Force-Sensing Touch Screen Calibration via Resistance Correction
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Solution Overview
Problem
Conventional touch screen displays face challenges in accurately determining the force applied by users due to inherent tolerance variations in the deposition process of transparent conductor materials like indium tin oxide, affecting the consistency of force sensing across different units.
Innovation Solution
A method involving calibration traces and factors to measure and correct the electrical resistance of the touch screen layers, allowing for precise determination of the force applied by subtracting corrected upper and lower layer components from the total resistance, and mapping this resistance to a force value using a calibrated curve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sputter deposition process is used to deposit transparent conductor material, then the touch screen can be manufactured, but significant tolerance variation occurs in the electrical properties from unit to unit
Solution Approach 1:
The patent applies preliminary action by measuring the actual resistance of calibration traces during manufacturing and storing these values in memory before the touch screen is used. This pre-measurement and storage of calibration data allows the system to compensate for process variations later, ensuring consistent force sensing across units despite variations in the sputter deposition process
Solution Approach 2:
The patent changes the parameter approach by transitioning from assuming fixed nominal resistance values to using actually measured resistance values from calibration traces. By measuring and storing actual resistance parameters during manufacturing and using these in force calculations, the system compensates for deposition process variations and achieves consistent force sensing across different units
2Ease of operation
If nominal resistance values are used for calculation, then the force sensing calculation can be performed, but accurate force determination is affected by process variations
Solution Approach 1:
The patent implements feedback by measuring the actual resistance of calibration traces during manufacturing, storing these measured values in memory, and using them in the force sensing calculation. This feedback loop from actual measurement to calculation ensures that process variations are compensated, improving force sensing accuracy while maintaining ease of operation through automated calculation
Solution Approach 2:
The patent applies preliminary action by pre-measuring and storing the actual resistance values of calibration traces before the touch screen enters service. This preliminary measurement and storage of accurate resistance data enables precise force determination during operation without requiring complex real-time calibration procedures
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 ensures consistent force sensing across units, providing accurate and reliable user input by accounting for production variations in the touch screen panels, enhancing the user experience by maintaining similar input results from one unit to another.
Implementation Method 1
a force sensing layer component, which is a resistance of the compressible material between the upper and lower layers
Implementation Method 2
transparent conductor material used in touch screens, such as, for example, indium tin oxide, is typically sputter deposited
Data Source
AI summary
A method and apparatus for calibrating a force sensing touch screen panel includes determining calibration factors for the position sensing layers of the touch screen panel, and applying those calibration factors to adjust nominal resistance values for resistance components of the position sensing layers when force is applied to the touch screen panel. The calibration factors result in a more accurate determination of the resistance of a force sensing layer which changes resistance as a function of force applied to the touch screen panel. The resistance of the force sensing layer can be used to determine the force applied based on a curve relating force to resistance.