Capacitive Touch Position Circuit With Dynamic Pen Detection Threshold
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Solution Overview
Problem
Conventional position detection systems using capacitance-type touch sensors falsely detect the touch position of a user's hand or finger as the pen position due to the downlink signal from an electronic pen passing through the human body, leading to incorrect position detection.
Innovation Solution
A position detection circuit that includes a first detection circuit for detecting a touch, a second detection circuit for detecting a first indicator's proximity, and a changing circuit that adjusts the threshold for detecting the first indicator based on touch detection, reducing the sensitivity of pen detection when a touch is detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a capacitance-type touch sensor is used to detect both pen position and touch position, then both positions can be detected using the same sensor, but false detection occurs where touch position is mistakenly identified as pen position
Solution Approach 1:
The patent applies local quality by setting different detection thresholds for different detection targets. When touch is detected, a first (higher) threshold is used for pen detection, while when touch is not detected, a second (lower) threshold is used. This localized adjustment of detection parameters in different operational contexts resolves the contradiction by maintaining high detection capability while preventing false detection at touch positions.
Solution Approach 2:
The patent implements dynamics by making the pen detection threshold variable rather than fixed. The threshold dynamically changes based on touch detection state: it increases to a first threshold value when touch is detected, and decreases to a second threshold value when touch is not detected. This dynamic adaptation allows the system to maintain versatility in detecting both pen and touch positions while ensuring measurement precision by preventing false positives.
2Measurement precision
If the detection threshold for pen proximity is kept low to ensure sensitive detection, then pen position can be detected accurately, but touch position may be falsely detected as pen position
Solution Approach 1:
The patent applies parameter changes by modifying the detection threshold parameter based on the touch detection state. The system changes the threshold from a second value (lower, for high sensitivity) to a first value (higher, for preventing false detection) when touch is detected. This parameter adjustment resolves the contradiction by maintaining detection sensitivity when needed while ensuring reliability by raising the threshold to prevent false positives at touch positions.
Solution Approach 2:
The patent implements feedback by using the touch detection result to control the pen detection threshold. The system continuously monitors touch detection status and adjusts the pen detection threshold accordingly: when touch is detected, the threshold is raised to prevent false detection; when touch is not detected, the threshold is lowered to maintain sensitivity. This feedback mechanism ensures both measurement precision and reliability in pen position 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 suppresses false detection of the touch position as the pen position by adjusting the detection threshold, ensuring accurate identification of the pen position and reducing false positives.
Implementation Method 1
detection of capacitive coupling between the hand or finger of the user and the touch sensor
Implementation Method 2
a touch sensor of capacitance type including a plurality of sensor electrodes to detect a position
Data Source
AI summary
Provided is a position detection circuit that uses a touch sensor of a capacitance type including sensor electrodes to detect a first position indicated by a first indicator that communicates with the touch sensor to indicate the first position and a second position indicated by a second indicator that indicates the second position without communicating with the touch sensor, the position detection circuit including a first detection circuit that detects a touch of the second indicator to an input surface arranged on the touch sensor, a second detection circuit that detects the first indicator when proximity information indicating a proximity of the first indicator to the touch sensor is equal to or greater than a threshold, and a changing circuit that changes the threshold to a larger value when the first detection circuit detects the touch compared to when the first detection circuit does not detect the touch.