Transparent Digitizer Using Magnetic Induction for Passive Stylus

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Solution Overview

Problem

Existing transparent digitizer technologies face challenges with high resistance conductive loops, leading to inaccurate stylus positioning due to high voltage requirements, parallax issues, and noise interference, especially in mobile devices where active styluses are impractical and non-transparent sensors are complex to integrate.

Innovation Solution

A transparent digitizer system using a sensing arrangement with differential amplifiers and organic conductive foils, integrated directly on a flat panel display, which detects electric fields generated by a passive stylus energized by an external excitation coil, minimizing noise and parallax errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If transparent conductive foils are used to create conductive loops, then transparency is improved, but resistance increases making the system impractical

Engineering Contradiction:

Improvedisplay transparencyVSAvoidsystem practicality

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The patent introduces an external excitation coil as an intermediary device that generates magnetic fields to energize the passive stylus. This mediator transfers energy wirelessly through the transparent sensor, eliminating the need for high-voltage power sources while maintaining stylus activation. The excitation coil acts as a bridge between the power source and the stylus, solving the contradiction between transparency and practicality.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the electrical field-based detection system with a magnetic field-based system. Instead of using high-voltage electrical loops, the invention uses magnetic fields generated by an excitation coil to interact with the stylus. This substitution eliminates the need for high-voltage transparent loops while maintaining detection capability, resolving the contradiction between transparency and system reliability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of manufacture

If non-transparent sensors are placed behind the display, then integration is simplified, but positioning accuracy deteriorates due to parallax

Engineering Contradiction:

Improvesensor integrationVSAvoidstylus positioning accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent inverts the traditional sensor placement approach by positioning the transparent sensor in front of the display rather than behind it. This inversion places the sensor closer to the stylus tip, eliminating parallax errors and improving positioning accuracy. The transparent nature of the sensor allows it to be positioned in front without obstructing the display, solving both accuracy and integration issues.

Inventive Principle:

Principle #13The other way round (Inversion)

3Reliability

If high voltage input is used to energize conductive loops, then conductivity is improved, but safety and practicality worsen

Engineering Contradiction:

Improveconductive loop performanceVSAvoidhigh voltage danger

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent substitutes electrical field-based energization with magnetic field-based energization. Instead of applying high voltage directly to transparent loops, the system uses magnetic fields generated by an excitation coil to induce currents in the stylus. This substitution eliminates high-voltage dangers while maintaining the ability to energize and detect the stylus, resolving the contradiction between reliability and safety.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 accurate and reliable stylus location with high resolution and low noise, overcoming the limitations of high resistance conductive loops and complex integration issues, while using passive styluses for improved durability and cost-effectiveness.

Implementation Method 1

an external excitation coil for energizing the passive stylus

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

which detects electric fields generated by a passive stylus

Methodology Applied

Scientific EffectElectric field detection: Electric Field

Data Source

PatentUS8217918B2Transparent digitiser

Publication Date: 2012.07.10 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

A digitizer for user interaction via an object with an electronically refreshable display screen, the digitizer comprising: a transparent sensing arrangement of detectors located at said electronically refreshable display screen for detecting an electric field of said object, said detectors having outputs, and an arrangement of differential amplifiers associated with said outputs, thereby to apply differential detection between said outputs.