Ultrasonic Touch Detection on Metal Surfaces
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Solution Overview
Problem
Current touch input detection technologies, such as capacitive, resistive, and inductive sensing, face challenges in creative industrial design due to limitations in touch input layout, system stack-up, and compatibility with metal surfaces, as well as reliability and waterproofing issues, particularly in detecting touch inputs on metal surfaces and in environments where mechanical switches are not suitable.
Innovation Solution
An ultrasound input device is used to detect touch inputs by positioning a sensor on the reverse side of the surface material, allowing for creative design implementations on various surfaces including metal, wood, glass, and leather, and enabling detection of specific objects like gloved fingers, with integrated analog and digital circuits for small form factor and low power operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitive sensing is used to detect touch inputs, then touch detection capability is improved, but compatibility with metal surfaces deteriorates and design flexibility is limited
Solution Approach 1:
The patent replaces capacitive sensing (electrical field-based) with ultrasonic sensing (acoustic wave-based). The ultrasonic transducer emits acoustic waves that interact with the touch surface and object, enabling detection on metal surfaces where capacitive sensing fails due to electrical conductivity interference.
Solution Approach 2:
The patent changes the detection parameter from electrical capacitance to acoustic wave properties (reflection, absorption, transmission). By measuring changes in ultrasonic wave characteristics when an object touches the surface, the system achieves both metal surface compatibility and accurate touch detection.
2Reliability
If mechanical switches are used for touch input, then reliability is improved, but aesthetic appearance and design flexibility deteriorate
Solution Approach 1:
The patent replaces mechanical switches with an ultrasonic sensing system that detects touch through acoustic wave interactions. This eliminates visible mechanical components while maintaining reliable touch detection, as the ultrasonic transducer can be positioned behind the surface material.
Solution Approach 2:
The patent moves the sensing mechanism to another dimension by positioning the ultrasonic transducer behind the surface material rather than on the visible face. This allows the surface to maintain its aesthetic appearance while the hidden transducer performs reliable touch detection.
3Measurement precision
If additional sensing layers are added to detect touch position, then touch position detection capability is improved, but device complexity and cost deteriorate
Solution Approach 1:
The patent makes the ultrasonic transducer multi-functional by enabling it to detect both the presence of touch and the position of the touched object using the same sensing layer. By analyzing the time-of-flight and reflection characteristics of ultrasonic waves, the system determines touch position without requiring additional capacitive layers.
4Measurement precision
If sensor is positioned on the visible surface, then touch detection accuracy is improved, but aesthetic appearance and environmental exposure deteriorate
Solution Approach 1:
The patent positions the ultrasonic transducer in another dimension - behind the surface material rather than on the visible surface. The transducer acoustically couples to the surface through the material, maintaining detection accuracy while being protected from environmental factors and hidden from view.
Solution Approach 2:
The surface material itself acts as an intermediary, transmitting ultrasonic waves from the hidden transducer to the touch interface. This allows the transducer to remain protected behind the surface while still accurately detecting touches through the mediating material layer.
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 ultrasound input device enhances aesthetic and reliability features over capacitive and mechanical devices, providing flexible programmability, hidden input capabilities, and extended battery life, while enabling multiple touch input detection and integration into IoT devices for local or remote network communication.
Implementation Method 1
The sensor can be a piezoelectric micromachined ultrasonic transducer
Implementation Method 2
A method to detect a touch input on a surface of an object can include emitting an ultrasonic signal toward the surface of the object, and detecting a reflected signal from the ultrasonic signal using the sensor
Data Source
AI summary
Touch events can be detected using an ultrasound input device coupled to a surface, such as a surface of a piece of furniture or electronic device. The ultrasound input device can generate ultrasonic waves in the surface, the reflections of which can be measured by the ultrasound input device. When a touch is made to the surface (e.g., opposite the ultrasound input device), the physical contact can absorb some of the energy of the outgoing ultrasonic waves (e.g., the originally transmitted wave and any subsequent outgoing reflections). Energy measurements associated with the measured reflections can thus be used to identify touch events. Various techniques can be used to make the energy measurements and reduce identification of false touch events.