Super Resolution Ultrasonic Imaging

High-resolution ultrasonic imaging systems are of significant interest in fields such as noninvasive diagnostics and nondestructive evaluation (NDE). However, conventional ultrasonic imaging techniques are fundamentally constrained by scattering phenomena and the diffraction limit, which restrict the achievable resolution to approximately half the operating wavelength. Recent advancements in metamaterial-based superlenses have demonstrated the ability to surpass the diffraction limit in both optical and acoustic regimes. Extending these concepts to the ultrasonic domain, however, poses unique challenges due to the shorter wavelengths involved and the requirement for precise wave reception, making practical implementation challenging. This chapter presents the authors’ investigations on periodic and nonperiodic (holey) metamaterial lenses (metalenses) designed for super-resolution ultrasonic imaging. The discussion includes presentations of the sub-wavelength imaging mechanism, physics of extraordinary acoustic transmission, and the design and optimization of holey metalenses. Furthermore, the chapter highlights the development of a portable, scalable imaging device that achieves super-resolution using commercial, off-the-shelf ultrasonic transducers, paving the way for practical applications in industrial inspection and biomedical diagnostics.