Multi-touch Force Sensing Touch-screen Devices
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Solution Overview
Problem
Multi-touch touch screens face errors in differentiating gestural inputs due to their small size and two-handed input modes, leading to unintended key presses and falsing, especially in QWERTY keypad usage, where single force sensors cannot accurately differentiate forces applied to multiple keys.
Innovation Solution
A multi-touch user input system incorporating a touch sensor layer and a stacked force sensor layer with an array of force sensors, where each force sensor is associated with specific locations on the touch screen, allowing for independent operation or collective force value computation to determine the intended key press by processing both touch and force inputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single force sensor is used to detect touch input, then the device structure remains simple, but it cannot accurately differentiate forces applied to multiple keys simultaneously
Solution Approach 1:
The force sensing capability is segmented by dividing the touch screen into multiple zones, each with its own force sensor. This allows independent measurement of force at different locations, enabling accurate differentiation of simultaneous key presses while maintaining a manageable sensor count through strategic placement rather than one-to-one mapping.
Solution Approach 2:
The patent adds a force dimension to the existing touch detection system. By stacking force sensors beneath the touch screen in a multi-layer configuration, the system captures force information as an additional dimension of data, enabling differentiation of simultaneous touches that spatial and temporal analysis alone cannot resolve.
2Area of stationary object
If the touch screen size is reduced for mobile devices, then portability improves, but error in differentiating gestural inputs increases
Solution Approach 1:
The system performs preliminary analysis of force magnitude and distribution patterns before final gesture recognition. By evaluating the force dimension in advance, the system can pre-filter and differentiate gestural inputs more accurately, reducing errors in small-format touch screens where spatial resolution is limited.
3Loss of time
If predictive software methods are used to differentiate simultaneous touches, then response time is reduced, but accuracy decreases due to inability to validate intended input
Solution Approach 1:
The system incorporates force feedback as an additional validation layer. By measuring the force magnitude and distribution at each touch point, the system provides feedback that helps distinguish intentional key presses from accidental simultaneous touches, improving input validation accuracy without significantly increasing response time.
Data Source
AI summary
Described are methods and devices including a touch sensor layer configured to receive touch input and a force sensor layer stacked with the touch sensor layer, the force sensor layer includes an array of force sensors configured to receive force input. The force sensor array includes individual force sensors. Specific sensors of the disclosed force sensor array are associated with specific locations of the touch screen to add information that can be used to decipher which key is actually being pressed and may avoid falsing. Both a touch signal and a force signal are utilized to determine the validity of a user touch input. In one embodiment each force sensor may operate independently of the others. Particular embodiments are described that utilize a coarse grid to determine valid touch inputs and that make a determination of a centroid location based on a plurality of force sensors to determine valid touch inputs.