Title :
Scanning tomographic acoustic microscopy using shear waves
Author :
Ko, Daesik ; Meyyappan, A.
Author_Institution :
Dept. of Electron. Eng., Mok-Won Univ., Taejon, South Korea
fDate :
3/1/1997 12:00:00 AM
Abstract :
We propose to use shear waves instead of longitudinal waves in a novel scanning tomographic acoustic microscope (STAM) in which the specimens are solid. When a specimen with a shear modulus is immersed in the microscope´s water bath, mode conversion takes place at the water-solid interface. The shear wave energy is detectable and can be used for image reconstruction. Although wave transmission in most solid specimens is limited to about 20/spl deg/ for longitudinal waves, it is about twice that for shear waves. Also, velocities of shear waves are lower than those of longitudinal waves and hence the wavelengths at the same frequency are smaller. For these and other reasons we can expect that for many specimens the resolution of a shear-wave STAM to be substantially better than that of a longitudinal-wave STAM. We use computer simulation in order to compare the operation of a shear-wave STAM with that of the conventional longitudinal-wave STAM. We have simulated tomographic reconstruction for each. The corresponding critical angles of incidence are computed and tomographic reconstructions of a particular solid specimen is obtained by using the back-and-forth propagation algorithm (BFP). Our simulation results show that shear-wave STAM has better resolution than longitudinal-wave STAM.
Keywords :
acoustic microscopy; acoustic tomography; back-and-forth propagation algorithm; computer simulation; critical angle of incidence; image reconstruction; resolution; scanning tomographic acoustic microscopy; shear-wave STAM; water-solid interface; Acoustic signal detection; Acoustic waves; Computational modeling; Computer simulation; Frequency; Image converters; Image reconstruction; Microscopy; Solids; Tomography;
Journal_Title :
Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on