Capacitive Sensor Patterns for Low-Latency Multi-Touch Detection
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Solution Overview
Problem
Current user input systems, particularly capacitive touch sensors, face challenges in achieving low latency and high accuracy due to interference and noise, which affect the reliability of touch event detection and user identification.
Innovation Solution
The implementation of a fast multi-touch sensor system using orthogonal signaling schemes, such as frequency-division multiplexing (FDM) and code-division multiplexing (CDM), along with noise reduction techniques like dynamic signal modulation and interference avoidance, to enhance signal-to-noise ratio and improve touch event detection and user identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional capacitive touch sensor patterns are used, then the sensor can detect touch events, but electromagnetic noise and interference reduce detection accuracy and reliability
Solution Approach 1:
The sensor pattern is divided into multiple independent conductive path segments arranged in orthogonal directions. Each segment acts as an independent signal carrier, allowing the system to segment the detection process and identify valid touch signals by checking for matching pairs of row and column segments, thereby filtering out electromagnetic noise that does not create matching pairs.
Solution Approach 2:
Different regions of the sensor pattern are assigned different functions: row segments transmit signals in one direction while column segments transmit in the orthogonal direction. This local differentiation allows the system to distinguish between genuine touch events (which affect both row and column segments) and electromagnetic noise (which typically affects only one direction), improving detection accuracy.
2Loss of time
If fast multi-touch detection is implemented, then touch response latency is reduced, but signal interference and noise increase
Solution Approach 1:
The sensor system uses periodic signal transmission along orthogonal conductive paths, where row and column segments alternately transmit signals in a coordinated manner. This periodic action enables fast sequential scanning of the entire sensor surface, reducing detection latency while the orthogonal arrangement ensures that interference from one transmission cycle does not corrupt the next, as each direction transmits at different times.
Solution Approach 2:
The system implements a feedback mechanism where the detection algorithm checks for matching signal pairs between row and column segments. Only when both a row segment and its corresponding column segment detect signals is a touch event confirmed. This feedback loop filters out false positives caused by signal interference, maintaining fast detection speed while improving reliability.
3Reliability
If orthogonal signaling schemes are used, then signal-to-noise ratio improves, but device complexity increases
Solution Approach 1:
The orthogonal conductive segments serve multiple functions: they act as signal transmission paths, noise filtering elements, and touch detection sensors simultaneously. Each row and column segment can both transmit signals and detect touches, eliminating the need for separate dedicated noise filtering components and reducing overall device complexity despite the sophisticated signaling scheme.
Solution Approach 2:
The patent merges the noise filtering function directly into the signal transmission paths by using the same orthogonal conductive segments for both purposes. Instead of adding separate filtering hardware, the system combines signal carriage and noise rejection into a unified orthogonal segment structure, improving signal-to-noise ratio without proportionally increasing 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
This approach enables low-latency and accurate detection of touch events with reduced noise interference, allowing for precise user input and identification, even in the presence of electromagnetic noise, thereby improving the overall performance of user input systems.
Implementation Method 1
Capacitive sensor patterns
Implementation Method 2
electromagnetic noise
Data Source
AI summary
Methods and devices for providing fast multi-touch sensors are disclosed. In an embodiment, a method is provided for design and manufacture of touch sensors for touch-sensitive devices. At least one behavioral quality is identified for the touch-sensitive devices. At least one parameter is selected, the parameter being associated with the composition or geometry of a stack of row conductors and column conductors on each of the touch sensors associated with the devices, the selection being based on the identified at least one behavioral quality. Multi-touch sensors are then manufactured by arranging a plurality of row conductors and a plurality of column conductors in a stack such that the stack or a component thereof has a geometry or composition that meets the at least one parameter. An orthogonal signal transmitter is provided for simultaneously transmitting each of a plurality of orthogonal row signals on a respective one of at least some of the plurality of row conductors. A detector is provided for detecting an amount of each of the plurality of orthogonal row signals present on each of the plurality of column conductors. Specific multi-touch sensors are also disclosed for hover applications, large screen applications, and others.