Capacitive Touch Sensor Palm Interference Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The position accuracy of capacitive touch sensor devices is poor during drag operations due to the influence of the palm, as the capacitance formed between the touch sensor and the palm superimposes on the signals detected by the signal processing circuit, making it difficult to accurately determine the position of the fingertip.
Innovation Solution
A touch sensor device with a detection circuit that outputs signals based on impedance changes, including a touch-on judging unit, a touch-off judging unit, a first position calculating unit, a second position calculating unit, a correction value calculating unit, and a third position calculating unit, which together calculate and correct the touch position to eliminate the influence of the palm, improving accuracy during drag operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the touch sensor device uses the capacitance formed between the transparent conductive layer and the palm for position detection, then the detection can be performed, but the detected position is shifted from the actual fingertip position due to palm influence
Solution Approach 1:
The patent segments the touch detection process into multiple phases: palm approach detection, fingertip contact detection, and position calculation. By dividing the detection signal into palm capacitance component and fingertip capacitance component, the system can separately process and correct each component to eliminate palm interference from the final position measurement.
Solution Approach 2:
The patent changes the detection parameter from simple capacitance value to capacitance change rate (dC/dt). By detecting the rate of change of capacitance rather than the absolute capacitance value, the system can distinguish between the slow capacitance change during palm approach and the rapid capacitance change during fingertip contact, thereby identifying and correcting palm-induced position shifts.
2Duration of action of moving object
If the touch sensor device detects capacitance changes during drag operations, then continuous position tracking is enabled, but the palm's capacitance superimposition causes cumulative position errors
Solution Approach 1:
The patent implements a feedback mechanism where the detected position is continuously corrected based on the calculated palm influence. During drag operations, the system constantly monitors capacitance changes, calculates the palm-induced position shift, and applies correction to the detected position in real-time, preventing cumulative errors from building up during continuous tracking.
Solution Approach 2:
The patent performs preliminary detection of palm approach and calculates the expected palm capacitance influence before the fingertip contact occurs. By anticipating the palm's position and capacitance contribution in advance, the system can pre-calculate correction values that are applied during the actual drag operation, maintaining accuracy throughout the continuous movement.
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 solution significantly improves position accuracy during drag operations by effectively isolating and correcting for the palm's influence, reducing positional errors and enhancing the overall performance of capacitive touch sensors.
Implementation Method 1
When an indicator approaches the X-Y transparent electrodes, the capacitance between the electrodes is increased.
Implementation Method 2
a touch panel whose impedance changes according to existence of a touch of an indicator having an accompanying part and a touch position of the indicator
Data Source
AI summary
The present invention calculates a first detected position influenced by the palm and an accurate second detected position from which the influence of the palm is eliminated immediately after a touch-on is judged, and calculates a correction value based on the first detected position and the second detected position. In a period from the point at which the touch-on is judged to the point at which a touch-off is judged, the first detected position influenced by the palm is calculated once successively, and the first detected position is corrected by the correction value to calculate a third detected position to improve the position accuracy at the time of the drag operation thereby.