Ultrasound lens made of vibrating plate and perforated acoustic mask

What is it about?

This paper is on a new focusing method of midair ultrasound that are formed using a single planar plate in a flexural vibration mode, whose surface is partially covered with a planar ‘mask’ that was designed according to the spatial distribution of vibration phases on the plate and the position of the midair ultrasound focus to be created. Strong midair focusing of ultrasound has been utilized in many applications. However, conventional focusing methods, such as use of transducer phased array or fabrication of meta-surfaces, are expensive and/or difficult to implement, especially for creating a wide ultrasound emitting aperture that would allow application scenarios of midair focused ultrasound to be upsized to a whole-room scale. Our proposed method only requires a single metallic plate, a solid vibrator attached under it, and a newly designed amplitude mask that enables the surface ultrasound emission over the plate to be converted into a focus at a specific position. The designing procedure of the mask we derived in this paper is very simple and fabrication of the mask is readily and affordably done via laser-machining of an acrylic plate. We fabricated a prototype focusing system and experimentally assessed its focusing performance, which showed successful ultrasound energy convergence around the designated focusing region with its spatial tract limited within a couple of wavelength in air.

Featured Image

Photo by Pawel Czerwinski on Unsplash

Photo by Pawel Czerwinski on Unsplash

Why is it important?

All components in our method can be kept thin and easily widened in principle with no extreme additional expenditure, which we potentially believe to be a key technology to expedite the practical use of midair ultrasound in realistic application scenarios. Our method is available and open for many specialists, who do not have access to expensive and complicated conventional ultrasound-focusing devices such as phased array systems.

Perspectives