accurate location information, and magnetometer-based approaches are hindered by interference from the earth's magnetic field and device-generated fields, making it difficult to accurately sense the location of a stylus with respect to a host electronic device.
Innovation Solution
The use of a magnetic field generator in the stylus and directional magnetometers in the host electronic device to sense and compensate for background magnetic fields, allowing for precise determination of the stylus location through the measurement and triangulation of magnetic field vectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large number of coils are used in the grid, then location accuracy is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent replaces the mechanical coil grid system with a magnetic field-based sensing system. Instead of using numerous physical coils embedded in the display surface, the invention uses a magnetic field generator in the stylus that interacts with magnetometers in the host device, eliminating the need for a complex coil infrastructure while maintaining location sensing capability
Solution Approach 2:
The magnetometer array serves multiple functions: it detects magnetic field vectors for location determination, compensates for background magnetic fields, and enables three-dimensional tracking. This multi-functionality replaces what would otherwise require separate systems, reducing overall device complexity
2Device complexity
If magnetometers are used to sense stylus location, then device complexity is reduced, but measurement precision deteriorates due to background magnetic field interference
Solution Approach 1:
The system performs preliminary measurement of the background magnetic field when the stylus is not present or at known positions. This background field data is stored and subsequently subtracted from measurements taken during stylus interaction, effectively compensating for Earth's magnetic field and device-generated fields before location calculation
Solution Approach 2:
The system uses feedback from multiple magnetometer readings to continuously refine location determination. By measuring magnetic field vectors at multiple points and using triangulation algorithms, the system compensates for background interference and improves measurement precision through iterative calculation
3Device complexity
If a single compass is used for gesture detection, then device complexity is reduced, but location sensing capability is lost due to magnetic field interference
Solution Approach 1:
Instead of using a single compass for multiple purposes, the patent segments the sensing function by deploying multiple magnetometers at known positions throughout the host device. Each magnetometer provides localized magnetic field data, and collectively they enable precise location determination through triangulation, separating gesture detection from location sensing functions
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 method enables accurate and reliable stylus location sensing by compensating for background magnetic fields, improving location accuracy and reducing the need for numerous coils, while allowing for potential three-dimensional tracking.
Implementation Method 1
a magnetic field generator of a stylus generates a magnetic field that is sensed by a first directional magnetometer of the electronic device and at least one second directional magnetometer of the electronic device
Implementation Method 2
Commonly, such devices utilize a Hall sensor, which senses the voltage difference produced across a current-carrying conductor in the presence of a magnetic field
Implementation Method 3
or a magnetostrictive sensor
Data Source
AI summary
The present disclosure provides a host electronic device, a stylus and a method for determining the location of a stylus with respect to a host electronic device. A magnetic field generator of the stylus is energized and a first magnetic field is sensed at two or more magnetometers of the host electronic device. The location of the stylus with respect to the host electronic device is determined dependent upon the first magnetic field. A second magnetic field may be sensed, while the magnetic field generator is either deactivated or energized with an opposite polarity, to correct for the presence of a background magnetic field. The magnetometers may be directional magnetometers and may be arranged in an array.