Composite Trapezoidal Capacitive Sensor for Narrow Pen Detection
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Solution Overview
Problem
Capacitive touch sensors with rhombus-shaped elements face challenges in detecting narrow pen touches due to increased coplanar capacitance and reduced Signal-to-Noise Ratio (SNR) when the number of elements is increased to reduce the short diagonal length.
Innovation Solution
Employing a capacitance detection sensor composed of composite trapezoidal shapes that allow detection of vertical pen touch movements without increasing the number of detection sensors, using a Primary Shape CDA with vertically stacked Secondary Shape CDAs formed by combining two trapezoids and applying alternating voltages through Voltage Forcing Lines (VFLs) to detect object capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of rhombus-shaped detection elements is increased to reduce the short diagonal length for detecting narrow pen touches, then the detection capability for narrow touches is improved, but the coplanar capacitance increases and the Signal-to-Noise Ratio (SNR) decreases
Solution Approach 1:
The detection sensor is divided into multiple sub-shapes (first sub-shape, second sub-shape, third sub-shape, fourth sub-shape) that collectively form the composite trapezoidal shape. Each sub-shape contributes to the overall detection capability while maintaining lower individual coplanar capacitance values, thereby improving narrow touch detection without sacrificing SNR.
Solution Approach 2:
The patent employs a composite trapezoidal shape with asymmetric configuration of sub-shapes rather than symmetric rhombus shapes. The first and second sub-shapes have different orientations and positions relative to the third and fourth sub-shapes, creating an asymmetric layout that optimizes the detection of vertical pen touch movements while controlling coplanar capacitance.
2Measurement precision
If the number of detection sensors is increased to detect vertical pen touch movements, then the detection precision for vertical coordinates is improved, but the device complexity and coplanar capacitance increase
Solution Approach 1:
The patent achieves vertical coordinate detection by utilizing the asymmetric spatial arrangement of sub-shapes within the composite trapezoidal sensor, rather than stacking multiple sensors vertically. The differential capacitance changes across the asymmetric sub-shape configuration enable vertical position detection while maintaining a single-layer sensor structure, thus avoiding increased device complexity.
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
Enhances touch sensitivity and improves SNR by accurately detecting vertical coordinates without increasing the number of sub-CDAs, thereby reducing errors and maintaining detection precision.
Implementation Method 1
capacitance detection sensor composed of a composite trapezoid... detects changes in capacitance that occur when an object (e.g., a finger or pen) approaches (e.g., hovers) or touches the surface
Data Source
AI summary
The present invention relates to a capacitive touch input device utilizing the capacitive sensing method for detecting touch inputs from a finger or a similar conductive object. More specifically, it pertains to a capacitance detection device designed to facilitate the detection of touch coordinates based on the vertical movement of a pen by employing a capacitive detection sensor composed of a composite trapezoidal shape.