The theory of three-dimensional imaging of strong scatterers in scanning acoustic microscopy

Abstract The angular spectrum approach to three-dimensional image formation of strong scatterers in scanning acoustic microscopy is developed. It is shown that in the case of strong scatterers the image can be represented as a twofold two-dimensional Fourier transform of a far field scattering amplitude of the object. The proposed theory provides the opportunity to investigate the imaging process for objects having an arbitrary shape. The common features of images are demonstrated by using a disk and an elastic sphere as examples. It is shown that contrast in reflection microscopy is mainly due to scattering from the boundary of the object and can be described as a thin layer whose medium surface is in coincidence with the boundary of the objects. The thickness of the layer is equal to the lateral resolution of the microscope. For transmission acoustic microscopes the contrast is connected with the contour of the object.