Browsing by Subject "Optical transfer function"

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    Modulation transfer function for the acoustic microscope
    (The Institution of Engineering and Technology, 1979-05-24) Atalar, Abdullah
    A simple method to measure the modulation transfer function of an acoustic microscope is described. Theoretical results are compared with experimental measurements. An explanation of `shadowing´ found in acoustic images is given.
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    Resonances and nonuniformities in CMUT elements or arrays
    (IEEE, 2014-09) Atalar, Abdullah; Köymen, Hayrettin
    We determine the response of individual cells of a CMUT array immersed in water using the small-signal equivalent circuit of a single cell and radiation impedances. Using a numerically efficient technique, we are able to simulate large arrays. The results indicate the presence of resonances at low frequencies where Rayleigh-Bloch waves are excited on the surface of the array. Reflections from the edges cause standing-wave patterns. Above the cut-off frequency of Rayleigh-Bloch waves, no standing-wave pattern exists. However, there is nonuniformity among cell velocities mainly due to unequal radiation impedance seen by the cells. Rayleigh-Bloch waves and nonuniformity in cell velocities do not cause a significant degradation in the point spread function, but the oscillations extend the duration of impulse response, limiting the dynamic range. © 2014 IEEE.