Blind-label acoustic subwavelength imaging

There is a long-existing tradeoff between the imaging resolution and the penetration depth in acoustic imaging caused by the diffraction limit. Most of the existing subwavelength imaging approaches that address this trade-off require exogenous “labels,” such as metamaterials or contrast agents, to be deposited close to the objects. Those labels need to either remain static or be tracked precisely during imaging, therefore, are extremely restrictive in practical applications. This talk will present our recent work on a “blind label” approach for acoustic subwavelength imaging. The “blind labels” are randomly distributed acoustic scatterers with deep-subwavelength sizes whose exact locations and trajectories are unknown. A hardware/software co-design framework is developed that is composed of two parts: 1) spatial mixing: a physical process that converts the originally evanescent components in the scattered waves from the object to propagating components that can reach the far-field detector; 2) computational image reconstruction. Our experiments both in air at KHz frequency range and in water at MHz frequency range achieved multi-fold resolution enhancement. The proposed “blind-label” approach relaxes the restrictions of depositing controlled labels close to the object, therefore significantly improving the practicality of acoustic subwavelength imaging in acoustic sensing, imaging, and communication applications.