Radial Acoustic Wave Touch Sensor Multi-Touch Ambiguity
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Solution Overview
Problem
Conventional surface acoustic wave touch sensors face ambiguity in detecting multiple simultaneous touches, as they often incorrectly associate X and Y attenuation coordinates, leading to unclear identification of touch locations.
Innovation Solution
The implementation of a touch sensor system that utilizes radial transducers to generate and receive surface acoustic waves with a divergent pattern of at least 20°, allowing for accurate detection of touch points by analyzing attenuation angles and patterns across a radial touch region, eliminating ambiguity through a combination of radial and linear transducer arrays and reflective arrays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional linear transducers are used to generate surface acoustic waves, then the device structure is simple, but multiple simultaneous touches cannot be correctly located due to ambiguity in associating X and Y attenuation coordinates
Solution Approach 1:
The patent transitions from conventional linear transducer arrays operating in orthogonal X and Y dimensions to radial transducers that operate in angular dimensions. By generating acoustic waves that propagate radially outward at different angles, the system adds an angular dimension to touch detection, enabling unambiguous identification of multiple simultaneous touch locations through angle-of-arrival measurement at the receive transducer.
Solution Approach 2:
The patent divides the acoustic wave generation into multiple discrete radial transducers positioned at different angular locations around the touch surface. Each transducer generates waves at a specific angle, and the receive transducer segments the incoming wavefronts by their arrival angles, allowing precise localization of multiple touches through angular segmentation of the detection space.
2Reliability
If radial transducers with divergent wave patterns are used, then multiple simultaneous touches can be accurately detected, but the device complexity increases
Solution Approach 1:
The radial transducer design serves multiple functions simultaneously: it generates surface acoustic waves, defines angular propagation directions, and enables multi-touch detection through its divergent wave pattern. The receive transducer similarly performs multiple functions by detecting waves from multiple angles and determining both the presence and location of multiple simultaneous touches, reducing the need for separate detection mechanisms.
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 touch locations even with multiple simultaneous touches, enhancing the accuracy and reliability of touch detection without the need for additional information or guessing, by using a radial wave pattern that covers the entire touch surface effectively.
Implementation Method 1
A piezoelectric element 30 mounted on the top back surface (also referred to as a first surface) of the wedge generates bulk pressure acoustic waves
Implementation Method 2
surface acoustic waves, represented by ray 5, are generated that propagate across the touch substrate 10
Implementation Method 3
Transmit reflective arrays proximate the edges of the touch substrate and spaced along the axes reflect the transmitted surface acoustic waves
Implementation Method 4
When a touch occurs on the touch surface, the touch causes attenuation of the surface acoustic waves at corresponding locations along the two axes, X and Y
Data Source
AI summary
Surface acoustic waves in a radial pattern are used to detect touch. Different radial transducer arrangements may allow for locating multiple simultaneous touches without ambiguity. Instead of transmitting along a line to be reflected at multiple points, the surface acoustic waves are transmitted radially. The surface acoustic waves are transmitted along different angles in an angular span spread out over at least part of the touch region. Using acoustic waves traveling along intersecting paths, a point location of a touch may be determined by detection, in part, of at least one angle.