Capacitance Sensor Finger Palm Discrimination via Dynamic Thresholding
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Solution Overview
Problem
Existing input devices face challenges in accurately distinguishing between finger and palm proximity using capacitance sensors due to issues with threshold value settings, leading to difficulties in discrimination and increased processing time.
Innovation Solution
An input device with a sensor unit that detects proximity at multiple positions, a peak position specifying unit, a threshold value setting unit, an evaluation value calculation unit, and a determination unit, which sets a threshold value based on peak proximity data and calculates an evaluation value from the area occupied by detection positions exceeding the threshold, to accurately determine whether an object is a finger or a palm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequency spectrum analysis is used to evaluate the steepness of capacitance distribution, then discrimination accuracy between finger and palm is improved, but calculation amount increases and processing time becomes long
Solution Approach 1:
The patent extracts only the essential feature (peak position and its surrounding capacitance values) from the complete capacitance distribution, eliminating the need for comprehensive frequency spectrum analysis. This selective extraction maintains discrimination accuracy while dramatically reducing calculation complexity and processing time.
Solution Approach 2:
The patent performs preliminary identification of the peak position before conducting full analysis. By first locating the maximum capacitance point and then analyzing only the local distribution around this peak, the system prepares the data in advance for efficient evaluation, avoiding unnecessary processing of the entire capacitance map.
2Reliability
If a low threshold value is used for capacitance change detection, then weak contact detection is improved, but discrimination between finger and palm becomes difficult
Solution Approach 1:
The patent applies different evaluation criteria to different regions of the capacitance distribution. Instead of using a single global threshold, it analyzes the local capacitance values around the peak position with relative thresholding. This allows the system to detect weak contacts by examining local variations while maintaining discrimination accuracy through position-aware evaluation.
Solution Approach 2:
The patent employs dynamic thresholding where the threshold value is not fixed but adapts based on the detected peak position and local capacitance characteristics. This dynamic approach allows the system to adjust its sensitivity locally, detecting weak contacts in appropriate regions while maintaining robust discrimination between finger and palm contacts.
3Measurement precision
If a high threshold value is used for capacitance change detection, then discrimination between finger and palm is improved, but weak contact detection becomes difficult
Solution Approach 1:
The patent applies different evaluation criteria to different regions of the capacitance distribution. Instead of using a single global threshold, it analyzes the local capacitance values around the peak position with relative thresholding. This allows the system to detect weak contacts by examining local variations while maintaining discrimination accuracy through position-aware evaluation.
4Device complexity
If simple counting of sensor electrodes above threshold is used, then processing complexity is reduced, but discrimination accuracy between finger and palm decreases
Solution Approach 1:
The patent performs preliminary identification of the peak position before conducting full analysis. By first locating the maximum capacitance point and then analyzing only the local distribution around this peak, the system prepares the data in advance for efficient evaluation, avoiding unnecessary processing of the entire capacitance map.
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 enables accurate discrimination between finger and palm proximity with a simple process, improving the difference in evaluation values and reducing processing complexity, thus enhancing the accuracy of input device operations.
Implementation Method 1
a sensor unit configured to detect a degree of the proximity of the object at a plurality of detection positions on the detection surface, and generate detection data indicating a result of the detection
Data Source
AI summary
Threshold values smaller than degrees of proximity of an object indicated by detection data at peak positions are set based on detection data of the peak positions at which a degree of proximity of the object is higher than that of surrounding detection positions. An evaluation value according to an area of a region on a detection surface occupied by a group of detection positions, including the peak positions, in which degrees of proximity of the object indicated by detection data are higher than the threshold values, is calculated, and it is determined whether the object in proximity to the peak position is a finger or a palm based on the evaluation value.