Delay-and-Sum Processing of Echo Data of Transducers Focused by 3D Printed Lenses

This contribution deals with focusing piezoelectric ultrasonic transducers with 3D printed lenses. Transducers focused with a fixed focus lens are often used, e. g., in scanning acoustic microscopy because of their high lateral spatial resolution in the focal zone. 3D printing enables rapid and easy production of such a lens. To verify the desired behavior, results of sound field mappings are presented for both a focused and an unfocused transducer. A limitation of focused transducers is the decreasing spatial resolution with increasing distance to the focus. This can be counteracted by post-processing acquired B-mode images with Synthetic Aperture Focusing Techniques. A widespread one of these techniques, which is based on rather simple assumptions, is the Delay-and-Sum (DAS) algorithm. Using echo data measured on a wire reflector with a transducer focused by a 3D printed lens, we show that with DAS post-processing, the lateral resolution remains approximately constant over a large depth range.