Dual-Function Transducer for Multi-Touch Force Sensing
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Solution Overview
Problem
Current touch screen technologies, particularly projected capacitive systems, cannot detect the force of touch input and are unable to recognize touch input from non-conductive objects, limiting their utility in accurately measuring multiple simultaneous touch events.
Innovation Solution
A dual-function transducer system that combines projected capacitive sensing and strain gauge force sensing, allowing for the detection of both location and force of multiple simultaneous touch inputs using an electrode array with distinct driving methods for capacitance and strain measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If projected capacitive sensing is used to detect multiple simultaneous touch input events, then multi-touch capability is improved, but the ability to detect force of touch input and non-conductive objects is lost
Solution Approach 1:
The patent merges projected capacitive sensing electrodes with strain gauge force sensing into a single integrated electrode array. The same electrodes serve dual functions: detecting touch location through capacitive coupling and measuring force through strain-induced resistance changes. This combination resolves the contradiction by enabling both multi-touch capability and force detection without requiring separate sensor systems.
Solution Approach 2:
The electrode array is designed to perform multiple functions simultaneously. The same electrodes that detect touch location through capacitance changes also detect force magnitude through resistance changes when strained. This multi-functionality allows the system to maintain multi-touch capability while adding force detection and non-conductive object recognition without increasing device complexity.
2Measurement precision
If separate force sensing devices are incorporated into projected capacitive touch panels, then force detection capability is improved, but device complexity increases
Solution Approach 1:
Instead of incorporating separate force sensing devices, the patent combines force sensing functionality directly into the existing electrode array. The electrodes are patterned with strain-sensitive geometries (such as meander or zigzag patterns) that convert mechanical strain into measurable resistance changes. This merging approach eliminates the need for additional force sensing components and reduces system complexity while maintaining force detection capability.
Solution Approach 2:
The electrode array serves as both the capacitive touch sensor and the force sensor. By designing the electrodes to be strain-sensitive, the same structural element performs dual functions: capacitive coupling for location detection and resistance measurement for force detection. This universality prevents the increase in device complexity that would result from adding separate force sensing devices.
3Device complexity
If the same electrode array is used for both capacitance and strain measurement, then device complexity is reduced, but measurement precision for both functions may be compromised
Solution Approach 1:
The measurement process is segmented into distinct phases: capacitance measurement for touch location detection and resistance measurement for force detection. The controller sequentially performs different measurement routines depending on the detection mode required. This temporal segmentation allows the same electrode array to accurately perform both functions without cross-interference, maintaining measurement precision while reducing device complexity.
Solution Approach 2:
The electrode array's electrical properties are dynamically utilized based on measurement needs. The same electrodes exhibit different electrical behaviors (capacitive vs. resistive) that are exploited differently depending on whether location or force detection is required. This dynamic usage of electrode properties enables dual-function measurement with a single sensor system while maintaining accuracy for both functions.
Data Source
AI summary
A dual-function transducer for a force-sensitive multi-touch screen, including a first substrate, at least one electrode array formed on the first substrate, the at least one electrode array including first and second electrodes, and circuitry operatively coupled to the first and second electrodes. The circuitry is configured to measure first and second electrical properties of the electrode array, the first and second electrical properties corresponding to touch and strain, respectively.