Projected Capacitive Touch Sensor Low-Latency Detection

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current user input systems face challenges in providing low-latency touch detection and distinguishing multiple simultaneous touch events on transparent surfaces while maintaining robustness and cost-effectiveness.

Innovation Solution

A projected capacitive touch sensor system using orthogonal sinusoidal signals transmitted across rows and columns, with receivers measuring signal coupling to detect touch events and determine touch location, area, and pressure, employing modulation techniques to reduce interference and enable low-latency, high-update-rate performance on transparent display surfaces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If orthogonal sinusoidal signals are transmitted simultaneously across rows and columns, then multiple simultaneous touch events can be detected and distinguished, but signal interference and noise increase

Engineering Contradiction:

Improvecapability to detect multiple simultaneous touch eventsVSAvoidsignal interference and noise

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent segments the touch detection process by assigning unique orthogonal sinusoidal signals to different row and column electrodes. Each touch event is detected by measuring the coupling capacitance between specific row and column electrodes, effectively segmenting the detection of multiple simultaneous touches into independent measurement channels that can be processed separately.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs parameter changes by using orthogonal sinusoidal signals with different frequencies for different electrodes. This frequency differentiation allows the system to distinguish between signals from different electrodes even when multiple touches occur simultaneously, reducing signal interference through frequency-domain separation.

Inventive Principle:

Principle #35Parameter changes

2Speed

If high-frequency signals are used for fast touch detection, then update rate increases and latency decreases, but susceptibility to noise and interference increases

Engineering Contradiction:

Improvetouch detection speed and update rateVSAvoidnoise and interference susceptibility

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The patent uses periodic sinusoidal signals at carefully selected frequencies to drive the electrodes. This periodic action allows for synchronous detection techniques where the measurement system is tuned to the specific frequencies of interest, enabling fast detection while filtering out non-synchronous noise and interference through frequency selectivity.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent implements feedback by continuously monitoring the coupling capacitance between electrodes and using this information to determine touch events. The system measures the amplitude and phase of the received signals, providing feedback that enables real-time detection and discrimination of multiple touches while maintaining robustness against noise through signal processing.

Inventive Principle:

Principle #23Feedback

3Illumination intensity

If transparent conductive materials are used for electrodes on display surfaces, then visual appearance is improved, but manufacturing complexity and cost increase

Engineering Contradiction:

Improvetransparency of display surfaceVSAvoidmanufacturing complexity and cost

Core Design Contradiction:

Illumination intensityVSEase of manufacture

Solution Approach 1:

The patent uses transparent conductive materials that serve multiple functions: they act as electrodes for capacitive touch sensing while simultaneously maintaining the visual transparency of the display surface. This multi-functionality eliminates the need for separate transparent electrode layers and opaque conductive traces, simplifying manufacturing and reducing cost while achieving both transparency and touch detection capabilities.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

Enables detection of multiple simultaneous touch events with low latency (less than one millisecond) and provides sensitive, robust measurements, suitable for transparent display surfaces, while minimizing interference and allowing for economical manufacturing.

Implementation Method 1

A touch applied to a given node of the panel changes a capacitive coupling between a given drive and sense electrode of the touch panel

Methodology Applied

Scientific EffectCapacitive coupling: Capacitance

Data Source

PatentEP2972702B1Low-latency touch sensitive device

Publication Date: 2021.05.26 TACTUAL LABS CO

Figure 1
Figure 2

AI summary

Disclosed are a sensor and method that provide detection of touch events from human fingers on a two-dimensional manifold with the capability for multiple simultaneous touch events to be detected and distinguished from each other. In accordance with an embodiment, the touch events are detected, processed and supplied to downstream computational processes with very low latency, i.e. on the order of one millisecond or less. Disclosed is a projected capacitive method that has been enhanced for high update rate and low latency measurements of touch events. The technique can use parallel hardware and higher frequency waveforms to gain the above advantages. Also disclosed are methods to make the measurements sensitive and robust, allow the technique to be used on transparent display surfaces and permit economical manufacturing of products which employ the technique.