Capacitive Position Detection Circuit for Finger-Palm Touch Discrimination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing position detection systems fail to accurately differentiate between intended and unintended touches, particularly when a user's hand slowly approaches a touch panel, leading to unintended operation results.
Innovation Solution
A position detection circuit that utilizes a capacitance system to calculate a total value of capacitance values in a calculation region surrounding a touch region, comparing this value to a threshold to determine whether the touch is made by a finger or a larger object like a palm, and only outputs the position when the total value is within a predetermined range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the touch region area threshold is used to invalidate touches, then large-area touches (palm) are invalidated, but small-area touches at the beginning of hand approach are mistakenly invalidated
Solution Approach 1:
The patent divides the touch detection into multiple evaluation stages: first evaluating touch region area, then evaluating capacitance value changes over time. This segmentation allows the system to handle different touch types (finger vs palm) at different stages of hand approach, preventing premature invalidation while maintaining accurate differentiation.
Solution Approach 2:
The patent performs preliminary evaluation of touch region area to identify potential touches, then applies additional capacitance-based validation. This preliminary action filters out obvious palm touches early while preserving finger touches that may initially appear small, allowing the system to make more informed decisions about touch validity.
2Adaptability or versatility
If the touch region area is used for touch validation, then palm touches are detected as invalid, but the system cannot distinguish between intentional small touches and unintended contacts
Solution Approach 1:
The patent changes the evaluation parameter from static touch region area to dynamic capacitance value changes over time. By monitoring how capacitance values change during the touch event, the system can distinguish between intentional finger touches (with specific capacitance change patterns) and unintended contacts, improving both adaptability and reliability.
Solution Approach 2:
The patent uses feedback from capacitance value changes to validate or invalidate touch inputs. The system continuously monitors capacitance changes and uses this feedback to determine whether a touch should be recognized, allowing for more accurate differentiation between intended and unintended touches based on the temporal pattern of capacitance changes.
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 effectively suppresses unintended operation results by accurately distinguishing between finger and palm touches, ensuring that only intended inputs are recognized and processed.
Implementation Method 1
a touch sensor of a capacitance system
Data Source
AI summary
A position detection circuit for detecting, by using a touch sensor, a position indicated by a passive pointer to a touch surface disposed on the touch sensor. The position detection circuit includes a detection circuit that detects a touch of the passive pointer to the touch surface, a calculation circuit that calculates a total value of capacitance values in a calculation region surrounding at least part of a touch region indicating a region of the touch, and an output circuit that outputs an indicated position that is indicated by the touch, based on the total value of the capacitance values. The output circuit outputs the indicated position when the total value is equal to or less than a threshold value, and does not output the indicated position or invalidates the indicated position and outputs the indicated position that has been invalidated, when the total value exceeds the threshold value.