Article

Acoustic Hologram Design Using Differentiable Simulation (en)

* Presenting author
Day / Time: 08.03.2023, 09:00-09:20
Room: Saal Y9
Typ: Vortrag (strukturierte Sitzung)
Abstract: Various methods have been proposed for the design of acoustic holograms, however, these typically have relied on approximate physical models. For example, many works use a thin-element approximation, modelling pixels as 1D resonators that introduce a thickness-dependent phase and amplitude shift at each point. This neglects scattering off the profile and considers reverberations as occurring within isolated columns, potentially resulting in model/experiment mismatch. Here, we investigate whether by using accurate and differentiable acoustic simulations it is possible to exploit these interactions (i.e., multiple scattering, absorption), to enhance the fidelity of the generated fields.The wave propagation is modelled using an in-house differentiable simulator named j-Wave [Stanziola et al., 2022, DOI: 10.48550/arXiv.2207.01499]. Initially, the hologram has uniform speed of sound, density, and absorption. The gradient of these parameters with respect to a loss-function encapsulating the target field (e.g., normalised cross-correlation with the target image regularised by the field norm) is calculated with backpropagation and optimised using gradient descent. The method is then validated using holograms fabricated using a Stratasys J835 multi-material 3D printer. It's found that using a more accurate physical model that accounts for absorption and multiple scattering can enhance the fidelity of the resulting fields.
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