Blind-label acoustic subwavelength imaging with static random scatterers

The resolution of conventional acoustic sensing and imaging systems suffers from the diffraction limit. Most of existing technologies addressing this limit require controlled “labels,” i.e., metamaterials or contrast agents, to be deposited close to the objects and to either remain static or be tracked precisely during imaging, restricting their practical applications. We proposed a “blind-label” approach for acoustic subwavelength imaging. In our previous work, the blind labels are randomly distributed microspheres that move freely around the objects. The originally evanescent components in the scattered waves from the object are first converted to propagating components and then extracted by advanced computational algorithms. In this work, we extend the applicable scenarios of our previous work by exploiting static random scatterers as the blind labels instead of moving ones. We conduct experiments to detect wires with subwavelength separations buried in silicone polymer, with a thin layer of microspheres deposited around the wires as the blind labels. Measurements for reconstruction are taken by exciting plane waves of different incident angles. Our subwavelength imaging system can now be applied to various scenarios where intrinsic random scattering media is accessible, such as detecting cracks buried in inhomogeneous structures or small lesions embedded in tissue.