Dual Touch Sensor Architecture for Accurate Touch-Press Differentiation
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Solution Overview
Problem
Existing touch sensing technologies for mobile devices struggle to accurately differentiate between button-touch and button-press events, particularly on deflectable surfaces, leading to potential false registrations due to surface deflection and ground capacitance interference.
Innovation Solution
A dual touch sensor architecture incorporating both XY-position and Z-force sensing, utilizing a capacitive XY-position sensor and an inductive or capacitive Z-force sensor, with sensor electronics that detect button-touch and button-press events contemporaneously, and employing differential electrodes to distinguish between genuine and false button presses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single touch sensor is used to detect both XY position and Z-force, then device complexity is reduced, but measurement precision deteriorates due to inability to accurately differentiate button-touch and button-press events
Solution Approach 1:
The touch sensing function is segmented into two independent sensor systems: an XY-position sensor for detecting touch location and a Z-force sensor for detecting press depth. This segmentation allows each sensor to specialize in its specific measurement function, thereby improving overall measurement precision while maintaining reasonable device complexity through modular architecture.
Solution Approach 2:
The sensing capability is extended from two dimensions (XY position) to three dimensions by adding the Z-force dimension. The XY-position sensor captures the horizontal location of touch, while the Z-force sensor captures the vertical press depth, creating a comprehensive 3D touch profile that enables accurate differentiation between button-touch and button-press events.
2Measurement precision
If surface deflection sensing is used to detect button presses, then button-press detection capability is improved, but false registration increases due to ground capacitance interference
Solution Approach 1:
A dedicated Z-force sensor acts as an intermediary between the touch surface and the detection system. This specialized sensor is designed to respond only to vertical force applied to the button area, filtering out horizontal capacitance variations and ground interference that would otherwise cause false registrations. The Z-force sensor translates mechanical press depth into an electrical signal that is independent of lateral capacitance changes.
3Measurement precision
If dual XY/Z touch sensing is implemented, then button event differentiation accuracy is improved, but device complexity increases due to multiple sensors and electronics
Solution Approach 1:
The XY-position sensor and Z-force sensor are merged into a single integrated sensor assembly that shares common structural elements, signal processing electronics, and control logic. This merging approach allows the dual-sensor system to achieve high measurement precision while minimizing the increase in device complexity through shared resources and compact integration.
Solution Approach 2:
The sensor assembly is designed with multi-functionality, where the same structural components and electronics serve both XY-position detection and Z-force detection functions. The XY-electrode and Z-electrode configurations are optimized to perform their specific functions while contributing to the overall versatility of the touch sensing system, reducing the need for separate dedicated components for each sensing modality.
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 solution effectively differentiates button-touch and button-press events, reducing false registrations and enhancing the accuracy of touch input on mobile devices by combining precise position and force sensing, while minimizing interference from surface capacitance.
Implementation Method 1
an XY-position sensor including an XY electrode disposed at the backside of the touch surface opposite the button area to define an XY sensing area corresponding to the button area, the XY-position sensor to sense a touch within the XY sensing area
Implementation Method 2
a Z-force sensor including a Z-electrode to sense touch-pressure deflection of the touch surface, including to sense a touch-pressure deflection that exceeds a button-press threshold as a button-press event
Implementation Method 3
an inductive Z-Force sensor, including a Z inductor coil, a Z conductive target disposed between the Z inductor coil, and the XY capacitive electrode, with elastic insulator material disposed between the XY capacitive electrode and the Z conductive target, and between the Z conductive target and the Z inductor coil, such that the touch-pressure deflection of the surface causes a corresponding movement of the Z conductive target toward the Z inductor coil
Implementation Method 4
a capacitive Z-force sensor, including a Z conductive target, and a Z capacitive electrode disposed between the Z conductive target, and the XY capacitive electrode, with elastic insulator material disposed between the XY capacitive electrode and the Z capacitive electrode, and between the Z capacitive electrode, and the Z conductive target, such that the touch-pressure deflection of the surface causes a corresponding movement of the Z capacitive electrode toward the Z conductive target
Data Source
AI summary
A dual touch sensor with XY-position and Z-force sensing, such as for implementing a touch button, includes a touch sensor assembly with: (a) an XY-position sensor (such as capacitive, single ended or differential) including an XY electrode disposed at the backside of the touch surface opposite the button area to define an XY sensing area corresponding to the button area, the XY-position sensor to sense a touch within the XY sensing area, as a button-touch event; and (b) a Z-force sensor (such as inductive or capacitive) including a Z-electrode to sense touch-pressure deflection of the touch surface, including to sense a touch-pressure deflection that exceeds a button-press threshold as a button-press event. Sensor electronics coupled to the XY-position sensor and the Z-force sensor detects, as a button touch-press condition, the capacitive XY-position sensor sensing a button-touch event, substantially contemporaneous with the Z-Force sensor sensing a button-press event.