An ultrasound focusing lens design incorporating high transmission and minimum diffraction

Abstract

An improved design of ultrasound focusing lens is reported, in which a periodical array of grooves were carved on the surface of a conventional lens. With vibrations produced by a planar wave transducer coupled to the lens’s left surface, each groove could be treated as a point source as long as the groove widths are much smaller than the acoustic wavelength. Several uncommon acoustic effects (e.g., collimation and enhanced acoustic transmission) have been incorporated into the designing, providing the benefits ranging from transferring acoustic energies, suppressing the side-lobes, and minimizing shifting of the focal point. It is demonstrated theoretically and experimentally that acoustic focusing achieved by using the lens can suppress the relative side-lobe amplitudes, enhance the focal gain, and minimize the shifting of the focus. The application of the corrugated lens can make a reduction of about 3 dB in the relative side-lobe amplitudes, a 3.6-dB increase in main-lobe amplitude, and reduction or even elimination of the focus shift which could be enormously valuable in enhancing the safety of noninvasive HIFU therapy. Enlarging the number of grooves could even further enhance the capabilities of improving the focusing efficiency and reducing the relative side-lobe amplitudes.