Capacitance Touch Panel Reference Value Reset for Palm Detection Errors
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Solution Overview
Problem
Capacitance type touch panels face errors in determining touch operations due to ambient temperature changes and large-area touches, such as those made by a palm, which alter the dielectric constants of materials like the cover lens and adhesive, leading to false operation detection.
Innovation Solution
An electronic device with a capacitance type touch panel and a control method that includes a measurement unit and a control unit to reset the reference value based on measured capacitance differences, preventing determination errors by identifying and correcting for improper touch operations that exceed a threshold for a predetermined time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fan is arranged to cool the touch panel and maintain constant ambient temperature, then touch operation accuracy is improved, but device size and cost increase
Solution Approach 1:
The touch panel system automatically performs self-diagnosis and self-correction by detecting capacitance changes caused by palm touches and autonomously resetting reference values, eliminating the need for external cooling fans or temperature control mechanisms
Solution Approach 2:
The system dynamically adjusts the reference capacitance values based on detected temperature-induced changes, allowing the touch panel to adapt to temperature variations without physical cooling components
2Manufacturing precision
If a cover lens and adhesive are used to fix electrostatic sensor patterns, then manufacturing precision is improved, but determination accuracy deteriorates due to dielectric constant changes from palm temperature
Solution Approach 1:
The system continuously monitors capacitance values and uses feedback to detect when temperature changes affect the cover lens and adhesive, then automatically resets reference values to compensate for these changes
Solution Approach 2:
The system performs preliminary detection of capacitance changes caused by palm temperature before they lead to erroneous operation determination, and proactively resets reference values to prevent false positives
3Ease of operation
If the touch panel operates without reference value reset during prolonged palm contact, then ease of operation is maintained, but reliability deteriorates due to erroneous operation determination
Solution Approach 1:
The touch panel system autonomously monitors its own state and automatically resets reference values when palm-induced temperature changes are detected, maintaining reliability without requiring user intervention or system shutdown
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
Prevents erroneous touch operation determination by accurately differentiating between valid and invalid touch operations, ensuring reliable device functionality even with large-area touches.
Implementation Method 1
a capacitance type touch panel having a plurality of electrodes; a measurement unit configured to measure capacitances respectively caused by the plurality of electrodes
Implementation Method 2
the temperature of the palm of the user is normally higher than that of the touch panel, and when a touch state of the palm on the entire touch panel continues for a long period of time, the entire touch panel is heated by the palm. As a result, dielectric constants of materials such as the cover lens and adhesive in the vicinity of the electrostatic sensor pattern are changed unwantedly
Data Source
AI summary
Capacitances caused by respective electrodes of a touch panel, which is used to detect an instruction position of the user based on a change in capacitance, are measured, and it is determined whether or not a difference between the measured value and a reference value is larger than a threshold. When it is determined that the difference is larger than the threshold, a portion corresponding to the electrode on the touch panel is detected as the instruction position of the user. After detection, when the difference continues for a predetermined period time, the measured value is set as a new reference value.