Acoustic Touch Sensor Multi-Touch Coordinate Resolution
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Solution Overview
Problem
Acoustic touch sensors face difficulties in accurately determining the coordinates of multiple simultaneous touches due to insufficient clear coordinate information, leading to ambiguity in matching X and Y coordinates, especially as the number of touches increases.
Innovation Solution
The implementation of a touch sensor design that utilizes sets of two to four signals providing time delay information perpendicular to the acoustic path, allowing for rough measurement of coordinates and separating overlapping shadows by identifying minimum width linear combinations of signals, thereby resolving the ambiguity issue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional acoustic touch sensors use only two transducers per coordinate axis, then the device complexity is reduced, but the measurement precision of multi-touch coordinates deteriorates due to insufficient clear coordinate information
Solution Approach 1:
The patent segments the coordinate determination process by using multiple signal sets (two to four signals) per coordinate axis, where each signal provides time delay information for a specific direction. This segmentation allows the system to resolve coordinate ambiguity without requiring a proportional increase in total transducer count, thereby maintaining device complexity while improving measurement precision for multi-touch detection.
Solution Approach 2:
The patent introduces an additional dimension of measurement by utilizing signals that provide time delay information perpendicular to the acoustic path through the touch area. This dimensional approach enables the system to separate overlapping touch shadows and resolve coordinate ambiguities, improving multi-touch precision without simply adding more transducers in the traditional sense.
2Adaptability or versatility
If acoustic touch sensors process multiple simultaneous touches, then the adaptability of the touch system is improved, but the difficulty of detecting and measuring coordinates increases due to overlapping shadows and false associations
Solution Approach 1:
The patent introduces intermediate processing steps that use multiple signal sets to create redundant coordinate information. These intermediate measurements serve as mediators that help resolve the ambiguity of overlapping touch shadows, making the detection and measurement process more manageable even as multi-touch capability increases.
Solution Approach 2:
The patent changes the parameters used for coordinate detection by utilizing time delay information from multiple signal sets rather than relying on a single measurement approach. This parameter change enables the system to distinguish between overlapping touches by analyzing variations in time delay patterns, thereby reducing detection difficulty while maintaining multi-touch adaptability.
3Reliability
If the substrate thickness is increased to allow surface acoustic wave propagation, then the acoustic touch sensor functionality is enabled, but the device becomes less suitable for modern bezel-less designs
Solution Approach 1:
The patent changes the substrate thickness parameter to optimize both acoustic wave propagation and aesthetic design requirements. By carefully selecting and adjusting the thickness parameter, the system maintains reliable surface acoustic wave propagation while achieving thinner substrates that are compatible with modern bezel-less device designs.
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 precise determination of coordinates for multiple touches, reducing the risk of false associations and improving the accuracy of multi-touch recognition, even with three or more simultaneous touches.
Implementation Method 1
a first transmitting transducer generates surface acoustic waves
Implementation Method 2
The first reflective array is adapted to reflect portions of a surface acoustic wave perpendicularly across the substrate along plural parallel paths
Implementation Method 3
Touching the substrate surface at a point causes a loss of energy by the surface acoustic waves passing through the point of touch. This is manifested as an attenuation of the surface acoustic waves.
Implementation Method 4
Detection circuitry associated with each receiving transducer detects the attenuation as a perturbation in the surface acoustic wave signal
Data Source
Figure 1
Figure 2
Figure 3a
AI summary
An acoustic touch apparatus that utilizes the transfer of surface acoustic waves from one surface, through the touch substrate, to another surface to enable multi-touch capabilities.