Orthogonal Signal Stylus Sensor for Low Latency Touch
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Solution Overview
Problem
Existing user input systems face challenges in achieving low latency and high accuracy for detecting touch events and stylus inputs on capacitive touch surfaces, particularly in environments with noise interference and complex user interactions.
Innovation Solution
The system employs a fast multi-touch sensor with a projected capacitive method using orthogonal signals transmitted across rows and columns, combined with advanced signal processing techniques like frequency modulation and direct sequence spread spectrum modulation, to differentiate and filter touch events with low latency and high accuracy, and includes an active optical stylus for precise input detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional capacitive touch sensing methods are used, then the system can detect touch events, but the detection latency is high and accuracy is reduced in noisy environments
Solution Approach 1:
The system uses periodic transmission of orthogonal signals at different frequencies across row and column conductors, with synchronized sampling at specific phases. This periodic action enables continuous monitoring while maintaining low latency through regular update cycles, resolving the contradiction between continuous detection accuracy and response time.
Solution Approach 2:
The system changes signal parameters by using multiple orthogonal frequencies and modulation schemes (FSK, PSK, QAM) to encode touch information. By varying frequency, phase, and amplitude parameters, the system achieves high detection accuracy while maintaining fast response through efficient signal encoding that requires minimal processing time.
2Measurement precision
If multiple signals are transmitted simultaneously across the touch surface, then detection accuracy improves, but signal interference and noise increase
Solution Approach 1:
The system segments the touch surface into orthogonal row and column conductor sets, with each conductor transmitting or receiving distinct frequency-modulated signals. This segmentation allows simultaneous multi-signal transmission while maintaining signal integrity through spatial and frequency separation, reducing interference between signals.
Solution Approach 2:
The system uses orthogonal signaling as an intermediary mechanism where signals on row and column conductors are mathematically orthogonal (perpendicular in signal space). This orthogonality acts as a mediator that allows multiple signals to coexist without interference, as each signal can be independently extracted through correlation detection, eliminating cross-talk between simultaneous transmissions.
3Reliability
If advanced signal processing techniques are implemented, then detection accuracy and noise filtering improve, but system complexity increases
Solution Approach 1:
The system performs preliminary signal processing by pre-correlating received signals with expected orthogonal signal patterns before full detection. This preliminary action filters out noise and interference early in the processing chain, improving reliability while reducing the computational complexity of subsequent processing steps, as only correlated signals require further analysis.
4Measurement precision
If orthogonal signals with multiple frequencies are used, then multi-touch detection accuracy improves, but processing time increases
Solution Approach 1:
The system uses periodic sampling synchronized with the transmission frequencies of orthogonal signals. By sampling at regular intervals that align with signal periods, the system efficiently captures multi-touch information without requiring continuous processing, thus maintaining high detection accuracy while minimizing processing time through time-synchronized operations.
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 detection of touch events and stylus inputs with high accuracy, even in noisy environments, and allows for precise tracking of user interactions, including stylus tilt and rotation, while minimizing interference and improving user identification.
Implementation Method 1
capacitive sense array
Implementation Method 2
active optical stylus for precise input detection
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A stylus and touch sensitive device are disclosed. The stylus includes a stylus transmitter for transmitting a stylus signal. The touch sensitive device includes row conductors, each of which is associated with a row transmitter and a row receiver. The row transmitter is adapted to simultaneously transmit row signals, each on its associated row conductor, each of the row signals being orthogonal to each other of the plurality of row signals transmitted on each other of the row conductors. The row receiver is adapted to detect the stylus signal. Column conductors are provided, each associated with a column receiver that is adapted to detect the presence of each of the row signals transmitted by the row transmitter and the stylus signal.