Capacitive Touch Screen Calibration for Ghost Touch Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Capacitive touch screens face issues with ghost detections due to environmental changes, such as temperature variations, which can lead to false positives and degrade performance over time, making it challenging to maintain accurate calibration without causing erroneous recalibration.
Innovation Solution
A dynamic calibration method that adjusts the threshold code based on recent ADC code history, allowing for adaptation to environmental conditions by resetting the baseline code when distorted and performing after-market calibration to ensure accurate touch detection without operator errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the touch screen uses a fixed threshold code for touch detection, then the detection process is simple, but ghost detections occur due to environmental changes such as temperature variations
Solution Approach 1:
The patent implements dynamic calibration by periodically updating the threshold code based on recent ADC code history. Instead of using a fixed threshold, the system adapts the threshold code over time to account for environmental changes such as temperature variations, thereby preventing ghost detections while maintaining detection accuracy.
Solution Approach 2:
The system uses feedback from recent ADC code readings to dynamically adjust the threshold code. By monitoring the history of ADC codes and comparing them against the adaptive threshold, the system continuously refines its detection criteria to distinguish genuine touches from environmental noise, resolving the contradiction between reliability and complexity.
2Measurement precision
If the touch screen performs frequent recalibration to adapt to environmental changes, then detection accuracy is maintained, but false positives and erroneous recalibration increase
Solution Approach 1:
The patent performs calibration selectively rather than continuously. It uses a predetermined number of recent ADC codes to update the threshold code only when necessary, avoiding excessive recalibration that could lead to false positives. This partial action approach maintains precision while preventing erroneous recalibration.
Solution Approach 2:
The system prepares for potential environmental changes by maintaining a history of recent ADC codes before they are needed for threshold updates. This preliminary accumulation of data allows the system to make informed calibration decisions only when environmental drift is detected, preventing premature or erroneous recalibration while maintaining detection precision.
3Reliability
If the touch screen uses a dynamic threshold code based on recent ADC history, then ghost detections are reduced, but the processing complexity increases
Solution Approach 1:
The patent segments the ADC code history into a predetermined number of recent samples that are used to calculate the dynamic threshold code. By processing only a limited segment of historical data rather than all available data, the system reduces ghost detections through adaptive thresholding while keeping processing complexity manageable through segmentation of the data stream.
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 method effectively reduces ghost touch detections and ensures stable touch operation by dynamically adjusting the threshold code and recalibrating the touch screen to match current characteristics, enhancing user experience and device reliability.
Implementation Method 1
capacitive-type touch screen may include an array of capacitive sensors, where the capacitance of the capacitive sensors changes as a function of the proximity of a conductive object (such as a finger or stylus) to the capacitive sensor
Data Source
Figure 1~3
Figure 4~5
Figure 6A~8
AI summary
In an embodiment, a method includes performing a calibration of a first touch cell of a touch screen, where performing the calibration includes: receiving a first code associated with the first touch cell; receiving a second code associated with the first touch cell; determining (908) whether there is an indication of a touch of the touch screen based on the first and second codes; generating (916) a raw code based on the first or second codes; receiving a third code associated with the first touch cell; determining (920) whether the third code matches the raw code; and in response to determining that there is no indication of a touch of the touch screen based on the first and second codes, and that the third code matches the raw code, updating (922) a calibration code associated with the first touch cell based on the raw code or the third code.