10 April 1997 Improving the signal-to-noise ratio of a Schlieren system for characterizing ultrasonic transducers
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The acousto-optical schlieren method for the measurement of ultrasonic transducer field characteristics has been established as a fast way to veil the beam pattern and directivity of such devices. At the Pennsylvania State University, an Optison schlieren System made by Intec Research is used to analyze transducer beam profiles in both continuous wave and pulsed modes. The schlieren system works by suspending a transducer in a tank of water and sending a pulsed beam of coherent monochromatic light transverse to the beam path. The light received through the tank is focused on a CCD camera. The pressure of the water in the beam path changes the optical index of refraction of the water which in turn results in an image caused by Raman-Nath scattering which can be seen by the camera. Minor fluctuations in the temperature of the water, small bubbles, and particles present in the water (even after filtering the water) can cause noise in the image seen by the camera. In this paper the results of using multiple frame filtering techniques and particle perturbation are analyzed for delivering improved images. This allows better dynamic range and better spatial resolution of actual beam information. Since multiple frames are used, no blurring or other false artifacts are introduce to the images or the reconstructed beam information.
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Manjirnath A. Chatterjee, Manjirnath A. Chatterjee, K. Kirk Shung, K. Kirk Shung, } "Improving the signal-to-noise ratio of a Schlieren system for characterizing ultrasonic transducers", Proc. SPIE 3037, Medical Imaging 1997: Ultrasonic Transducer Engineering, (10 April 1997); doi: 10.1117/12.271330; https://doi.org/10.1117/12.271330

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