Lamb Wave Multitouch Ultrasonic Touchscreen

Abstract

Touchscreen sensors are widely used in many devices such as smart phones, tablets, and laptops with diverse applications. We present the design, analysis, and implementation of an ultrasonic touchscreen system that utilizes the interaction of transient Lamb waves with objects in contact with the screen. It attempts to improve on the existing ultrasound technologies, with the potential of addressing some of the weaknesses of the dominant technologies, such as the capacitive or resistive ones. Compared with the existing ultrasonic and acoustic modalities, among other advantages, it provides the capability of detecting several simultaneous touch points and also a more robust performance. The localization algorithm, given the hardware design, can detect several touch points with a very limited number of measurements (one or two). This in turn can significantly reduce the manufacturing cost.

Ultrasonic Touch Sensing System Based on Lamb Waves and Convolutional Neural Network

“…Existing ultrasound touchscreens generally utilize surface acoustic waves (SAWs) for tactile sensing [1][2][3]. However, in recent years, the feasibility of using Lamb waves (or plate waves) to realize touchscreens on solid plates has gained increasing attention [4][5][6][7][8][9][10][11][12]. Depending on how the wave energy is generated, Lamb-wave-based touchscreens can be classified as either passive or active.…”

“…However, while such devices have the advantages of structural and operational simplicity, they cannot operate for a still finger touch on the plate. In active Lamb-wave touchscreens [7][8][9][10][11][12], the Lamb waves are typically generated and detected by piezoelectric transducers, which are attached to the plate and constantly excited by an electrical signal [13,14]. Both anti-symmetrical modes [7][8][9] and symmetrical modes [10][11][12] of Lamb waves had been applied.…”

“…In active Lamb-wave touchscreens [7][8][9][10][11][12], the Lamb waves are typically generated and detected by piezoelectric transducers, which are attached to the plate and constantly excited by an electrical signal [13,14]. Both anti-symmetrical modes [7][8][9] and symmetrical modes [10][11][12] of Lamb waves had been applied. For anti-symmetrical modes, the waves were excited by attaching piezoelectric transducers on the planar surfaces of the plate [7][8][9]13,14].…”

Virtual Touch Sensor Using a Depth Camera

“…However, the price of a device using capacitive sensing increases as a panel size increases, since the touch interface device should be combined with the panel. Instead of the capacitive sensing method, methods using an infrared sensor [8,9,10] and an ultrasonic sensor [11,12,13] can be used to detect touch on a large screen. In the touch detection methods using infrared sensors, infrared emitter sensors attached to the screen emit infrared rays and then infrared detection sensors on the opposite side detect the infrared rays.…”

Localization of weak objects in reverberant fields using waveform inversion

“…In reverberant fields, training or learning have widely been applied in different contexts such as localization and classification of defects and flaws in solid substrates, 14 localization of tactile objects in contact with a plate, 5,6,15,16 and localization by probabilistic pattern recognition. 17 In training methods, generally the system is looked at as a black box and any (a posteriori) measured data is matched with a set of a priori measured data.…”