Volume imaging in anisotropic media by synthetic aperture technique

摘要

Numerical modelling of wave propagation in anisotropic single crystal is based on the angular spectrum technique. The decomposition of initial acoustic signal distribution into its angular spectrum is performed by the calculation of 2D Fourier transformation. Phase shift of each harmonic plane wave component depends on the distance between initial and observation planes and the normal component of the wave phase slowness vector. In anisotropic media slowness depends on direction of propagation vector and on polarisation. In acoustics directionally depending phase velocities are calculated from Christoffel equation. Decomposition of initial distribution and superposition of plane waves in observation plane is performed by the use of FFT algorithm. One may use this procedure in forward or back propagation. Here we use this technique for reconstruction of point source and a structure located inside of a single crystal. The complex data sets of synthetic aperture type were measured by scanning ultrasonic microscope with phase contrast.