Visualization of airborne ultrasound field using thermal images

TL;DR

This paper demonstrates that thermal imaging can visualize airborne ultrasound fields in real-time, enabling precise localization of acoustic focus and advancing applications like mid-air haptics and acoustic levitation.

Contribution

It introduces a novel method using thermal images to visualize airborne ultrasound fields, achieving high-resolution acoustic measurements beyond traditional techniques.

Findings

Thermal responses to airborne ultrasounds can be used for acoustic visualization.

Thermography enables real-time 3D visualization of ultrasound fields.

The method allows precise determination of ultrasound focus position.

Abstract

Thermoacoustics, the interaction between heat and acoustic waves, is used in a wide range of advanced technological applications. Conversion of ultrasound waves into heat is employed in medical applications, including tumor ablation. However, thermal responses to airborne ultrasounds have not been extensively studied. Herein, we show that thermal responses to high-intensity airborne ultrasounds above 1000 Pa can be used for acoustic measurements. Thermal images on a mesh screen enabled the real-time visualization of three-dimensional acoustic fields. Based on the temperature distribution on a surface that reflects ultrasound waves, it was possible to determine the ultrasound focus position with a resolution much finer than the wavelength. Our results demonstrate that thermography observations based on ultrasound-temperature conversion can be used to visualize acoustic fields, which are conventionally difficult to observe. Our findings will advance technologies that use strong airborne ultrasound, such as mid-air haptics and acoustic levitation, and provide new scientific and technical tools for detecting surface properties and composition, including cells and fragile materials.