Article
Seeing Sound: Visualising Ultrasonic Pressure Fields with Schlieren for Acoustic Levitation (en)
* Presenting author
Abstract:
Acoustic levitation employs ultrasonic pressure fields to levitate multiple objects independentlyin a 3D volume, providing a multitude of (potential) applications like volumetric displays and electronicassembly processes. However, accurately observing the ultrasound field remains a challenge,as conventional microphone measurements are time-consuming and prone to distorting the assessedfields. Schlieren imaging provides a non-invasive alternative by purely relying on the deflectionof light when the rays traverse a medium containing a refractive index gradient. Given that thepressure fields in acoustic levitation are linearly dependent on the refractive index, we can use thisoptical method to visualise the ultrasound field gradients. This poster presents our recent findingsfor employing schlieren to observe the ultrasonic pressure fields used for acoustic levitation. Wecommence with the measurements of a single transducer field and advance to fields created by arraysof transducers hosting the levitation traps. We show schlieren measurements of fields containingmultiple traps and address the observation of parasitic effects such as transducer heating and ultrasoundreflections. Our obtained results demonstrate that with schlieren we reach a comprehensivevisualisation of ultrasound field gradients and validate schlieren as a useful tool to gain a betterunderstanding of acoustic levitation.