Orthogonal Signaling Touch Discrimination for Multi-User Input
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Solution Overview
Problem
Current user input systems face challenges in accurately distinguishing between touch points generated by different hands, users, or objects on a touch surface, particularly in fast multi-touch sensors, leading to issues with noise reduction and interference.
Innovation Solution
The implementation of an orthogonal signaling touch user, hand, and object discrimination system that uses capacitive touch sensors with multiplexing schemes like frequency-division multiplexing (FDM), code-division multiplexing (CDM), or hybrid modulation techniques to differentiate between touch events by transmitting orthogonal signals on rows and receiving them on columns, allowing for precise identification of touch sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional touch sensing methods are used, then touch detection is achieved, but discrimination between different users, hands, and objects is insufficient
Solution Approach 1:
The patent segments the touch sensing problem by analyzing different signal characteristics (capacitive coupling patterns, signal strength, frequency responses) to distinguish between different touch sources. By dividing the discrimination task into multiple measurable parameters, the system can identify whether touches come from the same user, different hands, or different objects without requiring a completely new sensing architecture.
Solution Approach 2:
The patent changes multiple signal parameters simultaneously (capacitive coupling strength, signal frequency, phase relationships) to create a multidimensional signature for each touch source. By monitoring how these parameters change across different touch scenarios, the system achieves accurate discrimination while using existing sensor hardware, thus improving measurement precision without proportionally increasing device complexity.
2Speed
If fast multi-touch sensing is implemented, then response speed is improved, but noise interference and signal discrimination become more difficult
Solution Approach 1:
The patent employs feedback mechanisms where the system continuously monitors signal characteristics from multiple touches and adjusts its discrimination algorithms in real-time. By using feedback from capacitive coupling patterns and signal strength variations, the system can filter noise more effectively during fast multi-touch events, maintaining high response speed while reducing the impact of interference through adaptive signal processing.
Solution Approach 2:
The patent performs preliminary analysis of signal characteristics by examining capacitive coupling patterns and frequency responses before final touch identification. This preliminary action allows the system to pre-filter noise and establish baseline signatures for different touch sources, enabling faster and more accurate discrimination during subsequent high-speed multi-touch events without compromising response time.
3Measurement precision
If orthogonal signaling with multiplexing is used, then touch point discrimination is enhanced, but system complexity increases
Solution Approach 1:
The patent makes existing sensor components multi-functional by using the same capacitive touch sensor array to perform both traditional touch detection and advanced discrimination functions. The orthogonal signaling approach allows the system to extract multiple types of information (touch location, user identity, hand identification, object recognition) from a single sensor infrastructure, enhancing discrimination capability without proportionally increasing hardware complexity.
Solution Approach 2:
The patent introduces signal processing intermediaries (capacitive coupling analysis, frequency domain transformations) that mediate between the raw sensor signals and final touch identification. These intermediary processing steps decode the orthogonal signaling patterns into meaningful discrimination data, enabling enhanced touch point discrimination while keeping the physical sensor system relatively simple by performing complex analysis in the signal domain rather than requiring additional physical sensors.
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 efficient discrimination between touch points, reduces noise interference, and maintains high signal integrity, allowing for accurate and fast multi-touch input processing with low latency.
Implementation Method 1
capacitive touch sensors with multiplexing schemes
Data Source
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AI summary
A system and method for distinguishing between sources of simultaneous touch events on a touch sensitive device are disclosed. The touch sensitive device includes row conductors and column conductors, the path of each of the row conductors crossing the path of each of the column conductors. Orthogonal row signals are generated on the row conductors and orthogonal column signals are generated on the column conductors. In an embodiment, an amount of each of the plurality of orthogonal row signals present on each of the plurality of row conductors is detected, an amount of each of the plurality of orthogonal column signals present on each of the plurality of column conductors is detected, and at least one of such amounts is used to associate each of the plurality of simultaneous touch events with a discrete source. The strength of such detected "crosstalk" between row conductors can be used to distinguish two or more touch events, such as by distinguishing a two-handed gesture from a one-handed gesture, distinguishing two touch events as having been initiated by different users, distinguishing a passive object from a hand, identifying a passive object, improving palm rejection and improving accidental-touch rejection.