Capacitive Sensor System for Touchless Gesture Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing capacitive sensing systems face challenges in simultaneous multi-finger 2D touch detection, hover detection, and 3D position tracking due to high maximum delay in first-touch detection, reduced sensitivity, and noise susceptibility, particularly in time-multiplexing systems which compromise performance by alternating between 2D and 3D scanning modes.
Innovation Solution
A sensor system that combines drive signals for both 2D and 3D detection systems using a drive sequence of elementary acquisition cycles with alternating main phases, allowing continuous electrical measurements on nodes A and B, enabling seamless transition between touch, hover, and gesture detection without the limitations of time-multiplexing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If time-multiplexing is used between 2D touch detection and 3D gesture detection, then both detection functions can be provided by the same sensor system, but the maximum delay in first-touch detection increases significantly
Solution Approach 1:
The sensor system segments the detection space into two distinct operational modes: 2D touch detection mode for contact events and 3D gesture detection mode for hover events. By segmenting the detection functions and assigning dedicated time slots to each mode, the system eliminates the multiplexing delay that previously affected touch detection response time.
Solution Approach 2:
The system dynamically switches between 2D and 3D detection modes based on real-time detection needs. When a touch event is detected, the system transitions to 2D-only mode for immediate response; otherwise, it operates in 3D scanning mode for gesture detection, optimizing performance for each operational state.
2Adaptability or versatility
If time-multiplexing alternates between 2D and 3D scanning modes, then a single sensor system can perform multiple detection tasks, but the received signal energy and measurement sensitivity are reduced
Solution Approach 1:
The system performs preliminary detection in 3D mode to identify hover gestures before they become full touches. By detecting the approaching object in advance and transitioning to 2D mode upon touch detection, the system maximizes signal energy utilization for each detection phase without compromising overall sensitivity.
3Device complexity
If time-multiplexing is used to share sensor channels between 2D and 3D detection, then device complexity is reduced, but noise suppression capability deteriorates
Solution Approach 1:
The system implements periodic scanning cycles with distinct 2D and 3D detection phases. Each mode operates continuously during its assigned time slot with consistent signal characteristics, enabling effective digital filtering and noise suppression while maintaining a unified sensor hardware structure.
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 eliminates additional delay in first-touch detection, enhances sensitivity and noise robustness, and allows for continuous data acquisition, enabling reliable near-distance hover detection and mid-range position estimation with improved signal-to-noise ratio and reduced electromagnetic emission.
Implementation Method 1
The gesture detection unit's measurement value, among others, depends on the position of a target object (finger/hand) in the sensor electrode's vicinity which influences the capacitive coupling between electrode and target, yielding a target measurement signal depending on the distortion of the alternating electric field.
Implementation Method 2
a highly sensitive capacitive sensing technology used for non-touching gesture detection using an alternating electric near field, for example around 40-250 kHz
Data Source
AI summary
A sensor system combining first and second detection systems supplies drive signals to nodes A and B electrodes of these systems. A drive sequence consists of a repetition of an elementary acquisition cycle having two consecutive main phases with pre-charge and acquisition phases. During a first pre-charge phase, node A is driven to a first electrical potential for and during a first acquisition phase, to a first intermediate electrical potential, and node B is driven to a second electrical potential and thereafter switches node B into high-impedance at DC, and during a second pre-charge phase, node A is driven to a third electrical potential and, during a second acquisition phase, to a second intermediate electrical potential, and node B is driven to a fourth potential and thereafter switches node B into high-impedance at DC. The first and second detection systems perform an electrical measurement on node A and B, respectively.