Capacitive Touch Panel Pressure Detection Correction
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Solution Overview
Problem
Touch panels using pyroelectric bodies face challenges in accurately detecting finger position and pressure due to heat-generated objects and temperature differences between the finger and the pyroelectric body, leading to erroneous detections.
Innovation Solution
A capacitive touch panel system with a controller that corrects pressure detection signals using position detection signals, featuring overlapping electrodes and dielectric layers to minimize the influence of heat, allowing for accurate detection of pointer position and pressure without relying on pyroelectric effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pyroelectric body is used to detect finger position and pressure, then the touch panel can detect the approach of heat generating objects, but it may erroneously detect heat generating objects other than fingers as finger approach
Solution Approach 1:
The touch panel is divided into multiple independent detection systems: a capacitive touch panel for position detection and a piezoelectric body for pressure detection. This segmentation allows each system to specialize in one type of detection, avoiding the heat interference problems that affect pyroelectric detection of both position and pressure
Solution Approach 2:
The capacitive touch panel serves multiple functions: it detects both the position of the finger and provides a baseline for pressure measurement. The piezoelectric body supplements this by providing accurate pressure detection. Together, they create a multi-functional detection system that overcomes the limitations of using a single pyroelectric body for both position and pressure detection
2Measurement precision
If the temperatures of the pyroelectric body and the finger are almost the same, then the pyroelectric effect is difficult to obtain, but the touch panel still needs to detect the position of the finger
Solution Approach 1:
The patent replaces the pyroelectric detection mechanism (which relies on temperature difference) with a capacitive detection mechanism for position detection. The capacitive system detects changes in electrical capacitance caused by the proximity of the finger, which does not depend on temperature difference. For pressure detection, it uses the piezoelectric effect which responds to mechanical stress rather than temperature
Solution Approach 2:
The invention changes the detection parameter from temperature-based (pyroelectric effect) to electrical property-based (capacitive and piezoelectric effects). By detecting changes in capacitance and piezoelectric charge rather than temperature changes, the system can detect finger position and pressure even when temperature differences are minimal
3Device complexity
If pressure detection electrodes and position detection electrodes are separated, then the structure is simpler, but the detection accuracy and heat resistance are reduced
Solution Approach 1:
The patent combines position detection electrodes and pressure detection electrodes into a single integrated electrode structure. The same electrode patterns on the touch panel serve dual purposes: detecting position through capacitive changes and detecting pressure through piezoelectric effects. This merging eliminates the need for separate electrode systems while maintaining high detection accuracy for both parameters
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
The system effectively reduces heat-related errors in detecting finger position and pressure, ensuring accurate operation across varying temperatures and environments.
Implementation Method 1
the touch panel includes a first substrate, a second substrate, a first dielectric layer located between the first substrate and the second substrate, a plurality of drive electrodes located on the first substrate
Implementation Method 2
the touch panel detects the position the finger is getting closer using the pyroelectric effect of the pyroelectric body and detects the pressure of the finger using the piezoelectric effect of the pyroelectric body
Data Source
AI summary
A touch panel system includes a capacitive touch panel and a controller that controls the touch panel. The touch panel includes a plurality of drive electrodes and a plurality of floating island electrodes located on a first substrate and a plurality of pressure detection electrodes and a plurality of position detection electrodes located on a second substrate. The controller provides a drive signal to the drive electrodes and corrects a pressure detection signal obtained from each of the pressure detection electrodes by using a position detection signal obtained from the position detection electrode.