Diverging Polymer Lens Design and Fabrication for Row-Column Addressed Transducers

Double-curved diverging lenses mounted on flat 2D Row-Column Addressed (RCA) transducers have shown the potential to extend the Field of View (FOV) from a rectilinear to a curvilinear volume region and thereby enable real-time 3D imaging of large organs. Such lenses are usually made of off-the-shelf pieces of materials, which leaves no room for optimization. In this work, acoustic lenses have been fabricated in a fast, inexpensive and flexible manner using a combination of 3D printing and casting or CNC machining techniques. The lenses are made either in a concave or convex double-curved shape and from thermoplastics and thermosetting polymers. PMMA (Polymethyl methacrylate), PP (Polypropylene), RTV (Room-temperature-vulcanizing silicone) and PDMS (Polydimethylsiloxane) diverging lenses have been fabricated and mounted on a 128+128 6 MHz Row-Column Vermon transducer. The -3 dB FOV of each lensed array has been measured and results in a maximum of 16° for a 43 mm radius PMMA lens. This work shows that thermoplastics are suitable material for fabricating low-attenuation convex or flat compound diverging lenses for 2D transducers. These lenses are highly desired for achieving volumetric anatomical imaging of large organs.