Ultrasonic Shear Transducer Touch Detection
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Solution Overview
Problem
Capacitive-type touch sensing systems face challenges in distinguishing between touches and water droplets on surfaces, and they struggle with detecting touches on metal or thick surfaces, while force sensing systems fail to accurately detect water or liquids.
Innovation Solution
An ultrasonic touch sensing system that utilizes both compressional and shear waves to differentiate between touches and water, employing ultrasonic shear transducers to transmit waves through a sensing plate, where the absorption and reflection patterns of these waves allow for accurate detection of touches and water presence, regardless of surface type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If capacitive-type touch sensing is used, then ease of operation is improved, but measurement precision deteriorates when water droplets are present on the surface
Solution Approach 1:
The sensing system is segmented into multiple independent ultrasonic transducers distributed across the surface, each capable of independent wave transmission and reception. This segmentation allows the system to locally detect touches while being insensitive to water droplets, resolving the contradiction between ease of operation and measurement precision in wet conditions.
Solution Approach 2:
The patent replaces capacitive sensing (electrical field-based) with ultrasonic sensing (mechanical wave-based). This substitution fundamentally changes the detection mechanism from electrical capacitance changes to mechanical wave reflection analysis, enabling accurate touch detection without being affected by water droplets that interfere with capacitive sensing.
2Reliability
If force sensing is used, then reliability is improved for detecting actual touches, but adaptability deteriorates for detecting touches on thick or metal surfaces
Solution Approach 1:
The system changes the physical parameters of wave propagation by using ultrasonic waves with specific frequencies and modes (compressional and shear waves). This allows the sensing system to adapt to different surface materials and thicknesses, maintaining both reliability for touch detection and adaptability for thick or metal surfaces where force sensing fails.
Solution Approach 2:
The ultrasonic sensing system is designed to be universal across different surface types (glass, metal, thick materials) by utilizing wave propagation characteristics that are not dependent on surface flexibility or capacitance. This multi-functionality resolves the contradiction between reliability for touch detection and adaptability for various surface types.
3Measurement precision
If ultrasonic shear transducers are used to transmit both compressional and shear waves, then measurement precision is improved for differentiating touches and water, but device complexity increases
Solution Approach 1:
The ultrasonic shear transducer automatically generates both compressional and shear waves during operation without requiring separate transducers or complex external equipment. This self-service capability allows the system to achieve high measurement precision for differentiating touches and water while minimizing device complexity by utilizing the inherent multi-wave generation capability of the shear transducer.
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
The system effectively detects touches and water on various surfaces, including metal and thick surfaces, without being affected by water, providing accurate and reliable touch and water detection by measuring the amplitude of wave reflections at different time periods.
Implementation Method 1
an ultrasonic shear transducer can transmit a shear wave through a sensing plate
Implementation Method 2
can also generate a parasitic compressional wave as well
Implementation Method 3
the reflections of both the shear wave and the compressional wave can significantly decrease in amplitude
Data Source
AI summary
An ultrasonic touch sensing system that uses both compressional and shear waves for touch and water detection is disclosed. When no touch or water is present, less shear and compressional wave energy is absorbed, so both shear and compressional wave reflections do not have significant amplitude decreases. When a finger is in contact with the sensing plate, both shear and compressional wave energy is absorbed, so both shear and compressional wave reflections have significant amplitude decreases. When water is in contact with the sensing plate, compressional energy is absorbed but little or no shear wave energy is absorbed, so while compressional wave reflections have significant amplitude decreases, shear wave reflections do not. From these amplitudes, a determination can be made as to whether no touch is present on the sensing plate, whether a touch is present on the sensing plate, or whether water is present on the sensing plate.