Planar focusing lens for enhanced far-field ultrasonic imaging

This paper presents a far-field enhanced-resolution underwater ultrasonic imaging on the basis of a single-slit structured planar focusing lens. The iterative angular spectrum approach was employed to optimize the planar focusing lens from a designated focal pattern, characterized by focal length and full width at half maxima. Numerical simulations and experimental investigations were conducted on different target objects. Compared to the conventional method, both results showed that the performance of far-field ultrasonic imaging was comprehensively enhanced with the proposed planar focusing lens, in terms of resolving capability, working distance, operational bandwidth, and robustness. The single-slit structured planar focusing lens is cost effective and easy to fabricate, which would greatly benefit ultrasonic imaging and drive new applications of ultrasound in various scenarios.