3D Touch Sensing System with Oscillating Plane for Extended Distance
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Solution Overview
Problem
Current capacitive touch sensing systems are limited in their ability to detect three-dimensional touch inputs at distances greater than 20-30 cm due to sensitivity issues with small capacitive perturbations and suffer from ghost effects during multi-touch interactions, which restricts their effectiveness in large-area interactive spaces.
Innovation Solution
A three-dimensional touch sensing system that incorporates a plurality of capacitive touch sensing electrodes with an oscillating plane below the touch surface, using frequency modulation to detect changes in capacitance and determine distance and location, and employs high-Q oscillators to filter noise, reducing electrostatic coupling and enhancing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If self-capacitance sensing is used to extend sensing distance, then sensing distance is improved, but ghost effects occur during multi-touch
Solution Approach 1:
The system divides the sensing function into two independent parts: self-capacitance sensing for distance detection and mutual-capacitance sensing for multi-touch detection. This segmentation allows each sensing mode to operate optimally without interfering with the other, resolving the ghost effect problem while maintaining extended sensing distance capability.
Solution Approach 2:
The system uses an intermediary processing stage that separates and independently processes signals from self-capacitance and mutual-capacitance sensing channels. This intermediary processing allows the system to combine the advantages of both sensing methods while eliminating their respective drawbacks, particularly the ghost effects in multi-touch scenarios.
2Device complexity
If traditional capacitive sensing is used, then device complexity is reduced, but sensing distance is limited to less than 20-30 cm
Solution Approach 1:
The system implements a universal sensing platform that integrates both self-capacitance and mutual-capacitance sensing capabilities within a single touch sensor structure. This multi-functional design enables the system to achieve extended sensing distances of 20-30 cm while maintaining relatively simple device architecture and avoiding the need for completely separate sensing systems.
3Measurement precision
If sensing sensitivity is increased to detect small capacitive perturbations, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The system employs periodic scanning of the electrode array combined with signal integration over multiple measurement cycles. This periodic action allows the system to accumulate weak capacitive signals over time, improving measurement precision for small perturbations while keeping the sensing electrodes in a low-power state between measurements, thus controlling overall power consumption.
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 system achieves extended sensing distances of up to 30 cm with high signal-to-noise ratio and accurate touch detection, reducing power consumption and electrode channel requirements, while minimizing ghost effects and electrostatic interference.
Implementation Method 1
An oscillating plane is disposed below the touch surface... drive the oscillating plane to the touch frequency
Implementation Method 2
each electrode having a baseline capacitance and a touch capacitance based on the touch input
Implementation Method 3
sensing the small capacitive perturbations caused by user interaction with sensing electrodes
Implementation Method 4
An inductive loop may be coupled to the capacitance-to-frequency conversion circuitry, the frequency-readout IC being inductively coupled to the inductive loop
Data Source
AI summary
A three dimensional touch sensing system having a touch surface configured to detect a touch input located above the touch surface is disclosed. The system includes a plurality of capacitive touch sensing electrodes disposed on the touch surface, each electrode having a baseline capacitance and a touch capacitance based on the touch input. An oscillating plane is disposed below the touch surface. A touch detector is configured to drive one of the touch sensing electrodes with an AC signal having a frequency that shifts from a baseline frequency to a touch frequency based on the change in electrode capacitance from the baseline capacitance to the touch capacitance. The touch detector is configured to drive the oscillating plane to the touch frequency.