Dielectric Thickness Profile Determination for Input Device Force Sensing
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Solution Overview
Problem
The accuracy of force sensing measurements in input devices, such as touchpads and touch screens, depends on the controlled thickness of sensor electrode layers and their mechanical accuracy relative to conductive elements, which can vary between devices and over time, affecting the reliability of force detection.
Innovation Solution
The implementation of a method to determine the thickness profile of a dielectric layer between the sensing assembly and the conductive reference element using capacitive measurements acquired with different reference voltages, allowing for compensation of force measurements and independent force sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the thickness of sensor electrode layers and their mechanical accuracy are controlled, then the accuracy of force sensing measurements is improved, but the manufacturing complexity and variability between devices increase
Solution Approach 1:
The patent applies preliminary action by measuring the thickness profile of the dielectric layer during the manufacturing process before the device is fully assembled. This early measurement allows the system to compensate for thickness variations later during operation, rather than requiring perfectly controlled manufacturing. The thickness profile measurement is performed as a preliminary step that enables subsequent compensation algorithms to correct for manufacturing variations.
Solution Approach 2:
The patent utilizes parameter changes by measuring capacitance at multiple different reference voltages to determine the thickness profile of the dielectric layer. By varying the reference voltage parameter and observing the resulting capacitance changes, the system can calculate the thickness profile without requiring direct physical measurement. This approach converts an manufacturing precision problem into a measurable electrical parameter variation.
2Reliability
If capacitive measurements are acquired with different reference voltages to determine thickness profile, then the reliability of force sensing is improved, but the complexity of the sensing system increases
Solution Approach 1:
The patent applies universality by using the same sensor electrodes and capacitive measurement circuitry for multiple purposes: both for standard capacitive touch sensing and for thickness profile measurement. The system switches between different reference voltage configurations to perform different measurement functions with the same hardware, rather than requiring separate dedicated measurement systems. This multi-functional approach improves reliability without proportionally increasing hardware complexity.
Solution Approach 2:
The patent uses the dielectric layer itself as an intermediary to enable thickness measurement. By measuring the capacitance through the dielectric layer at different reference voltages, the system indirectly determines the thickness profile without requiring direct physical access or additional measurement probes. The dielectric layer mediates between the sensor electrodes and the thickness information, allowing non-invasive measurement that integrates seamlessly into the existing device structure.
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 enhances the accuracy and reliability of force sensing by accounting for variations in layer thickness, improving the precision of input device interactions.
Implementation Method 1
The sensing assembly comprises a plurality of sensor electrodes capacitively coupled with the conductive reference element
Implementation Method 2
a thickness profile of a dielectric layer disposed between the sensing assembly and the conductive reference element
Data Source
AI summary
An input device and related method and processing system are disclosed. The input device comprises a sensing assembly attached with a conductive reference element, the sensing assembly comprising a plurality of sensor electrodes capacitively coupled with the conductive reference element and defining a surface. The input device further comprises a switching element configured to couple the conductive reference element with a selected one of a plurality of reference voltages. A first capacitive measurement is acquired while the conductive reference element is coupled with a first reference voltage, and a second capacitive measurement is acquired while the conductive reference element is coupled with a second reference voltage.