Capacitive Touch Screen Adaptive Threshold Parabolic Sharpness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional capacitive touch screens face challenges in accurately distinguishing between touch and hover events, particularly when detecting stylus inputs, due to the need for adjusting threshold values, which can lead to premature and incorrect touch detection, affecting the accuracy and reliability of user interactions.
Innovation Solution
A capacitive touch system that fits a parabolic curve to sensed capacitance data and determines its sharpness to dynamically set a touch detection threshold, allowing for adaptive thresholding based on the sharpness of the curve to differentiate between actual touches and hover conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed threshold value is used for touch detection, then the system is simple to operate, but it cannot accurately distinguish between touch and hover events, leading to premature and incorrect touch detection
Solution Approach 1:
The patent applies dynamics by transforming the fixed threshold into a dynamic threshold that adapts to different touch conditions. The threshold is no longer static but varies based on the sharpness parameter calculated from capacitance data, allowing the system to automatically adjust to distinguish between touch and hover events accurately.
Solution Approach 2:
The patent changes the threshold parameter from a fixed value to a variable value determined by the sharpness parameter. By calculating the sharpness from capacitance data and using it to determine the threshold, the system transforms a single parameter (threshold) into a multi-parameter system (capacitance data + sharpness + adaptive threshold) that provides more nuanced detection.
2Reliability
If the threshold value is lowered to detect stylus touches, then stylus input detection is improved, but hover events are incorrectly detected as touches, reducing reliability
Solution Approach 1:
The patent applies local quality by making the threshold locally adapted to each detection context rather than globally fixed. The sharpness parameter provides local information about the capacitance distribution shape, allowing the threshold to be customized for each specific touch or hover situation, thereby reliably distinguishing between them.
Solution Approach 2:
The patent implements feedback by using the calculated sharpness parameter to adjust the threshold in real-time. The system continuously monitors capacitance data, calculates sharpness, and uses this feedback to determine the appropriate threshold, creating a closed-loop system that improves reliability by adapting to actual touch conditions.
3Measurement precision
If a high threshold is used to prevent false hover detection, then false positive detection is reduced, but actual stylus touches are not detected, losing sensitivity
Solution Approach 1:
The patent makes the threshold dynamic by base it on the sharpness parameter calculated from actual capacitance data. This allows the threshold to automatically be high for hover events (preventing false positives) and low for actual touches (maintaining sensitivity), resolving the contradiction between false detection prevention and actual touch detection.
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 accurate detection of touch events by stylus and finger, preventing premature touch detection and improving the reliability of capacitive touch screens by using a threshold that varies with the sharpness of the parabolic fit to the touch profile, thus enhancing user experience in applications requiring precise timing.
Implementation Method 1
The capacitor 12c at each sense node 12 will exhibit an associated mutual (or coupling) capacitance value as known in the art. The presence of an object, such as a human body part (for example, a finger) or device (for example, a stylus) near the sense node 12 causes a change in the mutual (or coupling) capacitance for the capacitor 12c at that sense node 12.
Implementation Method 2
the AC signal applied by a drive circuit 20 to a given drive line 14 is coupled through the capacitor 12c at a sense node 12 to the crossing sense line 16
Data Source
AI summary
A capacitive touch system generates data indicative of sensed capacitance measured at capacitive sensing nodes of a capacitive touch panel. A signal processing circuit is coupled to receive the data indicative of sensed capacitance from the capacitive touch system. The signal processing circuit operates to fit a parabolic curve to the data indicative of sensed capacitance. A sharpness of the fit parabolic curve is indicative of whether touch versus hover interaction with the capacitive touch panel. A touch detection threshold is as a function of the determined sharpness. The set touch detection threshold is then applied against the data indicative of sensed capacitance in order to make a touch detection.