Capacitive Touch Panel Baseline Correction for Temperature Drift
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Solution Overview
Problem
Existing touch panel devices face erroneous detection due to varying capacitance caused by rapid temperature changes, which complicates the configuration with additional proximity detection units and non-uniform capacitance across different locations.
Innovation Solution
A touch panel device with a baseline value correction unit that adjusts the update frequency and upper limit value of baseline values based on the capacitance of each electrode pair, preventing erroneous detection by varying these parameters according to the capacitance variation, without requiring additional proximity detection units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the baseline value is updated to follow capacitance changes due to temperature variations, then false detection is prevented, but the device complexity increases due to the need for additional proximity detection units
Solution Approach 1:
The system uses the existing capacitance measurement unit to serve dual purposes: both detecting touch events and monitoring temperature-induced capacitance changes. By analyzing capacitance variations over time without additional sensors, the baseline value is automatically adjusted to account for temperature effects, eliminating the need for separate proximity detection units while maintaining detection accuracy
Solution Approach 2:
The baseline value correction unit dynamically adjusts the baseline capacitance values based on measured capacitance variations. When capacitance changes exceed a predetermined threshold (indicating temperature change), the system modifies baseline values accordingly. This parameter adjustment approach allows the system to compensate for temperature effects using only the existing measurement infrastructure
2Reliability
If the baseline value changes quickly to follow temperature changes, then temperature-induced false detection is prevented, but the position detection precision deteriorates when an object is approaching
Solution Approach 1:
The system dynamically adjusts the rate of baseline value changes based on detected conditions. When temperature changes are detected (capacitance exceeds threshold), the baseline updates more rapidly to track temperature effects. When an object is approaching (capacitance increases gradually), the system slows baseline updates to preserve position detection sensitivity. This dynamic adaptation resolves the contradiction between response speed and detection precision
Solution Approach 2:
The system performs preliminary analysis of capacitance change patterns to distinguish between temperature-induced changes and object approach. By monitoring the rate and pattern of capacitance variation before finalizing baseline adjustments, the system prepares appropriate correction parameters in advance, ensuring that baseline changes occur at optimal rates for both temperature compensation and touch detection
3Device complexity
If the baseline value is set uniformly across all electrode pairs, then the device complexity is reduced, but false detection occurs in regions with naturally higher capacitance during rapid temperature changes
Solution Approach 1:
The system determines individual baseline values for each electrode pair based on their specific capacitance characteristics. During calibration, the system measures actual capacitance at each electrode location and establishes location-specific baseline values. This local customization ensures that each electrode pair has an appropriate baseline accounting for its unique capacitance properties, preventing false detections in high-capacitance regions while maintaining manageable system complexity through automated individual baseline determination
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
Prevents erroneous detection during rapid temperature changes by individually setting the baseline value correction parameters for each electrode pair, simplifying the device configuration and improving position detection accuracy.
Implementation Method 1
a capacitance measurement unit that measures a capacitance between each pair of the electrodes intersecting each other
Implementation Method 2
a temperature detection unit that is configured to detect an ambient temperature of the touch panel
Data Source
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AI summary
To provide a touch panel device capable of preventing erroneous detection at the time of a rapid temperature change due to variation in capacitance without complicating a configuration. A touch panel device (100) includes a capacitance type touch panel (110) having a plurality of electrodes arranged in directions intersecting each other, a capacitance measurement unit (120) that measures capacitance of each electrode pair, a baseline value setting unit (150) that sets the capacitance of each electrode pair in a state where an indicator is not in contact as a baseline value, a position detection unit (140) that detects a contact position of the indicator by comparing the capacitance of each electrode pair measured by the capacitance measurement unit (120) with the baseline value, and a baseline value correction unit (160) that varies the baseline value in accordance with the variation when the capacitance of each electrode pair varies with the lapse of time. The baseline value correction unit (160) sets the time X for varying the baseline value and the upper limit value Y thereof for each electrode pair according to the capacitance of each electrode pair.