Touch Position Detection in Ultra-Thin Electronic Devices
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Solution Overview
Problem
In ultra-thin display devices, such as organic EL display devices, the reduction in thickness leads to decreased touch-position detection accuracy due to close proximity of the finger to the sensor electrode, causing negative signals in mutual capacitance sensing, which disrupts signal distribution and prevents accurate touch position specification.
Innovation Solution
An electronic device with a touch panel that employs both self-capacitance and mutual capacitance systems for touch position detection, where negative-value data from mutual capacitance sensing is corrected using self-capacitance data when specific conditions are met, allowing for accurate touch position specification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If thickness reduction is implemented using cover film instead of cover glass, then device thickness is reduced, but touch-position detection accuracy deteriorates due to negative signals in mutual capacitance sensing
Solution Approach 1:
The patent combines self-capacitance sensing and mutual capacitance sensing into a unified touch detection system. The position detection circuit integrates both sensing methods, using self-capacitance data to correct negative signals in mutual capacitance data, thereby maintaining high detection accuracy while enabling ultra-thin device construction with cover film.
Solution Approach 2:
The patent changes the detection parameters by switching between self-capacitance and mutual capacitance sensing modes. When negative signals are detected in mutual capacitance sensing (indicating proximity touch), the system switches to or combines with self-capacitance sensing, which does not produce negative signals, thereby correcting the detection accuracy without requiring increased device thickness.
2Ease of operation
If mutual capacitance sensing is used for touch detection, then touch position can be detected, but negative signals occur when finger is close to sensor electrode, disrupting signal distribution
Solution Approach 1:
The position detection circuit uses feedback from self-capacitance sensing to detect and correct negative signals in mutual capacitance sensing. When negative signals are detected, the system uses the corresponding self-capacitance data to correct the mutual capacitance data, ensuring reliable signal distribution and accurate touch position detection.
Solution Approach 2:
The patent introduces self-capacitance sensing as an intermediary to mediate the problems caused by mutual capacitance sensing. The self-capacitance data serves as a reference that corrects the negative signals in mutual capacitance data, allowing the system to maintain the advantages of mutual capacitance sensing while eliminating its harmful effects.
3Length of stationary object
If cover film with circular polarization plate is used instead of cover glass, then device thickness is reduced, but coupling between finger and adjacent sensor electrode increases, causing negative signals
Solution Approach 1:
The patent converts the harmful effect of increased capacitive coupling (which causes negative signals) into a beneficial detection mechanism. By detecting negative signals as indicators of proximity touch, the system switches to or combines with self-capacitance sensing, which is less susceptible to capacitive coupling effects, thereby turning the harmful coupling into a useful detection cue.
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 enables high-accuracy touch position detection even in ultra-thin displays by stabilizing mutual capacitance detection data with self-capacitance data, effectively removing the influence of negative signals and ensuring precise touch position determination.
Implementation Method 1
The self-capacitance system is a system of measuring the position of a recognition object by detecting an increase in electrostatic capacitance caused by contact or approach of the recognition object to a touch panel
Implementation Method 2
The mutual capacitance system is a system of measuring the position of a recognition object on the basis of the difference in electrostatic capacitance between adjacent sensors caused by contact or approach of the recognition object to a touch panel
Implementation Method 3
there may be an influence of coupling (capacitive coupling) between the finger and the sensor electrode (hereinafter referred to as 'adjacent sensor electrode') adjacent to the sensor electrode corresponding to the touch position
Data Source
AI summary
There is achieved an electronic device including a position detector that can detect a touch position with high accuracy even when thickness reduction proceeds. A touch position detection method includes: a first determination step (S710) of determining whether or not negative-value data is included in mutual capacitance detection data; a second determination step (S720) of determining whether or not a mutual capacitance detection region and a self-capacitance detection region overlap; a third determination step (S730) of determining whether or not the maximum value of the absolute value of negative-value data and the area of a negative-value data region are equal to or greater than thresholds; a correction step (S740) of correcting the mutual capacitance detection data on the basis of self-capacitance detection data; and a touch position specification step (S750) of specifying a touch position on the basis of the mutual capacitance detection data after the correction.