Ultrasonic Transducers Characterization by Means of Double-Exposure Holographic Interferometry.

Experimental measurements of the surface displacements of ultrasonic transducers were performed. The method used double-exposure holographic interferometry to calculate the displacement of the entire surface of the transducer. Six electrode shape transducers were investigated: full circular, strip, rectangular, rosette, square, and linear phase array electrode. Acoustic pressure field calculations in the near and far fields were obtained using the surface displacements. Comparison with calculations using the geometry of the electrode revealed the importance of considering the total surface of the transducer. The side lobes and the maxima and the minima in the near field can be reduced with properly shaped electrode geometry design. The same method was utilized to measure ultrasonic wavelengths for three ultrasonic transducers resonating at different frequencies. The results were used to calculate the true ultrasonic frequency of the transducers. During the course of these experiments an example of image enhancement using phase modulation was performed and it will be presented. Initial results of visualization of ultrasonic pulse wave fronts using pulse lasers is included.