A matched model-based synthetic aperture focusing technique for acoustic microscopy

This contribution deals with an advanced synthetic aperture focusing technique for acoustic microscopy, which enables an almost precise reconstruction of the reflectivity distribution of both fluid-like and solid specimen. The presented approach is designed for single-element ultrasonic immersion transducers as they are commonly used in scanning acoustic microscopes. In practice, the resulting images offer at least lateral and axial resolutions of a focused image, which was acquired by a transducer with double center frequency. Moreover, the results show very low side lobe levels and the approach reconstructs the shape of inner defects even in images with present multiple reflections. A comparison with the well-known delay-and-sum technique reveals that the introduced approach offers a significantly more precise reconstruction of the given reflectivity distribution, especially when a complex reflectivity distribution is investigated. The advanced synthetic aperture focusing technique is applied to a generic test samples and to a curved multi-layered compound specimen.